Should We Be Rethinking the "Ant Problem" in Fruit Trees?

I get alot of questions on how to control ants in fruit trees. Is it really necessary? Are we doing the right thing when we eradicte them? (Posted originally at Washington State University's Orchard Pest Management online and can be found at http://jenny.tfrec.wsu.edu/opm/displayspecies.php?pn=890 ) Ants
-- Greg Paulson and Everett C. Burts (originally published 1993)

 

Ants are the most efficient and numerous of all predaceous insects. Some ants, such as certain species of Formica, can be used in orchards to help control pests and reduce reliance on pesticides.

Hosts

Ants can prey on a wide variety of insects. Their primary role in orchards is as predators of pear psylla on pear.

Life stages

Egg: The egg is white and oval.

Larva: The larva is shiny white and elongated.

Pupa: The pupa is a dull white or tan.

Adult: Adults range in size from about 1/12 inch (2 mm) to 1/2 inch (12 mm). Many are black, but there are also red, brown and yellow species. The head is large with long, elbowed antennae and is joined to the thorax by a thin neck. The thorax is connected to the abdomen by a narrow, flexible waist, or petiole. In some species, the petiole is just one segment, while in others it is two segments. The swollen part of the abdomen behind the petiole is known as the gaster. During part of their life cycle, when they mate and disperse, the reproductive ants have wings.

Life history

 

A typical ant colony consists of sterile female workers and soldier ants governed by one or more queens. The queen lays eggs. Worker ants forage for food, maintain the nest and care for the queen and her developing brood. Soldiers defend the colony and its resources from enemies. Ants overwinter as adults in a colony. In the spring, the queen resumes egg laying. A queen can lay thousands of eggs each year. Workers carry the eggs to nursery chambers in the nest. Larvae are fed and cared for by workers.

After several weeks, the larvae develop into pupae from which worker and soldier ants later emerge. Once or twice a year, usually in the late spring and early fall, a special brood of eggs develops into winged male and female reproductive ants. Swarms of these ants leave the nest to mate and disperse. After mating, new queens either move away to establish new colonies or, in species that have more than one queen per colony, they may stay in the nest. Once established in a nest, the queen sheds her wings. Males die or are killed soon after mating. Queens usually mate only once and use stored sperm to fertilize eggs for the rest of their lives.

Management

Ants as biological control agents Over the centuries, predaceous ants have been exploited in countries around the world to control a variety of pests. Ants can be used in orchards to help control pests such as pear psylla and reduce reliance on pesticides. Ants eat psylla nymphs and young adults and also remove honeydew, reducing fruit russet. Some ant species will farm, or tend, other plant-damaging insects. For example, the ants may feed on sugar produced by aphids and protect the aphids from predators and parasites in return. But some researchers believe that honeydew-producing insects such as aphids help scatter the ants throughout the tree, enabling them to protect the plant better from other, more damaging pests. If undisturbed, ants will establish permanent colonies and build up to large numbers.

Introducing ant colonies In most orchards, ants have been eradicated by pesticides. However, ant colonies can be collected and reintroduced. If the mosaic can be preserved in an orchard, predatory ants can contribute significantly to pest control within two years of introduction. Formica neoclara and Formica podzolica are appropriate species to use in orchards. Both are indigenous to Washington's pear growing regions. They have more than one queen, which greatly increases the reproductive capacity of the colonies and lessens the risk of a colony failing to become established if a queen dies. They are not aggressive, do not sting, and seldom tend aphids. Both species nest in the soil, forming low mounds that are easy to excavate and do not interfere with orchard equipment. Other closely related species, such as Formica montane, could also be used.

Protecting ant colonies After ant colonies have been introduced, they must be protected and allowed to spread throughout the orchard. The two greatest threats to ant colonies, particularly new ones, are pesticides and physical damage to the nests. Most orchard practices do not harm ant colonies, with the exception of disk tillage to control weeds, which destroys nests. Other weed controls, such as herbicides, should be used if ants are in the orchard.

It is relatively easy to conserve ant populations in organic orchards because pesticides such as Bacillus thuringiensis (Bt), granulosis virus, rotenone and other products certified for use in organic orchards are not toxic to ants. In conventional orchards, apply pesticides when ants are least active and use compounds that are the least toxic to ants. Ants are not yet active when dormant sprays are applied. Later in the season, ants are least active between about 10 p.m. and 4 a.m. They are also relatively inactive from about 11 a.m. to 4 p.m., particularly on hot days. Organophosphate and carbamate insecticides are highly toxic to ants, and their residual effect can last for up to two weeks. Synthetic pyrethroids also are toxic to ants, but they are effective for only about a week. The best compounds to use with ants for pear psylla control would be insect growth regulators, which have little effect on foraging ants. Good dormant control of pear psylla is essential where ants are used as biological control agents. Pear psylla begin to reproduce at least a month before ants become active in the spring. Early season chemical control is needed to keep psylla populations below damaging levels until the ants begin foraging.

Note: so far, we do not have pear psylla in fruit trees in the Las Vegas Valley.

Why ants are good natural enemies

 

Ants can be very effective biological control agents for several reasons:

• Colonies contain large numbers of ants that consume large quantities of food.
• A colony with multiple queens can have an enormous number of workers, perhaps 300,000 or more. Often, there are networks of colonies containing millions of foraging workers.
• Predation is not limited to a particular prey species or stage.
• Worker ants will continue to forage even when satisfied. They hunt for the brood, the queens, and other workers in the nest.
• Ants can survive temporary food shortages by living on stored food reserves.
• Ants forage throughout the orchard and can efficiently exploit new food sources through chemical communication.
• Ants are active for long periods, both on a daily and seasonal basis.

Transplanting an ant colony

Use wooden nesting boxes to collect, transport and transplant ant colonies. The box size depends on the size of the colony, but usually a box measuring 12 inches by 24 inches and 16 inches high is large enough. The best material is a low-grade white pine. Do not use treated lumber and wood products, such as particle board and plywood, as they contain compounds that could harm the ants.
Heavy plastic garbage bags, doubled for extra strength, can be used instead of wooden boxes, but they do not protect the colony very well during handling.

