Q. I have two Palo Verde trees in front of my house. One seems to be fine while the other has struggled for four years. I am told the tree is healthy but every summer it leaks white, sticky foam from the trunk. This foam attracts bees and beetles. The tree has received professional borer treatments twice a year but it’s still bad. Foam coming from trees that attract flies and other insects are a good sign of slime flux or wetwood disease. A. Save your money. This is not an insect problem. It is a disease problem but a disease that will not kill the tree. Let me explain.             You mentioned bees and beetles are attracted to this foam. I am 99% sure, based on the picture you sent and your description, this is a disease called slime flux, sometimes called bacterial wetwood. It is a nonlethal disease to the tree. It attacks only dead or dying wood inside the core of the tree.             Nonliving wood inside the tree cannot fight off disease microorganisms because it is dead. The only microorganisms which feed on this wood are “saprophytes”. Similar microorganisms feed in compost piles and convert raw waste into compost.             These microorganisms do not feed on living parts of the tree because living parts of healthy trees can “fight back”. Bacteria involved with slime flux create a foam with a characteristic smell of fermenting yeast or brewing beer. This “yeasty” smell attracts flies, bees and other insects such as beetles because this smell resembles rotting or fermenting fruit.             Normally, this disease bothers us because of these insects and its general “ugliness”. It does not hurt the tree. It may bother us because the foam dripping down the trunk of the tree causes discoloration of the trunk and unsightliness.             Probably this infection was transferred to this tree by unsanitary pruning practices. I always emphasize sanitizing and sharpening pruning equipment. When a tree is infected with a disease, it is extremely important to sanitize the pruning equipment before pruning a new tree.            There is no cure for this problem. You and the tree must live with it.             Some arborists may drill a hole into the tree trunk and insert a metal tube just below the foam and sticks out of the trunk. This foam drains inside the tube and drips to the ground without touching the trunk. Make sure any tools and equipment which touches the inside of the tree has been sanitized thoroughly.

Q. I’ve read somewhere that you should not place black plastic under rock used for desert landscaping. I have it there. We are an older couple and cannot remove it easily. Can we do anything else? Black plastic under rock mulch tears and deteriorates in a few years. Shouldn’t be used under rock. A. I realize you understand that using black plastic is not a good idea under the rock. Using plastic under rock mulch in desert landscapes prevents air from reaching the roots. Roots need water, but they also need to “breathe”. Black plastic is not permanent while rock is. Sooner or later, this black plastic will begin poking through the rock mulch as it is punctured and disintegrates.             Consider punching air holes through the plastic at the base of trees and other plants to help air reach the roots. The downside of this recommendation is it may cause the black plastic to rip and disintegrates sooner, peaking its ugly head through the rock.             Don’t think you have to remove all this plastic at once. If you see some sticking up through the rocks, remove it until more appears.             A more expensive option instead of plastic is called a “weed barrier”. This is spun or woven material that “breathes”, allowing air and water movement. I personally don’t particularly like weed barriers because they do not prevent many of our most troubling weeds like common Bermudagrass and nutgrass. Instead I would recommend spending a little bit more money on rock mulch and applying it thicker, perhaps 3 – 4 inches deep instead of two.

Viragrow: Why Some Iron Products Work and Others Not: Q. I see you mention a specific iron product every year, but I decided to buy it for use early next spring. We prefer to buy it online. When…

Q. I’m not sure if the branch at the bottom of my lemon is a sucker or a real branch.  I know if it comes from below the graft to remove it, but I can’t see where it comes from exactly. The leaves from this growth are huge, too.  It’s about 6-8 inches from the soil. Picture of trifoliate orange thorns A. Look for long thorns. The rootstock used for citrus in our climate is frequently trifoliate orange, which produces an extremely sour, nonedible citrus fruit. It has huge thorns, up to 2 inches long! If this growth does not have thorns, or it they are small, it is probably lemon. The sucker is right on the edge, but I think it is coming from the scion (lemon).             If you applied compost to the tree as it is growing, it may make some huge leaves. If you use compost as a fertilizer, apply it each year after you harvest the fruit. Water it in thoroughly.             If you applied woodchips to the soil beneath the tree, apply it in a larger area under the tree as the tree gets bigger. Apply enough so it is at least four inches deep. Keep woodchips 6 inches from the trunk or it can rot it.

