Q. I think I have an ash tree. I’ve been reading about ash tree decline disease with some apprehension. I noticed my tree has bark with damp spots and it’s starting to separate from the trunk. Is this a sign of ash tree decline or something else? As you can see, ash decline looks exactly like the tree is not getting enough water. This is because the disease plugs up the tubes carrying water from the roots to the tops. A. Probably not. Ash decline starts as dieback of the limbs from the outside, higher up on the tree. A common problem on many ash trees is sunscald or severe sunburn of the trunk and limbs in full sunlight.             In our climate, sunlight is very intense and will “sunburn” exposed surfaces of some trees. These exposed surfaces can be the trunk, limbs and even the unprotected fruit of some fruit trees. Most of this sort of damage is seen on the West or South sides of tree trunks or on the upper surfaces of large limbs.             We see this most often on trees that have thin bark covering the trunk and limbs such as some ash trees, locust and honeylocust, and many fruit trees. We don’t see it as often on trees with thick bark covering the trunk and limbs such as pine trees.             It can be important to leave small stems growing from the trunk and limbs so they provide shade to help prevent damage from intense sunlight. Remove these small limbs when they get bigger than pencil-sized in diameter.             Scientists don’t agree if these sunburned areas attract boring insects or not. It’s a “chicken and egg” kind of thing; did sunscald attract the borers or borers contribute to the sunscald? Regardless, oftentimes borers are found damaging the tree near these areas.             It will not hurt the tree to remove the dead surface of the trunk or limb for a closer inspection. Either pull the loose bark from this area or cut it away with a clean knife. Inspect these areas for borer damage. Removing this dead surface area with a sharp knife helps the trunk or limbs heal more quickly. Make sure the tree is getting enough water at each watering and correct an irrigation problem if one is found.              If you see some borer activity in fresh wood in the sunburned area, the tree will probably recover unless the damage is severe. Get the tree healthy and let it heal on its own. 

Q. I have a lemon tree with some possible “issues”. It has been in the ground 10 years, about 8 feet tall, but recently the leaves are turning yellow to brown and the branches are losing leaves in some spots. There is about 3-4″ of rock under tree and thick weedblock under the rock. In our Mojave Desert soils sometimes using rorck mulch on the soil surface can create problems. A. If you read my column regularly, you may know what I’m about to say. In our desert soils, placing rock on the soil surface beneath fruit trees is a no-no. You might get away with it in other deserts where there has been some form of agriculture, but not here. Frankly, I’m surprised it has taken 10 years for the leaves to begin yellowing and browning. That may be a new record!             Soils are made up of two major components; the mineral component which is sand, silt and clay and organic component. Our desert soils are extremely low in the organics; the “good stuff” that make soils come alive. We refer to this component as the organic component or “organics” or “organic matter” of the soil.             Organics in the soil should rot or break down over a few years and disappear if not replaced regularly; every year in vegetable and herb beds or at least every 2 to 3 years around trees, fruit trees and shrubs. Trees and shrubs that originate in deserts, i.e., desert adapted, can tolerate soils with little organics in them. But that’s not true of plants that don’t come from deserts. This includes citrus.             Your lemon tree is “behind the curve” regarding organics in the soil. The soil is probably extremely depleted. Adding compost or other sources of organics to the soil surface may not make much difference for a couple of years.             I would remove the rock, punch holes in the soil, pour compost in these holes so that compost can impact the roots quickly. Or lightly mix compost into the upper surface of the soil. Compost tea may help. Add a cup of compost to a 5-gallon bucket of water, stir it, let it seep for a couple of hours and pour it over the top of the rocks. But ultimately you must get organics into the soil near the tree roots.             Check the irrigation and make sure the tree is getting enough water. An 8-foot citrus tree should get about 20 – 30 gallons of water each time it’s irrigated. The water should be applied to at least half the area under the tree. Next February, add iron chelate to the soil to correct andy possible leaf yellowing due to iron chlorosis.

Q. I want to grow grapes to provide a screen between my neighbor’s yard and mine. We have a five-foot block wall between us. I want to grow grape vines to seven feet and two feet away yet parallel to the wall. This wall faces south and receives full sun all day. I want a variety that tolerates the sun and heat in this spot. If using grapes as part of your landscape be aware that they can be “buggy” due to skeletonizers, leafhoppers, whitefiles and all. A. Most hot climate grapes handle the heat extremely well. You probably want a table or desert grape. Most of the grapes available in grocery stores can be grown in the hot desert. The most popular table grape is Thompson seedless and handles the heat and southern exposure very well.             When growing grapes, remember the problems with varmints that many landscape plants don’t have. Insect problems include the skeletonizer, leafhoppers, whiteflies and a few other lesser problem insects.             Birds are a big problem with grapes as well as ground squirrels if ground squirrels are in the area. As the berries begin to ripen and get sweet, it will be a battle for the fruit between you and them.             Remember these plants are deciduous so they drop their leaves in the winter. They won’t provide much of a visual barrier during the winter. Prune to keep them productive year after year.

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.