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18 April
au
31 December 2016

Sélectivité des produits de protection des plantes à l’égard des arthropodes utiles

Selectivity of plant protection products with respect to useful arthropods

Context

Many crop pests are controlled naturally by various predatory and parasitic insects, generally referred to as ‘biological control agents’, ‘useful arthropods’ or ‘natural enemies’. Biological control using such insects permits savings on insecticide treatment in many cases. On the other hand, the elimination of the pests’ natural enemies due to the use of toxic plant protection products often leads to a higher incidence of pests. In the most extreme cases, increased pest infestation and the emergence of secondary pests lead to multiple insecticide treatments and the development of resistance. The use of the most selective plant protection products with respect to the pests’ natural enemies is part of sustainable agriculture and is economical in terms of input, environmentally compatible and favourable to public health.

Objectives

The aim of this research is to determine the toxicity of various pesticides used on field crops (wheat, potatoes) and in market gardening (carrots, peas, beans, etc.) with respect to the main useful arthropods occurring in Belgium and to disseminate the findings to farmers.

Description of tasks

The toxicity of the plant protection products used on winter wheat was determined with respect to the three main natural enemies of ear and leaf aphids, namely the cereal aphid parasitoid Aphidius rhopalosiphi (DESTEFANI-PEREZ) (Hym.; Aphidiidae) and aphid-eating syrphids and ladybirds. Nine insecticides and forty-six fungicides were assessed on A. rhopalosiphi and nine insecticides on syrphids and ladybirds. Suitable methods for the different species studied first had to be developed as a preliminary to this work. In order to draw up potato selectivity lists nineteen fungicides, eleven insecticides and four post-emergence herbicides were assessed on A. rhopalosiphi, the syrphid Episyrphus balteatus (Degeer) (Dip.; Syrphidae) and the ladybird Adalia bipunctata (L.) (Col.; Coccinellidae). The methods used involved both biological tests and chemical determination of pesticide deposits, carried out by the University’s Pesticide Research Laboratory. Based on the methods developed for the potato, the same species and two ground-acting useful arthropods, the rove beetle Aleochara bilineata Gyll. (Col.; Staphylinidae) and the ground beetle Bembidion lampros (Herbst) (Col.; Carabidae) were also included when drawing up selectivity lists for market garden crops, in view of their significance in this sector.

Results obtained

In the case of winter wheat, the research revealed the low general effect of fungicides on cereal aphid parasites. By limiting the use of some fungicides, it is possible that winter wheat can be protected in a way that is efficacious and cost-effective while preserving this important natural enemy. The results for insecticides are more uneven. While these products ultimately have little effect on cereal aphid parasites due to their relative resistance at the nymphal stage, none of the currently authorised insecticides are selective to both syrphids and ladybirds. Results for potatoes are similar to those for cereals. Spraying of potatoes against mildew has relatively little effect on aphid parasites and predators with the notable exception of one product which must not be used at certain times of year, as it promotes aphid growth. In the case of insecticides one recently authorised active ingredient is selective to aphid parasites, syrphids and ladybirds and stands out clearly from the other products, some of which are selective to one or two species but not to all of the useful insect fauna studied. In market garden crops first results indicate that many of the insecticides used as soil treatment to control the carrot fly are highly toxic to its predators, which hampers their use as part of integrated pest management programmes.

Contribution

Development of methods for assessing the effects of plant protection products on useful arthropods and use of these methods to determine toxicity in various crops. Extension booklet on the use of selective plant protection products in potato growing, available in French and Dutch.

Partners

-Gembloux Agricultural University, Pesticide Research Laboratory -IOBC Pesticides and Beneficial Organisms Working Group

Funding

  • FASFC - Federal Agency for the Security of the Food Chain
  • CRA-W - Walloon Agricultural Research Centre
  • SPF Public Health

Team