Effect of Insecticide Treatments on Root Lodging and Yields of Maize in Controlled Infestations of Western Corn Rootworms (Coleoptera: Chrysomelidae)

Influence of Western Corn Rootworm (Coleoptera: Chrysomelidae) Larval Injury on Yield of Different Types of Maize

“…Low levels of rootworm injury did not signiÞcantly affect grain yield even though reductions in photosynthetic rate and growth response patterns could be measured during vegetative growth stages (Urṍas-Ló pez et al 2000). This supports the idea (Sutter et al 1990, Gray et al 1993) that maize can tolerate and compensate for some level of early season larval injury without sustaining signiÞcant yield loss.…”

“…A relationship between root injury and yield loss was established by Turpin et al (1972) and has been modiÞed in subsequent studies (Stamm et al 1985, Mayo 1986, Sutter et al 1990, Davis 1994, Gray and Steffey 1998. Root damage scales based on levels of larval injury (i.e., Mayo 1986) at the end of the larval period have been used as economic injury indices.…”

“…A root rating of 3.0 (Mayo 1986) on a 1Ð 6 scale (Hills and Peters 1971) has been commonly used by researchers and industry as an index of the level of root injury that potentially could lead to economic yield loss. However, results of some studies indicate that economic loss may not occur under certain conditions until root injury ratings are much greater than 3.0 (Sutter et al 1990, Gray et al 1993, Davis 1994. Gray and Steffey (1998) in a recent study found that hybrid characteristics and environmental conditions greatly inßuence the level of root injury needed to cause economic loss.…”

Adult Susceptibility of Nebraska Western Corn Rootworm (Coleoptera: Chrysomelidae) Populations to Selected Insecticides

“…In the western Corn Belt, growing corn in the same field for 2 or more successive years (continuous corn) is the best economic option for many producers. In continuous corn, root feeding by larvae of the western corn rootworm, Diabrotica virgifera virgifera LeConte, can cause substantial injury to corn plants (Sutter et aL 1990;Spike and Tollefson 1991a;Godfrey et aL 1993a, b) and reduce yields (Spike andTollefson 1991b, Godfrey et aL 1993b). Crop losses and control expenses attributed to corn rootworms annually cost producers millions of dollars.…”

Effects of soil insecticide treatments on northern corn rootworm, Diabrotica barberi [Coleoptera : Chrysomelidae] populations and on corn yield

“…Jackson (1996) also did not observe corn yields to be related to the number of WCR adults between treatments. Plots had to be infested with at least 1200 WCR eggs per plant in order to show a significant yield réduc-tion (Chiang et al 1980;Sutter et al 1990). Since NCR causes less damage than WCR (Fisher 1985), an even higher level of infestation is needed to observe yield réduction.…”