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Population fluctuations of the diamondback moth, Plutella xylostella (L.) on cabbages in Bacillus thuringiensis sprayed and non sprayed plots and factors affecting within‐generation survival of immatures
Author(s) -
Annamalai Sivapragasam,
Itô Yosiaki,
Saito Tetsuo
Publication year - 1988
Publication title -
population ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.819
H-Index - 59
eISSN - 1438-390X
pISSN - 1438-3896
DOI - 10.1007/bf02513253
Subject(s) - diamondback moth , plutella , biology , apanteles , parasitoid , population , larva , bacillus thuringiensis , population dynamics , abiotic component , pupa , trichogramma , predation , pest analysis , toxicology , ecology , horticulture , braconidae , fecundity , demography , genetics , sociology , bacteria
Summary The population fluctuations and within‐generation survival of immatures stages of the diamondback moth, Plutella xylostella on summer cabbages, were examined in unsprayed plots in 1984 and 1985 and in plots sprayed with two formulations of Bacillus thuringiensis in 1985. There was two distincy generations per crop and no noticeable difference in population fluctuations were observed in unsprayed plots between years. There was distinct difference between unsprayed and sprayed plots in 1985, from the larval period onwards. However, the survivorship patterns in all plots in both years were a Type 2 based on Deevey 's (1947) classification. Life table studies showed that there was essentially no difference in the mortality agents acting on each of the stages except for numerical differences in the within‐generation mortality rates. The major mortality rates during the egg stage were the parasitoid, Trichogramma spp. and unknown factors including rainfall; in the larval 1 stage was unknown mortality; in the larval 2 stage was the parasitoid, Apanteles plutellae and during the pupal stage was unknown mortality and parasitoid, Diadromus subtilicornis . Adult mortality was determined for generation 2. It was relatively higher in the unsprayed plots compared to the B. thuringiensis sprayed plots. The contribution of abiotic factors such as rainfall and temperature, and biotic factors such as parasitoids and predators in determining within‐generation population levels and the fluctuation of populations on cabbage were discussed.