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Monday, November 5, 2018

Las Vegas Fruit Tree Pruning Classes Announced for December

I will conduct fruit tree pruning classes every Friday afternoon and Saturday morning at the Orchard at Ahern in downtown Las Vegas. Fruit trees include peach, nectarine, apricot, plum, pluot, apple, cherry, hybrids and pear. The first class begins Friday, November 30 and the last class of December concludes on Saturday, December 22.

Pruning specialty fruit trees like pomegranate, persimmon and jujube will be conducted in January. This orchard in historic downtown Las Vegas has about 2600 young fruit trees varying in age from one – three years in the ground.

Click here to enroll in one or more of these classes

Classes are two hours long. The Ahern Orchard is a privately owned orchard located in the heart of Las Vegas, near West Bonanza and Clarkway. Class is hands-on so bring your pruning shears. Class size is limited. That's why it is repeated during the month of December.


Use Orchid Tree in Mojave Desert Landscapes

Q. I bought an Anacacho Orchid Tree at the Springs Preserve plant sale. Everyone tells me it needs rapidly drained soil, so I will use cactus soil. Should I put a couple inches of compost on top to enrich it? 

A. Interesting plant you bought. Not used much in the Las Vegas area because it’s not available but more popular in Arizona and Texas. Native to the Chihuahuan Desert. It’s a good choice for a desert landscape here.I don't have a picture of one but you can look at it if you click on the post below.


            It’s a small tree, roundish up to about 12 feet but can get 20 feet tall if well-managed and planted in rich, moist soils.
            Drainage is correct. The soil must have good drainage so with no drainage problems in your soils it should be fine. Avoid layering soil. This impedes drainage. A cactus soil is not necessary but amended soil throughout the planting hole will provide enough good drainage.
            Mix maybe 20% compost with the soil used for backfilling around the roots or use a ready-made soil mix. It is native to the Chihuahuan Desert which has more organics in the soil than soils in the Mojave Desert. Compost amendments improve drainage through the soil. Rich compost provides fertilizer. With a rich compost, no need to fertilize for about two years.
            Make sure the soil at the bottom of the planting hole drains water. That’s important. The hole should drain water overnight or sooner after filling it. If not, plant it on a mound.
            Avoid extremely hot locations in the landscape such as South facing exposures near hot, radiating walls. The southern exposure is okay but don’t put it close to a hot wall. This plant grows in desert canyons in the wild. What does that tell you? Deep watering, open spaces surrounded by desert soils and rock and possible protection from late afternoon sun.  
            Most cold winters it should be deciduous in Las Vegas unlike places with warmer winters. Not terribly pretty during the winter months but it should give you good floral displays if pruned during the winter and not during the months.

Lawn Grasses That Grow in the Las Vegas Valley

Q. Are there other lawn grasses besides tall fescue and Bermudagrass that will grow here?
I took this picture many years ago to show the difference in leaf texture between some of the old-fashioned tall fescue and Kentucky bluegrass. The newer tall fescue lawn grasses have a much finer texture than the older ones but they are still a little bit itchy compared to the soft touch of Kentucky bluegrass and perennial rye.

A. Many different lawn grasses will grow in Las Vegas, but the problems are availability and which cultivars or varieties to use. Most people want what’s available currently in the Las Vegas markets because they are in a hurry and that narrows your selection to mostly tall fescue, sometimes called “fescue” by some.
This is St. Augustine grass growing in the Las Vegas Valley. It was substituted for Bermuda grass when shade was a problem. Like Bermuda grass, it is a warm season grass which means it turns brown in the winter. The major reason most folks don't use warm season grasses in the Las Vegas Valley is because it turns brown in the winter. But they can use considerably less water than cool season lawn grasses.

            Las Vegas sits in, using landscape lingo, the “Transition” zone for growing lawn grasses. There are three identified zones in the United States for lawn grasses; cool season in the northern states and warm season in the southern states. Just like onions.


            We sit in a third zone between them both called, you guessed it, the “Transition zone”. We can grow both cool season and warm season grasses. It’s the same with onions. In our location we grow both northern and southern onions. The same is true of our lawn grass. That can be an advantage, it can also be a problem. Our climate is not clearly cool season and not clearly warm season and so we have problems with both.
For identification of cool season grasses I use a combination of things but one is the leaf veination as you see in this picture. Both tall fescue and annual ryegrass have identical veins that run the length of the leaf blade. Perennial ryegrass, in the center, has that strong midvein.

