Tag Archives: mortality

465-470 L. Metspalu, K. Jõgar, A. Ploomi, K. Hiiesaar, I. Kivimägi and A. Luik
Effects of biopesticide Neem EC on the Mamestra brassicae L. (Lepidoptera, Noctuidae)
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Effects of biopesticide Neem EC on the Mamestra brassicae L. (Lepidoptera, Noctuidae)

L. Metspalu, K. Jõgar, A. Ploomi, K. Hiiesaar, I. Kivimägi and A. Luik

Estonian University of Life Sciences, Institute of Agricultural and EnvironmentalSciences, Kreutzwaldi Str. 64, 51014 Tartu, Estonia; e-mail: Luule.Metspalu@emu.ee

Abstract:

Third instars larvae of the cabbage moth, Mamestra brassicae L. were exposed to Neem EC (M/S RYM Exports, The Indian Neem Tree Company) by a leaf-dip experiment (concentration of azadirachtin – 100 ppm). The after-treatment parameters studied the duration of the larval stage, mortality, and weight of pupae. Neem EC has shown significant prolongation in the development of larvae of M. brassicae: 18.5 days in the test variant, versus 14.8 days in the control. Neem EC also caused lethal failure of larval-larval and larval-pupal ecdysis, which is typical for insecticides possessing morphogenetic activity commonly referred to as IGR-activity. The mortality of larvae, prepupae and pupae in the test variant was significantly higher than in the control. The experiment in laboratory revealed that Neem EC inhibited larval development, greatly increased mortality, had antifeedant/deterrent effects and acted as a growth regulator for M brassicae larvae and pupae.

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21–30 K. Hiiesaar, L. Metspalu, J. Jõudu and K. Jõgar
Over-wintering of the Colorado potato beetle (Leptinotarsa decemlineata Say) in field conditions and factors affecting its population density in Estonia
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Over-wintering of the Colorado potato beetle (Leptinotarsa decemlineata Say) in field conditions and factors affecting its population density in Estonia

K. Hiiesaar, L. Metspalu, J. Jõudu and K. Jõgar

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

Abstract:

The adaptation of Colorado potato beetles (CPB) (Leptinotarsa decemlineata Say) to low temperatures has been the basis for the formation of a local permanent population in Estonia. The number of this pest fluctuates in different years on a large scale. The hibernation of the beetles in field conditions during the years 2000–2005 was observed and some factors influencing the beetles’ mortality was discussed in this study. Soil with a lighter texture – loamy sand proved better for the hibernation of CPB than clay loam soil with a heavier texture. 30 cm confirmed to be more suitable depth for hibernation than 50 cm, demonstrating lower mortality rate. Every autumn CPB populations were differently prepared for hibernation: part of the beetles burrowed themselves into the soil considered to be ready for over-wintering, and there were more survivals than among the beetles staying on the soil surface: that could not complete their maturation feeding. The temperature may become lethal for a majority of the hibernating population only during extreme winters when the temperature falls to -30oC for a longer period of time. During our observation period, it happened only once: in 2002/2003. In more mild winters there were no problems with over-wintering: about two third of the beetles survived in clay sand and about a half in loamy clay soil. It is difficult to predict the annual damage caused by CPB because the Estonian population consists of adapted over-wintered beetles and beetles migrated from southern regions. In some years we have had a great number of immigrant beetles and, in some years, no immigration has occurred.

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