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Cutworm

Closer Look Of The CutwormThe cutworm, of the order Lepidoptera, is a catchall name for many species of different moths. Most are 1 1/2 to 2 inches long, brown & dull gray moth larva caterpillar, with dark lines sideways down the back. The larva attack vegetables, corn, fruits and many other crops by climbing or tunneling. Larva are soft, fat, greasy and ugly and will curl-up when touched, sleeping during the day but eating at night; adults are usually small (1 1/2"), plain-looking brown moths. Up to five generations of cutworms can occur in a single year.


Adult

Cutworm MothThe adult is a mottled grayish-brown moth with a wingspan of about 1 1/2", which is normally nocturnal, but can sometimes be seen during the day resting on leaves or in leave piles. They are strongly attracted to lights at night.


Eggs

Cutworm EggsAfter mating, the female moths live about 2 weeks, but during their short life lay between 200-400 small eggs normally laid in the soil. The eggs are usually in the form of a sticky mass and can be white, pale green or pale yellow in color, and which hatch in only a few days. If you see these eggs, spray them off with water or a solution of insecticidal soap and water.


Larvae

Cutworm LarvaeYoung cutworms, which are known as larvae, are about 1/4" long, but quickly grow to their full 1 1/2" to 2" size, eating everything in sight and living for about 3 weeks. This is their most destructive stage when they do the most damage, usually feeding at night, eating holes in the green leaves of your crops and felling small seedlings. If your plants were okay the previous day but damaged overnight, then suspect a cutworm attack. If it looks like a lawn mower went over your young plants and felled them, suspect cutworms too.


Pupa

Cutworm PupaThen they form a cocoon, normally on the underside of the leaves or in nearby brush piles, and begin to pupate. The cutworms enclose themselves in a white thread-like cocoon that's about 3/4" long, the caterpillars turning copper brown in several days. What's happening here is that the caterpillar is metamorphosing from a caterpillar larva into an adult moth. After about 10 days in the cocoon, they emerge as winged adult moths and the life cycle begins all over again (mating, laying eggs, etc). Depending upon the temperature and weather, as many as three or four generations of cutworms can be produced during the summer growing season, averaging about one generation every three to four weeks. So the pest will attack your garden crops from late spring, all summer long and into early fall, a good frost being needed to kill them.


Vegetables That Cutworms Like To Eat

Beets Cauliflower Lettuce Potatoes
Broccoli Chinese cabbage Lima beans Radishes
Brussels sprouts Collards Parsley Snap beans
Cabbage Cucumbers Parsnip Spinach
Cantaloupe Kale Peppers Squash

Control

 

Protect young plants with a paper cup (bottom cut off) buried half way into soilThe easiest control method is to push a 3 inch collar made from stiff paper or plastic around the base of young plants, several inches deep. This simple trick normally keeps most cutworms away from the delicate stem, which the cutworms like to eat. Otherwise, sprinkle a teaspoon or cornmeal around each plant, which causes the cutworm to die when he eats it.

Using the insecticide BT will normally control young cutworms, but is less effective with mature adults, being aware that BT won't kill them for several days, but the cutworms should stop eating right away. A good thing about BT is that it is not harmful to bees and is considered a natural, organic substance (approved by organic gardeners). Apply BTK (the kurstaki variation of BT) in early evening when the winds have died down and no bees or butterflies are present, as some studies suggest that BT can be harmful to Monarch butterflies. BT breaks down quickly, so its toxicity will be much less the next day. Remember that BT is only effective when an insect is in its larval (eating) stage, such as when the cut worm is in the caterpillar phase of its life. It does no good to apply BT to eggs, pupae or spray it on an adult moth. It is only effective against actively feeding caterpillar cut worms. When you see young caterpillars, then spray, but not before they hatch from their eggs. Finally, if you spray cut worms with BT (var. kurstaki), and they don't stop eating and die after several days, it could be that your BT is old and no longer effective, a common problem with home gardeners. If this happens, purchase a fresh bottle of BT and try again. Sevin, Malathion and Diazinon are also effective but are much stronger insecticides. Pyrethrins or neem are less effective but are more natural and organic in nature, so try these second to BT. Finally, hand picking the cutworms is feasible for small gardens, putting them in a small pail of water to drown. If you don't want to touch the caterpillars, make a simple caterpillar picker.

 
 



 


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