            The major limiting factor is winter low temperatures that can kill some lawn grasses.
            The warm season grasses include all the different varieties of Bermudagrass but also zoysia, St. Augustine, Buffalo, centipedegrass and others. The cool season grasses include tall fescues but also Kentucky bluegrasses and perennial ryegrass. All warm season and all cool season grasses grow here but heat tolerance is very important with bluegrass and ryegrass lawns because of our high summer temperatures.
            Cool season lawns can stay green 12 months of the year here. Warm season lawns turn brown during the late fall and winter months. Some can handle overseeding in the fall with ryegrass if  a green lawn is wanted through the winter, but some do not.
            The predominant lawns in Las Vegas during the 1980s and earlier were Kentucky bluegrass for high-end lawns and common Bermudagrass for low-end lawns. Heat tolerant perennial ryegrass started making appearances in the late 1980s. Annual ryegrass was used for overseeding common Bermuda during the winter while managed back to common Bermuda in mid spring.
            The variety of a plant chosen, whether it’s a lawn grass or a vegetable, can be just as important as the kind selected. This is an important concept to learn.

Too Many Flies


Q. I have houseflies all over my lantana and roses! I find little black dots, which I guess to be eggs, on the leaves of those plants. I have sprayed with neem oil and Ortho Home Defense to get rid of them, but they keep coming. I don’t see damage to the plants, but I don’t want to have a fly breeding grounds in my garden. 
Flies are there for a reason. What do they need? Food and a place to breed. Flies usually indicate a manure problem and/or accessible food. Clean them up and the flies are gone.

A. Sounds like these flies are using your lantana and roses as a bordello. I don’t think the black spots are eggs. I think it is insect poop. Their poop from the sound of it.
            We will have to follow the KISS principle on this one. This means they are probably attracted to something to eat nearby such as dog food, animal poop, garbage cans, etc. Find the source of their food, control it and the flies will move on. That’s the only way I know to achieve long lasting, sustainable control. If you relied on sprays or traps it would be a never-ending battle.

Italian Cypress Gets Droopy from Watering Too Often


Q. I read your article in the newspaper regarding the effects on limbs from overwatering of Italian Cypress. I have 15 mature Cypress along a back wall. They are about 18 years old and 30 feet in height with 7 to 9-inch diameter trunks. They are watered 3 to 4 days a week in the summer, three cycles per day and 5 to 8 minutes per cycle. They each have three drip emitters with 10 gallons per hour. I’m afraid to change the watering cycle for fear the trees are used to more frequent watering.  I just don’t know.
When Italian Cypress has a droopy branches like this one, it is usually an indicator that it's getting watered too often. These are Mediterranean plants. They respond to water by growing more, similar to desert plants. When they grow more, this growth is frequently weak and can't support itself so it becomes "floppy". Notice this Italian Cypress is close to a lawn that requires frequent irrigation.

 A. Don’t argue with success if there are no problems. If the trees are healthy and you are happy with their appearance I would not change anything. Tree roots adjust to the location and number of emitters that are used. Once you begin changing this it requires the tree to adapt to the change.
            You are right. If you do change the watering pattern, do it in increments and don’t do it all at once. Do it gradually.
Italian Cypress should grow upright without floppy branches. It helps if they are surrounded by dry soil. Dry soil "pulls" water from the wet areas and helps them to dry out faster.

            But you should be aware of several things about watering trees. First, it is best if trees are watered less often but with more water. I think a saving grace for you is that you give one day of “rest”, without water, between irrigations. This gives the soil a chance to drain and the roots a chance to “breathe”.
            If soils around the roots of Italian Cypress are kept constantly wet, the tree can grow very rapidly. This is good, and this is bad. If Italian Cypress grows very rapidly then the limbs can become very long and weak. Limbs may begin to droop and not give the tree its characteristic rocket like shape.
            Secondly, the roots will grow near the surface of the soil, shallow, because they can’t get a good mixture of air and water to grow deeper. The soil is too wet. This may not help the tree anchor itself in the soil during strong winds. It might blow over easier. Perhaps the saving grace in all this has been a lack of applied fertilizer. I’m not sure.
            Thirdly, as trees get larger they need water applied further and further from the trunk. These additional drip emitters give the roots a chance to grow further from the trunk and provide better anchorage in the soil.
            Perhaps there are other plants growing close enough, or even a lawn, where the Italian Cypress can take on water. But only three emitters per tree, watering trees of this size, does not spread the water out far enough to give them strong support to keep them upright in strong winds.

