Nutritional ecology bridges the gap between mites’ biological and ecological research results under Mediterranean environment

Document Type : Original research articles

Author

Plant Protection Research Institute, Agric. Res. Center, Giza, Egypt

Abstract

Under Mediterranean conditions a conflict between mite laboratory studies concerning thermal effects on growth durations, rates, life table parameters and field population dynamics was observed. Laboratory studies aim at determining growth rates at different temperatures are conducted to elucidate field ecological patterns. Laboratory growth rate results can be presented mathematically within a certain range as linear relationship. It is the base of Degree–Day models used for prediction models. Under field conditions maximum and minimum temperatures and mean RH are considered as the influential weather factors. Under Mediterranean moderate climate and artificial irrigation systems, annual crops are produced throughout the year and some crops and perennials grow year around. The change in mite pest populations shows non–linear relationships during each plant growth seasons regardless of the change in environmental factors. This contradicts lab results at constant temperatures. Considering nutritional ecology bridges this gap. The change in available nutritional value (which is variable during the growing season) becomes the main factor. This factor is affected by host plant biological phenomena (different stages of growth and their nutritional contents). This factor is a dynamic one and can be included mathematically as plant age of the third degree (i.e. X, X2 andX3, respectively) in a polynomial equation along with other environmental factors. The regression model becomes (Y = a ± b1 Tmax ± b2 Tmin± b3 RH ± b4 X ± b5 X2 ± b6 X3). Published results reveal that this factor is more influential on mite population dynamics than environmental ones.

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