To stop ants escaping, make sure the box's joints fit tightly. Use duct tape as a sealant. Collect the colonies by carefully shoveling nests directly into the nesting boxes.

During collection, separate and discard empty nesting material, rocks and debris from material containing brood and workers and discard. It is best to collect colonies in the early spring before they become active. Also, more ants will survive transplanting during mild spring weather.

Before sealing the boxes, put cotton saturated with honey and water inside with each colony. If the nesting material is very dry spray a little water into the box. After sealing the boxes, try not to disturb them. Keep boxed colonies for one to two days in a cool, dry, shady place before burying them in the orchard. Holding the ants increases the chances of successful introduction.

In the orchard, dig a hole for the box in an area that will not be disturbed or flooded by irrigation. Ideally the site should be exposed to morning sunlight but shaded in the afternoon. Drill several exit holes, about 1 inch (2.5 cm) in diameter, through each side of the box before lowering it into the hole and burying it under 3 to 4 inches (7 to 10 cm) of soil.

Ant colonies usually do not stay in the nesting boxes, but establish new nests nearby. The box protects the ants during transit and their early days in the orchard. With careful handling, most ant colonies will survive.

Pruning Peach Trees Now Might Lead Toward Disaster

Q. Our Desert Rose peach tree is eight years old and finished harvesting for the year. We would like to know what branches, if any, we can trim now and not harm the tree or cut off all next years peaches. We have six to eight inch in length branches that come off small branches that have no leaves and appear dead, and we have other small branches that have a six to eight inch span in between leaves that we had peaches on both parts this year. We usually trim what we think is dead or excessive growth wood in January. We thinned the peaches really well, but we lost two, four to eight inch circumference branches this spring do in part to wind and the weight of the peaches. Any information you can provide is greatly appreciated.

 

A. I don’t know the Desert Rose peach but should be no different than the others.  Any time we are in the hot parts of the summer it is wise to be very careful when pruning.  Pruning at this time should be light at best if at all. 

Right now we should be still pruning our fruit trees lightly, removing only new, young shoots that are too close together or shading the leaves too much.  We’re cutting back or removing some of this year’s growth which has been too vigorous. 

Do not prune so much that you open the canopy and risk the possibility of sunburn on some of your major limbs.  However, if the canopy is too dense then you should do some thinning of the canopy to allow some light to enter.  If you need to determine if the canopy is too dense, look at the ground under the canopy. 

Remove NEW shoots anywhere in the canopy that are growing straight up or straight down. Remove enough so that you see speckled light on the ground through the canopy. Then stop. Removing too much can cause damage this time of year (June/July).

 

The shadow of the canopy on the ground should be speckled with light.  If it is a solid shadow, then a few small branches should be removed until you see speckling in the shadow.  Only remove a few small branches to accomplish this.  No more.  Reserve the rest of your pruning for winter time when the leaves have dropped.

Camelias Not for the Inexperienced Gardener in the Desert

Q. I wonder if you can help me diagnose a problem with my camellia, the variety is "Marie Bracey". I had it in a container while it was young and my husband moved it for me to our back yard where it gets the morning sun and afternoon shade which is what the card read that was attached. It was growing fine but now there are about 30  leaves that have brown tips. Another question, the card says to cut back after flowering, which has not happened yet but it does not explain how to cut it and to what level.

A. You are fighting an “uphill battle” growing camellias in the Las Vegas valley since they require similar conditions to azaleas and rhododendrons. Not that you can’t do  it but it will take quite a bit of care on your part.

There are camellia societies, the counterparts to rose societies, on the southern east coastal areas and west coastal areas and inland in northern California. You have the Japanese camellia type. These plants are medium to large shrubs and even trees so it may take some time for it to get big enough to flower.

Link to International Camelia Society
Link to American Camelia Society
Nice link to information and pictures of Camelias

Another camellia I know you are familiar with is Chinese camellia, the plant that is used to make teas like black teas, green teas and Oolongs. So this plant does not come from the desert parts of the world. This will give you some insight as to what you will have to do; improve the soil a lot and give it some protection from the harsh desert environment.

You did that by following the card attached to it. But just a warning. That card was not intended for Las Vegas but for more friendly camellia environments so you may need to take what it says a step further. Even morning sun may be too intense for it if it extends into late morning and thus contribute to the browning of the leaf edges.

Other things that can contribute to leaf scorch are the poor soil conditions we have and the salty water coming from Lake Mead to our taps. Those people with well water frequently have much better water than the water coming from our taps.

Another problem you will most likely have will be yellowing leaves. Camellias like the soil to be slightly acid and our soils are not. This will mean that iron will be tough for the plant to get in a form it can use.

The only way to provide that kind of iron is to make the soil more acid or give it iron in a form it can use. Lots of decayed or decaying organic material will help in the soil around the roots and on the soil surface on top of the roots.

Sulfur applications will also help but the sulfur should be pulverized into a powder, not like little rocks if it is to be effective. So usually the more effective way to apply iron so the plant can use it is to use chelates. Like the broken record I am, the chelate EDDHA combined with the iron is the most effective way for iron to reach the plants in our soils.

Sulfur granules applied to the soil surface two years later. The granules are too
large and breakdown slowly. Also these plants are on drip irrigation so the
sulfur never comes in contact with water ...unless it rains...in the desert?

So what to do? Make sure the plant had lots of GOOD compost mixed into the soil at planting time. I would also put some sulfur with that planting soil. If you are not sure, replant it carefully this fall around the first week of October.

Mulch the soil surface with organic or wood mulch. This is very important with camellia since it has a very shallow root system. Make sure the soil drains easily. Find a place that gives it early morning sun and not late morning sun, out of strong winds and not near a hot wall. Filtered light from a tree that allows scattered light on the ground with plenty of air movement (but not strong wind) would even be better but not total shade.

Next spring after all danger of frost has passed (usually around the first to the middle of March) fertilize the plant with an azalea or rose fertilizer and add iron chelate as well. Expect that your camellia will not be picture perfect since it is not growing in an ideal climate and soil. Contact me next spring and let me know how it is doing and we can take it to the next step.

