The role of Chrysopa carnea (Steph.) as a predator of the green peach aphid Myzus persicae (Sulzer) on sugar beet Beta vulgaris was demonstrated in six greenhouse experiments using different predator/prey ratios. Each experiment continued for 4 to 5 months. Releases of early second stage Chrysopa larvae at the predator/prey ratios of 1:5, 1:10, 1:20 and 1:40 successfully controlled M. persicae. Each Chrysopa release at these ratios completely eliminated the pest. Adequate control was provided for 5 to 6 weeks when the ratios of 1:5 and 1:10 were used, and 3 to 4 weeks when the ratios of 1:20 and 1:40 were used. At the predator/prey ratios of 1:50 and 1:60, Chrysopa releases did not eliminate the green peach aphids but notably reduced its numbers. While the Chrysopa treated plants reached normal size, the untreated control plants died during the first 2 months of the experiments. The side effects of 14 pesticides on Chrysopa was tested in the laboratory by exposing 2nd stage larvae on fresh dry pesticide films applied on glass plates at dosages similar to those used in practice. Six of these pesticides were further tested in the field by directly spraying of sugar beet plots on which Chrysopa larvae were released. The herbicides Pyramin, Betanal and Illoxan were harmless, Aretit flüssig was harmful. The insecticides Pirimor‐Granulat, Nexion‐stark, Hostaquick, Dipterex WP 80 were harmless to slightly harmful but Dimilin 25 WP, Sumicidin 30, Rogor, Tamaron, Dursban flüssig and Ultracid WP 40 were harmful to the Chrysopa larvae. Zusammenfassung Die Wirkung des Blattlausräubers Chrysopa carnea in Zuckerrübenkulturen und die Einwirkung von Pflanzenschutzmitteln auf diesen Nützling Die Nutzleistung von Chrysopa carnea (Steph.) bei der Bekämpfung der Grünen Pfirsichblattlaus Myzus persicae (Sulzer) an Zuckerrüben wurde in 6 Gewächshausversuchen mit verschiedenen Räuber/Beute‐Verhältnissen demonstriert. Jeder Versuch dauerte 4 bis 5 Monate. Mit Freilassungen von Chrysopa‐Larven im frühen Zweitstadium in den Räuber/Beute‐Verhältnissen von 1:5, 1:10, 1:20 und 1:40 konnte M. persicae an Zuckerrübenpflanzen erfolgreich bekämpft werden. Jede Freilassung in diesen Verhältnissen führte zur totalen Ausschaltung der Blattläuse. Mit den Räuber/Beute‐Verhältnissen von 1:5 und 1:10 konnte eine ausreichende Bekämpfung für die Dauer von 5 bis 6 Wochen erzielt werden, mit den Verhältnissen von 1:20 und 1:40 für die Dauer von 3 bis 4 Wochen. In den Versuchen mit den Verhältnissen von 1:50 und 1:60 konnte Chrysopa die Blattläuse zwar nicht völlig ausschalten, jedoch wesentlich reduzieren. Während die Zuckerrübenpflanzen in den Chrysopa‐Behandlungsparzellen ihre normale Größe erreichten, erfolgte in den nicht behandelten Parzellen die totale Zerstörung der Pflanzen im Verlauf der beiden ersten Monate des Versuches. Die Nebenwirkungen von 14 Pflanzenschutzmitteln auf Chrysopa wurden im Labortest untersucht, wobei Larven des Nützlings im frühen Zweitstadium frisch applizierten, trockenen Belägen der Präparate in normalen Anwendungsk...

The parasitoid Diaeretiella rapae accepted all stages of the cabbage aphid Brevicoryne brassicae. The average number of mummies produced per female parasitoid was 42.8. Diaeretiella rapae did not show preference between young (first-second instars) and old (fourth instars) nymphs of the aphid. Nymph aphids younger than 4 days (third instars) produced no offspring after parasitism. The average number of offspring per aphid that was parasitized at day 5-6 (third-fourth instars) and day 7 (adults) were 3.1 and 15.3, respectively, which were much less compared with the aphid that was not parasitized (38.1). The average reproduction period for the aphids that were parasitized at day 5-6 and day 7 were 1.9 and 4.4 days, respectively and that for non-parasitized aphids was 14.9 days. Cage experiments showed that at the ratio of 1.2 : 1 (six female wasps : five aphid adults), with three releases on day 1, 3 and 6, the percent parasitism of the offspring on day 20 was 88.9%, and the aphids were successfully controlled by the second generation of the released parasitoids. Release of cabbage plants that included both mummies and young aphids in a broccoli field, with a dose of about 2 mummies/m 2 , resulted in higher percentage of the broccoli plants with mummies in the treated plot compared with the control plot. The percent parasitism of the aphids on broccoli plants in the treated plot was also, with one exception, significantly higher. Seven weeks after the release of the parasitoid, the percentage of the broccoli plants with mummies was 93.3% in the treated plot and 56.7% in the control plot; the percent parasitism of the aphids were 6.7 and 1.4% in the treated and control plots, respectively. These results indicated that one release of the cabbage plants with mummies enhanced the spread of the parasitoid D. rapae and increased parasitism of the aphids in the field. More releases of the parasitoid are needed to control the aphid effectively.

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