Rosemary Dies When the Soil Is Kept Wet

Q. Last January we had our yard professionally landscaped which included 4 rosemary bushes near a west facing block wall. The bushes were thriving, doubling in size until the middle of summer. Unfortunately, three have died and the fourth nearly gone. Can you offer some suggestion as to how I can stop this problem from spreading?

Rosemary is a tough plant. It can handle some very tough locations. But it cannot handle soil that is constantly wet. The roots of this plant suffocate easily in wet soils, particularly during the heat of the summer.

A. Rosemary is susceptible to root rot diseases if the soil is kept wet. This can happen if it is watered too often, planted in soil that does not drain water easily or covered in rock so it never dries out. Plant death from root rot is frequently seen during the heat of the summer. This is not a problem that should spread beyond the rosemary.
This picture of Rosemary was taken in the middle of winter. It's one of those plants that blooms a lot and attracts honeybees when there isn't much else around that's flowering. It's a good plant to have near fruit trees that are early bloomers in the spring. It will handle about the same frequency of irrigation as fruit trees.
            Landscapers set the irrigation clock to water frequently after planting. This can be important during the first two or three weeks while plants get established in their new location, but irrigations should be less often once the plants begin growing. They assume that someone will adjust the irrigations later and not let them run daily.
This is what Rosemary will start doing when it's getting watered too often. First you see a small stem start to die, and then the center starts to die and then the whole plant dies. You drowned it. It's dead.

            Some soils do not drain water easily. In these soils it is best to plant on raised mounds or mounded soil so plant roots can grow into the surrounding dry soil in these raised areas. Use a similar soil to the existing one, just amend it with planting mix or compost.
            It is common for landscape soils to be covered with 2 inches of rock. Because the surface is covered in rock they are called “desert landscapes” which is arguably not true. Keep rock or any kind of surface mulch at least 6 inches from the base of the plant when it's young. Surface mulch will keep the soil from drying out and may contribute to the loss of plants if they are watered frequently.
            What to do now? You will probably plant again. Don’t plant in the same holes because the soil in these holes have a buildup of disease organisms. Plant at least 12 inches from these locations and reroute the irrigation. Water them daily the first week to get them established and then begin watering less often. In this case too much applied water is not important as how often it is applied. Water less often but give  them a generous amount when you do.

Consider Miniature or Genetic Dwarf Fruit Trees for Small Size


Q. I am interested in planting a fruit tree in my yard. After reading your blog, I was thinking of a fig tree, however I have been told that they can get very large. I wanted to stay under 8 feet tall and not difficult to grow. When should I plant it and where?
Fig trees like this one can be cut very short when they are older and they will still sucker and sprout, regrowing again.

A. Fig trees will grow very large but they can be severely cut back near the ground, if needed, and they will grow again. But I don’t think you want that kind of work and maintenance. There are some smaller fig trees like Black Jack fig but generally figs are large trees.
            Fruit trees that fit your description are called miniatures or genetic dwarf fruit trees. They stay very small but produce a lot of fruit of normal size. In my opinion, fruit produced by miniature fruit trees do not taste not as good as some fruit from regular fruit trees but pretty good for the casual backyard producer.
Genetic dwarf fruit trees, sometimes called correctly miniatures, stay small without a great deal of pruning but there are not hundreds of varieties to pick from. This is Apple Babe, a miniature apple tree growing in the Las Vegas Valley.

