Treating for bagworms to planting pumpkins

By John Fulton

[June 10, 2008]  After some very severe infestations of bagworms the past several years, the calls have been coming in all year on 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 opposite is true for a very warm spring. The idea is to have all the eggs hatched before treatment but not wait until the bagworms are almost mature.

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 they 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.

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. The spring we have had is probably going to add a week to the timing, meaning the last week or so of June should be ideal.

Most people think that bagworms only affect evergreens. While evergreens may be their preferred host group, 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. Make sure to check the tops of tall trees. An infestation may get started in a tall tree simply because you can't reach the top when applying a control. In that case, you'll have to use a taller ladder.

Island chlorosis of hackberry

There is a disease of hackberry leaves that appears as blocky yellow spots. The spots often have green tissue surrounding them (but not always), so the disease has earned the name of island chlorosis. In addition to causing the yellowing symptoms, the chlorosis can cause some leaf drop. The disease is mainly a curiosity on established hackberry trees and causes little damage.

Branch dieback of juniper and arborvitae

After several years of relatively few problems of junipers and arborvitae, we've had a resurgence in the shoot blights.

The most common is phomopsis tip blight, which affects the new growth. New growth is susceptible until it loses its lighter color. Symptoms are a "shepherd's crook" shape to the dead tips and the small black dots of the fungal fruiting bodies. Control consists of removing infected areas and spraying new growth with protectant fungicides until it gets the dark green color.

Kabatina and Cercospora blights affect older needles of evergreens. Kabatina blight is not as common, and it is not controlled by fungicides. Cercospora blight tends to infect the older needles on lower branches first. The appearance of branches is having only the new growth at the branch tips being green. Repeated applications of fungicides will have some effect on Cercospora.

There are varieties resistant to these diseases, but you can't find one resistant to all three.

Pumpkins

With the weather we've had, gardening has either been a chore or it has been ignored. We are to the normal planting time for Halloween pumpkins. Father's Day is a good time to plant them in order to have them ripen for the fall decoration season but not ripen too early to have rot problems in advance.

[By JOHN FULTON, University of Illinois Extension, Logan County]