Results of the second joint pesticide testing programme by the IOBC/WPRS-Working Group “Pesticides and Beneficial Arthropods”1

Calibration of laboratory derived indices for non-target arthropod risk assessment with field data for plant protection products

The Hazard Quotient (HQ) compares field application rate to intrinsic toxicity assessed with sensitive indicator species. As a hazard indicator for risk assessment, the HQ must be calibrated against measured effects under field conditions. Because protection goals may be context specific, we analyse how choice of acceptance criteria affects setting of the HQ and calibrate HQ for various scenarios under the strict condition that no false negative conclusions may be reached. We use Non-Target Arthropod toxicity data from laboratory studies on inert (Tier 1) and on natural substrates (Tier 2) and calibrate the HQ using application rates and arthropod abundance counts from field studies in orchards, arable fields, and hay meadows in 34 locations in Western Europe. With 21 formulations (17 active substances) tested in mostly multi-rate field studies, our reference data base has 120/121 values at Tier 1/Tier 2, respectively. We use the Proportion of Affected Taxa and Duration of Effect to jointly define acceptance criteria, starting with No Observed Effects. Absence of field effects is correctly predicted with HQ < 1.3 at Tier 1 and HQ < 0.48 at Tier 2, but these settings result in a high proportion of false positive outcomes. Increasing accepted duration of effect from 0 to 4 to 8 weeks results in HQ-threshold changes from 1.3 to 6.4 to 250 for Tier 1 studies and from 0.48 to 1.1 to 5.7 for Tier 2 studies. This coincides with a clear decrease in false positive outcomes. Recovery within a year is correctly concluded for 73% of the products passing the corresponding Tier 1 HQ < 2600 and for 92% of products at Tier 2 (HQ <230). Our analysis shows that the calibration is appropriate for a broad geographical range, for in-field and off-field situations and for phytophagous and non-phytophagous species alike.

Susceptibility of different developmental stages of Trichogramma parasitoids to insecticides commonly used in the Mediterranean olive agroecosystem

Insecticide application and augmentative parasitoid releases are often considered incompatible. However, pesticide applications and parasitoid releases can be integrated into a pest management scheme if there is careful time scheduling of these interventions. In this study, we assessed the influence of commonly used insecticides (chlorpyrifos-methyl, deltamethrin, pyriproxyfen, thiamethoxam) in olive agroecosystems to two currently present Trichogramma parasitoids in the Mediterranean basin. Exposure to insecticides in relation to parasitoid's development was also tested. Both, insecticide type and application time influenced parasitism and the emergence rates of the two parasitoid species. Chlorpyrifos-methyl had the strongest impact on parasitoids resulting in low numbers of emerged adults followed by deltamethrin. The two parasitoids also exhibited different levels of susceptibility to the insecticides used. Potential integration of insecticides to integrated pest management using Trichogramma parasitoids is discussed.

Spiders (Araneae) in the pesticide world: an ecotoxicological review

Being one of the most abundant and species-rich groups of natural enemies occurring in all agroecosystems, spiders are variably affected by pesticide applications. Here, a review is given of research on spider ecotoxicology. More than 40 species of spiders and almost 130 pesticides (acaricides, insecticides, fungicides and herbicides) have been tested so far in the field or under laboratory conditions. Field studies show that the degree of population reduction following pesticide application is a function of a number of factors inherent to pesticides, crops and spider species (guilds). These studies also revealed indirect effects via habitat and prey disruption. Among laboratory studies, a number of papers have investigated only the direct lethal effect. A meta-analysis of these data reveals that spiders are mainly affected by acaricides and insecticides, particularly neurotoxic substances. Currently, ecotoxicological research on spiders is focused more on direct sublethal effects on a variety of behavioural traits (locomotion, predation, web-building, reproduction, development) and physiology. Yet a standardised approach to the evaluation of sublethal effects is lacking. A few studies have provided some evidence for hormesis in spiders. Future research should be more concentrated on sublethal effects and the estimation of long-term changes in spider populations as a result of pesticide treatment.

