Establishment of the Parasite Anagyrus antoninae in Florida for Control of Rhodesgrass Scale

Abstract

Rhodesgrass scale Antonina graminis (Mask.) was first reported in the United States from southern Texas in 1942. By 1950 it had been reported from 21 counties in Texas, one parish in Louisiana, and three counties in Florida (Chada and Riherd, 1950) and it has now become widespread in southern and central Florida. It attacks a number of grasses and is often a serious pest of Para, Carib, St. Augustine, and other pasture grasses. It also contributes to the unthriftiness of St. Augustine and Bermudagrass lawns and turf. Merrill (1953) reported that the species has become of economic importance on lawns and golf greens and Kelsheimer and Kerr (1957) stated that it is the most widely damaging of the grass scales in Florida. Some ranchers in the Everglades area have complained of considerable loss from this scale. Since Rhodesgrass scale couldi not be economically controlled in pastures with insecticides, parasites were introduced in 1954. In July the senior author released 800 parasites, Anagyrs antoninae Timberlake, near Clewiston, Florida, for control of this scale. The wasps were reared by and received from Herbert A. Dean of the Texas Agricultural Experiment Station and the USDA Agricultural Research Service, Weslaco, Texas. The original release was made on Paragrass heavily infested with this scale, after collections had shown that this parasite was not already in the area. The initial introduction at Clewiston was comprised of free-living adults, but subsequent releases were made by placing stems of grasses infested with parasitized scales about infested pastures. The parasites then emerge into a suitable environment. Under this method parasite mortality is probably much lighter than where previously reared and handled adults are released. The parasitized material should be placed near fence rows, ditches, or in other protected situations where excessive grazing has not occurred. To ascertain if the parasite introduction was successful, host grass from the vicinity of the release point was collected. Samples were taken from several spots to make a composite sample, which was placed in a cardboard box and sealed tightly. Test tubes containing alcohol were inserted into two or three holes that had been made in one side of each box, and slanted slightly downward. A positive phototropic response caused the emerging adult parasites to move toward the light, and they were thus trapped in the tubes containing alcohol. In the summer of 1956 a survey was made to determine the dispersal and concentration of population at various distances from the releases made in 1954. Less than one pound of scale-infested Paragrass was collected