Field and greenhouse studies were conducted to determine the proclivity of Bacillus thuringiensis (Bt) (Berliner)‐transgenic corn (Zea mays L.) to form an endophytic relationship with Beauveria bassiana, and to evaluate the corn for possible plant pathological effects associated with this relationship. Beauveria bassiana (Balsamo) Vuillemin was applied as a granular formulation to two separate lines of corn, expressing Bt events MON802 and MON810, and their corresponding isolines. There were no significant differences in levels of endophytism between transgenic events or their near‐isolines. In greenhouse studies, B. bassiana was applied as a liquid seed treatment to Bt transgenic corn hybrids Pioneer 34R06 (event MON810) and Ciba Max 454 (event 176) and their near isolines at a rate of 2 × 1010 conidia per ml. There were no significant differences in seed germination or presence of root pathogens in transgenic or isoline seeds soaked in a B. bassiana suspension. The same lines of corn were used in field experiments with treatments of seeds soaked in a suspension of B. bassiana, a foliar application of a granular formulation of B. bassiana, and corresponding untreated checks. Plants were sampled throughout the growing season and evaluated for growth of individual plant components, including sheaths, leaves, stem, husk, ear, plant leaf‐to‐stem ratio and overall plant growth. There were no significant differences in overall plant growth between the B. bassiana treatments or in the growth of each plant component. The results of this study indicate that B. bassiana readily forms an endophytic relationship with transgenic and non‐transgenic corn and causes no plant pathology.

Nosema pyrausta (Paillot) (Microsporida: Nosematidae) is an obligatory intracellular parasite of the European corn borer, Ostrinia nubilalis (Hu¨bner) (Lepidoptera: Crambidae). This pathogen is maintained in natural populations of O. nubilalis by both horizontal and vertical transmission. The impact of N. pyrausta on fecundity of adults and survival of larvae has been well documented in laboratory and field research. In an extensive study covering a 6 year period at one site, we described the effect of N. pyrausta within O. nubilalis populations in a continuous corn following corn ecosystem. We documented the presence of the pathogen through all life stages of O. nubilalis (egg, larva, pupa, adult), by collecting throughout the crop season and examining each insect stage in the laboratory for the frequency of infection with N. pyrausta. The percentage of infection with N. pyrausta and magnitude of the O. nubilalis population fluctuated throughout generation 1 and generation 2. Both horizontal and vertical transmission played a role in maintaining N. pyrausta in the population in both generations. There were strong correlations between percentage adults with N. pyrausta and percentage larvae with N. pyrausta, and between percentage eggs with N. pyrausta and percentage larvae with N. pyrausta. There was a weak correlation between percentage adults with N. pyrausta and percentage eggs with N. pyrausta. The percentage of insects infected with N. pyrausta was always lowest in the egg.

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European corn borer, Ostrinia nubilalis (Hu¨bner) (Lepidoptera: Crambidae); western corn rootworm (WCRW), Diabrotica virgifera virgifera LeConte; and northern corn rootworm (NCRW), Diabrotica barberi (Smith & Lawrence) (Coleoptera: Chrysomelidae) are important pests of corn, Zea mays L., that occur simultaneously in the US Corn Belt. Areawide management strategies for northern and western corn rootworm in Iowa, Kansas, South Dakota, Illinois, and Indiana, and for the Mexican strain in Texas, use SLAM Ò , which contains cucurbitacin, a feeding stimulant, and a small amount of the insecticide carbaryl. This management strategy is environmentally sound because it introduces a substantially lesser amount of chemical insecticide into the environment than prophylactic soil insecticide applications for WCRW management. To develop a management program for both corn pests, the compatibility of SLAM Ò to control CRW, along with a biological agent to manage European corn borer, was investigated. Laboratory studies were conducted using the egg parasitoid Trichogramma brassicae (Bezdenko) (Hymenoptera: Trichogrammatidae). In experiments in which SLAM Ò and T. brassicae were evaluated as components of a management system, SLAM Ò did not affect parasitism or parasitoid emergence rates. Trichogramma brassicae displayed vigorous biotic fitness, emergence rates, sex ratios, and fecundity over the duration of the study. Data collected under these laboratory conditions indicated that SLAM Ò had no adverse effect on the quality of T. brassicae, indicated by its ability to reproduce in the filial generation.