Q. Last Spring(2017) the leaves looked like they were being eaten.  Upon searching thoroughly, I couldn’t see any creatures. Tree seemed to be losing some leaves early…some were speckled as shown in attached picture.  I thought the tree would die..Spring 2018…tree in full bloom (with exception of a few branches)…bees were loving it.  Now, it’s back to  chewed leaves.  What can be done to establish a healthy tree again. Today, it was fed and watered with attached…what can be done to bring it back to good health. Leafcutter bee circles in plant leaves. They are good guys. This is Eastern Redbud. They cannot handle desert soils very well and certainly not rock mulch. Try to find Western Redbud. But use woodchip mulch and apply compost to the soil . Work it into the soil where the roots are. Its okay but you need compost, soil amendment added to the soil to make it alive again. Q. The first picture is leafcutter bee. I advocate to do nothing. They are vegetable pollinators primarily since they come out late. http://xtremehorticulture.blogspot.com/2014/05/leafcutter-bee-perfect-circles-now-seen.html http://xtremehorticulture.blogspot.com/2014/09/leaf-cutter-bees-destroying-leaves-on.html As far as the plant health, this is EASTERN redbud. It doesn’t care for our desert soils much. If you put it in soil covered in surface rock mulch get rid of it and use woodchip mulch. Before you apply it, put about ½ bag of good compost like Viragrow’s Soil Pro and water it in.  Next time you plant, use half and half soil from the hole and compost and then plant it as you water it in the soil making a slurry. Then cover the rootball area with woodchips and not rock. Eastern plants like Eastern soils. Next time try a Western Redbud. Likes our soils much better. Check and make sure it is getting enough water each time its watered. Not frequency, how often it is applied, but amount of water.

Q. I have a tomato garden 4x8x1 foot deep. Ever year I put in 3 new plants of early girl, champion, roma.  I redo soil every year and plants get very big with lots of flowers and tomatoes. My problem is tomatoes only get about 2 inches in diameter what am I doing wrong? Celebrity and Beefmaster from a reader in the Mojave Desert A. Remember to rotate your tomato family of plants to new locations each year. Try to replant in the same area every five years if possible. Do it AT LEAST every three years to minimize potential disease problems. To learn more about rotating vegetables in the garden go here. All three varieties of tomatoes are solid producers for the desert. There are several things you can try to get larger fruit. Varieties of tomatoes will have a maximum fruit size dictated by the variety. Heavy crop loads lead toward smaller fruit. Soil enrichment Make sure the soil is amended, biologically active and easy to work before planting. A good quality compost goes a long way to improve the soil in all of these regards. When planting, it should be easy to insert a garden trowel into the soil. No digging with a shovel should be necessary after it has been amended. Fertilizer applications Fruit size can be affected by fertilizers. Use a pre-planting phosphorus application to the soil at the time of planting. One pre-plant application of phosphorus each growing season should be plenty. Don’t forget potassium. Phosphorus is frequently high-end compost but potassium is oftentimes low. Having a little extra potassium in the soil will not cause problems like high amounts of phosphorus can.  Use light, monthly applications of nitrogen to the soil as a side dressing to boost performance and keep growth at its peak. I like to tell my students, when the soil is giving to the plants, you must give to the soil. When you take from the plants, give something to the plants. Light, continual applications of fertilizer will maximize production. Bone meal is high in phosphorus Water This is a very important limiting factor in fruit size. Smaller fruit are frequently more intensely flavored than larger fruit coming from the same variety. However, we are conditioned to think that bigger is better. If plants are water stressed when the fruit is gaining size, it will result in smaller fruit. This can be good or bad. Of course soil moisture monitoring is important but what can even be more important is the use of mulch on the soil surface when air temperatures start reaching about 80° F. I don’t like straw much because it’s hard to work into the soil at the end of the growing season. A light covering, no more than half inch, is all that you need.  Pine shavings dissolve into the soil quickly and are not a problem when intensely gardening. I like things you can apply to the surface that dissolve into the soil easier like shredded newspaper, rice hulls, pine shavings used for animal bedding, etc. yes, they can rob the soil of nitrogen but if you’re constantly feeding your vegetables it won’t make any difference.

