How to Prevent Tree Stumps from Re-Sprouting

Q. You mentioned to drill holes in the trunk of the Cypress and pour a solution into the holes to encourage decay. Can you tell me again what that solution was? I can't read my own writing!

A. I would use diluted Roundup if the tree is still standing and you want to kill it. Use the most concentrated form allowed on label. Either buy it in the diluted form or dilute a concentrated form but do not use it full strength unless it is already diluted.

            Drill the holes as close to the ground as you can and at a downward angle. Use something like a syringe or other disposable item to force dilute Roundup down the holes that are freshly drilled. Fill the holes every hour three times to get plenty of chemical in the tree if you want to kill it.Make sure you wear unlined gloves during the application to protect your hands.

            There is a product that you can buy which you can apply to the stump after the tree has been cut down. Once the tree has been cut down, drill holes in the stump vertically and fill the holes with this product.The product comes under several names such as Stump Remover, Stump out, etc. Follow the directions on the label. Hope this helps.

Citrus Leaves Curling Yellowing Dropping

Q. Hello again! 

I have a puzzling issue happening with a few citrus trees (out of many).  The leaves are curling, yellowing, and ultimately dropping. I attached a few pictures in hopes you could shed some light on the issue. (Any iron deficiencies you see are from trying to extend the time between treatments, something I've been trying to perfect; seems like every 6 weeks is the sweet spot.)

I appreciate any help you can give me, I'd hate to see these trees die! 

Leaf rolling like this on citrus can be a watering problem

Add caption

A. If the leaves are rolling or curling into a cigar shape, then this is typically a lack of water. The leaves can turn yellow and drop from the tree if it continues. A lack of water can be from not giving each tree enough water or it can result from not watering frequently enough. 

Strangely, the same can result if you are watering too often but it almost never results from giving a tree too much water in a single application. My suggestion to you, if these trees aren't drip emitters, is to make sure that each tree has at least four drip emitters. 

Replace these emitters with emitters that double the application rate. In other words, if these are 2 gallon per our email letters, replace them with 4 gallon per hour emitters. This allows you to keep the same number of minutes on your irrigation timer and not overwatering other plants on the same valve. 

I would strongly advise you not to use adjustable drip emitters for this purpose. They can be extremely difficult to adjust properly since they seem to act like "whack a mole" when you try to adjust them.

Visit this page from the University of Arizona on citrus problems in the landscape

White Whiskers on My Brick Wall

Q. I have a high brick wall in my backyard that has white crystals, or “whiskers”, forming on it.  This is because of the over watering by my neighbor on the other side of the wall.  I asked my neighbor if they would decrease their watering but that hasn’t happened.  I have used vinegar and brushed it off with a stiff brush. I also tried brushing it with a dry brush.  They are not working.  I bought some muriatic acid, but I am afraid to try it because I have plants and trees right by the wall.  I would appreciate any advice you can give me to solve this problem.

Soft deposits on a porous wall are "fuzzy" or can look like white whiskers.

A.  You are correct.  This white, “powder” or “whiskers” is because of the water coming through the wall from your neighbor.  When the wall dries, white “salts” are left behind on the surface of the wall which were previously dissolved in the irrigation water. 

            The only long-term solution is to reduce the amount of water applied on the other side of your wall.  Eventually irrigation water coming through the wall and containing salts will undermine the strength of the wall.

Phosphoric acid is better for the plants than muriatic acid

            I am afraid this is a common problem with no easy solution if your neighbor is not willing to help.  In the meantime, use phosphoric acid rather than muriatic acid to remove white “whiskers” from the wall.  Phosphoric acid is safer to use and the phosphorus contained in the acid is a plant nutrient. 

            Muriatic acid contains chlorine, also a plant nutrient, but needed in very small quantities by plants compared to phosphorus.  Chlorine can be toxic to plants if too much is available.  

            Ultimately, your neighbor’s landscape should have a “dry zone” at least 3 feet wide next to this wall.  This dry zone does not have to be void of plants.  It can contain water conserving plants irrigated with drip emitters. 

