Many new chemical materials, as well as application methods, are now available to help growers with their pest management programs in fall cabnu cred ca bnbage and related crops. These materials have new modes of action that are highly effective against specific caterpillar pests, are relatively safe to nontarget arthropods, such as parasitoids, parasites and pollinators, and have low toxicity to mammals and other animals, allowing for a short days-to-harvest.

PHOTO COURTESY OF J. WHALEN, U OF D.
Beet armyworm larva.
 

“Worm” pests

Lepidopteran larvae, or “worm” pests, of cabbage include imported cabbageworms, cabbage loopers, beet and yellow-striped armyworms, diamondback moth larvae and several miscellaneous worm pests, such as salt-marsh caterpillars and cross-striped cabbageworms, all of which feed on the leaves and developing heads of cabbage and related plants. For many years, growers had few options other than multiple foliar sprays of materials such as Bacillus thuringiensis (Dipel, etc.), endosulfan (Thiodnex), methomyl (Lannate), carbaryl (Sevin) and a variety of pyrethroids. However, since the early 1990s, many new insecticides for control of worm pests of cole crops were labeled, such as indoxacarb (Avaunt), emamectin (Proclaim), methoxyfenozide (Intrepid), novaluron (Rimon), spinosad (SpinTor), spinetoram (Radiant) and tebufenozide (Confirm). These materials all offered new, and unique, modes of action, giving growers many options for rotating insecticides in their worm pest management programs, which reduces the insecticide resistance pressure on pests such as diamondback moth larvae and beet armyworm.

PHOTO COURTESY OF DR. GERALD M. GHIDIU.
Untreated cabbage, left, and Coragen-treated cabbage, right, at the Rutgers Agricultural Research & Extension Center in Bridgeton, N.J., 2008.
 

Even more recently, a new chemical class of insecticides called ryanodine receptor modulators has been developed and labeled for use against worm pests of cole crops. Insecticides that belong to this class disrupt the calcium balance in muscle cells of certain lepidoptera larvae, causing the insect to stop feeding. Both flubendiamide (Synapse) and chlorantraniliprole (Coragen) belong to this class of insecticides and are effective against all the worm pests of cole crops. Because these materials have selective activity against specific lepidoptera larvae, they pose minimal to zero risk to pollinators and other beneficial arthropods.

New application tactics

Chlorantraniliprole (Coragen) was originally labeled as a foliar spray, but can now be applied as an in-furrow spray at planting, a transplant water treatment or hill drench, a surface band at planting, a soil shank injection or as a drip chemigation application. Research conducted at the Rutgers Agricultural Research and Extension Center in Bridgeton, N.J., demonstrated the effectiveness of a soil application of this material applied at planting to cabbage (Table 1). Similar results were obtained in trials conducted by Dr. Tom Kuhar at the University of Virginia Eastern Shore Agricultural Research and Extension Center in Painter, Va., where excellent control of the beet armyworm and cabbage webworm were obtained using a single soil-applied transplant application.

Another just-labeled product that growers can use on head and stem and leafy brassica crops is a chlorantraniliprole plus thiamethoxam combination called Durivo. This material can also be applied at planting, in furrow at transplanting, as a transplant drench or hill drench or post-transplant application, through the drip irrigation system, or as a rootzone and shank application. However, with the addition of thiamethoxam, not only are the worm pests controlled, but also flea beetles, thrips, aphids and whiteflies. Thus, growers have more options than ever for effective management of the wide range of insect pests of various brassica crops.

The author is a professor in the entomology department at Rutgers, The State University of New Jersey, working at the Rutgers Agricultural Research and Extension Center in Bridgeton, N.J. He has worked as an extension specialist in vegetable entomology since 1980.