The Sub-lethal Effect of Pesticides on Beneficial Arthropods

Pesticides are designed to be toxic to target noxious organisms that cause damage on crops and economic losses. However, some active ingredients can be harmful to the environment and to non-target organisms (99, 101) despite the efforts of research to develop and promote ecologically safer and more selective molecules. Among non-target organisms, arthropod natural enemies are particularly important for crop pests control and in case of disruption of this activity due to pesticides, pest outbreaks may occur. For this reason a large number of laboratory, semi-field and field studies have been carried out in the last decades evaluating the acute or chronic toxic effects of chemicals on the biology and behavior of beneficial in terms of disruption of life span, development rate, fertility, searching behavior, etc. (103, 104).

One of the major purposes of Integrated Pest Management (IPM) strategies is to combine the safe and sustainable use of pesticides with biological control agents. Therefore, the correct evaluation of side-effects of pesticides on beneficial is a crucial point for the application of current IPM strategies (103) which are widely and successfully adopted in Italian citrus groves. Estimating the compatibility of pesticides with biological control agents is a work in progress and a continuous information upgrade is needed on newly authorized agrochemicals and their side-effects, particularly in complex agroecosystems such as citrus.

A key element of pest management programs in agroecosystems is to build an understanding of the impacts on non-target and beneficial insects (106). The use of insecticides against insect-pests still prevails as one of the main pest management tools in most agricultural settings, in addition to having potential consequences for arthropod pest resurgence (108).

Insecticides may block some physiological or biochemical processes, impacting survival, growth, development, reproduction and behavior of natural enemies of insect pests (106). Even at non-lethal levels, insecticides can still influence behavior, although there have been few detailed studies concerning the potential effects of sublethal insecticide doses on the behavior of beneficial arthropods. In general, sublethal insecticides levels affect reproduction, orientation, feeding, oviposition and learning.

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