FORAGE CROP TECHNICAL UPDATE

Crops at Risk.

Kales, swedes, stubble turnips, forage rapes, spring drilled oilseed rape and most cultivated brassicas.

Life Cycle.

The beetles emerge in spring and start feeding on suitable plants. On warm days they can fly considerable distances between newly sown crops. Eggs are laid on or in the soil near brassica plants in May and June. After hatching the larvae feed on the plant roots and after two or three weeks they change into adults and start feeding on the foliage. Development from egg to adult is 6 – 8 weeks.

Damage.

Adults attack the plants eating holes in the leaves and stems of the seedlings in April and May. Attacks can occur well into summer months, even after the first true leaves. Loss is usually greatest in a dry spell when brassica seedlings are slow growing. Two or three sowings may be destroyed unless preventive actions are taken.

Control Measures

There are two seed treatments for fleabeetle attack. Combicoat and Ultrastrike. Both need the beetle to pierce the leaf to take in the insecticide that then kills them. In situations of very high fleabeetle populations all the beetles have to pierce the leaf to die.

That many attacks on the leaf will kill the plant anyway. Seed treatments will buy you time to see if you have a problem that needs spraying.

There are many proprietary sprays available to control flea beetles in the field. Please call Ben or your local Wynnstay Arable Agronomist for advice.