Season of moths far from over

This was a big year for moths and we aren't done yet. There will probably be more to come later. These include moths such as the Ghost moth, Bagworm moths, Leopard moth and Carpenter moth. Their emergence was related directly to winter and spring rains that would produce an abundance of leaves and desert flowers. Somehow they knew they were coming. Leaves and flowers provide food. In some cases flowers are essential to certain moth's life cycles.

As the desert dries up this summer we will see desert pests invading home landscapes looking for food and shelter. Those landscapes closest to desert areas will have the most feeding pressure from desert insects.

Moths probably did more pollinating for us this year than they have in past years. Since most moths are night-flying, moth-pollinated flowers typically are white or pale colors so they will be at least somewhat visible on a moonlit night. However there were so many this year we could see them during the day on landscape plants with flower colors in the reds.

Often, moth-pollinated flowers may only be open at night. They typically use a strong, sweet perfume to advertise their presence in the darkness, and typically this odor is only exuded at night. Much is talked about the wildflower display this year but the perfumes released at night by the flowers is incredible.

Moths are hover-feeders, so moth-pollinated flowers typically have deep tubes to precisely match the mouthparts of the moth. Desert moths are frequently timed perfectly to their host plant that it needs for food or reproduction. Perhaps the most famous desert moths are the yucca moths and the creosote bagworm.

When we see yucca pods on a yucca plant yucca moths have been busy because the yucca is pollinated in no other way. The yucca plant and the yucca moth are essential to each other. There are several different species of yucca moth. The immature form of the moth, the larvae or caterpillars, only the eat yucca seeds of a specific species of yucca.

It sounds contradictory but the yucca plant needs the moth to help produce its seeds. The larva only eats a few of the seeds, leaving the majority for the plants possible reproduction. Plant reproduction and seedling growth, just like moth emergence, is also tied directly to the rains.

The yucca moth pollinates the flowers at night. Yucca male and female moths also mate inside yucca flowers, a convenient place to find each other. The female then lays her eggs in the base of the flower where the emerging larva is protected by the seed pod and feeds on the seeds. The hatching of the moth eggs and the development of the yucca pod are perfectly synchronized.

When the moth larvae are mature, they chew through the pod and drop to the ground where they burrow and create a cocoon. Most emerge as moths the next year. However, some types of yucca moth may emerge only when another rain comes of sufficient quantity to provide food and shelter for its life cycle. This period of time has been recorded as long as 19 years.

The creosote bagworm is not so specific about its host. It can be found feeding and developing on over 128 different species of plants. What is so uncommon about this moth is that it can feed and develop on creosotebush. Not many insects even bother creosote. It is called a bagworm because of the silken bag it forms the hangs from the branches of creosote. The moth larvae uses the bag for protection from birds and other predators where it feeds on the leaves.

The adult female moth never develops wings. She remains inside the bag all her life where she relies on the male to find her, probably releasing female sex hormones to help.

Later this year watch in the evening for the hummingbird moths which will be pollinating flowers at dusk and the large and beautiful sphinx moths.

A good Web site for learning more about our desert moths can be found at nitro.biosci.arizona.edu/zeeb/butterflies/spectacular.html.

This is the time of year that we should be protecting those trees and large shrubs from potential borer problems. Plants that commonly get borers are loquat, pyracantha, Arizona cypress, twisted juniper, flowering plum and other stone fruit trees. Other plants that do get them, but less frequently, are palo verde, mesquite, roses, agaves in the roots, poplars and Leylandi cypress. Reasons for their attack are unusually stress related, frequently due to our interference.

Some simple precautions to take for prevention include preventing stress in the plants by not pruning these plants severely and not letting them get into a droughty condition. Some plants are so hard hit by borers, like the loquat and cypresses, it makes you wonder if they should even be planted at all in this climate. Others are more of a management problem and can be addressed by making sure the trunk and lower limbs are well shaded by the upper canopy. Painting the lower trunk and scaffold limbs of young trees with diluted white latex paint (50/50 with water) also helps.

Here are sprays that can be applied for borer control but should be used only if the threat from borers is actual and not just a preventive treatment. These can be found at your nursery, garden center or landscape supply company.

Many plants can survive for several years after initial borer attacks. You just have to be aware of their potential damage and watch for it. For most gardeners the signs they recognize as a borer attacks are branch dieback and sap oozing from limbs or trunks.

Branch dieback is oftentimes a sign when borers have been attacking the plants for several years already. Sap oozing can be from other problems such as mechanical damage to limbs or the trunk, high temperature stress damage to some trees and a few disease problems like slime flux.

Even seeing holes in the trunk may not be a sure sign of borers. Some birds cause similar types of damage but usually this damage is seen along a line, in a row, nearly horizontal on the trunk.

Question: I have a tree whose roots I don't want spreading under my driveway. Is there any way I can keep the roots contained so they don't do any damage?

Answer: Not very effectively. The usual method used to contain roots are mechanical root barriers that are planted around the tree. The idea is that these barriers are buried deep enough so that the roots come in contact with these walls, grow deep to get under them and stay deep. They are supposed to grow at that depth the rest of their lives and never come to the surface again.

Well, they don't work. The roots come in contact with the barrier and grow under it. After the roots get on the other side of the barrier, the roots then grow back up to the depth they were on the other side. Roots are lazy. Roots grow best where they have the best air, water and fertilizer.

If the soil is too dry near the surface, the roots grow deeper where the air and water mixture are more favorable for growth. If the soil is too wet, roots grow closer to the surface where the air and water mixture are more favorable for growth. Roots grow closer to the soil surface in heavier, clay soils where air is more available.

In sandy soils, air can penetrate deeper in the soil and so roots will grow more deeply. Some trees, like mulberry, willow and poplars or cottonwoods have roots that are naturally shallow-rooted. There isn't much you can do to get these roots to grow deep. Their genetics dictate shallow roots.

The way to keep a tree from damaging a driveway, wall or patio is to select a tree whose roots naturally grow deep and don't plant it close to your driveway. The larger the tree's mature height, the further it should be planted from your driveway, wall or patio.

You can contain the roots of plants in a desert landscape with drip emitters surrounded by dry soil. The dry soil acts like the edge of a container and can help contain the roots. If the tree is large and the roots are contained by drip irrigation in too small of an area, the tree could blow over.