The feasibility and efficacy of early-season releases of a generalist predator (Forficula auricularia L.) to control populations of the RAA (Dysaphis plantaginea Passerini) in Southeastern France.

Augmentative biological control is not commonly used in commercial orchards. We used an exclusion system to evaluate the potential of early-season releases of the European earwig (Forficula auricularia L., Dermaptera: Forficulidae) for control of the rosy apple aphid (Dysaphis plantaginea Passerini, Hemiptera: Aphididae) in the spring of 2009 in two pesticide-free apple orchards. In order to conduct this experiment we successfully reared earwigs with a high survival rate of nymphs (more than 96%) which may have commercial application. There were three treatments in the study: (i) a 'release treatment' where we confined the released earwigs in the canopy by using a barrier system; (ii) an 'exclusion treatment' where we blocked free access of earwigs into the canopy using the same barrier system; and (iii) a 'control treatment' that represented the natural situation. Contrary to expectations, earwig releases did not reduce D. plantaginea populations. In general, the abundance of natural enemies and their groups did not differ significantly among treatments, except for earwigs. We observed that the exclusion systems we used successfully kept both earwigs and ants away from tree canopies; total numbers on trees in the 'exclusion treatment' were significantly lower than on the other two treatments. Due to the complexity and difficulty of evaluating augmentative releases of natural enemies in open orchard conditions, we conclude that new technical approaches to control site conditions are needed when conducting such studies.

Avoidance behaviour response and esterase inhibition in the earthworm, Lumbricus terrestris, after exposure to chlorpyrifos.

The avoidance response of earthworms to polluted soils has been standardised using a simple and low-cost test, which facilitates soil toxicity screening. In this study, the avoidance response of Lumbricus terrestris was quantified in chlorpyrifos-spiked soils, depending on the pesticide concentration and exposure duration. The inhibition of acetylcholinesterase (AChE) and carboxylesterase (CbE) activities was also determined as indirect measures of pesticide bioavailability. The effects of different chlorpyrifos concentrations were examined in a standardised test (two-chamber system) with 0.6, 3 and 15 mg/kg chlorpyrifos. A modification of the test involved a pre-exposure step (24, 48 or 72 h) in soils spiked with 15 mg/kg. In both protocols, earthworms were unable to avoid the contaminated soils. However, the esterase activities showed that all earthworms were exposed to chlorpyrifos. Acetylcholinesterase activity did not change in earthworms in the standardised behavioural test (0.58 ± 0.20 U/mg protein, mean ± SD; n = 72), whereas the CbE activity was significantly inhibited (62-87 % inhibition) in earthworms exposed to 3 and 15 mg/kg. In the modified test, earthworms had greatly inhibited AChE activity (0.088 ± 0.034 U/mg protein, n = 72), which was supported by reactivation of the inhibited enzyme activity in the presence of pralidoxime (2-PAM). Similarly, the CbE activity was significantly inhibited in earthworms with all treatments. This study suggests that the avoidance behaviour test for organophosphorus-contaminated soils could be supported by specific biomarkers to facilitate a better understanding of pesticide exposure and toxicity during this test.

Inhibition, recovery and oxime-induced reactivation of muscle esterases following chlorpyrifos exposure in the earthworm Lumbricus terrestris.

Assessment of wildlife exposure to organophosphorus (OP) pesticides generally involves the measurement of cholinesterase (ChE) inhibition, and complementary biomarkers (or related endpoints) are rarely included. Herein, we investigated the time course inhibition and recovery of ChE and carboxylesterase (CE) activities in the earthworm Lumbricus terrestris exposed to chlorpyrifos, and the ability of oximes to reactivate the phosphorylated ChE activity. Results indicated that these esterase activities are a suitable multibiomarker scheme for monitoring OP exposure due to their high sensitivity to OP inhibition and slow recovery to full activity levels following pesticide exposure. Moreover, oximes reactivated the inhibited ChE activity of the earthworms exposed to 12 and 48 mg kg(-1) chlorpyrifos during the first week following pesticide exposure. This methodology is useful for providing evidence for OP-mediated ChE inhibition in individuals with a short history of OP exposure (< or = 1 week); resulting a valuable approach for assessing multiple OP exposure episodes in the field.

Procedures for determining the pesticide sensitivity of indigenous soil algae: a possible bioindicator of soil contamination?

Soil algae are present in all kinds of soils, both arable and virgin, in large amounts and in great diversity. These photosynthetic microorganisms, which are concentrated in the top few centimeters of the soil profile, are organized in a community structure that varies depending on soil type, farming method and pesticide application. We first tested several extraction and conservation methods for soil algae, and a 14C incorporation procedure to evaluate the photosynthetic activity of these micro-organisms. In a second study, we assessed the sensitivity to atrazine of soil microalgae from two corn fields managed by different agricultural practices (conventional vs. organic). Changes in indigenous diatom communities were monitored, together with photosynthetic tests performed on the whole algal community. Comparison of the data for the treated field with those for the reference, untreated organic cornfield showed that previous atrazine application in the conventional cornfield had changed the species composition of the soil diatom communities. Short-term ecotoxicological tests, using photosynthetic activity as endpoint, also showed that the communities that had developed under pesticide stress were more tolerant to further atrazine application than the control communities. The stress caused by major environmental disturbances, such as ground dressing, was not sufficient to mask the difference between the two crops, suggesting that telluric microalgae could be used as indicators of xenobiotic contamination in soils. These initial findings about using soil microalgal communities as bioindicators are promising. In addition, their photosynthetic activity, which reflects their sensitivity to xenobiotic compounds, seems to be a relevant bioindicator of soil contamination.

Does the spatial distribution of the parasitic mite varroa jacobsoni oud. (Mesostigmata: varroidae) in worker brood of honey bee apis mellifera L. (Hymenoptera: apidae) rely on an aggregative process?

Varroa jacobsoni is an ectoparasite of honey bees which reproduces in capped brood cells. Multi-infestation is frequently observed in worker brood and can be interpreted as an aggregative phenomenon. The aim of this study was to determine whether the distribution of V. jacobsoni in worker brood cells relies on a random or an aggregative process. We studied the distribution of Varroa females in capped worker brood at similar age by comparing, by a Monte Carlo test, the observed frequency distribution of mites per cell to simulated distributions based on a random process. A complementary approach, using the "nearest neighbor distances" (NND) with Monte Carlo tests, was investigated to study the spatial distribution (a) between mites in different cells and (b) between infested cells in brood. The observed distributions did not differ significantly from that expected by a random process, and we conclude that there is no aggregation during invasion of V. jacobsoni in worker brood.