Beschreibung:
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<jats:title>Abstract</jats:title>
<jats:p>Increasing resistance to chemical insecticides in field populations of the
diamondback moth (Plutella xylostella) has stimulated research on
alternative control measures. The entomopathogenic nematode Steinernema
carpocapsae may be one such alternative, particularly against the third
larval instar of P. xylostella. The LC50 for the second instar is 38, the
third 13 and the fourth 22 nematodes/larva. Plutella xylostella pupae were
not affected by the nematodes, although mortality in leaf disk bioassays
after application of nematodes in water seldom surpassed 50%. Therefore,
additives were tested to improve nematode performance. Only Triton X-100
(0.3%) caused phytotoxic effects. The addition of xanthan gum or potassium
alginate resulted in a two-fold increase of insect mortality at 80% relative
humidity (RH) and a five-fold increase at 60% RH. Mixtures of 0.3% xanthan
or alginate with 0.3% surfactants further improved efficacy. In water the
LT50 for S. carpocapsae against P. xylostella larvae was > 40 h. Using a
mixture of 0.3% xanthan or 0.3% alginate with 0.3% surfactant, the LT50 was
reduced to < 25 h.</jats:p>
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