Minioasis landscape design

            An even better solution is to convert this landscape to a “desert landscape” using a minioasis landscape design.  Minioasis landscape designs feature high water use areas of the landscape close to the house, located where people like to congregate.  The other areas are designed and landscaped to use less water by having fewer and smaller desert adapted plants.

Tree Dead on the Inside is Normal

Q. What’s wrong with my tree? The tree is dying from the inside to the outside.  I can see dead wood on the inside that is rotting through a big hole in the side of the tree.

All trees that are not in the grass family, such as palm trees, are dead on the inside and the living part is just under the bark.

A.  Older trees are dead on the inside and have a cylinder of living tissue just under the bark.  If the dead wood inside of the tree becomes infected with wood-rotting microorganisms, they can consume the entire inside of the tree, eventually leaving it hollow but alive. 

            The center of the tree can get infected with these microorganisms when large branches break or they are removed with an unsanitary chain saw.  It is important to remove broken branches as soon as possible with a sanitized chainsaw or hand saw.  The remaining wound is left to heal on its own without any sealer being applied.

            The dead wood inside the tree has little chance of fighting off wood-rotting microorganisms.  Once infected, these microorganisms spread easily through the dead, internal parts of the tree. 

            These microorganisms do not invade or damage healthy, living parts of the tree.  Keep trees healthy with appropriate irrigations.  Fertilize them once a year in early spring.  Sanitize and sharpen any tools that cut into any healthy parts of the tree.  

Limb Damaged. Will It Survive?

Q. Can you tell me if this tree will survive and what I need to do we have three purple plums and do not want to loose. 

A. Judith. Let me tell you what I think happened and then I will explain whether it will survive or not. This tree appears to be the purple leaf Plum. I see some branches coming from this large limb on the upper surface of it. Perhaps the started growing about three years ago?

There is damage to at least one side of this limb. My guess is that this damage faces the South or West. I am guessing that several years ago this limb received sunburn damage to this side. Shortly after this damage or possibly even before this damage, boring insects or borers entered this limb. The female borer is a small beetle about 3/8 inch long and she deposits her eggs close to these damaged areas.

This borer damage started as sunburn to the trunk of this ash tree.

The young from these eggs burrow into the limb where they feed on the soft, juicy, sweet tissue just under the bark. This feeding causes the limb to die in a larger area usually only near this sunburned area. Areas not in direct sunlight, like the top and bottom of the limbs, are usually not damaged.

Borer damage to ornamental plum again for the same reason, it started with the sun damage and then progressed to insect damage.

I cannot tell how much damage this limb has without a closer look but I am guessing it is not bad enough to remove unless there is extensive dying of the smaller limbs attached to it. You can apply an insecticide around the base of the tree called Bayer Advanced Tree and Shrub Protect and feed which will kill the boring insects inside the limb and protect the tree for as long as 12 months. This may give the tree enough time for recovery to begin.

A word of caution: the active ingredient in this insecticide has been implicated in honeybee decline but not proven. There is evidence both pro and con. But it is best to apply this after the tree has finished flowering.

Make sure the tree has enough water so that it is not getting water stressed. This means make sure there are enough drip emitters or they are large enough to support the tree. This tree probably needs somewhere around 30 gallons each time it's watered. Watering once to twice a week is enough. Around May, that will change to two three times per week. This tree grows best if the top of the soil under its canopy is covered in 3 to 4 inches of wood chip mulch, not rock mulch.

Bougainvillea Comes Back from the Dead

Q. I came from Southern California where I had beautiful red and yellow bougainvillea that grew with little help. I tried to save my beautiful pink bougainvillea last year by moving it onto my patio close to the house. I covered it every night, uncovering it in the daytime. It appeared dead this spring but just now I see some very tiny green leaves close to the bottom. Do you think this bougainvillea can come back?

Even a light freeze will damage bougainvillea like this.

A. Yes, it will come back. Bougainvillea is a frost indicator plant. In other words, if the temperature drops one degree below freezing, you will see damage to this plant. If the temperature is freezing for several hours combined with strong winds, it will die to the ground.

            Bougainvillea frequently dies to the ground each winter it freezes and resprouts from its “crown” in the spring. The crown is where the top attaches to the roots and grows just below soil level.

