Pickleworm Control – Identification and Treatment

What Are Pickleworms?

Pickleworms [Diaphania nitidalis] feed on cucurbits, which includes all types of cucumbers, squash, pumpkins, and melons. Their life cycle is approximately one month. Overlapping generations occur.

Their minute eggs are white when deposited on the buds, flowers, and other portions of the plant, but change to yellow after the first day. They are distributed in small groups, usually less than a dozen per cluster. Hatching takes about four days.

Larval development time is about two weeks. After which the moths emerge, they are primarily nocturnal. Moths are not found in the field during the daylight hours, and probably disperse to adjacent wooded or weedy areas during the heat of the day. Moths do not produce eggs until they are several days old.

Praying Mantis are recommended if not used in conjunction with chemicals as they as well as bats are among the few nocturnal predators of moths.

The pickleworm can cause severe damage. Young pickleworms generally feed on small leaves at the growing tips of vines or within blossoms. When they about half grown, they bore into fruits and continue to feast, causing internal damage and leaving behind an excrement trail.

Fruits at all stages of development are attacked, but young fruits are attacked more frequently. Pickleworm holes lead to decay and rot, cantaloupes and muskmelon develop a sour taste.

Pickleworm Control and Treatment

Diverse gardens that include a symbiotic mingling of flowers and vegetables are a poor environment for insect pests as they also attract many natural predators. Pickleworms have several natural enemies, such as Lady Bugs. Praying Mantis will feed on the moths by night.

Beneficial Nematodes

When sprayed directly on the plant do a good job, they survive several days inside the flowers where the pickleworms roam and can greatly deplete their populations. None of the predators will eliminate pickleworms entirely.

Bacillus Thuringiensis

Bt is the safest and surest weapon against this pest. Bt is rarely harmful to beneficial insects.

Bt bacillus thuringiensisorganic pesticide is the best bet against pickleworm, it is a bacterium that is known to kill all worms, and is readily available to home gardeners. It’s harmless to people and pets. Apply it at either bloom or petal fall, or both. 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.

Diazinon can be applied at petal fall but is not as eco-friendly as the bio-pesticides listed above as it is toxic to beneficial insects and pollinators.


Other Broad-spectrum organic insecticides, such as Pyrethin or malathion only as a last resort, generally used commercially and not really advisable for smaller plantings or home gardeners. Broad-spectrum insecticides, such as pyrethrin or malathion only as a last resort.

Sprays/Pesticides must be applied in the pre-bloom stage to prevent injury. Pesticides such as pyrethroids that are more effective in cool than warm weather will work more efficiently against Fruitworms earlier in the season, and is the recommended early season chemical treatment for most Fruitworms.

Pollinators, particularly bees, are very important in cucurbit production, and insecticide application can interfere with pollination by killing bees. If insecticides are to be applied when blossoms are present, it is advisable to use insecticides with little residual activity, and to apply insecticides late in the day or early evening, when honeybee activity is minimal.

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.