||Flea Beetles - (many species)
Whitney Cranshaw, Colorado State University, www.forestryimages.org
UC - Davis, Pests of the Garden and Small Farm - Puplication #3332
LIFE CYCLE: There are numerous species of the flea beetles (4000 species of Phyllotreta in the world). Flea beetle species are fairly host specific in their general feeding habits. Flea beetle biology is not completely understood. They overwinter as adults in the soil in protected areas. Beetles emerge early in the spring and begin feeding on plants and weeds as soon as daytime temperatures consistently reach 40° F. Depending on weather conditions, there are 1- 4 generations per year. Adults can feed for up to 2 months. They lay eggs on the soil around plants and larvae feed on host plant roots. Except for the flea beetles that feed on potatoes, root feeding generally causes little injury.
Cultural: Know which flea beetle you have and rotate crops accordingly. For example, if you have flea beetles that feed on broccoli but not solanaceous crops, rotate with potatoes following cabbage family crops. Flea beetles are highly mobile, but you can give transplants a head start by planting susceptible crops where non-susceptible crops grew for 2 previous seasons.
Cover transplants with polyspun fabric row covers (i.e. remay). As long as you are rotating susceptible crops, overwintering beetles should not emerge under the row cover. Row covers will not work if flea beetles have overwintered in the soil beneath the row covers because they will emerge inside the covers.
If you have the kind of flea beetles that feed on broccoli and other plants in the cabbage family, you can intercrop with plants the beetles may prefer, such as radish cultivars like Chinese Daikon, White Gem Radish, and Snow Belle. This technique is called "trap cropping". You can also use mustard varieties such as white mustard, Red Giant, Chinese Southern Giant, and Green Wave Mustards. Important points to consider when using trap crops are:
--There should always be a healthy, growing trap crop or flea beetles will move to the plants you are trying to protect. Regular sowings of trap crops throughout the season are required.
--Don't let your trap crop go to seed; it could become a weed.
--The above trap crops will NOT protect Asian cruciferous vegetable crops, such as Napa cabbage, mustard greens, or arugula.
--Climate and weather during a particular growing season will affect the efficiency of trap crops.
--You might consider controlling flea beetles on the trap crop as beetle populations increase. (See LTO chemical control below.)
Sticky traps (white and yellow sticky card traps) encircling susceptible plantings reportedly catch large numbers of flea beetles, but will not control a large population.
Flea beetles can be vacuumed off crops with a handheld, portable vacuum daily to reduce populations.
Biological: Predatory nematodes can be applied to moist soil and watered in afterwards.
Chemical: Trilogy 90EC (Neem oil) gave the best results in a CA test.
Pyrellin EC (pyrethrin/rotenone concentrate: 0.6% pyrethrins, 0.5% rotenone, 0.5% other cube root resins) provided some control of adult flea beetles.
Plant Wash (a soap-based fatty acid insecticide) also provided some flea beetle control.