            After the first freeze in the fall, cut it to the ground and cover the area with 3 to 4 inches of woodchip mulch. I will sometimes use a nursery container turned upside down with the bottom cut off. I place this over the trimmed bougainvillea and fill it with mulch.

            Never fertilize bougainvillea after August 1. High nitrogen fertilizers make sensitive plants more tender when the freezing weather comes. But always continue to water it through the winter months every 10 days to two weeks.

'Barbara Karst' Bougainvillea With leaf cutter be damage

            As soon as freezing weather has passed (tomatoes have been planted), uncover it and let the sun warm the soil. As soon as you see new leaves sprout, fertilize it or apply compost. One fertilizer application is probably all it will need for the whole year. 

Let's Talk Wind Damage

            Let’s talk about wind damage. If you didn’t sustain wind damage to your landscape, you are extremely lucky. It was fortunate these high winds occurred early in the season and many trees were not yet full of leaves. If it had been a few weeks later, the damage would have been worse.

Ornamental Plum, wind damage to the leaves

            New leaves just coming out were shredded by these winds or new young shoots were broken. You might not see the damage at first but after a few days the damage will turn brown. Seeing this, you might think insects or diseases. Don’t worry. Some light pruning will remove the damage and new growth will cover it in less than a week.

Wind damage to persimmon on the lower leaves while the new leaves (closest) that emerged after the wind are undamaged

            Branches and trunks of trees split or broke. If you think you can bandage the damage, think again. If the wood inside of the split has dried, even for a couple of hours, joining the two together will not heal the split. It’s a goner.

Peach wind damage to the leaves.

            You might be able to salvage the tree by cutting below the break on the trunk. See if it will begin suckering beneath this cut. Make the cut about 1 foot above where you want new branches to emerge.

Corn wind damage blown over

            If a branch split, cut it back to a side branch. Whether it will grow back or how it will grow back depends on the kind of break, where it occurred and the type of tree. If it is aesthetically important to the landscape, remove it and replant. It could take years before it will look good again unless it is a fast grower.

            Leave shredding and breakage also happens to vegetables. Most can be pruned, a very light application of fertilizer and watered to help them regrow.

Traditional Pesticides to Control Leaf Footed Plant Bug

Q. I was just reading up on the leaf footed plant bug and came across this link:

http://ipm.ucanr.edu/PMG/r3301011.html

Does this mean that bifenthrin is their top choice for chemical control? Is synthetic pyrethrin (what I am using now) the same or similar? I see that some Ortho products for lawn and garden contain bifenthrin. Could those be used to spray the almond and pistachio every 2-3 weeks until it gets hot (and early or late in the day when bees are not present).

Leaf footed plant bugs mating on pomegranate. Please don't stare!

Leaf footed plant bug on citrus

Leaf footed plant bug on edible prickly pear cactus, tunas and nopales

Leaf footed plant bug wee one, Highly enlarged, courtesy Auburn University

A. Good detective work. Yes, Bifenthrin is a synthetic pyrethrin or pyrethroid (the chemical name ends in -thrin) and it gives good control of leaf footed plant bug as does pyrethrin. Sevin insecticide also gives pretty good control but is also lethal on honeybees.

Bifenthrin:

• Highly toxic to bees so always spray either on a cloudy day (lots of luck here) or at dusk when bees have gone home. 
• Protect yourself. It has a low toxicity to humans but it is still a poison. Protect your face mostly because it enters the body most easily through moist tissue (nose, mouth, ears, etc). Whatever you use, follow the label on when to respray and stop spraying the number of days it tells you for harvesting. 

Unfortunately this insect is not easily controlled since it has wings, can fly and come from or go to neighbors. They may be spending the winter as adults on evergreens on your property. Not pines but broadleaf evergreens like bottlebrush.

http://npic.orst.edu/factsheets/bifgen.html

Its also really good at controlling home pests like cockroaches, black widows, scorpions, etc.

How to Irrigate Vegetable Beds with Drip Tubing

Q. 1) what should the watering times be for Vegetable beds planted with typical vegetable seeds at this time of year?

2) Should the length of time be different when the beds are first seeded, as opposed to a month later when there are plants growing?

