Estimating ecotoxicological effects of pesticide drift on nontarget arthropods in field hedgerows

Abstract

When hedgerows grow in orchards where pesticides are applied, they can play a double role: Providing a barrier for chemical spray drift and as a refuge for beneficial arthropods such as pollinators and predators. Effectiveness of hedgerows as barriers to drift depends mainly on canopy density (that can be estimated through optical porosity) and wind speed. When optical porosity is low, the hedgerow can intercept a significant amount of spray drift and act as an effective barrier, but the intercepted pesticide can negatively affect the beneficial arthropods living there. A drift model was used to simulate drift in a hedgerow- vineyard system, and a deposition distribution model was used to calculate the pesticide spatial pattern distribution on a hedgerow with different optical porosity and wind speed conditions. The possible ecotoxicological effects were estimated for 28 active ingredients with different median lethal rates for two nontarget arthropods, Aphidius rhopalosiphi and Typhlodromus pyri. A spatialized risk assessment for a hedgerow is suggested to improve procedures based on application rate, standard drift, and vegetation distribution values, as in the hazard quotient approach. An alternative method for calculation of the exposure is also proposed, with a step-by-step example of a toxicity/exposure ratio calculation. The results highlighted the importance of the spatial pattern of drift and proved that a hedgerow can be an effective barrier against spray drift. Analysis of the toxicity/exposure ratio values showed that a hedgerow can continue its shelter and feeding function for nontarget arthropods when low-toxicity pesticides are used, there is no significant wind interference, or both.

Factors affecting the diet of the red fox (Vulpes vulpes) in a heterogeneousMediterranean landscape

“…They are mostly captured in oak forests and less in agricultural areas. This could be explained by the application of insecticides in agricultural crops, which eradicates invertebrate populations (Otto et al, 2009). Carnivores represented a small percentage in the red fox diet (Table 1), indicating that they are an alternative prey, as reported in other studies (Cavallini and Lovari, 1991;Lucherini et al, 1995;Palomares and Caro, 1999).…”

“…They are mostly captured in oak forests and less in agricultural areas. This could be explained by the application of insecticides in agricultural crops, which eradicates invertebrate populations (Otto et al, 2009).…”

Temperate Agroforestry Systems and Insect Pollinators: A Review

“…[ [125][126][127][128][129][130][131][132][133] Pesticide runoff mitigation Agroforestry practices can reduce pesticide exposure to pollinators by helping to capture pesticide runoff, prevent or slow pesticide movement through soil, and help break down some pesticides. [134][135][136][137][138] Refuge from pesticides Agroforestry practices may serve as a safe haven for pollinators from pesticides, if adequately protected from spray drift.…”

“…Pesticide spray drift can be divided into thermal drift (lighter droplets transported to high altitude), vapor drift (volatilization from target), and droplet drift (droplets moved off-target by ambient wind) [129]. By reducing wind speeds and trapping particles, windbreaks and other linear agroforestry plantings can decrease pesticide droplet drift by up to 80%-90% and thereby reduce direct exposure to pollinators [126][127][128][129]137,142,161,162]. These practices can be used to minimize drift from either leaving or coming onto a site.…”

A novel method for assessing risks to pollinators from plant protection products using honeybees as a model species

“…In a first attempt a default average LAI derived from Otto et al (2009) (for hedgerows and vegetation beneath the hedgerows: 3.5) was used to calculate the plant concentration.…”