Miniature Peach Poor Growth in Container Might Be Container Size

Q. I have this miniature Bonanza peach tree in a large pot for 4 years the first year several large peaches since then nothing. The second and third year flowers and fruit buds, but then they fell off and I was told by a nursery that it was because of all the high winds we had. Then this year I moved it out of the wind and same thing happened and the leaves were kind of narrow and had some tan spots on them, I sprayed it with a fungicide and it took care of the tan spots but the leaves still look anemic.

Readers Bonanza peach tree with poor growth, sparse canopy and poor color.

 

A. You are right. The plant does look anemic. The leaves are light green at best and doesn't really show much new growth. On peaches and nectarines the fruit is produced on one year old branches. This means that the fruit that will be produced in 2012 will appear on stems that grew in 2011.

The contaimer looks small to me for a tree that old. I will bet the roots will be rootbound (circling in the container). Having a plant with rootbound roots can cause the poor growth.



Readers Bonanza peach tree in a container, closeup.

If the growth of a peach or a nectarine is poor and very small then there may be little or no room on this one year old growth to produce fruit. This might be because of the soil that was used in the container. If the soil was bad to begin with then your tree will show evidence of slow decline and lack of fruit production.

The poor growth could be due to several things. Make sure it is getting enough water. The volume of water that you apply needs to be enough so that water drains from the bottom of the container.

Secondly, poor drainage. Water applied to the top of the soil in the container should drain easily into and through the soil.

I could not tell exactly but on your picture there appears to be some flowers. That is a key question to ask yourself if your peach tree produced no fruit; “Did the tree have flowers?” If there were flowers present but no fruit then something happened after flowering that caused the fruit to drop from the tree.

Nearly all peaches and nectarines are self-fertile or in other words do not need a pollinator tree. So a lack of pollination is unlikely to cause the fruit drop.

Either poor drainage or not enough water could also cause fruit to drop.

The question is what to do now. I would probably start over. This is a bad time of the year to try to pull this tree out of the container and try replanting it. At this point in time you could try replanting with a totally new plant. If you plan to keep it for several years I would look at a larger container.

If you keep this one, rinse the inside of the container with a 5% Clorox solution and let it air dry. Make sure the container drains easily after it is full of soil. Don't skimp on soil amendments. Use a top-quality compost amendment or good soil at the very beginning.

Plant tree at the correct depth. Stake it first year of growth. Fertilize once a year in the spring and combine that with an iron chelate. Water the soil until water comes out the bottom of the container and then stop watering. I hope this helps.

Pomegranate Fruit Failure May Be Due to Funny Looking Bug

Q. I wonder if you could tell me why my pomegranate tree is not letting the pomegranates ripen on the tree.  I have many but they are falling before their time. I would greatly appreciate an answer.



Leaffooted or Leaf footed plant bug on pomegranate.

A. For pomegranates to fall to the ground before they are ready would be highly unusual. My guess is that your tree may have been attacked by the leaf footed plant bug. This insect is in the valley and can attack many different fruit trees but is notorious for causing early nut drop in pistachio and almond. It can also cause early fruit drop in pomegranates.

            A close examination of the tree may reveal these insects in the hundreds. Look for them. I have attached a picture of them on pomegranate. If this is the case, you will require an insecticide application starting around late May or June. The preferred insecticide is probably going to be one of these synthetic pyrethroids.

            This is not the name which you will see on the label. This is the active ingredient. There are many, many manufacturers of this type of insecticide so I cannot tell you the exact trade name on the label. It will vary among companies.

            The label should recommend it for fruit and vegetables and the active ingredients should have some sort of pyrethroid or permethrin or something very similar to this.

            I wish I could tell you exactly the name but the nurseries carry different products. The other option is to spray it with a traditional insecticide for fruit such as Sevin. Both will work.

            The pyrethroids are a bit more kind to other insects and the environment. Both of these products will hurt honey bees so make sure you spray at dusk or just before sunrise when the bees have not started to look for food.

Bitter Peaches

Q. We have two peach trees that are 7 years old.  This year the peaches on both trees taste bitter.  I don't recall doing anything differently. One of the trees produced bitter peaches the year after we planted it. but has been fine until this year.  Do you have any thoughts on this?

A. You don’t mention if the peach is a miniature or not. There is variation on the quality of fruit produced on fruit trees and much of that is surrounding the weather during the growing year.

One of the genetic dwarf peaches at the UNCE Orchard in North Las Vegas with full-sized peach fruits because of thinning, pruning and proper care.

For instance this year our early peaches and even our early apricots did not have the same quality in flavor due to our unusually cool spring. And they did not ripen evenly as well.

Many of our fruit needs to have consistently warm or even hot temperatures during its development to develop good flavor and lots of sugar. Otherwise they can be bland or worse.

I have also noticed that miniature peaches such as Bonanza produce fruit that is very variable in quality from year to year. It is nothing you did and there really is not much you can do about it.

Have you heard about wines having good years and bad years? Well it is the same with most fruit. I think your fruit, and unfortunately you, had a bad year. When the weather is good during fruit development in future years the quality will be better as well.

Magnolia, Persimmon and Crepe Myrtle Growing Perhaps Too Fast

Q. My trees are growing quite well and I was wondering what to do next to my magnolia, persimmon and crepe myrtle.

 

A. Thank you for the great pictures and breaking them into two emails. That helped quite a bit. Here are some comments on what I saw.

First general comments. The plants are actually doing quite well, maybe even a bit too well. There is plenty of new growth which is what you want but because they are so “happy” they are growing very quickly and thus you are getting big spaces between leaves and buds. This results in an “open” appearance.

Many of your plants, now that they are getting lots of nutrients, water and in a great growing condition are now growing as fast as they can. This will result in larger plants that will start to flower or fruit further and further from the ground as they get closer to their mature size. Plants do this naturally because in nature they are always competing for sunlight and other resources that keep them alive.

