For Release June 5, 2001

AGRI-VIEWS
by Chuck Otte, Geary County Extension Agent

The past several years have been very devastating for junipers. They have come under increasingly heavy pressure from bagworms. Let’s clear up one point of confusion right now. Bagworms are the small insects that create a little bag that is covered with foliage from the host plant. Do not confuse bagworms with the insects that create a big webby mass either in the crotch of limbs or out on the ends of branches. Those are tent caterpillars or webworms (different insects) and neither is as destructive as bagworms.

Bagworms overwinter as eggs in some of those little bags still hanging on your juniper tree or shrub. (By the way, those little bags do not fall off after you spray and kill them.) In late May and early June, these eggs hatch and the tiny little caterpillars (they do turn into moths) start feeding. For the first several weeks they are very hard to see and they do very little damage. As they get bigger, they eat more and almost overnight, serious damage can show up on your junipers. By the time that the bagworms, and their damage, are noticeable they are very hard to control because of their size.

The time to start treating is now. If you had bagworms last year (even if you sprayed to control them) or if your neighbors had bagworms, then it probably wouldn’t hurt to spray. By starting a control program now, you can use some of the biological control products. Bacillus thuringiensis is a biological control that is sold under various names including Dipel, Thuricide or just Bt.

You can also use any one of a number of chemical controls. Virtually any of the standard lawn and garden chemicals will control bagworms. Check the label and see if junipers and bagworms are listed. I would be hesitant to use Sevin right now however. We are seeing mite problems crop up on several species, including junipers. Sevin will not control mites and will often make a mite problems worse as it will kill many of the mite predators.

What may be as important as what you use, is how you apply it. You must use a lot of water so that you get a good thorough drenching of all foliage, to the point that there is water dripping off the foliage. It is difficult to do this with a pump up, canister type of sprayer. You are better off using a hose end sprayer that allows you to apply a lot of water quickly and easily. I would also encourage multiple treatments as the recent cooler weather has slowed down the hatch of bagworm eggs. Check the label of the product you are using and retreat every 7 to 10 days, as directed, from now until early July. Three or four treatments should give you excellent control.

I indicated that mites have been showing up on many species recently, including junipers. Mites are tough rascals to control because they are hard to see, there are a lot of them and they reproduce quickly. On junipers and other ornamentals I recommend using dicofol which is commonly sold as Kelthane. Kelthane is a mite control product and will offer better control, especially of eggs and young mites. Many other products will also control mites, except Sevin, just not quite as well as Kelthane. As with the bagworm spray, application with a hose end sprayer is preferable and try to spray up under the leaves if you can. For an organic control you can spray with an insecticidal soap every few days, making sure to use lots of water.

Mites and bagworms can both kill junipers. The problems come on slowly and can catch you off guard if you aren’t prepared. Even with a spray program, you need to diligently inspect your junipers, and other landscape plants, on a regular basis.

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