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Featured Pest

As usual, if there's a particular pest you'd like me to address, just drop me a line at shell@michellesgarden.com.


Colorado Potato Beetle

Colorado potato beetles can devastate plantings of potatoes and tomatoes. Both adults and larvae chew on leaves and stems.

Description

Adults are yellowish orange beetles, 1/3 inch (8.5 mm) long, with ten lengthwise black stripes on the wing covers and many black spots on the midsection behind the head. Larvae are dark orange, humpbacked grubs, 1/16-1/2 inch (2-10 mm) long, with a row of black spots along each side. Eggs are bright yellow ovals.

Range

Throughout North America, except California, Nevada, and west coast of Canada.

Plants Affected

Potato, tomato, eggplant, and related plants, including petunia.

Damage

Both adults and larvae chew on leaves and stems. Younger plants may be killed and older plants severely defoliated. Although the yield of defoliated plants is reduced or destroyed, a moderate amount of feeding on leaves has little effect on potato yields.

Life Cycle

Adults and sometimes pupae overwinter 2-14 inches (5-35 cm) deep in the soil (deeper in colder areas). They emerge in spring to feed on potato plants as soon as the first shoots appear. After mating, females lay eggs on end in upright clusters on the undersides of leaves; they produce up to 1,000 eggs during their life span of several months. Eggs hatch in 4-9 days, and larvae feed for 2-3 weeks. They pupate in soil for another 2-3 weeks, and adults emerge in 5-10 days. Two generations per year in most areas, a third generation in Southern states.

Prevention

Plant potato cultivars with some resistance, such as 'Katadin' and 'Sequoia'. Plant pollen and nectar flowers to attract native predators and parasites. Mulch plants with deep straw, which seems to impede the movement of emerging beetles in early spring before they have fed enough to be able to fly. Cover plants with floating row covers until midseason. Till the soil in fall to kill overwintering beetles.

Control

Eliminate the first generation for good control through the season. Starting in early spring, inspect shoots and undersides of leaves for adults, egg masses, and larvae. Crush any egg masses. Handpick adults, or shake them from plants onto a ground sheet early in morning, then drown beetles in soapy water (this is very effective if started as soon as overwintering adults emerge). To control larvae, handpick or spray the biological control BTSD. Spray weekly with pyrethrin, rotenone, ryania, or neem (when registered for use on food plants) to control adults and larvae. Experimental biological controls for larger gardens include spined soldier bugs (release at rate of two to five bugs per square yard [one to four bugs per square meter] or plants) or the tiny parasitic wasp Edovum puttleri, which should be released in time to attack second-generation larvae.


The brightly colored larvae are easy to spot.
Handpicking the adults and larvae can be an effective control.


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