How do slow them down? We focus on two things: reduce those “goodies” they are getting that encourage a lot of growth (water, fertilizer) and (this next part is harder to realize a bit) get the plant to reduce its own growth in each of its growing branches by increasing the total number of branches it has to support. This then causes the “goodies” that encourages growth to be divided up among many more growing points and slows it down. It’s like having an income of $50,000 a year and having to support three children or 20 children; your resources are divided up many more times  so each “child” gets less.

Generally speaking, reduce “goodies” by reducing your watering frequency (how many times you water per week if possible but not by too much) and cut your fertilizer application in half (but not to the point where it is starving or gets leaf scorch) and (increase the number of growing points or "children") prune. The type of pruning you will mostly do this winter will be what I call “heading cuts” rather “thinning cuts”. Heading cuts increase the total number of shoots in a tree while thinning cuts typically do not. If you want to see the difference, please visit my Youtube video on this subject

http://www.youtube.com/watch?v=yKDSzCfvqe0

Now your individual trees, you must decide what you want for the ultimate height on these trees. If you want them to be large (such as flowering trees for beauty, shade or screening) then let them go and don’t do much pruning.



Crape myrtle showing some impressive growth

If you want trees to be smaller and more compact (fruiting and harvest for instance) then you will cut them back pretty hard and take away from them their luxurious growth. You will prune these trees twice each year; once in the winter and again (taking away new fast luxurious growth) in April (summer pruning).

Crape myrtle. I would assume you want a larger tree, perhaps with multiple trunks (3 to 5) coming from the ground. Don’t reduce the height. Let it go. Pruning will focus on removing dead, twiggy growth (it has lots of these due to flowering) and use thinning cuts to eliminate branches growing too close together, one branch growing on top of another, branches crossing each other, etc.).

You can reduce the height by making thinning cuts and removing the tallest limbs and branches back to a “crotch”. I would not do much of this until it gets closer to the height you want it to get. You will fertilize in January with an all-purpose soil applied fertilizer such as 16-16-16 or even a rose fertilizer. You will see benefits from adding iron chelate to the soil in January and foliar applied fertilizers such as Miracle Gro about two or three weeks after the leaves emerge in the spring.



Magnolia open growth with sparse leaves

Magnolia. This is another tree you could elect to let it grow. Having a multiple trunked tree will help
to keep it smaller. You realize that this tree is not a terribly good choice for our climate so you will spend more effort and money on this tree than many others. It will need the mulch which you are doing. This will give it some soil improvement near the soil surface as it decomposes.

It will require a fertilizer application in January to push new, healthy growth. It will also benefit from an iron chelate. It will not most likely need a foliar fertilizer but it will not hurt it if you chose to apply it in February or March. Your choice but it might do better if it is kept smaller than the mature height it will try to reach. Perhaps if you can keep it in the 25 to 30 ft. range it will be easier to keep healthy.

Perhaps saucer or star magnolia might work better in the future. Not as pretty but still pretty. There is a southern magnolia called Little Gem that is smaller.

 



Persimmon growing perhaps a bit too erect and fast for
its own good

Persimmon. Cut this tree back hard if you want your fruit closer to the ground. Your tree is too lanky. Cut back into older wood about half way in where it is too long in late January or early February. Don’t be afraid to do this. It will handle the hard cuts. Fruit is produced on current season wood so it will flower and fruit from new growth.

I hope this helps.

How To Determine When and How Much to Irrigate (the long version)

Q. I read your article this morning in the RJ and found there to be a significant difference in the watering recommendation  you gave versus that from Springs Preserve. Currently, we have set our drip system to three days a week for one hour each day. We're using one and two gallon emitters on shrubs and multiple four gallon emitters on palms and trees. We have read our water meter and my wife is aghast. For the one hour we are using approximately 975 gallons without using any other water in the house. We have no grass. If we cut back to two days a week, what should we look for in terms of adverse effects?

A. Sorry, I am not aware of what they recommend so I don’t follow the Springs Preserve recommendations. It is difficult to give one recommendation for everyone who lives in the Las Vegas Valley because there are so many different soils, microclimates and irrigation systems. I base my recommendations on a few things that I will cover here as a result of your question. And yours is a good one.

One major piece of research I follow for the area is the plant water demand (called PET; Potential Evapo-Transpiration) that we developed in the Las Vegas valley about ten years ago. Water District. I attached the PET table for all 12 months for you to see.

PET table for the Las Vegas Valley. This table tells you how much water (in a range of low to high and an average) tall fescue turfgrass will use each month. So in one year tall fescue will use anywhere from about 84 to 96 inches of water with an average around 90 inches. It also gives you monthly average water use in the same table, again in inches. I know, I know.....but my  controller is in MINUTES!

 

This is the same PET information but in graphical form. Notice how PET, or plant water use, changes through the calendar years. Water use in June and July are about 8 times more than in January and December.

 

When we irrigate there are three questions we have to answer to set a controller;

1. How many minutes should I set the controller (volume of water applied)?

2. Which day or how many days of the week should it come on (frequency of application)?

3. What time of day should I start watering?

These questions don’t relate at all to what the plant needs and how it should be watered. Here is where the confusion lies. The questions are only directed at the setting an irrigation controller. By answering these questions we hope to try and match the plant water needs. We hope we enter enough minutes and water frequently enough that the plants get enough water.

 

A major problem with irrigating plants in any landscape with an irrigation system of pipes and valves is that the plant receiving the LEAST amount of water drives the setting of the irrigation controller. If we see a plant not getting enough water (and it might be only one plant in the entire irrigation circuit) we rightfully increase the amount of water it gets. Unfortunately, ALL the plants on the same irrigation circuit are increased as well...whether they need it or not. If one plant is not getting enough water, it is possible then that we might over irrigate everything else just to give one underwatered plant enough water. This is why it is critical that the number and placement of emitters for plants on the same irrigation circuit be determined all at the same time, not independently of each other. I will explain how to do that in another blog entry.

 

I will make a separate posting of how to choose drip emmitters and how many to use for each plant. If I forget PLEASE remind me to post it!

A plant should be watered at each irrigation so that the applied water wets the soil under the canopy of the plant to a depth just past the majority of its root system. We are filling a water reservoir in the soil for the plant to draw upon, like a gas tank for a car. The water should come on again when about half of the water in the soil is gone (gas tank is half empty). We then fill this tank again to the brim and start over again.


