Rehabilitate plants damaged by chewing insects

A: The photo of leaves you sent show uneven missing parts, many areas with parts missing down to the veins of the leaf. This type of damage is from insects that have mouths specialized for chewing leaves. Heavy damage means there is a large population you have not seen in the past.

Unless you see this type of damage throughout the year, there is no reason to spray chemicals now. Damage from these types of insects is probably over. Instead, concentrate on getting the plant to produce replacement leaves. Let me explain why.

Common insects that chew leaves include grasshoppers, many different types of beetles, weevils and others. Some of these insects chew leaves throughout their entire life cycle (grasshoppers) and others only during part of their life cycle (mostly beetles). Sometimes the damage progressively gets worse (grasshoppers and some weevils), and other times it lasts only two or three weeks and it’s gone (many beetles).

Most of this type of damage that begins in summer lasts perhaps three weeks and stops. This is because the damaging stage of this insect is over. The life cycle of this insect has moved to another stage of development and most likely will not be a problem. If you spray now, you wasted your money and time.

When this type of damage suddenly occurs this time of year, it is usually from the adult stage of large insects such as scarab beetles. They feed for two or three weeks before they die. An example is the June beetle.

Chewing damage from smaller beetles, such as flea beetles, occurs earlier in late spring. Smaller insects such as flea beetles can produce a second crop of adults so sometimes damage is seen in the fall as well. But the damage comes on fast and it’s over fast.

Exceptions are grasshoppers where all stages of their life cycles have chewing mouthparts. With insects like grasshoppers, we see leaf damage early in the season that progressively gets worse as the season wears on. Grasshopper control is best done as soon as possible if there have been problems in the past.

Chemical pesticides reduce damage next year if you kill the chewing adults as soon as damage starts. If you wait until the damage is extensive, it’s too late. The leaf-damaging adults are gone, the damage has been done and they have laid their eggs for next year.

Instead, concentrate your efforts in rebuilding what was lost. Apply fertilizers to the soil and water them in. During hot summer months, use half of the recommended rate on the bag or container. Apply it twice, four weeks apart. Avoid applying fertilizers after Aug. 1 to plants that are tender during cold winter months.

Q: Mushrooms have sprung up overnight around some new daylilies we planted in a new raised bed. My husband thinks the soil the plants came in contained mushroom spores. We’ve never had mushrooms in our yard due to our dry air. Are these toxic? Will they hurt the plants?

A: Don’t worry about mushrooms popping up in planted areas. This is quite normal, particularly after a rain, during periods of high humidity and particularly where there is shade. The potential for growing mushrooms exists anywhere dead wood can rot or decompose.

Mushrooms pop up from soil mixed with woodchips, a thin layer of wood chip mulch on the surface of the soil, tree roots that have died, wood from construction that was buried and from the dead interior of trunks of even living trees.

Mushrooms are the sexual stage of many different fungi and easily identifies them as part of the rotting process. The sexual stage just means that these mushrooms release mushroom spores from the caps of the mushroom. The spores are moved about by air currents.

A few fungi are bad guys and create plant diseases. Others are good guys and responsible for breaking down undecomposed wood into humus, compost or what might be called black gold. Your mushrooms are from good guys. But that doesn’t mean they are safe to eat.

Most fungi that make mushrooms are classified as saprophytes. This term means they feed off only dead things, not living things. In other words, they are decomposers and not responsible for killing plants.

Do not worry about these mushrooms harming your plants but I would still knock them over and let them rot so they aren’t accidentally eaten. Once knocked over, they will shrivel into nothing very quickly.

Mushrooms oftentimes pop up after rains or during periods of high humidity and disappear in two or three days when things dry out. The fungus network that created the mushrooms is still there, decomposing away, but does not send up any new mushrooms again unless there is rain or high humidity and plenty of wood to decompose.

Q: My cactus is falling over. I think I gave it too much water.

A: Rather than too much I think you are watering too often. There is a subtle difference. Let the soil dry more between irrigations. Other factors can contribute to this problem.

The term “watering too much” has two different meetings: watering too often or giving the plant more water than it needs each time it’s watered. Both refer to “watering too much” but may produce two different results. Frequent watering damages plants that originate from environments where they don’t receive water frequently.

If the soil dries between waterings and forces the cactus to use its own stored internal water, then this will slow its growth. If the cactus is never forced to use its own internal water, the plant grows unchecked, using whatever water is available.

Desert plants, including many cacti and succulents, are water opportunists. When water is present, they suck it up, which feeds new growth. Frequent watering of cacti causes new growth to become succulent. This type of growth is easily damaged by wind or even by its own weight.

If the roots of these cacti also are restricted by the container, or water is applied close to its trunk, the top may get too large to support itself. We say it is top-heavy. It is very likely to fall over or break during winds or heavy rain.

Other factors can increase succulence. These include fertilizing too often with high nitrogen fertilizers and not providing enough light.

Provide your cactus a container or pot that is wide. It doesn’t have to be deep but water should drain from it soon after watering. Apply fertilizer once a year about one month before you expect it to bloom. Apply water when the soil is dry. When watering, you are telling it to grow.

Q: I have a golden rain tree in a pot I got several years ago. It’s about 10 feet high with a diameter of about 1.5 inches. What are the pros and cons of planting it in a desert landscape here in Las Vegas? What planting recommendations would you give?

A: I think it’s a good, nondesert tree. It is better suited growing further north than us but it handles dry arid environments very well. It is considered drought tolerant in Midwestern or California landscapes, but it is not a desert tree. I would put it on an irrigation valve with other nondesert trees like most ash and pine trees.

Because this tree has been left in its container for a few years, the roots will most likely be rootbound. There is not much you can do to correct this problem if it’s there. This tree may never fully establish in the landscape because of the circling roots inside the container.

I have never seen it grown with rock mulch covering the soil surface, but I don’t think it would be a good soil environment for it in years to come. It would, like most ash trees, grow better in soils covered in woodchip mulch.

Even though it can handle a southern landscape exposure if it isn’t intensely hot, I would plant it on the east or north side of the home if possible. If that’s not possible, then surround it with other plants to keep it a bit cooler and the roots moist and give the roots somewhere to grow. The trunk sunburns easily so leave lower limbs on the tree until it gets older.

Because this is the Mojave Desert, plant this tree in soil mixed with compost. The soil should be dug three times wider than the container and the excavated soil should be mixed with compost when it is replanted. Be sure to run water from the hose as you are planting this tree to remove air pockets. Stake this tree upright for one growing season before they are removed.

Bob Morris is a horticulture expert and professor emeritus of the University of Nevada, Las Vegas. Visit his blog at xtremehorticulture.blogspot.com. Send questions to Extremehort@aol.com.