            The problem is terminology; the terms used to describe these types of fruit trees. The terms thrown around in nurseries casually are “dwarf”, “semi dwarf”, “miniature” and “genetic dwarf”. I just looked online and these terms are confused in most, if not all the online fruit tree nurseries. I’m assuming they’re confused in local nurseries as well.
This is a genetic dwarf or miniature peach tree growing in the Las Vegas Valley. There aren't as many varieties to pick from but they offer a fruit tree that stays small but still requires pruning for good production.

            A dwarf or semi dwarf fruit tree can be created by grafting a dwarfing rootstock onto a normal fruit tree. This could be called a “dwarf” or “semi dwarf” fruit tree. They will not meet your eight-foot tall criterion in most cases. The possible exception could be apple trees.
This is Gold Kist apricot on a semi-dwarfing rootstock. Many apricots are not large trees anyway but when put on some rootstocks they stay relatively small. This apricot did not need pruning for four years and was still very productive. An excellent landscape tree.

            Miniatures are sometimes the same as semi dwarf. Miniatures are sometimes genetic dwarfs. It depends on the nursery and their definitions of these terms. Sometimes nurseries create these names for marketing purposes and, in my opinion, cause a great deal of confusion.
When considering fruit trees for containers you might want to look closely at genetic dwarf fruit trees as a possibility.

            In most cases you are looking for what is called a “genetic dwarf”. But like I said, sometimes these are called miniatures. The only real way to know is to find out their true mature size. Nurseries think that small size can be a big selling advantage.
            If the term “dwarf”, “semi dwarf”, “miniature” or “genetic dwarf” is used in its description, check its mature size. It may not be exactly what you think it is. If the mature size is not listed, don’t get sucked in by the marketing. Assume it is larger than you think.
            The very small sized fruit trees that I refer to as miniature or genetic dwarf can be found in almond, peach, nectarine, and apple and vary in height from 6 to 12 feet tall.

Tuesday, October 16, 2018

Fruit of Flowering Plum is Edible

Q. I have an ornamental, purple leaf plum that’s producing fruit. My dog has been eating the fruit. Is it safe to eat?
Purple leaf or flowering plum in a rock landscape

A. The purple leaf plum used in landscaping was selected as a variant of a plum used in the orchard industry for many years. A similar plum that produces more fruit, Cherry Plum or Myrobalan plum, is grown for its tart fruit with a very high sugar content. Two varieties of this plum, Sprite and Delight, are personal favorites of mine. Another variant of this fruit tree is used as a rootstock for other plums. A very versatile plum!
Cherry  plum or Myrobolan plum fruit tree
Cherry plum fruit
            The purple leaf plums (there are several different types) were selected for their leaf color and low fruit production but ornamental beauty. However, occasionally they do produce a fair amount of edible fruit. This fruit is good for making jams and jellies, adding to pies and pastries and flavoring gelato and juices but tart when eating fresh.

Monday, October 15, 2018

Where to Buy Good Roses

Q. Can you please advise me: where I can buy GOOD Roses to plant in my garden, in Las Vegas.
All my roses are ab out 30 or so years old and I got them from Jackson+Perkins when they were still in Oregon! The one I bought 2 or so years ago from them, WERE DEAD ON ARRIVAL!
And what I see in the nurseries her in Vegas, do not look good enough for all the work to plant them.
Nevada Rose

A. I know which roses are better roses and usually J&P are good ones. I like Weeks Roses but they are hard to find now I think since Plant World is no longer in business.
Yes, you can have roses like this in the Mojave Desert. These are growing in Las Vegas!

Maybe some Rosatians who read this post can answer. Jackson Perkins in the past had very good roses. They had award winners up until 2013 or so. They had a very good breeding program. The company has gone through several change of hands in the last decade plus so I don't know anymore. 

Please Don't Do These Things to Roses

Do more than sprinkle compost on top of rock around roses


Don't plant them surrounded by rock.
Don't prune and care for them like this.

Weeks Roses

Personally, I have always liked Weeks Roses. They are wholesalers so you cant buy directly from them but they sell to nurseries. They are higher priced so they are not common in the boxed stores but good nurseries that have a following from locals can afford to sell them. That group of loyal good gardeners is disappearing and the numbers dont support buying local anymore. Plant World Nursery on Charleston, used to carry them because the Las Vegas Valley Rose Society asked them to. Plant World Nursery is replaced now and that association is gone.Their website has lots of good information or general rose care. There is a list of roses they update for different climates. In the Mojave Desert we would select from the Hot and Dry List that you can find below:


I don't know where to tell you to go locally. Just buy one that has good form. Watch a video I uploaded from Weeks Roses home page for those of you not terribly computer savvy. Otherwise, please visit them and browse their catalog online. 