3) How should those times change seasonally with the temperature changes, that is, spring, summer, fall and winter?

A. Those are great questions and thank you for asking them. I hope that you will take my suggestions as just suggestions, and not as the "gospel". It's better if you use these as starting points and adjust my advice to fit your needs. I use 1/2 inch drip tubing with the emitters embedded into the walls of the tubing every 12 inches. I use 1 gallon per hour emitters. 

When installing this drip tubing, I make sure that the neighboring irrigation emitters offset the neighboring emitters by 6 inches. In other words, the emitters are spaced from each other in a diamond or triangular pattern.

Drip tubing with embedded drip emitters every 12 inches and spaced in a diamond or triangular pattern on a raised bed without permanent sidewalls

Let me go through a list of general rules that I use and let's go from there.

I soak large seed such as corn, peas, beans and even garlic cloves in tepid water for several hours before I plant it. The first step in seed germination is the uptake or imbibition of water. Doing this can speed up germination and reduce it by two or more days. Otherwise, you have to keep the soil constantly wet and can be nearly impossible for seed germination when air temperature gets above 90° F.

 

Raised vegetable bed mulched after seeding and irrigated using drip tape.

I mulch the area where seed is sown with a 1/2 inch layer to help keep the soil and seed wet. I have tried a number of different mulches including sand, straw, compost, perlite, vermiculite, and peat moss and found that bedding used for horses (pine shavings) to be the best. These thin shavings "dissolve" into the soil over several weeks while straw does not and can sometimes interfere with soil preparation. This can be bought at Viragrow (www.viragrow.com) or any farm supply stores. 

Seedlings mulched with horse bedding, pine shavings, to help preserve a soil moisture after seeding and seedling emergence.

I work with 12 inch spacing so the number of minutes of run time may be shorter or longer for spacing different from this. The number of minutes should be long enough to get water the entire 12 inch depth each time you water. Use a soil moisture meter (like for houseplants) to see how deep it goes.

 

Houseplant moisture meter used to gauge the depth of watering.

Surface mulch helps when starting plants from seed in containers.

1) what should the watering times be for beds planted with typical vegetable seeds at this time of year?

Make sure the seeds are planted the proper depth and it's best if they are covered with a 1/2 inch layer of horse bedding/mulch. If it is, you can water daily for 30 minutes. If you don't cover it with mulch, small seeds planted shallow, water three times a day for 15 minutes each. Large seed, 1 to 2 times per day for 15 minutes. It's easier with mulch. After the seeds germinate and you see their first true leaves, switch to once per day.

Seedling emergence through the surface mulch. Drip tape used for irrigation.

2) And, should the  length of time be different when the beds are first seeded, as opposed to a month later when there are plants growing?

A month later you could be watering once a day at 8:53 AM just before it starts to get warm. You want the plants to have access to water before he gets warm or windy. If these are smaller plants, water them for 30 minutes. If these are large plants, water them for 60 minutes. The progression of watering is from frequent, shallow irrigations after seeding or transplanting to deeper more widely spaced irrigations as they get more mature and bigger.

3) How should those times change seasonally with the temperature changes, that is, spring, summer, fall and winter?

Plant water use increases by 400% from the first month, January to the sixth and seventh months, June and July, in Las Vegas Nevada. Inches of water per day.

Water use in December and January is about 1/10 of an inch per day. In June and July it is about 4/10’s of an inch per day, a 400% increase. The change is in the frequency water is applied, not necessarily the number of minutes. So, after germination and establishment the water might be on for 60 minutes in December, the same amount in July. The difference is that watering in December might be every four days while in July it is daily.

Mulch, as I described above, really helps a lot when temperatures get above 90° F. You will see a difference in the plants when mulch is applied to the soil surface. Pine shavings such as horse bedding disappears in about 2 to 3 months and needs to be renewed.

