Correlation between Coleoptera abundance in cattle excrements and pesticide contamination of nature conservation areas grazed by cattle.

The aim of this study was to explore the relationship between pesticide contamination at 16 locations in 14 Dutch nature conservation areas and the abundance of Coleoptera (among which dung beetles) in excrements of grazing cattle. A wide spectrum of pesticides was measured in soil, vegetation and excrements of cattle, obtained from all locations. In the fresh dung pats sampled for chemical analysis, beetle numbers were counted and beetle species were identified. In total, 31 different pesticides (including some metabolites) were detected: 14 in fresh excrements, 17 in soil and 20 in vegetation. Total pesticide concentrations in soil, vegetation and excrements varied between 2.6 and 200 µg kg -1 dry matter. In vegetation, the most frequently encountered classes of pesticides (including some of their metabolites) were fungicides (9), herbicides (4) and insecticides (6). The total number of Coleoptera beetles in dung pats correlated negatively with the total concentration of insecticides in vegetation (Kendall's τ -0.501 at p < 0.05). The total concentrations of herbicides and fungicides were not statistically significant correlated with Coleoptera beetle numbers in the dung pats. Yet, the concentration of one single herbicide, viz. chlorpropham in vegetation correlated significantly negative with Coleoptera counts (Kendall's τ -0.603 at p < 0.01).

Presence of pesticides and biocides at Dutch cattle farms participating in bird protection programs and potential impacts on entomofauna.

In spite of meadow bird protection programs, a severe decline of meadow birds is taking place in the Netherlands. It is hypothesized that pesticides and other agrochemicals may contribute to this decline through a negative impact on the entomofauna; a very important food source of meadow birds and especially of their chicks. The present study analysed the presence of 664 pesticides (including biocides and some metabolites) in soil, concentrated feed, manure and some fodder samples from 23 cattle farms in the province of Gelderland (the Netherlands). Furthermore, the presence of 21 anti-parasitic medicines in manure from storage facilities was analysed. For farms practicing field grazing, the number of dung beetles in field samples of fresh manure was determined and a potential relationship with the presence of pesticide residues was explored. Of the 23 farms included in present study, 22 participated in meadow bird protection schemes. A total of 129 different pesticides (including biocides and metabolites) was detected, of which 115 at the 15 conventional farms and 69 at the 8 certified organic farms. The average total amount of pesticide residues detected tended to be lower at organic cattle farms than at conventional farms; for organic concentrated feed this difference was significant at a factor of 3.7. A significant negative correlation was found between the estimated daily intake of insecticides by cattle through the consumption of concentrated feed and hay, and the numbers of dung beetles detected in fresh manure samples in the field. We discuss the most important insecticides detected in concentrated feed and hay, and conclude that their quantities in manure and feed, if compared with LR50 values, give a reason for concern. More research is needed to establish the role of agrochemicals in the decline of meadow birds.