Remember, roses do well for 8 months of the year in the Mojave Desert. Be sure to plant them properly and cover the soil around them with woodchip mulch. Watch this video on Weeks Roses Home Page but for those of you not terribly computer savvy here it is. Thanks Weeks Roses!






What to do About Dieback on Mesquite

Q. Can you help me identify what is causing Mesquite trees to stress? I have attached photos here on this email. There’s sap releasing from previous cuttings, but there has been more die back from the top (side of the south) at a faster rate, any clue what is happening?

Mesquite tree dieback mentioned in the question. See how helpful good pics can be?

A. Thanks for the detailed pictures. That helps. The second picture you sent clearly shows where the mesquite tree was pruned (actually it was a very bad pruning job called “topping”). The tree grew vigorously from these cuts and then this new growth died.

Nothing Common

Nothing I could find has been observed in mesquite like this in the past. We are going to have to start making some educated guesses. Because it is in the new growth and seems to be very closely associated with growth from previous pruning cuts, I would guess it is what we call “a vascular disease” that plugs up the water carrying vessels from the roots that travel up the trunk and through the limbs. 

Maybe Unsanitized Pruning Tools

My second guess is that it MIGHT have been carried to this tree through the pruning tools. This could be particularly true if the pruning tools were not sanitized before pruning. The most common reasons trees are pruned is to remove dead or dying limbs. If these limbs were infected with a disease, it is possible to take them from an infected tree and pass them off to an uninfected tree. Development of the disease takes time. But if it was an aggressive disease this could happen in a season. If not terribly aggressive, two or more seasons.

This kind of problem sometimes causes sap “bubbles” to form on limbs. I call it "stress related".


What to do? 

Cut the infected plant parts out of the tree using a sanitized chainsaw. Remove at least 12 inches of wood below where the infection started. Disinfect after every cut so that it is not spread to other locations.

Another possibility is borer damage. Less likely but possible. If this is the case, do the same and disinfect just in case.

Sunday, October 14, 2018

Viragrow: Better Mulch Than Woodchips around Vegetables Is A...

Viragrow: Better Mulch Than Woodchips around Vegetables Is A...: Q. I use woodchips around my vegetables, fruit trees and landscape plants. When I turn it over after the first freeze, what should I add ...

Control Nutgrass in Lawns with Sledgehammer

Q. We have a serious nutgrass problem. You recommended Sledgehammer herbicide to control it. I've been online looking to purchase it but I keep getting directed to "Sedgehammer" products. Are they one in the same and did you just get the name wrong?
This is a young not dress plant. It looks like a grass but it's not. It's a sedge and very difficult to control. It's missing the nut which was dislodged in the soil when it was pulled from the ground

A. Nutgrass is not really a grass at all but a sedge. Sedge usually has a way of regenerating itself when it dies and nutgrass was no exception. It’s called “nutgrass” because of the underground “nut” that remains in the soil if the top was pulled off or killed.
This is nutgrass found growing in the tropics, Philippines

            Hold on. I will get to your question in a second.
            Killing the top of the plant is easy. It could be killed with several types of weed killers, burned off with a fire weeder or removed with a hoe. But the underground nut causes a new plant to grow in its place.
            Usually not just one plant but two would regenerate from the nut to replace the one that was killed. With only those methods available, the only thing that works is to continually destroy the tops repeatedly until the nut is starved and gone.
This is the nut attached to nutgrass that causes all the problems of regrowth when it is pulled from the ground orders burned back with fire or chemicals.
            This works but required diligence. If you let the top grow back it would rebuild the nut and you have to start all over. But nutgrass in lawns was still a huge problem because these methods also damage lawn grasses.
            I worked with a chemical weed killer found to control nutgrass in lawns, without damaging lawn grasses, during the 1990’s. This weedkiller was different than others because it killed the nut but had no effect on lawn grasses. It was given the name “Manage” by the manufacturer. The rights were later sold to a different company but the name changed to “Sledghammer”. Same product but a different name.