Q. I discovered some white things on my grape leaves where it is connected to the branch of the trunk. The plant is only in its second year, bought from a local nursery last year. The leaves are green, but the vine does not grow. Please let me know what I should do. A. The picture you sent was not clear. But what I could see looked like nothing I had seen here before on grapes. Grapes, both wine and table grapes, are being grown more and more in the Las Vegas Valley. It’s only a matter of time before pest problems in grape growing areas will become our problems as well. Some of these problems can devastate grapes.             The first thing I noticed on the leaves of your grape plant were “shiny” leaves. The upper surface of the leaves was shiny and sticky to the touch. It was attracting ants and bees. This is from insects that entomologists call “piercing and sucking”. I pushed these leaves aside and found mealy bugs. This was a “new” insect for me on grapes growing in the Las Vegas Valley.             Piercing and sucking insects (aphids are in this group) damage the plant to get at plant juices that are full of sugar. These insects feed and defecate a concentrated, sugary residue that lands on the leaves. This sugary stuff is what attracts the bees and ants.             A control strategy, that doesn’t involve spraying chemicals on the plants, is controlling the ants. Ants like piercing and sucking insects because of the sugar. They will move young insects to uninfested locations to increase their supply of sugary “honeydew”. Controlling ants reduces the spread of these insects to new locations.             Soap and water sprays applied directly to mealy bugs and other piercing sucking insects will kill them. There is no poisonous residue left behind so it should be repeated every three or four days until the problem is under control.

Q. Do you have any ideas how to stop the flowers produced by mesquite trees? For the past two years mine seems to have gone crazy producing the little yellow flowers that create a constant scum of yellow on my pool all summer long. This mesquite has 1½ long spines on new growth together with the leaves. Native mesquite in the Mojave Desert just outside of Las Vegas, Nevada. Restrained growth and flowering because of the 4 inches of rainfall the Mojave Desert gets each year. A. The tree sounds like a native mesquite, perhaps the Honey Mesquite. This tree is native to our desert Southwest, a North American native plant.             Production of fruit by olives and pods in mesquite, can be controlled by spraying the tree when flowers are open. The flowers must be present and open for the spray to cause the fruit to abort. So, timing of the spray is critical for success. Chemicals like Florel and Olive Stop are used. But sprays to prevent flowering are more difficult to find and apply.             Under desert conditions of limited rain, flowers are produced only in the spring when temperatures warm up. If the soil has water in it, there will be lots of flowers. If the soil is dry, flowering is sparse. If this tree is watered freely then it is possible it can produce flowers, in waves, all summer long, with each flush of growth. Mesquite make a good looking landscape tree if pruned and managed correctly. The density of shade has much to do with how much irrigation water it gets in the desert. Infrequent watering would produce filtered shade. Frequent watering produces dense shade. They would grow too fast if grown in wet climates.             Desert plants, like this mesquite, are opportunists; they take advantage of water when it is present and restrict growth and flowering when water is not available. In other words, growth of all kinds including flowering is tied directly to irrigation. Mesquite trees do not belong in lawns and they should not have flowers growing beneath them. They are prefect for desert environments.             Manage its growth and flowering by managing its supply of water. Water less often but with lots of water when you do water. Give it water in the spring to so it can grow and flower and then restrict water the rest of its growing season.             This restriction of water will curtail its growth and flowering to once a year. At least then the yellow scum needs to be cleaned out of your pool for only three or four weeks each year. 

