Date: 3/30/99

Time: 2:25

Type: Symposium

Number: 151

Iowa areawide management project: off to a good start?

*J.J. Tollefson, E.C. Berry, T. Nowatzki, Dept. of Entomology, Iowa State University, Ames, IA 50011; H.J. Stockdale, , Iowa State University, Ames, IA 50011 and L.C. Lewis, USDA-ARS, Ames, IA 50010
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Iowa's Areawide Corn Rootworm Project began in 1997. The pest was monitored in 6,030 acres of field corn. When the economic threshold was exceeded and eggs were obvious in females, applications of Slam® were used to control the beetles. Initially 5,607 acres (93%) of corn were treated and 3,020 acres (54%) received a second application. Did these applications to suppress beetle populations prevent economic larval injury during the following growing season? To avoid economic damage, root-injury ratings should be less than 3. During 1998 the average root-injury rating where Slam had been used was 2.15 (range=1.3-3.3). This was comparable to where soil insecticides had been used to protect the roots (mean=2.01, range=1.5-2.7) and a dramatic reduction compared to where no insecticides were used (mean=3.51, range=2.1-5.0). There were fewer corn rootworms in 1998 than 1997. During 1997, 452,000 beetles per acre were produced where soil insecticides had been used. In 1998, there were 368,000 beetles produced per acre where no control had been used. In the management area, where beetle populations had been held below the economic threshold using prescription, broadcast applications of Slam, only 94,000 beetles/acre survived. Partly because rootworm populations were lower in 1998 but mainly due the suppression provided by the 1997 controls, only 3,082 acres of 6,829 acres scouted (45%) received Slam applications in 1998. Only a single 110-acre field received a second application. Areawide management to suppress corn rootworm populations appears to be off to a good start.

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