No abstract

Whole-culture extracts of Bacillus thuringiensis Berliner strains were assayed against larval and adult Drosophila suzukii (Matsumura), an important invasive pest of many thin-skinned soft fruit crops in North America. Of the 22 serovars tested versus larval D. suzukii, strains of Bacillus thuringiensis var. thuringiensis, kurstaki, thompsoni, bolivia, and pakistani caused high (75 to 100%) first-instar mortalities. Pupal mortality, measured as a failure of adults to emerge, varied with serovar. The first D. suzukii instar was the most susceptible of the three larval instars to B. thuringiensis var. kurstaki HD-1. Larval D. suzukii are shielded from crop treatments, as they develop under the skin of infested fruit, and adults would be a more vulnerable target for an efficacious strain of B. thuringiensis Only one of the 21 B. thuringiensis serovars, var. thuringiensis, prepared as oral suspensions in sucrose for adult D. suzukii ingestion resulted in significant, albeit low mortality within 7 d. It is not a candidate for use in pest management, as it produces β-exotoxin that is toxic to vertebrates.

Intraplant epizootics of entomopathogens, Beauveria bassiana (Balsamo) Vuillerain, and Nosema pyrausta (Paillot) were studied in a corn, Zea mays L., agroecosystern. Egg masses of the European corn borer, Ostrinia nubilalis (Hfibner), infected with N. pyrausta were placed on midwhorl-stage corn plants. Conidia of B: bassiana were applied in art aqueous suspension. Frass from the initial insects remaining within the plants was contaminated with sufficient N. pyrausta spores to infest 80 % of the filial generation in each year ofa 2-yr study. Viability ofN. pyrausta within the frass was monitored throughout the winter. Potential for impact of this inoculum on the filial generation is discussed.Conidia from cadavers of the European corn borer that were killed by the initial inoculum of B. bassiana and/or conidia from the initial inoculum of B. bassiana significantly reduced tunneling by the filial generation of the European corn borer. However, neither the concentration ofB. bassiana nor the age of the larvae exposed to B. bassiana, had any significant (P < .05) effect on tunneling by the 2nd-generation larvae.

No abstract

The impact of each of three microsporidia on the braconid parasitoid Macrocentrus grandii Goidanich within infected European corn borer, Ostrinia nubilalis (Hübner), hosts was studied. Nosema pyrausta (Paillot) and Nosema sp. infected M. grandii larval tissue. All three microsporidia decreased adult parasitoid eclosion. Female M. grandii eclosing after development in hosts infected with Vairimorpha necatrix (Kramer) or N. pyrausta lived for 10 to 14 days. Females infected with these two species did not transmit the pathogens transovarially to their offspring. Only male M. grandii adults eclosed from hosts infected with Nosema sp.