Q. I purchased a plumcot fruit tree years ago for my home in New Jersey. I got great tasting, sweet plumcots in early July every year. I never thought it could grow here. Yesterday, I was reading in the Real Estate Section that a house for sale had a plumcot on its grounds. Will they grow here or is it just that particular location? A plumcot called ‘Plum Parfait’ producing fruit in the Eastern Mojave Desert. Below is ‘Plum Parfait’ tree, about six years old and pruned to 8 feet tall entering into fall color in mid October. A. The plumcot is a man-made hybrid between a plum and apricot. Other hybrids between these two fruit trees, apriums and pluots, also exist. These types of hybrids don’t occur in nature and are not GMO’s but developed the old-fashioned way through plant breeding. Floyd Zaiger in a propagation house at Zaiger Genetics, one of the plant breeding companies responsible for hybrids like plumcots, apriums and pluots.             Our climate is a good climate for growing both plums and apricots as well as hybrids like plumcots. In fact, our desert climate is better for growing these types of fruit than the climate in New Jersey. Our intense sunlight and high temperatures help develop high sugar content and good flavor. Aprium tart made from interspecific hybrid fruit, the aprium.             Pick a location in the yard that has plenty of sun but away from walls that produce a lot of radiated heat or reflected light. Dig the planting hole plenty wide and mix a good quality compost with this soil when planting.             Add water to the hole as you are planting to help settle the soil and stake the tree for the first growing season. Cover the soil with a four-inch layer of wood chips after planting. These “dissolve” into the soil where there is water and continue to improve it in the years to come.

Q. The leaves on my fig tree appear burned after this rain. I foliar sprayed it with Neem oil and soap and fish protein isolate, These trees were planted last fall and mulched with 1 foot of woodchips and looked amazing until now. They are watered three times each week in the summer. A. The leaves do look like they are diseased. But I have a saying, “When the top looks bad, look at the ground.” First eliminate the easy problems before jumping to more difficult ones.             I wonder if that 12 inches of surface mulch is rotting the trunk of the tree. It is easy to kill young trees if they sink, the bottom of the trunks buried in dirt, into the planting hole after planting. Or if woodchip mulch on the soil surface is piled against the trunk and kept wet.             In both cases wet soil or wet mulch against the trunk can cause a disease called “collar rot”. The disease rots the trunk and “chokes” the top of the tree. When this happens, leaves look diseased or as if the plant isn’t getting enough water. This becomes very apparent during hot weather.             Start on your knees and pull the mulch away from the trunk. Keep it there permanently, 6 to 12 inches away. Next, carefully remove the soil from around the trunk until you find tree roots coming from the trunk growing horizontally.             If this small area of the trunk looks water soaked, there might be a problem. I will take a small penknife and cut away a narrow strip of the trunk that was buried in soil and mulch. The wood under the strip should be white or greenish white.             If there is more than ½ inch of soil covering the trunk, or the trunk was buried in wet mulch, the tree may develop collar rot. All you can do is let the covered part of the trunk air dry and hope for the best.             I have seen collar rot develop on the lower trunk young figs and pomegranate that are buried. Most figs and pomegranates are grown on their own roots. If the top of the tree dies, wait a couple of months and see if anything suckers from the roots or base of this tree. If it does, don’t replace the tree.             These basal suckers will grow very rapidly into a new tree because the tree already has established roots. When one of the suckers is 12 inches tall, remove the others for a single trunk tree or select 3 to 5 for a multi-trunk tree.             It’s possible these leaf problems are related to a leaf disease but I don’t recognize it. Sometimes when dead areas develop from disease pathogens, the dead area of the is bordered by yellow. This yellowing is where the plant tissue is still dying. Sometimes this yellowing doesn’t exist but only because the disease has stopped spreading.             The humidity in Las Vegas is unusually high right now because of the so-called “summer monsoon” and rains. I expect diseases to pop up during this kind of weather. Having leaf diseases on fruit trees would not be uncommon during this time of year.             Instead of spraying, driving using a passive approach towards controlling diseases. Remove extra leaves that might be blocking the movement of air and wind through the canopy. As you see leaf diseases, remove the infected leaves and dispose of them. The plant will grow new leaves in places where there is sunlight. Leaf diseases slow down or stop as the weather changes.