With mulch applied, daily irrigations are enough during the middle of summer. If no mulch is applied, you will probably have to irrigate twice a day; once in the morning For 60 minutes and a second one midafternoon for another 60 minutes. These irrigations will be different if these raised beds were not amended each year with fresh compost. Amending them each year keeps the pore spaces in the soils open and plant roots will grow deeper. Plants with deep roots are less likely to become stressed during the heat.

Moisture meters like this one for houseplants are very inexpensive and not very accurate, but accurate enough to gauge if a soil is wet, moist or dry. The moisture sensor is in the tip so this tip should be pushed deep enough in the soil to be in about the middle of where the roots are growing. After an irrigation the meter will read "WET". Water again when the meter reads smack dab in the center of "MOIST". Use the "DRY' side to tell you when to irrigate cacti and succulents again.

I coach people into using a soil moisture meter when they first start learning how to irrigate. After an irrigation, the moisture meter should be pegged all the way to the right….WET. Irrigate again when the meter at root depth is halfway to dry (smack dab in the middle of the meter,….MOIST)

Some Types of Sulfur Not Terribly Good at Dropping Soil pH

Q. Is there a mulch will not lower the pH of my garden beds as it decomposes? I have Goji berry plants which do best at a pH of 6.8 to 8.1.  I want to use something to protect the soil from the summer sun and to prevent the winds from blowing the soil away. 

A. Surface mulch always lowers pH as it decomposes. In normal desert soils, you can expect it to drop to about 7.6. 

Hopefully you used a good compost when you amended the soil at planting. This will also help a lot. If you want to drop it more than that you have some options such as sulfur that has been ground to a dust rather than large granules. 

Soil sulfur is granular sulfur and slowly breaks down in soils. Its effect at lowering soil pH is minimal at best in desert soils.

Water dispersible or degradable sulfur is like a powder or dust. Because of its small size and large surface area, it breaks down very rapidly in warm soils and is a bunch better choice to lower soil pH than granular sulfur.

An example is Dispersul which is water dispersable sulfur. Should sell for about $1 per pound or so. Sulfur granules just sit there and don’t dissolve in our soils and about the same price. Sulfur needs moisture and warm soil temperatures to work. 

I was surprised when this product dropped the pH of water down to 3.5 in about 15 seconds. It doesn't need warmth or microorganisms to work.

The other is a product I have worked with called Garden Magic which drops the soil pH without warm soils. It will drop pH in water to about 3.5. Works very very well and also sells for around $1 per pound and it is in a $30 bag. I think the Dispersul is a 50 lb bag. Both you can get at Viragrow in North Las Vegas. I don’t think any other retailer carries it. They all carry sulfur granules instead. The other option is aluminum sulfate.

African Sumac Too Close to a Wall?

Q. I am considering planting three, 22" box African sumacs along a 40' block wall behind a 1.5' retaining wall. Is this feasible? How far away should they be from the block wall? Is there a better option for shade that isn't poisonous to dogs and that have no invasive root issues?

African sumac planted near a wall flowering in February

 A. 80% of all landscape plants are poisonous. If your dogs eat enough of any of your plants, they can get sick. 

Plant them no closer than 3 feet to the wall and 4 feet would be better, and 8 feet is ideal. This tree can grow to 40 feet and consumes a fair amount of water. These trees are really not intended to be used for planting along tall walls because of their shape. 

Put your permanent irrigation away from the wall so that roots will grow in that direction and less towards the wall. It is very difficult for me to make plant recommendations when I don't know what is available. Consult sites such as the plant list found at the Las Vegas Valley water District  and consult with your local nursery about availability of the plants that you like.

Brown, Cigar Shaped, Alien-like Thing Found in Garden Bed

Q. The second pertains to the attached photo. Specifically, what will it develop into? I found only one of these, about 6" down as I turned over my garden beds. The last thing grown in the raised beds were two very successful crops of grape tomatoes. One in the spring, and another from the same plants in the fall.

Tomato hornworm pupa

Tomato hornworm larva before it turns into the pupa

Sphinx moth or Hummingbird moth, the adult which he emerges from the pupa. These 3 inch long moths fly at night and at dusk visiting the flowers of plants just like a hummingbird, hence the name.

