Vegetable Crops News

Releasing Twospotted Stink Bug for Control of Colorado Potato Beetle

The twospotted stink bug is a native North American predatory bug that can provide excellent control of the Colorado potato beetle, especially in small plantings. In most experiments the insects have been released as half-grown nymphs, but there are certain disadvantages to releasing this stage. Nymphs tend to be relatively fragile, so care must be taken to release them within a few days. Until they are released they need to be kept cool and provided with food and refuge sites (to prevent cannibalism). Finally it is time consuming to transfer the nymphs to potato foliage.

Twospotted stink bug eggs appear sturdy and are easier to handle quickly than nymphs. The eggs are normally laid in small groups, and can easily be removed from whatever they were laid on during mass rearing. The loose eggs can then be scattered or even mechanically dispersed in potato fields. In recent research, the efficacy of releasing twospotted stink bug as eggs instead of nymphs was tested. Eggs were either scattered loose on the foliage or placed in the field in protective screened containers. Very few of the unprotected eggs scattered on the foliage survived, probably because generalist predators consumed them. The screens, however, excluded predators and parasites of both eggs or newly hatched nymphs, so survival was good in these releases. More bugs survived in containers placed on the soil than in those placed in the foliage (eggs spilled before hatching, probably due to movement of the foliage by wind). Control of Colorado potato beetle was almost as good with protected egg releases as with releases of nymphs.

However, egg releases would require higher release rates than nymph releases to compensate for eggs that fail to hatch and mortality of newly hatched nymphs. Egg releases would have to be made earlier than nymph releases to allow time for hatching and development. Also, an inexpensive and convenient method of protecting the eggs from natural enemies would have to be devised to make this practical.

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