“The number of applications isn’t always a good indication of the efficacy of the insecticide. Sometimes where the female lays her eggs and many other factors can affect the time required to reach threshold levels,” Smith says.

Though Dipel performed well in the tests, it has a slower potency than other materials, so it should be applied when insects are small. Otherwise, insects like cabbage loopers that can destroy a lot of tissue in a short period, can do too much damage before they finally die.

Production of brassica crops, like collards and broccoli, is up in the Southeast and continued growth is highly contingent on managing insects.

Damage from insects can have a two-fold affect on vegetable crops — it can lower actual production and in some cases not reduce yield, but cause cosmetic damage that renders the vegetable unmarketable.

Broccoli production in particular is targeted for large increases in production over the next few years. A large multi-state program that includes major universities and commercial growers in the Southeast was funded in 2011, and has the potential to bring broccoli production into vogue throughout the region.

Three primary insects that impact production of brassica crops worldwide are the diamondback moth, cabbage worm, and cabbage looper. Diamondback moths and cabbage worms came to the U.S. with the pilgrims back in the 1500s and are proof that as brassica crops move around the world, so does its pests, Smith says.

Though imported cabbage worms devastate cabbage and collard production in gardens throughout South Carolina, they are rarely a problem in commercial operations.

Over the past 10 years or so, growers in the Southeast have been attentive to adopting IPM programs and as a result we have seen fewer and fewer populations diamondback moths over the past decade, he adds.

Diamondback moths attack only plants in the family Cruciferae. Virtually all cruciferous vegetable crops are eaten, including broccoli, Brussels sprouts, cabbage, Chinese cabbage, cauliflower, collard, kale, kohlrabi, mustard, radish, turnip, and watercress.

Though any of these commercially produced crops are hosts for diamondback moth, collards will usually be chosen by ovipositing moths relative to cabbage and other crops.

In addition to commercial vegetable crops, a number of commonly occurring weeds are important hosts in the Southeast, especially early in the season before cultivated crops are available.

Diamondback moth can cause significant economic losses in target vegetable crops, especially broccoli and cauliflower. Plant damage is caused by larval feeding.