A. The photo is the pupa of the humming bird moth aka tomato hornworm as a larva. Voracious feeder of many plants Including tomato, grapes and ornamentals.. A bad guy.

Easy to control the larva with handpicking in home gardens. Easy to see at night with a black, UV light because the irridesce green under a UV light. Otherwise they blend right into the foliage of the plants and are difficult to see during the day. 

Sprays of Bt (Dipel, Thuricide) or Spinosad. Don't spray Spinosad during daylight hours because it is lethal to honeybees.

Fruit Quality Related to Climate - Fuji Apple for the Desert

Q. After reading your list of recommended fruit trees I see that Fuji apple trees would do good in Las Vegas?

A. Yes, they will do well. Don’t expect to get the same quality of Fuji Apple you might expect when grown in cooler climates. The tree as well is the fruit itself will respond differently in our climate because of higher light intensity, temperatures, lower humidity and our alkaline soils.

Fuji Apple growing in North Las Vegas Nevada

             Apples grown in our climate tend to have a thicker skin and more wax development on the outside. Expect to get fruit with a higher sugar content and less acidity. The fruit may not be first-class but it will be better than what you’re buying in the grocery store.

            Most tree fruit is harvested too early; mature enough to meet the minimum requirements by the buyer but not fully ripened. You have the luxury of leaving the fruit longer on the tree where it will develop more sugar and flavor.

Majestic Ash Can Be Winter Damaged

Q. We have a ‘Majestic’ ash tree that was planted a few years ago.  It was doing extremely well until a year ago. All the new growth is just tiny bits of mostly dried green on the ends of the branches. A few leaves have appeared, but mostly it's just the little spikey tips. The older leaves are just fine. It just won't sprout new growth.  Any help?

A. I don't know this variety of ash but sometimes we collectively call this group of ash Shamel or Evergreen ash. It is evergreen, keeping its leaves all winter long, but that's only in warmer climates.

            When the temperatures drop into the 20s it drops its leaves and becomes deciduous. When the temperatures approach 20° F it is possible they can have winter dieback or cold damage, particularly if it was fertilized late in the summer.. This may be what you are seeing in your tree.

            As the tree gets older it should be more tolerant of freezing temperatures. The only other possibility is chemical damage from weed killers applied to close to the tree or during a time of heat and wind. If this has been winter damage and the tree has not been damaged too badly, it will come back very strong this growing season. Right now it's early in the season so give it a chance.

Carolina Cherry Laurel Leaf Edges Brown

Q. I have several Carolina Cherry Trees in my yard.  Last year the leaves started to turn brown and flake off.  I have attached some photos.  Can you tell me why they are doing this and how I can correct the problem.

A. I had to study your picture carefully and so some investigating on what might be going on. Let's get one point out of the way before we begin.

This plant is native to the southeastern United States

It is not native to the arid and desert southwestern United States. When it is grown in our climate and soils it will struggle compared to growing in the soils and climate of the Southeast. This means it requires extra care on your part when planting and growing it compared to growing it in the southeast.

Add amendments at the time of planting

Carolina Cherry Laurel here it is very important to add 50% compost to the planting mix and dig the hole at least three times the width of the container. Five times is better. Never cover the soil above the plant roots with rock. Always use organic mulches or groundcovers on top of the soil a distance equal to at least the diameter of the plant canopy. This would chip mulch, not bark mulch, should be at least 4 inches deep and renewed every 2 to 3 years as it "dissolves" into the soil as it decomposes and adds nutrients and organics back to the soil. This is very important for this plant. I believe that this is the reason why you are having problems with this plant in your location.

Many of the same problems as plums and peaches

The major problems with this plant, because it is so closely related to plums and peaches, are many of the same problems as fruit trees. When I look closely at the pictures you sent, which are very good and thank you very much, I see root weevil damage on the leaf edges. These are the notches that you see on the margins. These insects feed at night and are in the soil beneath the plant. There is not much you can do about them except perhaps apply a systemic insecticide around the roots after the plant has finished blooming. Use the Bayer insecticide if you go down this route.

Water/fertilizer/pruning problem

The second problem is probably the reason you are most concerned. This is the discoloration and death along the margins of the leaves. I believe this is primarily a water/fertilizer/pruning problem. Let me explain why.

