Larvae – The Corn earworm/ tomato fruitworm and sometimes called the cotton bollworm varies in color from light green or pink to dark gray but are generally lighter on their undersides and have alternating light and dark stripes along the length of their bodies.
The young larvae clip off silks and then proceed into the ear where they remain until ready to pupate in the soil. There are five to six larval stages and the appearance and color of the larvae change with each stage.
The moth is usually light yellowish-olive with a single dark spot near the center of each forewing.
Common hosts are Corn,Tomato, Eggplant ,snap beans, green beans, lettuce, peppers and others. They can cause severe damage to young seed pods ,early recognition is the key to control.
Corn earworm moths, like most moths are most active during evening hours. Praying Mantids Are highly effective at this stage.
Adult moths are about an inch long, robust and range from olive green to dark red in color. Their wingspan is about an inch long . The forewings are powdery with dark lines and or spots near the ends.
Eggs are laid singly, not in clusters, on the leaves of host plants. Corn tassels and silks are very attractive to these worms. Eggs are ribbed and spherical, less than 1/16 inch round.
They develop a red ring around the circumference shortly after being laid and will clearly show the black head of the larva just prior to hatching.
Eggs hatch in less than a week and the larvae begin feasting on host plants for a period of 3 to 4 weeks before burrowing back into the soil to pupate.
Two full generations of earworm development can occur annually. Second generation larvae and moths emerge during pollination. Their populations will spike in late summer.
They are cannibalistic, so even though more than one worm may infest a host, the dominant larvae will generally devour the weaker ones.
Corn earworm populations will generally die out over the winter in colder areas, but pupae can survive in the soil in more temperate regions.
Injury to plants ranges from decimation of the host plant to merely cosmetic damage. The corn earworm will devour buds and flowers of tomato, pepper and eggplants and will sometimes bore into the stems, it prefers unripe green fruits.
Larvae, after entering fruit generally go unnoticed until it’s too late and extensive damage has been done. The cavity created by their feeding is contaminated with wastes, becomes soggy and soft, and serves as an entry point for various microbes and plant diseases. Many of damaged fruits rot before they can be harvested.
Control of the Corn Ear Worm
Chemical control of the corn earworm is expensive, rarely cost effective for home gardeners and not eco-friendly. Also as the larvae migrate down the silks on corn or under the husk of the ear, insecticide sprays become ineffective.
For insecticides to work effectively, spray residues need to be present on the silks where the eggs hatch. Hand picking of infested plants is helpful but not always feasible.
The best control for corn earworm is Bt – bacillus thuringiensis. It has proven effective against almost all species of Moth and worm , it is a bacterium / organic pesticide that is readily available to home gardeners. It’s harmless to people and pets.
Apply it at either bloom or petal fall, or both. Bt It is a stomach poison and must be ingested . It is more effective when applied during warm, dry weather while the larvae are actively feeding. Bt breaks down quickly in nature so multiple treatments per season are necessary.
An ounce of prevention is worth a pound of cure ….
Proper sanitary practices are vital to the health of your garden. Proper sanitation can help to ensure disease-free pest-free and productive gardens. Try to keep the garden free of any diseased dead or damaged plant materials.
Remove cuttings from pruning and trimming and either destroy them – if diseased, or send them to the compost pile. Leaving rotting fruits and vegetables in the garden is like a written invitation to unwanted pests and diseases.
If a diseased or dead plant part has to be cut, the microorganism that caused the problem is probably on the tool you just used. Like a surgeon, sterilize all tools by washing in soap and water – rubbing alcohol wouldn’t hurt either.
If you pinch off diseased plant parts, wash hands before handling any other plants. Keep Weeds under control. Till the soil in the spring before planting to expose and kill larvae that wintered over in the soil.