Wednesday, May 20, 2015

Campaign Against a Flea Beetle Invasion


Sometimes, when conditions are just right you may find your garden besieged by bugs. That has been the case at our research and trial farms. A recent eggplant trial fell victim to a flea beetle attack, and we watched as the tiny seedlings struggled through what appeared to be the damage of an artillery battery of minute shotguns. As ours is a research farm, we were able to learn some valuable lessons from the event including which particular eggplant varieties were vigorous enough to recover from the assault. We also developed a plan to deal with future flea beetle issues.

Flea beetle control using conventional techniques usually amounts to full-out chemical warfare. While effective at killing the beetles, spraying toxic chemicals on crops can result in far-reaching toxic effects, systemic pollution, and devastating collateral damage. Most insecticides that kill flea beetles can also affect beneficial insects like lady bugs and honey bees. Organic methods can be more labor intensive, but they tend to have fewer adverse side effects. Combatting flea beetles is an ongoing enterprise at our certified organic & biodynamic research and trial grounds. We take a multi-layered approach to fighting these destructive bugs.

Flea beetles are tiny, shiny, usually black, foliage-feeding insects. They earn their name from their hopping ability, which mimics the springing step of fleas. The adults spend the winters in leafy debris or just under the soil surface, emerging in the spring when temperatures warm to about 50°F. They’ll then feed on the leaves of vegetable crops, making small, round shot holes and favoring brassicas, tomatoes, eggplants and peppers. Although the damage can be outgrown by most plants, heavy infestations can weaken, stunt, and even kill entire plantings. At the very least, the chewed holes in leafy greens, like mustards and Asian greens, are unappetizing signs of insect invasions—something most of us would rather not see on our dinner plate. Adult female flea beetles lay their eggs at the base of the plants, where the young hatch in about a week and live in the soil to feed on the plants’ roots. The nymph pupate in the soil, emerge as adults, and the process repeats.

Predatory Nematodes—The Boots in the Ground
Our friendly predatory nematodes are hard-working, soil-dwelling microorganism that feed on insect pests in the ground. Since part of the flea beetle lifecycle occurs in the soil, nematodes are an excellent, non-invasive method of controlling their populations before the young have an opportunity to mature. Applying nematodes is as simple as mixing them in water and irrigating the ground. Once present, these voracious little soldiers will search and destroy the flea beetle nymphs.

Silver Mulch—Camouflage in the Field
Plastic mulch has many benefits in the garden: it warms the soil, suppresses weeds, and conserves moisture. Reflective silver mulch takes its skills farther with its shiny surface illuminating crops to increase photosynthesis (a powerful benefit for winter gardens). But, its reflected glare also serves to confuse and repel flea beetles. The insects see the reflected light and are unable to discern the plants, so they bypass the crops in search of visible, recognizable food.  In side-by-side comparisons with colored mulch and non-mulched plants, the efficacy of reflective mulch is indisputable, with greatly reduced infestation issues on the plants in silver-mulched areas.

Trap Crop—Strategic Planting
Flea beetles eating a trap crop of mustard
Since flea beetles find certain plants irresistible, we give them what they want, sort of. Planting a border of a mustard cover crop around the perimeter of the field that we are protecting will draw the insects to the tender cover crop greens. With the cover crop up, growing, and luring in the hungry flea beetles, the real crops can then be introduced. Carefully removing the mustard plants at the height of infestation will effectively evacuate most of the flea beetles from the area, leaving the vegetable crops to thrive. There are different methods for handling the trap crop and its offending, very mobile insect population, but a clean and quick technique is burning the plants in place with a Weed Dragon garden torch. For smaller-scale operations like a home garden, pulling a shop vac out and vacuuming up the bugs is another chemical-free option for collecting them.

We find ourselves repeating, “It’s always something” when it comes to gardening. Whether you’re struggling with the weather, deer, moles, slugs, or bugs, there’s always a challenge to face. With a little foresight and planning, most of these obstacles can be overcome with non-invasive, toxic-free methods.

Author: Kat B,  Retail Store Coordinator

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