Bigger plants typically have deeper roots and a bigger size. This means that "big plants need more water than little plants".
I borrowed this picture from an Arizona publication on scheduling irrigations but I don't remember the title. A very nice publication.

 

With a normal gas tank for a car we might fill it when it is below 1/4 full. We can't do that with plants. At 1/4 tank there is not enough water in the soil to keep the plant from wilting or dying... with the exception of true desert plants like cacti. With true desert plants you can go longer between irrigations because many are drought tolerant (they can survive in drier soils).

 

Add emitters as the plant gets larger. The gas tank is made larger in diameter (not deeper) as the plant gets larger. The way we make the gas tank larger (make it wider in diameter but the same depth) is by adding emitters under the canopy. More later.

 

The amount of water we apply to the plant is basically the same each time we water, all year long. This is why I tell people to keep the number of minutes on the irrigation controller the same all year long. If you drive your car less you don’t stop and fill it up the same day each week. As you drive less (less water is used by the plant) you fill your gas tank less often. You change the frequency of application (days each week). But you want to fill the tank or reservoir with the same amount of water each time as long as the reservoir is half empty each time.

The water is used up because of 1. evaporation from the soil, 2. water used by the plant (transpiration), 3. drainage beyond the roots and can’t be recovered (lost). This does not translate into number of minutes, days of the week and time of day at all! So somehow we have to bridge the gap from what the plant needs and how we set the controller.

1. How Many Minutes Should I set My Clock and How Far Apart Should I Put My Emitters?

The number of minutes tells us (with some work on our part) how much water is applied. Let me explain. With drip emitters, the emitters are designated in gallons or liters per hour. One emitter only drips water in one spot.

Once the water enters the soil it moves both down and sideways (laterally). Gravity moves the water down. Water is moved laterally by two forces; the size of the spaces between soil particles (how sandy the soil is and how much organic matter it contains) and how dry the soil is surrounding the soil water reservoir. The dryness of the soil “pulls” the water laterally but the distance the water is pulled is controlled by the spaces between soil particles (how close together or far apart they are).

Sandy soils have particles that are very far apart and so water is not allowed to go very far. As we increase the organic matter in the soil, it increases the distance between soil particles. In sandy soils you can expect the water to move laterally in about a two foot diameter (one foot from the emitter) in all directions. This is why we normally recommend that emitters are spaced about two feet apart if we don’t know what the soil is (worst case scenario, sandy soil). In a clay soil, the water can move as far as six feet laterally! In a sandy soil a five foot tall shrub might need two or three emitters. In a clay soil the same shrub might need only one emitter. (However it is usually never a good idea to have only one emitter for a plant in case it plugs).

The real world. So how many minutes should you set it? Run it long enough so that the water from the emitter waters the entire root zone. The root zone on small plants would be one foot. The root zone of large trees would be two feet or more but two feet is usually adequate.

1. Run the circuit for 15 minutes.

2. Use a 3/8 rebar (long screwdriver if you have one, long pointy thing if you have one of these) and push it into the soil  a foot from the emitter and measure how far it moves into the soil with ease (the depth of wetness). It will move with difficulty when it hits dry soil or a rock. If you hit a rock, move over a few inches and try again. If it is not deep enough, immediately run it for another 15 minutes. Repeat until you have the water moving to the proper depth for the plant. The total number of minutes your ran it will determine the run time or how many minutes to fill the “gas tank”. This should rarely change through all seasons.

3.  To see how far laterally the water is moving, push the rebar into the soil further and further from the plant until you reach dry soil (pushes into the soil with some difficulty). Do this after 30 minutes so that the water has plenty of time to move laterally. Once you hit dry soil you can see how far the water moves from the emitter. This distance is the maximum distance emitters should be placed from small to medium-sized plants. Now double the distance from the emitter to dry soil. This is the maximum distance emitters should be placed if you want the soil wet between emitters and the maximum distance apart you can place multiple emitters around plants.

 

2. Which and How Many Days of the Week Should I Water?

This is another way of saying “frequency of application”. This is how many days we should wait before we fill the soil reservoir again. Remember, we want the plants to use half of the water in the reservoir before we fill it again. This is true of all nondesert plants including most ornamentals and fruit trees.

True desert plants are a different story. Generally speaking, these plants can handle drought or a lack of water more easily with less damage than nondesert plants. So we can actually let the reservoir become drier before we irrigate. This is the reason that we should put true desert plants on a separate circuit (valve) from normal ornamentals and fruit trees. You cannot adjust how often to fill the soil reservoir by adjusting the minutes or putting different emitters on the circuit. This can ONLY be done by selecting which days of the week or month to water. And this requires a separate circuit or different valve.

In order to answer the question, “Which days of the week” requires that you know how much water plants are using and how fast they are using it (inches of water per day, week or month). The PET of a plant or landscape answers this question. The graph and table above tells you the monthly average water use for a tall fescue lawn (PET of tall fescue). The PET graph contains adjusted values (adjusted for tall fescue) of the actual ET of plants. We took the actual ET measurement we determined from research and adjusted it for tall fescue because that is how it is conventionally used. You can convert it back to the actual ET by increasing the daily values during the cool months by 15% and decreasing the monthly values during the hot months by 5%. These values are so close to the PET values that I don’t even bother. I use the PET values as they are to determine plant or landscape water use.

Since the type of soil dictates how much water is in the gas tank and how deep the plants roots are determines the size of the gas tank it is impossible to come up with a generalization that fits everyone. For this reason I have taken the leap of blind faith used our watering schedule at the orchard as a typical landscape site for the valley. Therefore I arbitrarily tell people that for large trees and shrubs

1. Around February 1 we set watering for one day a week (fill the gas tank).
2. May 1 (the PET table makes a significant jump here) for twice a week
3. When it gets above 110F then I suggest three times a week

Disclaimers.

• Turfgrass, flower beds and vegetable gardens are different and are watered more often than this because they are more shallow rooted than trees and shrubs.
• These are for plants that are mulched, not growing in bare ground. Watering must be more often since they use water faster.
• Very sandy or soils with large rocks have smaller gas tanks and must be watered more often.
• Plants in poor health cannot handle stress as well and need water more often.

