Maize
Flea Beetles
Chrysomelidae
Insect
In a Nutshell
- Feeding damage with yellowing on leaves.
- Small shot-like holes.
- Small, dark and shiny or metallic beetles.
Maize
Symptoms
Adults feed on leaves. The damage appears as small scattered shot-like holes (1-2 mm), and small chewing cavities that do not cut across the leaf blade (pitting). A slight yellowing may occur around the damaged tissue. Tubers are bored with narrow, straight tunnels of varying depths depending on the species in question. Small raised bumps may also appear on the tuber surface as part of the damage.
Recommendations
Organic Control
Fungal pathogens, insecticidal soaps or the bacterial insecticide Spinosad can be used to reduce populations. The larvae of lacewing (Chrysopa spp.), adult damsel bugs (Nabis spp.) and some parasitoid wasps feed on or kill adult flea beetles. Some nematodes also kill the larvae that live in the soil.
Chemical Control
Always consider an integrated approach with preventive measures together with biological treatments if available. Insecticides should be applied during the beetle's susceptible period, that is when they appear on the leaves. Products based on chlorpyrifos work well to control populations.
What caused it?
There are many species of flea beetles affecting a variety of plants. Most adults are small (about 4mm), dark-colored, sometimes with a shiny or metallic aspect. They have an oval body and large hind legs for jumping. The larvae live in the soil and feed on roots or tubers whereas adults feed on young plants. Most flea beetles hibernate under plant residues, in the soil or on weeds around fields. They become active again during the spring. Depending on species and climate, 1-4 generations grow per year. Flea Beetles prefer warm, dry conditions.
Preventive Measures
- Adjust planting times (earlier or later) to avoid periods of peak adult activity.
- Plant trap crops that are attractive to the flea beetle.
- Plant non-hosts plants that repel or block insect pests.
- Add organic mulch as this interferes with the egg-laying and the larval stages.
- Monitor your plants, especially in spring.
- Supply the plants with essential nutrients in the frame of a balanced fertilization.
- Water regularly and in a reasonable manner.
- Rid your field of weeds or other host plants.
- Remove refuge sites by plowing and destroying crop residues.
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