Chemical Control for Sweet Corn


sweet-corn-The corn earworm (and the second-brood corn borer where present) is controlled with a DDT emulsion to which a light mineral oil is added. The later should be a refined, white mineral oil of 45-to 90-seconds saybolt viscosity. Three applications should be made; the first, the day after the silks appear; the second, three days later; and the third, another three days later. The spray or dust should be applied thoroughly to the silks.
The spray formulas for one acre or for a small plot are as follows; add one gallon of 25 per-cent DDT emulsifiable concentrate to 1 gallon of the light mineral oil; add water to make 25 gallons. This is sufficient for one acre. One-third pint of 25 per-cent DDT emulsifiable concentrate is added to one-third pint of the light mineral oil; add water to make a gallon. This is sufficient for a plot 17 by 100 feet (staff, 1957).
Dust formulas (MacGillavrary and Minges, 1956) are as follows: five per-cent DDT dusts is applied with a stencil or paint brush to each ear. Requires 30-35 pounds per acre.
Ground-dusters may be used for light-to-moderate infestations. Use 5 per-cent DDT dusts or granules at 35 to 40 pounds per acre. Make three to four applications at three- to four-day intervals. For heavier infestations, apply 10 per-cent DDT dusts by power-dusters or airplane sprayer.
DDT is a poisonous material and should be handled and stored with care. Follow directions carefully. Avoid having residues of DDT on the corn grains of more than 3.5 ppm.
Neither corn fodder nor husks should be fed to dairy cattle or animals being fed for the market.
For garden applications, use any type of hand-duster or sprayer. Tractor-mounted or high –clearance sprayers or dusters are used for commercial acreages. Machines should be equipped with a boom, with nozzles adjusted to each row. Pressures should range from 50 to 150 psi, depending on the number and types of nozzles, gallons applied per acre, and the speed of the sprayer. The usual type of row-crop dusters are not suitable for applying granules without adjustment. Adjust single-outlet applicators to deliver directly over the row. For multi-outlet applicators , close all outlets except those directly over the row (luckmann and others, 1957).
Under Alabama conditions, eden (1958) found that DDT applied daily as a 2-pound emulsion for 7 days, and then at 2-day intervals, was superior to Phosdrin at 0.25-pound and Chlorthion at 1.0-pound concentrations. Sevin gave results similar to DDT, but injured the foliage.
A survey of field corn 8 per cent, due largely to the rice weevil (sitophilus oryza). This loss increased during storage of 10 months to 22 per cent. The predisposing cause of the loss was bird damage to the husk. An application of one pound of endrin in one gallon of white mineral oil to the individual ears on July 6 and august 3 gave good protection against the weevil (Floyd and Powell, 1958).