Good Farming Helps Control Insects

W. A. Baker, O. R. Mathews.

Farmers combat insects when they follow good practices in tillage, crop rotations, planting dates, and field sanitation cultural methods that help control pests without extra costs in time, money, or convenience. Often they require only minor changes in the usual cropping procedures. They are particularly applicable to cereal and forage crops of too small an acre value to justify repeated sprayings. Some of them also can be applied to insects on vegetables, fruits, forest trees, and other crops.

Delaying the seeding of winter wheat until after the fly-free date gives protection against the hessian fly. Fall seeding is deferred so that the wheat does not come up until the fall flight of the insect is past. Only moderately late sowing should be practiced, however, because wheat sown extremely late is less productive than wheat planted at the optimum time and is more subject to winter injury by ground heaving or soil blowing. Tests as to planting dates have been conducted by entomologists for many years in the principal wheat-growing States. The tests have shown that the safe date for sowing winter wheat to escape fly injury in years of normal rainfall usually coincides nearly with the proper time for sowing in order to secure maximum yields of grain. Growers should consult their county agricultural agent or nearest experiment station to obtain information on safe sowing dates recommended for their immediate localities. The date depends on the latitude, altitude, longitude, weather fluctuations, and other local conditions. It varies considerably in broken or hilly country, even on the same farm it is considerably later on the southern slope of a hill than on the northern slope.

Moderately late plantings of corn are damaged less than early plantings by the corn rootworm, or budworm, in the Southeast and by the European corn borer in Northeastern and North Central States. Midseason plantings of corn in southeastern Texas can better survive attacks of the sugarcane borer than can early or late plantings. The corn thus escapes the first brood but attains enough growth before the appearance of later broods to withstand the pest more successfully than do late plantings.

Adjusting the time of planting of field dry beans, snap beans, and lima beans in upper New York State so that the beans do not sprout until the larvae of the seed-corn maggot are no longer active in the soil is highly important in avoiding damage by it. Usually that is accomplished by mid-season planting, but it is best to delay planting to avoid maggot injury until information is available as to maggot-free dates. Safe dates vary from year to year and the information can be had from county agents.

Grain sorghums planted in late April in southwestern Oklahoma mature with less chinch bug damage than do those planted in early June, although (if there were no insect damage) early June would be a more productive date. In the Gulf coast part of Texas grain sorghums often are planted in late February or March in order to be past the blooming period before many adults of the sorghum midge have emerged. In the potato-growing section of western Nebraska, June-planted potatoes need fewer insecticidal treatments for control of the Colorado potato beetle than early-planted potatoes. In areas in Louisiana subject to heavy damage to sugarcane from wireworms, planting of the cane as early in August as is agronomically practical gives better stands than when the plantings are made in late September or early October.

THE PROPER DISPOSAL Of crop residues often helps control insects.

The European corn borer survives the winter in the full-grown caterpillar stage, chiefly in the stalks of corn and coarse-stemmed weeds. In late spring or early summer the caterpillars change to moths, which fly to the new corn for egg laying. Complete disposal of the plant remnants in which the borers overwinter, by plowing them under or feeding them to livestock before spring emergence of the moth, is a good way to fight the insect.

The sugarcane borer has similar habits in sugarcane, sorghum; and corn along the Gulf coast, although the warmer climate there causes the adult moths to emerge earlier in the spring. Fall or winter disposal of the residues therefore also helps control the borer.

As to several wheat-infesting insects, among them hessian fly, wheat joint-worm, wheat straw-worm, and wheat stem sawfly, plowing under the wheat stubble in summer or early fall prevents their emergence and consequently their ability to infest the new crop and to breed in the volunteer wheat that would otherwise grow in the stubble fields.

Of proved value is the proper disposal of cotton stalks in August for control of the pink bollworm in Texas. Early picking of the cotton and immediate elimination of the stalks greatly reduce the numbers of weevils the following year. Growers of other crops also know how important it is to destroy infested residues as an aid in insect control sweetpotato weevil in the Gulf States, pepper weevil in California, pea weevil in Idaho, wheat stem sawfly in Montana and North Dakota, and wheat midge in the Pacific Northwest.

Other tillage practices 'strike directly at the insects while they are in vulnerable locations, particularly during hibernation. In the Lake Erie region, cultivation of vineyards in spring buries and helps destroy overwintering cocoons of the grape berry moth. A shallow covering of soil is enough to prevent the moths from coming out of the ground; it reduces the number of surviving insects so that a shortened spray schedule gives satisfactory control of the moth.

Most species of grasshoppers deposit their eggs in the ground in late summer and fall. The common injurious species spend 6 to 8 months of the year as eggs in the top 3 inches or so of soil. If the soil is plowed at least 5 inches deep some time during the period, preferably in the fall, and the surface layer well compacted by later cultivation, the hoppers hatching from the eggs cannot emerge.

Another method is to deprive insects of their food plants by tillage. The pale western cutworm, a serious pest of small grains in the Great Plains, cannot be controlled by spreading poisoned baits in infested fields, as can most cutworms, because it stays underground day and night and moves from plant to plant by burrowing along just beneath the surface. The worms die quickly after they hatch in the early spring, however, if all newly sprouted vegetation is killed by thorough cultivation as soon as the worms have had a little time to feed. They can survive for some time if they have had no food, but die quickly if they have once fed and then are deprived of food. The infested fields may therefore be kept clean by tillage for about 3 weeks, beginning soon after the worms have hatched, and then sown to spring grains with little subsequent injury to the crop.