European Corn Borer Parasitoids; Distribution in Southern Minnesota

During the 1940\u27s and 1950\u27s seven exotic parasitoids of the European corn borer (ECB) Ostrinia nubilalis (Hubner), were released in Minnesota. This study was done to determine which introduced parasitoids became established and their distribution in Minnesota. The experiment was conducted during the summer of 1977 and fall of 1977, 78, 79- and 80 in conjunction with the annual ECB population surveys in southern Minnesota by the State Department of Agriculture, Division of Plant Industry. Three introduced parasitoids, Macrocentrus grandii Goidanich, Eriborus Terebrans (Gravenhorst), and Sympiesis viridula (Thomson) and two native parasitoids, lshnus inquisitorius artricollaris (Walsh) and Aplomya caesar (Aldrich) were recovered. M. grandii was confined to the eastern portion, while E. terebrans was recovered from throughout southern Minnesota. S. viridula was found in only three counties, perhaps because of its biology it may have eluded recovery, resulting in underestimated distribution. The two native species, I. inquisitorius atricollaris and A. caesar, occur only occasionally in Minnesota

European Corn Borer Parasitoids; Distribution in Southern Minnesota

ABSTRACT -During the 1940's and 1950's seven exotic parasitoids of the European corn borer (ECB) Ostrinia nubilalis (Hubner), were released in Minnesota. This study was done to determine which introduced parasitoids became established and their distribution in Minnesota. The experiment was conducted during the summer of 1977 and fall of 1977, 78, 79-and 80 Larvae were collected in the summer of 1977 and fall of 1977 , 78, 79 , and 80 in conjunction with the ECB population survey conducted by the Minnesota Department of Agriculture, Division of Plant Industry. The area surveyed included the major corn growing districts of the state ( In the summer survey plants with ECB damage were dissected and the larvae present put in 25 mi. glass vials, the vials were plugged with cotton, and returned to the laboratory. In the laboratory and the larvae were given artificial diet, and allowed to complete development to adult ECB or parasitoid at 25 C., 85 percent R.H., and 16 hour photoperiod. In the fall surveys sections of corn stalks with evidence of recent ECB tunneling were cut from the plants and returned to the laboratory. In the laboratory the stalks were dissected, larvae present were put in 25 mi. glass vials and the vials plugged with cotton. Most of the larvae had completed larval development and were in diapause. Therefore , they were held at 15 C., 75 percent R .H., and 12 hour photoperiod for two months, then transferred to 25 C., 85 percent R .H., and 16 hour photoperiod to break diap ause and complete development to adult EC B or parasitoid . Most Parasitoid Recoveries in 1977 Summer The majority of the parasitoids were obtained from the summer 1977 survey. The larvae from the fall surveys had high mortality due to the entomophagous fungus, Beauveria bassiana (Bals.) and only a small number of parasitoids were obtained from these samples.