Effects of biopesticide Neem EC on the Large White Butterfly, Pieris brassicae L. (Lepidoptera, Pieridae)

M. Grišakova, L. Metspalu, K. Jõgar, K. Hiiesaar, A. Kuusik and P. Põldma

Institute of Agricultural and Environmental Sciences, Estonian University of Life Sciences,Kreutzwaldi St. 64, 51014 Tartu, Estonia; e-mail: luule.metspalu@emu.ee

Abstract:

The effects of Neem EC (M/S RYM Exports – The Indian Neem Tree Company, 1% azadirachtin) were assessed on the Large White Butterfly, Pieris brassicae – a major pest of cruciferous plants. Duration of the larval stage, mortality of larvae and prepupae, and weight of pupae were studied. The time needed for completion of the larval stages by individuals fed on treated cabbage increased significantly, compared with the control: 16–37 days in the test variant, versus 11–18 days in the control. Neem EC also induced high mortality, caused by lethal failures of larval-larval and larval-pupal ecdysis, which were typical for insecticides possessing morphogenetic activity commonly referred to as IGR-activity. The mortality of larvae and prepupae in the test variant was significantly higher than in the control. Considerably fewer pupae were gained in the test variant than in the control variant. The pupae of larvae that had been feeding on the control were significantly heavier than those of the larvae feeding on the treated plants. The experiment revealed that Neem EC had both toxic and antifeedant/deterrent effects but also acted as a growth regulator for P. brassicae larvae.

Key words:

Influence of food on the growth, development and hibernation of Large White Butterfly (Pieris brassicae)

L. Metspalu1, K. Hiiesaar1, J. Jõudu2 and A. Kuusik1

1Institute of Plant Protection, Estonian Agricultural University, Kreutzwaldi 64, 51014 Tartu, Estonia; e-mail: mluule@eau.ee
2Department of Field Crop Husbandry, Estonian Agricultural University, Kreutzwaldi 64, 51014 Tartu, Estonia

Abstract:

The abundance of Large White Butterfly (LWB), Pieris brassicae fluctuates from year to year, and a peak in the population is reached in every five to seven years, after which there occurs an abrupt decrease in the abundance. The natural checks of the population are primarily weather, parasitoids and pathogens, but the quality of food is also an important factor. The criteria for estimating the influence of food were the duration of caterpillar stage, the mortality rate of caterpillars and prepupae, the weight of pupae and the winter mortality of diapausing pupae. Foodplants: Brassica oleracea var. capitata f. alba, B. oleracea var. capitata f. rubra, B. oleracea var. gemmifera, B. oleracea var. botrytis, B. oleracea var. acephala, B. napus var. napobrassica, Tropaeolum majus, Armoracia rusticana.

In our experiments, the most unsuitable foodplants for larvae were Tropaeolum majus and Armoracia rusticana. There appeared a high mortality rate among caterpillars feeding on both of them as well as among their hibernating pupae. It can be concluded that one of the reasons for the remarkable decrease in the pest population following the massive reproduction of LWB is the high mortality rate of caterpillars growing on less valuable foodplants. The pupae are underweight and, in most cases, they perish during winter.

Key words:

foodplants, hibernation, Large White Butterfly, larval mortality, Pieris brassicae, pupal body mass