            Repeat applications are needed when using Sledgehammer herbicide because not all the nuts are killed. The tops die but a few of the nuts survive and send up a new plant. Reapplication timing of the chemical is critical or the nut will re-establish.
            You MUST reapply it when the new growth from nuts is young, about the four-leaf stage, or it will re-establish. If diligent, slowly you will extinguish the nuts and keep them from re-growing.
            I see it is available from Walmart and Domyown Pest Control online. Try entering sledgehammer AND nutgrass AND weed killer in your online search engine.

Heavenly Bamboo Performs Better When Soil Is Amended

Q. I have several heavenly bamboo that are well established in my yard. I recently noticed a lack of robust growth and signs of disease or pests or maybe both. I sent you some pictures. What do you think?
Leaf discoloration, marginal burning of heavenly bamboo aka Nandina, not a true bamboo.

This damage looks more like nutrient related but it could also be from water, too much or too little, or possibly salts. But this plan likes richer soils so I would dump some compost around the base of it and work it in.

This is different from the other pictures. It is probably not related to plant nutrients but it looks more like damage from thrips.

A. Heavenly bamboo, aka Nandina, is not a bamboo and not even closely related to it. It sort-of looks like a bamboo, hence its name. It comes from places where the soils have organics in them naturally. Not from deserts and it does not grow well in desert soils.
            In warmer climates it may keep its leaves during the winter. Usually not in Las Vegas. It drops its leaves due to leaf damage from winter cold.
When heavenly bamboo is surrounded by rock it usually turns yellow due to iron chlorosis. Heavenly bamboo does not come from soils like this so the problem is the rock mulch around them.
            Heavenly bamboo DOES NOT like desert soils unless organics like compost is added to it and the soil kept moist. So rock mulch and planting in a desert landscape with cacti is a no-no. Might work for the first couple of years and then they slowly turn yellow, scorch, decline in health, drop their leaves and look bad.
            The discoloration of the leaves, brown edges and yellowing, is probably related to the soil degrading and losing its organics over time. My guess, it has gotten progressively worse over the years.
The primary problem with this Nandina is a lack of soil improvement and in proper pruning. If this plant were pruned correctly and organics were added to the soil such as compost it would not be in its current condition
            Heavenly bamboo comes from Eastern Asia where soils are rich and not “deserty”. When surrounded by rock, Nandina declines in appearance and its health takes a dive over time. Nandina looks good after planting because of stored food supplies inside the plant and amendments added to the soil. But these both disappear in a few years.
            There does seem to be insect damage to the leaves, possibly by thrips. Thrips are very tiny insects that can fly only well enough to travel a few inches. Flower thrips like to feed on soft flower petals and other thrips on new, emerging leaves.
            Leaf damage to Nandina by thrips is a first for me in the desert so I had to do some digging in references. Fresh damage appears as “water soaked” areas. Later on these areas dry out and scarring or obvious surface damage appears as tiny brown or white spots on leaves.
Western flower thrips, even though they are very tiny, cause problems like this scarring from their feeding on young nectarine fruit.
            If there is rock surrounding them, rake it back and work some compost into the soil surface as deep as you can and water it in. Replace the rock on the soil surface with woodchips. Water enough in one day so you can skip at least s day in the summer and more when its cooler.
            Organic sprays such as Spinosad do a good job controlling thrips. Read the label.

Spider Mites Can Occur after Applying Hard Pesticides


Q. I have a fruit tree with leaves that are brown on the edges and a dust that covers the leaves. Some of the leaves are turning gray green on branches and the tree does not look healthy.
Spider mites our famous for causing damage to Italian cypress. They cause Browning and branch death, usually there is webbing seen as well. That's why these critters are called "spider" mites. But they are more closely related to spiders than they are insects.It's always a good idea to wash off Italian cypress with a hose when they get dusty.