 

3. What Time of Day Should I Water?

With drip irrigation it makes no difference except you must follow local guidelines and ordinances.

Container plants should be watered before the heat of the day to put water into the soil and cause the soil to heat up more slowly, and, hopefully, lower soil temperatures.

Turfgrass should be watered in the summer just before day break, some time after 2 AM if possible and finish by the time the sun rises. This gives turfgrass a chance to dry out and have fewer disease problems. It is less windy at this time. Wind will blow the water from sprinklers off course and can cause the irrigation system to put water down less uniformly. Less uniform applications of water means more water has to be applied to make up for shortcomings.

I hope this explains how I came to my recommendations.

Colorado Potato Beetle in Las Vegas? Maybe, Maybe Not.

Q. I've just spotted Colorado potato beetle bugs and larvae on my tomatillo plants. I didn't even know what they were until I did some research. I've never seen them out here before. I can't find an organic pesticide that will kill them without hurting the bees and other beneficial insects. Do you have any advice for me?

A. Make sure it is actually the Colorado potato beetle and not a look-alike insect called the Ten-Lined June Beetle. I have not seen the Colorado potato beetle in the Las Vegas area yet but it is possible. Until recently, Nevada was one of four US states that didn’t have this pest.

Ten-Lined June Beetle

            But I have seen the Ten Lined June beetle here and they look very similar to the Colorado potato beetle. I posted a picture of this critter on my blog. The safest way is to pick them off as you see them. In small garden plots this works well. You can also use a cordless vacuum cleaner and suck them up that way.

 

            As far as sprays go an organic/biological pesticide called Spinosad, which is available in many nurseries now, will give some control.

Colorado potato beetle adult (striped) and larvae without stripes on potato leaves in Kosovo.

            Another organic/biological control chemical is Bacillus thuringiensis (Bt) var. San Diego (also called variety tenebrionis) gives some control if they are not resistant. This particular type of Bt controls beetles. But this organic spray is hard to find locally. You will probably find it only online.

 

            There are Bt sprays in the nurseries but this is the wrong Bt spray for Colorado Potato Beetle. The one in the nurseries is Bt var. kurstaki (Btk). This Bt is used to control larvae or caterpillars that form moths and butterflies like the tomato fruit worm, tomato hornworm and grape leaf skeletonizer.

Another Report on White Fuzzies on Stems of Plants

Q. I check all my plants weekly for possible problems. I noticed what appears to be some kind of white fuzzy things on my pear tree leaves and sent you some pictures. I didn’t want to mess with them in case they were from beneficial insects. I’ve searched on line but can’t seem to find anything. Have you ever seen them before?

A. Yes, I have seen these white fuzzy, cottony things on all sorts of plants including herbs, citrus and vegetables. These are not good guys but they are also not terribly bad either. You can wipe them off or spray with soap and water.

            I have posted pictures of this before on my blog but I will repost it again. These are probably the egg masses of the sharpshooter insect or a close relative. Be sure they are not mealybugs. If you don't know what mealybugs are, ask and I will post some pictures. Truly one of the worst pests worldwide, particularly inside or in greenhouses but outside as well in wet climates.

Shoestring Acacia Leaning - What Should I Do?

 Q. I hope you can view the pictures that are attached. As you can see, one of my shoestring acacia is growing out on an angle and my fear is it will get to heavy and topple. Is there any way to save this tree by putting a support under the trunk or topping it by cutting it back? It was planted 7 years ago with two others and this is the only one that is doing this. It is about twenty feet high or so.

A. Thanks for the pictures. Actually your tree looks nice in your setting.

There are two things I am noticing from your pictures. First to answer your question, make sure the tree is getting water at distances equal to at least half the canopy area under the tree. You can do this by adding emitters or a water source in scattered areas under the canopy.

If the only water sources are close to the trunk, the roots may stay too close to the trunk and begin falling over when it gets top heavy. By putting water further from the trunk it encourages a larger area of support for the tree and its growing canopy. These emitters under the canopy can be used to support other plants as well so that it is not just watering the soil for weeds to grow.



b

Plant roots in container are circling. Bad, bad, bad.
Borrowed from
http://hort.ifas.ufl.edu/woody/container11.shtml

Lawns around trees also help to support tree root growth that keeps trees from toppling over. Roots do not grow “in search of water” but will grow only where there is water in the desert. Rainfall does not count in a true desert like ours in the Mojave.

If the tree or shrub was purchased in a container and the roots began circling in the container (the plant was overgrown in the container), they may continue to circle once planted and never create a strong foothold in our desert soil. The roots circle and circle and never spread out like they should.

When the top gets big, these trees with circling roots tend to lean or blow over in a strong wind. They can become a liability as they get older. Unfortunately these plants can never be rescued and must be removed to prevent loss of property or cause safety concerns.

Never buy plants in containers where the roots have grown in circles inside. They can never be established as healthy trees that are safe for public or private use.

What to do? Determine if the plant is a liability or not. If it is, remove it. To determine if it should be removed, put enough weight on the trunk to see if you can get the trunk to move enough to get it to move back and forth. While moving it back and forth, look at the soil beneath it and see if the soil is moving or if the trunk is securely anchored into the soil. If the soil moves around the tree, you will have to remove it. It is a liability.

If not, you have time to try to re-establish the roots farther from the trunk and give it more stability. This tree is too close to that wall and will probably damage the wall in future years.

Photinia in Rock Mulch Has Discolored Leaves

Q. Firstly, I enjoy reading your column and have learned many gardening tips with great results. Since moving into our home three years ago, the Photinia or Hawthorne patio tree has a recurring problem with discolored leaves, usually in the spring and fall. It has been treated with Bayer Disease Control, Dormant Oil and Ironite as recommended by others, along with the normal seasonal fertilization.  There are three, 4 gph emitters. Hopefully, from the photos, you will be able to shed some light on the problem.

A. I am sorry this is such a late posting back to you. What you have here basically is a nutrient deficiency problem. If these problems get to advanced they can be difficult to fix. When they're caught early, it is relatively easy.

