Bagworms and 'What's eating my flowers?'         

By John Fulton

[JUNE 12, 2006]  After some very severe infestations of bagworms the past few years, the calls have been coming in all year about the correct treatment times for bagworms this year. Year in and year out, the correct treatment time for bagworms is June 15. You can mark this date on your calendar for next year and be within a few days of the correct treatment time. With a very cool spring, a week later may be a possibility. The idea is to have all the eggs hatched before treatment.

The next problem is what to use. The traditional standby has been Sevin, but the Bt products such as Dipel and Thuricide have really taken their share of the market the past several years. The Bt products have several good points, including safety to mammals and toxicity to larger bagworms. Since the Bt products are bacteria that affect only the larvae of moths and butterflies, it does take a while for the bacteria to build up to the point where they can kill the bagworm. I won't get into the discussion about monarch butterflies lighting in the tree just after treatment (actually these products don't kill the butterflies -- only the larvae would be killed), as the subject of Bt and off-target moths and butterflies is still a hot one.

If you are in doubt about whether you have bagworms, check your trees and shrubs around June 15. You can actually see the small bags as the larvae build them. They become very noticeable at about one-sixteenth of an inch long. Treat bagworms early, since larger ones are more difficult to control, but waiting a week this year will allow the eggs to hatch into a controllable stage.

Most people think that bagworms affect only evergreens. True, that is their preferred host group, but bagworms have a huge number of potential hosts. Through the years I have seen them on oak trees, grapevines, apples and about any other growing thing you can think of.

What's eating my flowers?

Many have been complaining of flowers of all species being eaten off by something. As yet, that something hasn't been identified. Helping to cure the unknown is difficult, but here are some possible suggestions and treatments.

Insects can and do take most of the leaves off plants. Most noticeable is the cutworm family. There are some cutworms that clip only leaves, while others cut the plant off at the stem. There are also larvae and beetles that defoliate (see the flea beetle statement below). Treatments with Sevin or permethrin insecticide on the flowers and saturating the soil around the flowers will help.

"Furry critters" such as rabbits and squirrels also clip off plants of all kinds. Fences help with rabbits, but squirrels usually greet the challenge with gusto. Birds, such as robins, are also notorious for clipping plants. Individual protection with a fence, can or other means can help. You may also find some effectiveness from repellents, but they usually work about a quarter of the time.

Diseases can affect the plants as well. With wind or rain, the dried material tatters out or falls off, looking like something ate it. A change in weather stops many of the disease problems -- at least for a while. We can also add herbicide drift to this category. Vapor from many of the herbicides sprayed on fields and lawns can and does drift for up to a couple of weeks after the fact with hot and sunny conditions.

In the end, you'll have to decide if the plants are too damaged to go forth and grow properly -- if they are even alive. You can try to replace severely damaged ones with one or more of the treatments applied to protect them.

Flea beetles

Many homeowners are complaining of flea beetles attacking flowers and other plants. These beetles are small greenish-brown beetles that resemble small Japanese beetles in shape. They leave pinholes in leaves or skeletonize the leaves. Treatments with Sevin or other approved insecticides will quickly dispatch them.

Flea beetle

[John Fulton, unit leader, University of Illinois Extension, Logan County Unit]