A. Most likely the tree damage was caused by spider mites. Spider mites are a summer pest problem during hot, dry weather.
            Another telltale sign that you mentioned is the “dusty” appearance of the leaves. This “dust” results from dead spider mites left behind as the population grows.
            Look for feeding damage to the leaves caused by spider mites. This feeding damage causes tiny yellow dots scattered all over the surface of the leaf and accompanied by tiny black dots the size of this period. By the way, the tiny black dots is mite “poop”. Even though mites feed on leaf bottoms, the yellow dots can be seen on the top of leaves.
            A common misconception is that webbing must be present if mites are the problem. Spider mites leave behind “webbing”, like the weak form of a spider’s web. But not all mites that cause plant damage spin webs.


Leaf damage and webbing scene on tomatoes caused by spider mites.

            So, finding webs when there is damage is not a “dead giveaway” that the damage is from mites. It could be one indicator, though. There are real spiders who are “good guys” that spin webs and hang out in plants. These spiders can be beneficial.
            Mite attacks to plants may come after the application of a hard pesticide. Bad mites are always present on plants but their numbers are controlled by predatory insects and even “good mites”. So, applying a hard pesticide to control borers, for instance, could lead to an outbreak of spider mites because the predatory “good guys” were killed.
            What can you do? Confirm that spider mites are the problem. Use a white paper test. Shake or slap an infested branch on a white piece of paper or paper plate. Closely look at the white surface for tiny dots, the size of a period, crawling along the paper.
            Smear them with your fingers if you aren’t sure. If you see lots of them, along with plant damage that I described, you have confirmed mite damage.
            Multiple applications of soap and water sprays do a good job getting small outbreaks under control. Hosing the leaves of plants monthly, or after a dust storm, removes dust from the leaf surface which can increase spider mite populations.
            Severe infestations of spider mites may require a pesticide application. Whenever spider mites were problem during the year, be sure to apply two dormant oil sprays during the winter months.

Best Distance of Palms to Walls is Ten Feet


Q. I have two Mexican fan palms in my backyard that are 16-18 feet tall. One is 3 feet from a retaining wall and 6 feet from a pool. Another is 3 feet from the corner of my house which is on a slab. Do I need to worry about the roots damaging the wall, pool or slab?
Way too close for palms to be planted to a wall.

A. The short answer is you should be concerned anytime something that can get large is growing close to anything that can be damaged. The good news is that palm roots don’t typically damage walls, swimming pools and concrete slabs as much as other types of tree roots. But they can cause damage.
            Palms in general are not a good choice around pools but Mexican fan palms get huge and should never be planted close to structures. Smaller palms, such as windmill and Mediterranean fan palm, would be a better choice. The closest large fan palms should be planted to walls, swimming pools and house slabs are perhaps 10 feet away.
Palms look beautiful near a pool but they can cause problems and very messy when they drop seed.

            There are a couple of options if you don’t want to remove these palms. One is installing a root barrier so that palm roots are deflected away from structures that could be damaged. Root barriers are installed and extend about 30 inches deep or more and reside slightly above soil level.
            The second option is to use water for directing root growth. In deserts soils are normally dry due to a lack of rain. Tree roots grow where water is available. By placing irrigation water away from walls, cool decking or a house foundation we can direct tree root growth away from these potential problem areas.
            Water does not need to be applied evenly under plant canopies. I recommend keeping water 2 – 3 feet away from these potential problem areas.

Correcting Borer Damage in Italian Cypress


Q. My Italian cypress started to lose their color and then die. Upon inspection of the trunk, I saw borers in them. Borers seemed to take place within two months or so and killed a few mature trees. I treated them with Bayer Tree and Shrub Insect Control but wanted to know if there is anything else I can do to help save them.
Borer damage found in Italian cypress trunk
Bora damage found in another Italian cypress trunk