Much of this problem has to do with the soil and the use of rock mulches around certain plants that are not very tolerant of the soil conditions that develop under rock mulch. What basically happens is that the good stuff in the soil I like to refer to as organic material has essentially disappeared.

When plants are grown in rock mulches there is nothing decomposing and giving back to the soil and the soil becomes what we call “mineralized” or void of organic material. Organic material in the soil is very important to some plants. Photinia is one of them. When these plants are first put into the ground the soil is modified usually with some sort of planting mix. This planting mix is usually organic in nature.

This organic material modifies the soil as it is decomposing and provides many benefits to the plants that help to improve its general health. As this organic material decomposes and is lost over a period of 3 to 5 years, these benefits disappear and the plant health begins to diminish.

The leaf yellowing with green veins indicates a micro nutrient problem, like
iron. in our alkaline soils and alkaline water.

This is why would some plants organic mulches that slowly decompose can be very beneficial. Whereas rock mulches which do not add anything organic back to the soil tends to be harmful to these plants.

True desert plants are usually much tolerant of very low organic matter content in the soil. While other plants that originate from climates where the soils organic material tend to do poorly growing in rock mulches.

What to do? Obviously if we can add organic material like compost back to the soil it will help. Usually, however, by the time we notice it the condition is very advanced and recovery can be slow or nonexistent. The best thing to do is to get these plants growing back under organic mulches.

Organic mulches do not include bark mulches. These are almost as bad as rock mulch. Wood mulches decompose and add life back to the soil again. You can pick up this type of wood mulch free from our Orchard in North Las Vegas and a Tuesday or Saturday morning. This is a case where you have to drive in and load it yourself into containers, bags or even a pickup truck.

There is no charge for this organic mulch. This mulch is made from chipping trees that are cut down in Las Vegas neighborhoods. Instead of taking it to the dump and burying it, we have provided a location we can come in and pick it up for nothing. For more information on the mulch at the North Las Vegas orchard and how to get there, call 702-257-5555.

 

You can also try spraying the foliage with a liquid fertilizer such as miracle Gro and iron sprays. Make sure you use a wetting agent mixed in the liquid fertilizer so that it improves its chances of entering the leaves. The wetting agent could be a teaspoon of Ivory liquid in a gallon of water. Add the Ivory liquid to the water, not vice versa or you'll get a bunch of bubbles. This will take multiple applications of the iron chelate but only a single application of the fertilizer. You can also apply the iron chelate EDDHA to the soil around the plant and water it in. The only nursery that is caring it to my knowledge is plant world on Charleston. They have this iron chelate labeled with my name on it because I recommended so often. I do not get a kickback or anything else from recommending it. It works for reasons that would take too long to explain here. So in a nutshell, surround your plants with organic mulches that will decompose. Spray the plants with a liquid fertilizer combined with a wetting agent now. Also spray the plant with iron multiple times about a week apart and include the Ivory liquid. Apply the EDDHA chelate to the soil now. The last thing to do is cross your fingers and hope for the best. I hope this helps.

Tomato Not Setting or Producing Fruit

Q. I have some Early Girl tomatoes that I planted in March from plantlets that I bought. I talked to the Early Girls about a month later and told them that if they did not flower in the following week, I would feed them to the worms in my compost pile. Well they seemed to have listened, because they made lots of flowers but the flowers didn’t set fruit. What did I do wrong?

A. Tomatoes are pollinated by insects, primarily bees. However, if temperatures are in the 90's and above they have trouble setting fruit. They just don’t like those high temperatures for pollination. They set better when temperatures are in the high 60's and 70's up to about 85F.

Other reasons for flower drop and no fruit set might be uneven watering so it is a good idea to mulch the plants. Straw is a good choice. I think a bale of straw no goes for about $8 locally. Low night temperatures below 55F can cause flower drop as well.

 

Also over fertilizing with nitrogen fertilizer may cause no flower development until the nitrogen is depleted a bit from the soil.

 

If temperatures are good, the bee does not actually have to visit the flower. Vibrations from bee activity are enough to set the fruit. If tomatoes are grown in greenhouses for instance and there are no insects in the house, the movement of the plants from vibrations caused by an electric toothbrush is often times enough to get them to set.

So make sure you have pollinator activity when temperatures are appropriate for fruit set. Otherwise, gently shake them while you are talking to them. Maybe a slight physical threat might work.

Another thing you can do is buy some tomato fruit setting chemicals. These are synthetic copies of natural plant growth regulators called gibberellins. It is usually applied when temperatures are cool, not hot like they are now. They are sold in nurseries or garden centers with names like tomato fruit set or the like. Follow the label directions.

Separating the Worms from Worm Castings or Vermicompost

Q. How do I separate the worms from my compost? I bought a thousand worms from a worm farm online. They have multiplied into the zillions but I don’t want to give them to my neighbors when I give away the compost. Is there an easy way to separate worms from compost?

 

A. I am not sure how you are vermicomposting but if your compost with the worms is deep enough, the worms will be mostly in the top 4 to 6 inches of the compost. The casting should be at the bottom.



I had a chance to meet the vermiculture king in Zimbabwe, Eric 'WormMan' Harrison, on a trip to Zimbabwe. His book on farming in Zimbabwe before the Mugabe regime, JAMBANJA – The true life story of a Zimbabwean farmer  is worth reading. A true pioneering farmer in Zimbabwe's history. He also authored a book on vermiculture. He passed on March 26, 2012.
 http://www.cfuzim.org/index.php?option=com_content&view=article&id=2337:tribute-to-eric-harrison&catid=76:cfu-press-releases&Itemid=97

            So by scraping off the top layer and returning it to new compost for vermicomposting you should retrieve most of them. Also, if you can screen the compost with 1/4 inch wire mesh this should get the remainder.

            . If some of the compost does not fit through the wire mesh return this also to your vermicomposting bin for further processing. You will give some "starts" away. That is inevitable. You will recover most of them

            Worms like to feed on compost rather than kitchen scraps so vermicomposting can be a two-step process; first compost and then transfer the compost to the vermicomposting bin for further refining.

