Second and third generation larvae can be devastating. First-generation feeding include small holes, and small circular lesions in leaf tissue. Second-generation larvae tunnel extensively through the plant.
There are varieties of plants resistant to corn borer, there is even a genetically modified variety of corn known as Bt corn, a mix between bacillus thuringiensis and corn, which has had very good results. However this is not readily available to the Home Gardener. As with most worms and moth species the best control is Bt itself.
Bt - bacillus thuringiensis. has proven effective , 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.
is another biopesticide , correctly termed a microbial pesticide, harmless to humans. Spinosad will interfere with pollinators as well as pests - evening / night time use is advisable. Spray raspberry canes with active beetle populations as soon as possible, or wait till flower buds emerge to target the worms .
Sprays/Pesticides must be applied in the pre-bloom stage to prevent injury. Do not apply insecticides, even bio-pesticides during bloom time to protect vital pollinating insects. Pesticides such as Pyrethrin that are more effective in cool than warm weather will work more efficiently against Fruit worms earlier in the season, and is the recommended early season chemical for most types of worms.
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.