Plusia looper description
Plusia looper, also known as Cabbage looper or more correctly Trichoplusia ni are light green caterpillars with white or pale yellow stripes along the sides. It typically moves by arching the middle part of its body upward. The adult moth is active at night (about 1 ½ inches or 3.8 – 4.0 cm). They attack early in the growing season. The adult moth is actually easy to identify by the two silver spots in the middle of the two wings.
Looper caterpillars are easily recognized because they crawl by arching their backs. Their eggs are laid on the underside of mature leaves. They are similar to fruit worm eggs, but flatter, and have finer ridges radiating from the top.
Damage made by Plusia looper
Loopers eat holes in leaves which provides an entrance for other diseases into the plant. The holes are ragged in shape. When loopers attack seedlings considerable damage can occur. Most seedlings are severely eaten, are dead or become stunted. The undersides of leaves appear skeletonized between the veins.
Controlling Plusia looper
There are several important naturally occurring parasites that help control loopers in tomatoes. Conserving these parasites by not treating with disruptive pesticides, particularly early in the season before fruit begin to mature, is the preferred management approach. Biological control can be applied by using Bacillus thuringiensis sprays. Before spraying one should determine the extent of damage in the field. If damage is severe enough to expose fruit to sunburn, treat mid – to late-season foliage to maintain the plant canopy. Spot treat only severely infested areas. However biological control is not always possible.
The most common insect predator is Braconid wasps and yellow jackets. They feed on the eggs and larvae so try and supply enough plant pollen and nectar plants in the surrounding area. Ideal spots are on the side of pathways and inner roads. These areas are commonly not sprayed with chemicals so they are free to breed and feed. Ideally it should be controlled by Bacillus thuringiensis var. kurstaki, insecticidal soap or canola oil.