I believe if these plants were in good health you would see little to none of this type of damage. I believe the plants would be very full and the leaves would appear healthy. Make sure you apply either wood chip mulch around the trees as I suggested earlier and combine that with a yearly application of a tree/shrub fertilizer in late January or early February. Only use mineral fertilizers if you have wood chip mulch surrounding the trees. Again, I repeat. This should not be bark mulch if you want to improve plant health. Don't get me wrong. There is nothing wrong with bark mulch. It can be very beautiful but it adds nothing to the health of the plants. It is purely decorative. Wood chip mulch, trees and shrubs that are shredded in their entirety and applied to the soil surface, improve plant health when they begin to break down/decompose a.k.a. "melt" or "dissolve" back into the soil.

Irrigation should never be daily. 

Give these plants at least one day without irrigation so that water can drain from the soil. The roots of these plants are very susceptible to suffocation a.k.a. root rot when soils remain wet and cannot drain adequately.

Another problem with this plant is a plant disease called shot hole fungus. We see this leaf disease on peaches and plums when our humidity is too high. In climates with higher humidity, like some of those in California, this disease can be a severe problem. In fact, varieties of peaches and plums are grown in certain areas with high humidity strictly because of this disease problem. This disease causes spotting on the leaves and sometimes the leaf margins. As this disease worsens, sections inside of the spots die and drop from the leaf leaving "shot holes". Some varieties of plants are much higher susceptible than others. If the health of the plant is improved, I am guessing this disease will disappear or minimized.

Bottom line

Improve the soil and drainage. You can do this by drilling holes in the soil with an auger as deep as possible. Fill these holes as best you can with compost. This will improve the soil and improve drainage. Cover the soil with wood chip mulch at least 3 to 4 inches deep. Fertilize with compost this year and next year you can use a mineral fertilizer if you wish provided wood chip mulch has been on the surface of the soil for 12 months. Avoid daily irrigations.

Droplets on Plants May Be Guttation

Q. I have never seen this on a plant before and I have never had a problem with pests on this plant.  What am I dealing with here? 

A. Great pictures, that helps a lot. I am going to take an educated guess that this is water being released from small openings on the leaf edges called hydathodes. The release of excess water from inside the plant is called guttation. You can read more about hydathodes here.

https://en.wikipedia.org/wiki/Hydathode

http://www.sbs.utexas.edu/mauseth/weblab/webchap9secretory/9.3-10.htm

Pictures of guttational water

What is gutational water?

These can be very complicated explanations and I don't know about your background and whether they will confuse you or if you understand them. Basically, small plants can push a lot of water inside of them through a mechanism called root pressure. Root pressure takes water from the surrounding soil, if there's plenty of it, and push it inside the plant. Sometimes the root pressure can be so great that the plant needs to release some of this excess water. Many plants have specialized openings on the leaf edges called hydathodes that allow it to do this. Technically, the process of taking excess water inside the plant and releasing it through hydathoes is called guttation.

Back in the day….

Golf course superintendents are very familiar with this but may not know the correct scientific terms. Years ago golf course superintendents would go to the putting greens early in the morning and "whip the greens" with a long bamboo pole. It was found when plants are growing very close together in places like golf course greens that this excess water, guttational water, could encourage diseases if it was not removed from the leaf blades. They used to call it dew but the main problem was from guttational water full of plant sugars and a good "food" for plant diseases.Whipping the greens with a bamboo pole knocked the water off of the blades of grass and reduced the possibility of disease. Very few whip the greens anymore but instead they use a short irrigation cycle to wash off the leaves of guttational water (which is high in plant sugars and disease prone) and replaces it with irrigation water which has no sugars in it.

So what does this have to do with you? 

If this is guttational water it simply tells you that the soil is full of water. Little leaf Cordia is a desert adapted species and does not have to be irrigated frequently. It tells you that the soil around these plant roots is full of water and you may or may not be watering too much if you see this water present frequently. Make sure that you give the plants a "rest period" without water before the next irrigation. Other than that, nothing to worry about.