Suspected board damage found in Italian Cypress


A. Damage from borers or boring insects is typically a slower progression than a couple of months unless the plants are small. You are right, the progression in many plants is a change in color from a vibrant green to a dull, gray green color as the limb and leaves are dying from a lack of water.
            My guess is borer damage to your trees started before this year. Internal damage to the trunk from borers can be present for several years before enough damage has accumulated to result in the death of older trees. If trees are growing vigorously, they can recover from light borer damage on an annual basis.
            This color change due to damage starts in midsummer when air temperatures begin to heat up and plants require more water. Damage from boring insects begins in mid-spring (March) but get progressively more intense as these insects become larger and more voracious feeders.  By midsummer (June and later) internal damage to limbs and the trunk can be extensive, unrecoverable by the plant, and the supply of water from the roots is cut off.
Homeowners have this product available for borer control containing Imidacloprid in the active ingredients. It comes in other names as well. It is always best to check the active ingredients to make sure. Apply it late spring after any flowering has occured to avaid possible problems with honeybees. This chemical has been implicated, not proven, in colony collapse of honeybees. The safest way to apply it in our environment is a soil drench. Always read the label before applying any chemical.
            You chose the correct insecticide to use but it was probably applied too late. The best time to control boring insects with these types of insecticides is in mid spring when they first become active.
            Consider using pesticides as a last resort because they can be a bit like “whack-a-mole” and contribute to other pest problems. Death of boring insects can happen in a few days when systemic insecticides are applied as a liquid drench to the soil.

Repairing Plum Tree from Borer Damage


Q. I have a ‘Green Gage’ plum tree that is 18 years old and produces plenty of plums each year. In August I saw sap coming out of one branch and along the trunk in several places.  Last week the bark started to separate and it looks like the trunk is starting to split. The leaves on that limb are starting to die. This side of the tree receives the west sun. All the other branches on the tree appear to be fine.

A. Green Gauge is a good plum for our desert climate and 18 is not old for a plum tree. Plums can be “sappy” compared to other fruit trees but from your description it sure sounds like borers. You won’t hurt anything, but I would take a very sharp knife that has been sanitized and start actively looking for borers.
            It is possible to remove the outer layer of bark covering the trunk and limbs and reveal the immature form of this insect, called the larva, causing the damage. Once exposed like this, it will die.
            Expose all the damage caused by borers down to healthy wood. Leave this exposed area open for healing.  I would say that about 80% of the time this is an effective way to remove the borer and allow the limb to recover.

What I Would Do

I would first remove some bark on top of the area where I think borers might be residing. Hold the sharp knife nearly flat and push the blade away from you to remove the bark. After removal, inspect the wood to see if it is alive or dead. If it is alive, stop and don't do anything more. If it is dead, remove all of this dead bark until you see bark that is alive. If you find evidence of borers, try to find them in this dead area and remove them. If the borer damage is extensive it might require removal of the limb or branch. Do not paint this area but let it heal in the open air.
Using a sharp, sanitized knife to remove the bark that surrounds a borer infested limb.

Removal of the dead wood caused by borers
Successful removal of borers the previous year and the tree showing signs of healing.

African Sumac Attacked by Borers

Q. What should I do now with my 14-year-old, damaged African sumac? I think it had borers as you mentioned in a previous column, but the tree top is lush and green and showing no dieback of the limbs.

A. Many older trees damaged by borers show only subtle, outward signs of damage. Early borer damage is difficult to see. It isn’t until damage is extensive, usually from attacks every year, does it become obvious to the casual observer because of limb dieback.
This is a Purple Robe locust but it developed sunburn on the side facing the sun and this damaged area was followed up by an attack of borers. 
            I can see in the picture you sent that the borer damage to the trunk is healing. Encourage this type of healing with regular watering coupled with fertilizer applications twice a year. If it hasn’t been fertilized during the past 12 months, make an application when temperatures cool off a bit.
            The best time to see “hidden damage” in the spring done by borers is immediately after a good rain. Damage to trees due to borers is expressed through the wet trunk or limbs as a reddish, jellylike ooze. If not seen right away, this “jelly” dries in a day or two leaving reddish crystals behind.
Sap can sometimes be seen from trees attacked by boring insects. The best time to see this sap losing from the tree is immediately after rain.

            It looks like a limb broke and ripped the trunk, perhaps as it fell. This could have been because of previous borer problems that weakened the tree at this location. The central core of all trees is dead and surrounded by a cylinder of living tissue that can heal these types of wounds.
Sometimes trees can recover from an attack by boars if they are removed with a sharp knife or killed with a systemic insecticide.

            This living cylinder can be thick or thin depending on tree health. When trees are healthy and vigorous, this living cylinder repairs damage quickly by “rolling over” damaged areas as seen in your picture. Large areas can heal over in a couple seasons of growth if the tree is healthy.