|Byers R A,|
|Calvin D, - THE PENNA STATE UNIV|
Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 2, 1994
Publication Date: N/A
Interpretive Summary: Slugs are important pests of corn, but little is known about how their feeding on corn seedlings affects grain yield at harvest. Individual corn plants were infested with four different population densities of very young slugs at three different plant growth stages. Feeding damage to corn seedlings was observed as leaf area removed. Slug damage reached a peak level, then the plant usually recovered and grew to maturity. These peak level or maximum damage estimates were compared to yield of roots, stalks, and grain. The three-year average losses in grain yield were used to establish economic injury levels (EIL). Then these EIL levels were transformed to action levels for slug control, depending upon the cost of slug control and the value of the corn crop.
Technical Abstract: Slugs are important pests of corn but little is known about the effects of their feeding on corn seedlings upon growth and yields. Individual corn plants were infested with four different densities of juvenile slugs, Deroceras reticulatum (M¿eller) before seedling emergence and at the two- and four-leaf stage. Feeding damage to corn seedlings by slugs was visually scored for leaf area removed, and maximum damage estimates were regressed against yield of roots, stalks, and grain. Considerable corn plant mortality occurred for the highest slug density of 50/0.1 m2 in 1989 but less mortality was recorded at lower initial densities (up to 20/0.1 m2) used in 1990 and 1991. The quadratic regression equation of three year average losses in yield of grain from slug feeding were used to establish economic injury levels. No loss in yield of grain occurred when less than 25% of the leaf area was damaged by slugs. Economic injury levels varied above 25% to 50% damage depending upon the cost of control of slugs and the value of the corn crop.