Connie Nelson says:

June 4th, 2007 at 1:30 pm

Robyn,
Here’s everything you wanted to know aobut potato beetles from Jeff Hahn, an entomologist with the U of M extension service:

One of the most notorious insect pests in vegetable gardens is the Colorado potato beetle. Its favorite food is potatoes, although it also feasts occasionally on eggplants, tomatoes, peppers and similar plants. They can be difficult to control, but you can limit their damage in your garden with a combination of chemical and other means.

Colorado potato beetles spend the winter as adults.In spring, they lay a batch of bright orange eggs on plants as soon as potatoes are growing. These eggs hatch into reddish humpbacked larvae. Both adults and larvae feed on potato leaves. There are usually two generations of these pests each year. The different stages overlap and all forms of Colorado potato beetles may be seen on potatoes at any given time.

Potatoes can tolerate moderate amounts of beetle injury, but they’re more vulnerable to defoliation while the tubers are forming, usually in midsummer. Even with small amounts of defoliation, potatoes may put energy into developing more leaves instead of tubers. Keep your plants well-watered to keep them healthy and try to pick any Colorado potato beetles you find. Pick and remove beetles, and destroy the orange eggs if you have a small garden; it may not be practical in larger gardens.

You may need an insecticide. The most commonly used is carbaryl (sold as Sevin); however, many potato beetles are resistant to it.If Sevin doesn’t work, rotenone may. Bacillus thuringiensis (Bt) var. tenebrionis (M-One) is a bacterial insecticide that also is labeled for use against Colorado potato beetles. It is very low in toxicity and the beetles haven’t developed resistance to it. It’s only effective against eggs or newly emerged larvae, so the timing is critical.Because egg hatching can be prolonged and because Bt lasts only a
few days, apply it every three or four days.

Peter Hoh says:

June 4th, 2007 at 10:58 pm

These bugs attack my Chinese Lanterns. The larvae are yucky to squish, even for someone who has a pretty high tolerance for yuck. But squish them I do, once or twice a day. I find that the adults are hard to catch. They fly away when my hand approaches. But the eggs are easy to spot, and easy to get rid of.