Resource Guide for Organic Insect and Disease ... - Cornell University

in the soil as a grub (similar to a Japanese beetle grub), feeding on the roots in sod and weedy
gardens. The grubs (larvae) pupate early in the spring, and adults emerge in June-July and start
feeding on about a hundred species of flowers and garden vegetables. Peppers and eggplants
are favorites. The adults are round, cinnamon-to reddish-brown beetles (Photo 7.2). They eat
big, irregular holes in leaves and blossoms. They are often difficult to find because they feed
at night and burrow into the soil during the day. Evidence of Asiatic garden beetle includes
chewed leaves but no visible pests; checking plants at night often reveals cutworms, but more
and more growers are discovering Asiatic garden beetle as well.
Cultural Control:
1. Maintain good weed control in fields.
2. Fall clean up and tilling under crop debris will help.
3. If the beetle is not already hiding in the soil, row covers will protect crops from adult
feeding.
Materials Approved for Organic Production:
Growers report good control of adults with spinosad (Entrust).
COLORADO POTATO BEETLE (Leptinotarsa decemlineata)
Colorado potato beetles (CPB) overwinter as adults (Photo 7.3), hibernating in the soil near
previous host crop fields. They emerge in the spring and crawl to new hosts, where they feed
and lay eggs (Photo 7.4). The resulting larvae (Photo 7.5) and successive generations can
quickly defoliate a crop. The CPB prefers potatoes and eggplants but can also be a problem on
tomatoes and peppers.
Cultural Control:
1. Crop rotation to non-susceptible crops is the first line of defense, since CPB only feeds
on solanaceous plants. Greater distance between fields means that adults take longer
to find the current year’s crop. Rotating solanaceous crops as a group will concentrate
the population in one area of the farm, making distance rotation easier. Control of
solanaceous weeds (e.g., horse nettle) that can serve as hosts is important.
2. A plastic-lined barrier trench between the old field and new field of host crops will
catch and trap many crawling adults. This practice will reduce the overall population,
though supplemental control may still be required.
3. If young potato plants are infested, rapidly moving a flame from a propane torch over
the top of the plant has been shown to kill overwintered, adult CPBs, which tend to
feed at the top of the plant. Although this measure may singe plant tissue, there will be
no long-term damage to the plant if done carefully. Suction devices can also be used.
4. Mulching crops with straw or hay before adults arrive has been shown to significantly
reduce and delay CPB pressure.
5. For plantings less than two acres, hand-picking may be practical if the CPB pressure is
low.
6. Trap cropping with a potato variety that grows well in cool weather, such as “Superior,”
has been shown to be effective. Plant the trap crop between the previous and current
year’s fields (i.e., near CPB overwintering sites), and destroy beetles by flaming or with
insecticides when adult CPB numbers on the trap crop are high.
Materials Approved for Organic Production:
1. Spinosad: Recent studies showed 12 good and 2 fair results.
2. Neem products: Recent studies showed one good and two fair results. Generally, neem
is slow-acting, but it reduces overall damage and numbers of large larvae. Please see
the neem material fact sheet for a discussion of the different types of neem products.
3. Beauveria bassiana: Recent studies showed one good, one fair, and five poor results.
See the material fact sheet on Beauveria bassiana.
4. Bt tenebrionis (also called Bt san diego) - currently there are no approved formulations.
Organic Resource Guide 57