Lassoing Loopers: Why You Need To Care About Caterpillar Control

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on June 12 | in Ag News | by Jodie Deprez | with No Comments

Adapted from ONfloriculture by Sarah Jandricic, Greenhouse Floriculture IPM Specialist, OMAFRA

This article was originally written for the floriculture industry, but I have adapted it, with permission, as an awareness article for vegetable growers. — Janice

Know which looper species this is? Are you SURE? If not, keep reading, as some species could get your shipments detained at the border. Photo: Steve Hatch, Bugwood.org.

At this point, most field vegetable growers are focussed on getting the crops in and juggling early season field activities. If you’re thinking about caterpillars right now, it would probably be black cutworm. But recent alerts put out by the United States Department of Agriculture (USDA), bring a new emphasis to caterpillar control. Read on to understand what’s happening, and — for those with US customers — how to control occasional pests like cabbage looper, and avoid potential issues at the border.

Recently, the USDA informed the CFIA that the moth Chrysodeixis chalcites (known as tomato looper, or the golden twin spot moth) is an actionable pest in the U.S. This means they WILL take action on any shipments from Ontario they even suspect may contain this pest. Specifically, they may refuse or quarantine shipments, and/or increase inspections on shipments from Ontario.

“based on reports of the presence of Chrysodeixis chalcites in southern Ontario, they (USDA) intend to take quarantine action on any US bound shipments found to be infested by C. chalcites. C. chalcites is a pest of tomato, soybean, corn, pelargonium and other major agricultural crops and is considered to be an actionable pest by USDA-APHIS.” (USDA-APHIS)

So maybe you’re not a tomato grower shipping to the US. Why does this matter to you? Well…

The problem is two-fold. First, technically tomato looper can attack a wide range of plants, including tomato, snap beans, brassicas, peppers, and vine crops, among others (see point 6 here for an extensive list). But the bigger problem is that TOMATO LOOPER LOOKS JUST LIKE A LOT OF OTHER LOOPERS (e.g. moths in the family Noctuidae)*. For example, both the larval and adult forms of tomato looper are pretty indistinguishable from cabbage looper (see pictures below), which commonly attacks certain vegetable crops, and may be present at low levels in others.

*(Basically all the moths in this family look like indistinguishable stupid brown blobs and their larvae are even worse to tell apart. I’m pretty sure Noctuidae means “Boring Blob Moth”, but I haven’t actually looked that up).

Tomato Looper (Chrysodeixis chalcites; left) is only slightly less ugly than the Cabbage Looper (Trichoplusia ni ; right). Photos courtesy of Bugwood.org.

Unfortunately, the only way to accurately distinguish different looper species is by dissecting out the adult moth genitalia and comparing them (Yikes. I almost feel sorry for them; the people that have to do this I mean. Not the moths). This means that cases of mistaken identity at the border have the potential to occur, or shipments could be held until the identity of the culprit is confirmed.

Larvae of Tomato Looper (left) and Cabbage Looper (right) are extremely similar in appearance. DNA sequencing is the only way to accurately tell larvae apart. Photos courtesy of Bugwood.org.

For growers of some field vegetables, loopers have not been a pest of concern. But now, if the product will be going to the US, we should consider caterpillars more seriously in our pest control programs. Most potential host vegetable crops do have registered products for cabbage looper control.

Caterpillar Control 101:

Monitoring: Pheromone traps: sex pheromone lures specific to tomato looper, soybean looper or cabbage looper are all available. Black light traps (UV light) are another option, but will attract adult moths of many species so you need to be able to identify the moths of concern. If you aren’t using traps, intensive scouting will be required. Once you detect the presence of these pests, begin control while the larvae are small. Signs of an active infestation are webbing, feeding on foliage and pelletized excrement.

Loopers make irregular holes in leaves between the leaf veins and leave copious amounts of black excrement. Photo: A.M Valera.

Control: Registered cabbage looper insecticides (field vegetables) include:

Several carbamate and organophosphate insecticides (group 1A and 1B)
Several pyrethroid insecticides (group 3A)
Concept (group 3 and 4): head and stem brassica vegetables
Delegate (group 5): brassica head and stem vegetables, fruiting vegetables, leafy vegetables, root vegetables, leaves of root and tuber vegetables, leaf petiole vegetables
Entrust (group 5): root and tuber vegetables, leafy greens, brassica leafy greens, fruiting vegetables, brassica head and stem vegetables, stalk and stem vegetables, leafy petiole vegetables, basil, dill seed, potatoes,
Success (group 5): root and tuber vegetables, leafy greens, brassica leafy greens, fruiting vegetables, brassica head and stem vegetables, stalk and stem vegetables, leafy petiole vegetables, basil, dill seed
Bioprotec CAF (group 11): Asian radish, bok choy,
broccoli, Brussels sprouts, cabbage, cauliflower, celery, Chinese cabbage, Chinese broccoli, collards, kale, lettuce, mustard greens, parsley, potatoes, spinach, turnip greens, tomatoes, herbs and spices group
Dipel 2X DF (group 11): broccoli, cabbage, cauliflower, chinese cabbage, bok choy, chinese broccoli, asian radish, collards, herbs and spices group, kale, lettuce, mustard greens, parsley, potatoes, spinach, turnip greens, tomatoes
Rimon (group 15): brassica head and stem vegetables, leafy brassica greens
Intrepid (group 18): brassica leafy vegetables, cucurbit vegetables, fruiting vegetables, leafy vegetables, legume vegetables, tuberous and corm vegetables, herbs
Coragen (group 28): tuberous and corm vegetables, leafy vegetables, brassica vegetables, legume vegetables, fruiting vegetables, cucurbit vegetables, mint, globe artichokes
Exirel (group 28): tuberous and corm vegetables, root vegetables, leafy vegetables, brassica vegetables, legume vegetables, fruiting vegetables, cucurbit vegetables
Verimark (group 28): brassica vegetables

In all cases, see the label for a list of specific crops. Always read and follow label directions.

We know that repeated reliance on chemicals has resulted in lack of efficacy/resistance in looper pests in some crops. This has occurred across a wide range of chemical classes. So, rotate among chemical families and don’t forget about the biologicals (Bacillus thuringiensis), if you catch the infestation early.

The Bottom Line:

Although the potential to have shipments rejected at the U.S. border is real, looper pests ARE controllable, so just be on the look out and be prepared to add this pest to your regular scouting program if you have product going to the US. OMAFRA continues to work with CFIA, industry organizations, and the USDA to keep you posted on this issue.