Plants, fruit trees under attack by various insects

      The following are typical questions our Master Gardeners deal with daily at the Nevada Cooperative Extension. If you have gardening questions, call the Master Gardeners' hot line at 257-5555 between 9 a.m. and 4 p.m. Monday through Friday. There is also a gardening Web site at http://www. intermind.net/mgarden/.
     
      Right now we are seeing several plant problems occurring in Southern Nevada landscapes. Some include aphids, grape leaf skeletonizers, leaf cutter bee and squash bugs.
      Other problems include sap oozing from mesquite trees and from fruit. Sap coming from fruit trees may be a reaction to hot weather or overwatering, or can occur because of damage to the fruit by insects such as the leaf-footed plant bug. Check trees for this insect.
      The squash bug attacks many cucurbits but squash and pumpkin are preferred for laying eggs. There are a lot of differences among squash species and cultivars and how much they are attacked. Their preferences in order are pumpkin, squash, watermelon and cucumber. Some squash varieties resistant to squash bugs are Butternut, Royal Acorn and Sweet Cheese.
      The life cycle of squash bug, from egg to adult, usually takes six to eight weeks. Squash bugs may have two generations per year in Las Vegas. The squash bug lives through the winter as adults under crop debris, clods of soil or stones, but sometimes adults also are found in woodpiles or buildings.
      Eggs are laid in clusters on the lower surface of leaves, though sometimes on the upper surface or on leaf stalks. The football-shaped egg is somewhat flattened and bronze in color and very small but can be seen by the human eye. Females lay about 20 eggs in each egg cluster.
      The adult is dark grayish brown in color. In many cases the edge of the body has alternating gold and brown spots. Adults are long-lived, surviving an average of about 75 to 130 days. The adults, which are sometimes incorrectly called stink bugs, emit a foul odor when crushed.
      The squash bug causes severe damage to squash and pumpkins by feeding with a long needle-like mouth. The damage occurs because it injects highly toxic saliva into the plant when it feeds. The leaves usually show signs of damage, but feeding on the fruit can also be seen. The leaves first wilt, then blacken and die following feeding.
      Often an entire plant or section of a plant dies while nearby plants remain healthy.
      Placement of boards or other shelter for squash bugs causes the bugs to congregate there during the day and they can be easily found and crushed. Otherwise, pick them off of the plant when they are seen.
      There are several natural enemies of squash bugs, but it's not known if those enemies are present in Las Vegas. Regardless, it should be remembered that natural enemies of this bug exist, so the use of insecticides that kill all insects in general should be a last resort.
      Pollinators, particularly honeybees, are very important in producing squash. An insecticide application can interfere with pollination by killing honeybees.