I keep finding cabbage loopers in my Brussels sprouts. I pick them off, I use neem oil soapspray to try killing any eggs that might be hiding, but they come back full force within a couple of days. Other than covering my plants, is there anything else I can do? I'm at my wits end!
I've been taking the approach of attracting and supporting the predators that eat various pests. I often see birds hoping around my brassicas with caterpillars hanging out of their beaks. We still have some of these pests but the damage is minimal and not much to worry about. Here is some information from wikipedia specifically about cabbage loopers and what eats/kills them:
Enemies Predators General predators like spiders, ants, and lady beetles prey on cabbage looper eggs and larvae, removing 50% of the eggs and 25% of the larvae within three days. Lady beetles consume at the highest rate. Other common predators of cabbage looper larva include Orius tristicolor, Nabis americoferus, and Geocoris pallens.
Parasites While the cabbage looper frequently encounters parasites, its most common parasite is the tachinid fly. In one study, 90% of the parasitized larvae were due to the tachinid fly. It parasitizes most often in the late fall and winter, but it is capable of parasitizing year-round. Cabbage loopers at their third or fourth instar yield the most parasites. It is early enough in the larval stage that the maggots still have time to feed and grow before pupation can prevent parasite emergence. It is also late enough that the caterpillars are large enough to support the maggots. Fly oviposition is often triggered by the larva thrashing to repel the fly, regardless of whether the larvae are already parasitized. As a result, larvae are often overparasitized, overwhelming and killing smaller larvae. During oviposition, the mother glues the fly egg to the host. This helps the maggot burrow into the larva, where it remains until the third day. The maggot cuts a slit into the back and eats its way out of the larva.
Diseases The moth is susceptible to viral diseases including nucleopolyhedrovirus (NPV). This is a naturally occurring virus whose natural hosts include Lepidoptera, arthropods, and Hymenoptera. From the family Baculoviridae, it is a type of Alphabaculovirus and its genome is 80-180kb long. NPVs are commonly used as pesticides for the cabbage looper. There are numerous NPVs, many of which were isolated from the cabbage looper or the alfalfa looper. NPVs vary in infectivity and virulence. For example, the AcMNPV isolates are more infectious than the TnSNPV isolates in the first instar, while the TnSNPV isolates produced more occlusion bodies, protein structures that protect the virus and increase long term infectivity. TnSNPVs are their most lethal during the third and fourth instars; they have detrimental effects such as delayed development, reduced egg production, and fewer hatched eggs. These effects are significantly diminished when the larvae are infected during the fifth instar, suggesting that the earlier infection is more effective.
Bacillus thuringiensis (Bt) is a gram-positive soil bacterium from the phylum Firmicutes. It is often used as a biological insecticide for numerous insect pests, including the cabbage looper, and reduces both growth rate and pupal weight. The cabbage looper has demonstrated resistance to Bt, specifically the toxin Cry1Ac, due to an autosomal recessive allele. Although it is not entirely clear which gene causes the resistance phenotype, there is strong evidence supporting the correlation between a mutation in the membrane transporter ABCC2 and Bt resistance. Other studies with greenhouse-evolved population of Bt resistant cabbage looper demonstrate that the downregulation of the aminopeptidase N, APN1, results in its resistance.
Here are some basic ways to attract and support the predators that help keep pests in balance:
1. Plant flowers
2. Provide cover (hedgerows, trees, shrubs, log and rock piles, mulch, etc.)
3. Have a water source
4. Don't use any toxic chemicals
It takes time to attract the predators but it does work as long as you provide the habitat the predators need to thrive. Every year as I expand my food growing areas I'm adding more habitat for predators next to and even mixed in the food growing areas. I'm also going back through my older areas and adding more features (like log and rock piles) plus flowers to attract more predators. The result is each year I've got less pest issues despite growing more food.
I hope that helps and good luck!
Cultivate abundance for people, plants and animals - Wild Homesteading
I was picking catapillars out of my cabbage/broccoli.
Lookd over and a wasp was doing the same thing.
Going down between the leaves of cabbage and hunting them.
I encourage wasps and rarely have damage to my brocolli and my cabbage looks great.
It's red cabbage though,.. and I think that does better against the worms.
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