Screening Commercially Available Entomopathogenic Biocontrol Agents for the Control of Aethina tumida (Coleoptera: Nitidulidae) in the UK

The Small hive beetle, Aethina tumida, is an invasive pest of honey bees. Indigenous to sub-Saharan Africa, it has now become established in North America and Australia. It represents a serious threat to European honey bees. Commercially available entomopathogenic agents were screened for their potential to control beetle larvae. Entomopathogenic fungi investigated had minimal impact. The nematodes Steinernema kraussei and S. carpocapsae provided excellent control with 100% mortality of larvae being obtained. Sequential applications of the nematodes following larvae entering sand to pupate also provided excellent control for up to 3 weeks. The information gained supports the development of contingency plans to deal with A. tumida should it occur in the UK, and is relevant to the management of Small hive beetle where it is already present.

Characterisation of adult green lacewing (Chrysoperla carnea) digestive physiology: impact of a cysteine protease inhibitor and a synthetic pyrethroid

BACKGROUND

In spite of concern regarding potential non-target effects of GM crops, few studies have compared GM pest control with conventional methods. The impacts of cypermethrin and oilseed rape expressing oryzacystatin-1 (OC-1) were compared in this study on the predator Chrysoperla carnea (Stephens).

RESULTS

Adults fed purified rOC-1 showed a subtle shift in digestive protease profile, with an increasing reliance on serine proteases (chymotrypsin), increase in aspartic proteases and a slight reduction in elastase activity. Although there were no effects on mortality, onset of oviposition was delayed; however, once egg production commenced, egg laying and hatching success rates were comparable with those of controls. Oryzacystatin-1 expressed in pollen showed no detrimental effects. Cypermethrin had no effect on mortality owing to high levels of non-specific esterase activity resulting in partial breakdown of the insecticide. In spite of this, there was a significant delay in onset of oviposition and a significant reduction in egg production and viability.

CONCLUSION

This study demonstrates the potential for pest management to impact on predators, but importantly it highlights the ability of the predator to detoxify/respond to treatments with different modes of action. In this case, exposure to an insecticide carried a greater fitness cost than exposure to a protease inhibitor expressed in transgenic crops.

Susceptibility of adult Coccinella septempunctata (Coleoptera: Coccinellidae) to insecticides with different modes of action

Five insecticides (pyriproxifen, imidacloprid, deltamethrin + heptenophos, lambda-cyhalothrin and Bacillus thuringiensis Berliner subsp. tenebrionis) were examined in the laboratory for their acute detrimental side-effects at field rates on adult seven-spot ladybird beetle, Coccinella septempunctata L. The toxicity of the preparations was determined by measuring the acute surface contact effects (dried spray on leaves of Philadelphus coronarius L.), except for B. thuringiensis where mixed pollen was treated. Four to six concentrations were tested (pyriproxifen 12.5, 25, 50, 100, 200, 400 mg AI litre(-1); imidacloprid 62.4, 125, 250, 500 mg AI litre(-1); deltamethrin + heptenophos 26.4, 53.1, 106.3, 212.5 mg AI litre(-1); lambda-cyhalothrin 1.1, 3.4, 10, 30 mg AI litre(-1); B. thuringiensis 1.5, 3.0, 12.0, 48, 192, 768 mg AI litre(-1)), with 22 adults exposed per concentration. All tests were conducted in the laboratory of the Plant Protection Department (University of Debrecen, Hungary) at 22-25 degrees C, 40-60% RH, under a 16:8 h light:dark photoperiod in 1998-1999. Data were analyzed by probit analysis, probit transformation and analysis of variance. According to different categories of evaluation, pyriproxifen, imidacloprid and B. thuringiensis subsp. tenebrionis seem to be safe for C. septempunctata adults but the other two preparations were moderately harmful to them, which requires further semi-field or field tests to measure their real effect under field conditions.