Insects as Destroyers

Losses Caused by Insects

G. J. Haeussler.

Every minute of the day and night billions of insects are chewing, sucking, biting, and boring away at our crops, livestock, timber, gardens, homes, mills, warehouses, and ourselves.

How much damage they do is hard to say. Many variables and complicating factors are involved. The damage by one kind of insect to a crop differs from year to year and from one area to another. Pests cause losses in uncounted ways.

The infestations reduce the yield of crops, lower the quality, increase the cost of production and harvesting, and require outlays for materials and equipment to apply control measures. The products must be screened or washed to remove insects or insect fragments; washed, brushed, trimmed, or otherwise treated to remove insecticide residues; and graded to eliminate or otherwise allow for injury. Livestock pests lower the production of meat and milk and the value of hides.

Mosquitoes, house flies, ticks, and fleas exact a toll in human diseases and in efficiency and money time lost from work, the cost of screens on homes, interference with the cultivation or harvesting of crops, the loss of business at resort places.

Insects cause direct losses to timber production. They also cause indirect ones : The fire hazards of insect-killed trees in the forest, the effect on conservation, spoiling of beauty in parks and other scenic areas and on streets and properties in towns and cities.

Food and homes suffer. Insects attack grains while they are in farm storage and in transit and while they are stored in elevators. Others infest dried fruits during and after the drying process. Clothes moths, carpet beetles, pantry pests, and termites invade homes, infest food, ruin clothing, damage the timbers of houses.

A compilation of estimated losses due to 60-odd insects in the United States was made in 1938 by J. A. Hyslop, of the Department of Agriculture. He set the total damage, including the cost of control measures, at $1,601- $527,000 annually. His estimates were based on prices far lower than those of today and did not take into account all injurious insects.

We can be more specific now about losses to certain crops and commodities.

The European corn borer, one of our insect immigrants, has been one of the farmers' worst enemies. Surveys to determine its distribution, abundance, and damage show how the losses increased as the corn borer spread throughout the Corn Belt. In 1949, when conditions were especially favorable, the damage reached an all-time high. Fortunately weather conditions unfavorable to the borer and other natural factors sometimes check its ravages, as they did in 1950. Practical methods are now available for controlling it in field corn, sweet corn, and seed corn, but by no means has it been eliminated.

Estimated Value of Crops Destroyed by Grasshoppers and Saved by Control Measures.

Grasshoppers damage a variety of crops and range plants. More than 75 years ago C. V. Riley estimated that the grasshoppers caused crop losses amounting to 200 million dollars in a number of Western States from 1874. to 1877. Hyslop recorded that entomologists in 23 Western and Midwestern States estimated the average annual value of crops destroyed by grasshoppers from 1925 to 1934 at about 25 million dollars. The losses remain high, especially in outbreak years, but control campaigns and better control methods have meant great savings of crops. Now that practical, effective materials are available to the individual farmer, grasshoppers should never again be allowed to cause such losses as those in the 1930's.

Cereal and forage crops are attacked by many other pests. Among them are the corn earworm, hessian fly, chinch bug, velvetbean caterpillar, lygus bugs, and greenbug.

Among the many kinds of insects that attack vegetable and truck crops are aphids, leafhoppers, sucking bugs, beetles and weevils, caterpillars, thrips, spider mites, cutworms, wireworms, and mole crickets. Many cause direct injury. Certain aphids and leafhoppers and some others cause indirect damage by transmitting diseases to potatoes, sugar beets, and similar plants. No attempt has ever been made to bring together estimates of all these losses, but one of the tables gives some idea of them.

As for the fruit insects: Yearly losses in our apple crop because of the codling moth from 1940 to 1944 were set at about 15 percent of the crop value, or $25,245,000. That did not include the cost of measures to combat the pest, which cost an estimated 25 million dollars more. DDT has been used extensively and effectively against the codling moth, so that the average annual losses from codling moth from 1944 to 1948 were about 4 percent of the crop value, or $9,176,000.

The citrus crops of California are said to have suffered losses of about 10 million dollars in 1943-1944 because of the California red scale. In 1943 and 1944 losses to peach growers east of the Rocky Mountains because of the plum curculio and the cost of applying control measures have been estimated at nearly 8 million dollars a year. The peach tree borer is another serious pest over much of the eastern two-thirds of the country. If not controlled, infestations of the borers weaken and often kill peach trees. The extent of the damage is difficult to determine, but the annual cost of applying control measures alone was estimated at $3,200,000 in 1943 and 1944.

The boll weevil takes a big bite out of our cotton crop each year. The cut in production from 1909 to 1949 in the 13 States in which the boll weevil occurs meant an estimated average loss of cotton and cottonseed of more than 203 million dollars annually. The loss was more than 500 million dollars in each of 5 years, between 400 million and 500 million dollars a year, and between 300 million and 400 million dollars in each of 3 years. It was 200 million to 300 million dollars in each of 6 years. The estimated loss was below 100 million dollars in only 16 of the 41 years. The value of the cotton was computed at the seasonal average price received by farmers and does not consider what they might have received had the yield not been reduced by insects. To those losses must be added the damage caused by other insect pests. One of them, the bollworm, is estimated to have destroyed cotton in Texas alone to the extent of 85 million dollars in some years.