PLUM CURCULIO, a North American curculionid beetle, or weevil (Conotrackelus nenuphar). This insect is confined to North America east of the Rocky mountains. It ranges as far north as Manitoba and Quebec, and as far south as Victoria, Texas, and northern Florida. In this territory it is a serious enemy to stoneiruits and also attacks the apple and other pomaceous fruits. It is especially injurious to all varieties of plums, and to peaches and cherries. Its original food was probably the fruit of native Crataegus.
The adult curculio is small (about in. long), dark brown in colour, with whitish markings on the thorax and the hinder part of the wing-covers. It lays its eggs in holes next to a crescent shaped cut made in the skin by the beetle's beak. The function of the crescent-shaped cut is to kill the spot in the fruit containing the egg, so that the latter will not be crushed by the rapidly grow ing fruit. The larvae penetrate the flesh of the fruit, and a number of them may occur in the same plum or peach. On reaching full growth, the larva leaves the fruit and enters the soil, forming• a cell in which it transforms successively to the pupa and adult. It rests in the pupal stage for two or three weeks. The resulting beetles feed upon the fruit and foliage until the approach of cold weather, when they enter hibernating quarters in protected places such as under trash in the orchards or in near-by woods. In its more northern range the insect has but one generation annually. In the far south some individuals develop a second generation.
The plum curculio is a great enemy to orchards. It was esti
mated in 1938 that the annual loss through its work in the United States was about $1o,000.000. It has several natural enemies among the hymenopterous and dipterous parasites, and it is de stroyed by a few species of predatory insects. The fruit attacked by it often falls to the ground, and under such conditions poultry destroy many of the pests.
Fruit growers rely chiefly on spraying with lead arsenate for the control of the plum curculio. The foliage of the peach is par ticularly susceptible to injury by arsenicals, although most of this can be overcome by the addition of lime or of zinc sulphate and lime.
The sprays on peach are usually combined with a self-boiled lime sulphur or one of the so-called wettable sulphurs to control various diseases, especially brown rot, which often gains entrance into the fruit at points injured by the curculio.
In areas in which a second brood of the curculio develops and where the insect becomes especially abundant, spraying is supple mented by a number of other practices, including the jarring of the trees and the capturing of the beetles on sheets placed under neath, the picking up and destruction of infested wormy drop peaches, and cultivation during the period when the insect is transforming in the ground and when it is readily injured by any disturbance of the soil.
Detailed information on the control of the insect may be obtained from State Agricultural Experiment Stations or from the U.S. Department of Agriculture. (L. 0. H.)