When Do I Fertilize My Lawn and With What?

Q. What are the magic dates for fertilizing fescue and bermuda lawns that you had in the 9/30/2012 column?

A. The magic dates, easy to remember, for fescue is Labor Day, Memorial Day and Thanksgiving, the last one for keeping it green through the low temperatures of winter.

For Bermudagrass it is Labor Day, Memorial Day and Fourth of July. Use a slow release high nitrogen fertilizer made for lawns and mow with a recycling mower... one that mulches the clippings back into the lawn.

The best ratio of nitrogen to phophorus to potassium (the big NPK numbers on the bag) is approximately 3:1:2 or 4:1:2 or higher in potassium (the last number like even a 4:1:4). They do  not need to be a perfect ratio but close. The number should be HIGH:Low:Medium to High. What you DONT want to use a fertilizer high in phosphorus, the middle number.

Examples include 21:7:14; 12-4-8; 16-6-12; 15-5-15; etc.

the best type of  nitrogen is slow release nitrogen such as sulfur coated urea, ureaform, etc. At least half of the bag's nitrogen should be slow release. The best fertilizers I have used on turfgrass have been composted manures or vericompost. But they are expensive.

Good luck!

Pruning an Olive Tree With Two Leaders

Q. I have a non-fruiting Wilson Olive tree that was planted  last fall. It is approximately 5 ½ feet tall. I would like to prune it to be less like a bush and more like a tree with one trunk and a canopy. Since it is non-fruiting, I am not interested in pruning for better olive production and all advice on the internet seems geared toward that.

I have attached some photos of the tree. Here are some questions:

1) There are two main leaders growing up in the center. I would prefer one but am afraid if I take one out it will cause a big hole in the canopy. If I removed one leader would it eventually fill back in? I understand that olive trees are fairly slow growing so I am afraid the tree would look unsightly for quite some time.

2) There are smaller branches trying to grow horizontally from one of the leaders but the other leader is in the way.

3) Since the upright leaders are already touching, what will happen if I leave both of them as is?

4) Some of the leaves have brown tips-was this just from transplanting? Not enough water?

Would appreciate any advice you could give. Thank you.

(To the readers of this blog I apologize. I accidentally eliminated the photo from this reader. But the tree did have two leaders growing from the same area and  nearly the same size. The tree was already fairly large. Each occupied about half of the tree canopy. When trees  have two leaders in the center ,co-leaders, they both fight for the same light and usually have very weak attachments to the trunk due to what we call "narrow crotch angles.. As the tree gets older, these places where they attach to the trunk can become weak and one, usually the smaller of the two, will split from the trunk. If this is a large limb then this might create damages sto property. Regardless, if it splits when it is large it will definitely leave an ugly tree! My reasoning in this answer was that the tree did not have a heavy fruit load to support so that was not an issue. If two leaders are to be maintained as the tree gets larger and limbs become heavier, it is best to drill a hole through both co-leaders and put a threaded, stainless steel bar through both and secure with washers and nuts. Make sure it is clearly obvious as the tree gets older. You do not want someone with a chainsaw discovering a large, hidden steel bolt!)

A. I really don’t think it’s that bad. I would leave both leaders. You are right, it will leave a big hole and it will be unsightly for years to come. All your pruning cuts will be to eliminate branches so remove them at the source. Do not just cut limbs back. Remove branches at a crotch. All you have to do is remove crossed and broken branches. If two are crossed, remove the one which is more offensive. If you have new growth growing straight up, remove it at its point of origin. If there are limbs in the center interfering with each other, remove one or both if you have to. Do not leave stubs.

The brown leaf tips are from a lack of water. The tree is drought tolerant but will be nicer looking with more water. I would give it about 25 to 30 gallons each time you water. Water once a week now, deeply. In midsummer go to twice a week. In winter, once every two weeks or so. Fertilize the tree now by spreading some lawn fertilizer at the base and water it in with a few gallons. Spread the fertilizer under the canopy like you were salting a steak but the guy salting it uses way too much salt and has hypertension.

I hope this helps.

What Can I Plant if I Have Nematodes?

Thanks for keeping up with the blog. I LOVE it and always rely on it every time I need advice. You awesome! I do have a question for you and I'd really love your input.

 

Q. You have covered on one of your post about nematodes. Last fall, I pulled one of my cucumber plants. There were 4 plants in a row. One of the plants definitely had strange roots which I am almost positive were caused by root knot nematodes. I didn't do any solarization because it was cold during the time and I have read that it is best to do it during the hottest months. Are these nematodes harmful to humans and my dog? Will it give me a disease or a worm if I touched the soil?

You have covered that the only other way to fix this completely is through fumigation--which I can't really do since I only do organic gardening. Can I at least plant any other vegetables in the same raised bed, or will it cause me any ill effects after I eat the fruit/veggies that it bears? I was also thinking of maybe removing the soil from the raised bed and move them to the big pots where I will be planting citrus plants. Then I will replace the raised bed with new soil. Would this work well or will it just cause problems to my citrus plants? I'd love your input.

THANK YOU SO MUCH, Bob! I appreciate your the you are taking to read this.

A. Nematodes are very tough to impossible to get rid of if you have them. I should say they are basically impossible to get rid of. Be careful and do not move soil from this spot to other areas or you will move the nematodes as well.

Root knot nematode on tomato

 

Nematodes only infest plants, not animals so all animals are safe around these guys. Soil solarization will help knock back the populations but not get rid of them. There are some products like Clandosan (a naturalproduct) which are supposed to help but I would not be too optimistic. Even with fumigation it does not get rid of them buy just knocks them back.

Root knot nematode on mulberry roots

Use vegetables that are nematode resistant and fruit trees on rootstocks that resist nematodes. On vegetables they will have the designation "N" below the name somewhere. Other letters might also appear like "V" "F" and the like which just stands for resistant to other pest problems like verticillium (V) and Fusarium (F), two prominent disease problems. Nematode resistant rootstocks for fruit trees include Nemaguard, Citation, Viking, Atlas, Myrobalan, and Marianna. Hope this helps.