Onion maggot

From Gardening Wiki

Treatment for Onion Maggot

A poison-bait spray composed of one-fifth of an ounce of sodium arsenate dissolved in a gallon of boiling water, to which is later added one pint of molasses, furnishes a bait that is cheap, attractive to the pests, and effective.

The application of this bait is extremely easy and simple, for the reason that no attempt need be made to cover the foliage of the plant as is the case in ordinary spraying. On the contrary the bait should be applied in large scattering drops. An ordin ary hand syringe or a whisk broom dipped into a bucket of this solution and shaken about on each side of the operator will apply the liquid satisfactorily. It is possible in this manner to treat a strip thirty feet broad on each trip across the onion field. Apply once a week in fair weather; twice a week in showery weather, throughout the growing season. It is most needed when plants are small. The idea is to kill the adult fly before the egg-laying stage. In actual practice it has been found that a field may be treated in checkerboard fashion, or in alternate strips, leaving an untreated strip of a width similar to the treated areas, since the flies are strongly attracted to the poison-bait spray when freshly applied.