WSU Extension Q&A: Fall webworm wreaking havoc on tree

Q. There is a big, ugly nest of webbing and caterpillars in my poplar tree. What should I do?

A. If they are attacking your tree at this time of year, it is probably fall webworm. Larvae are capable of stripping all the leaves off a small tree, but on larger trees, they typically only attack individual limbs or parts of limbs. Small webs can be removed with pruning and disposal. Pesticide control is usually not warranted unless they are causing significant defoliation or attacking the fruit on apple trees. If needed, the insecticide product must be registered for use on that type of tree and effective in controlling webworm. Webs can be spot treated to limit the amount of pesticides used.

Q. My tomato plants are covered with aphids. What can I use on the plant and still eat the tomatoes?

A. Aphids can be controlled with acetamiprid, neem oils, insecticidal soap or pyrethroid-type insecticides. Be sure to read and follow label directions and adhere to pre-harvest intervals. Pre-harvest intervals is the amount of time (hours or days) that must pass after an insecticide application before the crop can be harvested.

Q. Should I be concerned about weeds, particularly common groundsel, in the hay I'm buying for my horses or livestock?

A. The chance of buying hay with a significant amount of common groundsel is extremely low. Most cases of acute liver failure in animals are because of the ingestion of 25 percent to 50 percent of their body weight of common groundsel over several months. However, in some cases, poisoning can occur at an exposure rate of 5 percent to 10 percent of body weight over a few days or weeks.

Always be cautious in purchasing hay contaminated with weeds. The old adage of "buyer beware" is applicable. There are a number of weeds that can be toxic to animals, and they can also be a significant contributing factor in moldy hay. Common groundsel (Senecio vulgaris) is a fairly common weed but not often found in hay. It is a winter annual that is not competitive in a good stand of forage, and most hay growers use herbicides to control it.

Q. My backyard grapes have a scorched look on the leaves, especially on the west side. Does the sun cause this?

A. Yes. To avoid sun-scorch, allow shoots to grow out on the west side of the canopy to shade the fruit.

-- Questions should be called in to the WSU Extension offices in Kennewick at 735-3551 or Pasco at 545-3511.

This story was originally published August 28, 2014 at 12:00 AM with the headline "WSU Extension Q&A: Fall webworm wreaking havoc on tree ."