Using organic-certified rather than synthetic pesticides may not be safer for biological control agents: Selectivity and side effects of 14 pesticides on the predator Orius laevigatus

The generalist predator Orius laevigatus (Fieber) (Hemiptera: Anthocoridae) is a key natural enemy of various arthropods in agricultural and natural ecosystems. Releases of this predator are frequently carried out, and it is included in the Integrated Pest Management (IPM) programs of several crops. The accurate assessment of the compatibility of various pesticides with predator activity is key for the success of this strategy. We assessed acute and sublethal toxicity of 14 pesticides on O. laevigatus adults under laboratory conditions. Pesticides commonly used in either conventional or organic farming were selected for the study, including six biopesticides, three synthetic insecticides, two sulfur compounds and three adjuvants. To assess the pesticides' residual persistence, the predator was exposed for 3 d to pesticide residues on tomato sprouts that had been treated 1 h, 7 d or 14 d prior to the assay. The percentage of mortality and the sublethal effects on predator reproductive capacity were summarized in a reduction coefficient (E-x) and the pesticides were classified according to the IOBC (International Organization for Biological Control) toxicity categories. The results showed that the pesticides greatly differed in their toxicity, both in terms of lethal and sub lethal effects, as well as in their persistence. In particular, abamectin was the most noxious and persistent, and was classified as harmful up to 14 d after the treatment, causing almost 100% mortality. Spinosad, emamectin, metaflumizone were moderately harmful until 7 d after the treatment, while the other pesticides were slightly harmful or harmless. The results, based on the combination of assessment of acute mortality, predator reproductive capacity pesticides residual and pesticides residual persistence, stress the need of using complementary bioassays (e.g. assessment of lethal and sublethal effects) to carefully select the pesticides to be used in IPM programs and appropriately time the pesticides application (as function of natural enemies present in crops) and potential releases of natural enemies like O. laevigatus. (C) 2012 Elsevier Ltd. All rights reserved

Life stage-dependent susceptibility of <em>Aphytis melinus</em> DeBach (Hymenoptera: Aphelinidae) to two pesticides commonly used in citrus orchards

International audienceThe assessment of pesticides compatibility with natural enemies is recommended before including agrochemicals in integrated and organic pest management schemes. The lethal and sublethal effects of a mineral oil and a juvenile hormone mimic (pyriproxyfen), on adults and larvae of Aphytis melinus, a key ectoparasitoid of armored scale insect pests of citrus, such as Aonidiella aurantii, were evaluated. Mineral oil caused very high mortality on the adults, while a lower acute toxicity was recorded on young instars. No significant effects on their reproduction capacity and on the sex-ratio of the progeny were observed. Pyriproxyfen had neither lethal nor sublethal effects (in terms of survived female fertility) on A. melinus adults. However, parasitoid larvae exposed to this insecticide suffered strong acute toxicity and fertility reduction (progeny number and proportion of female progeny). When adults were offered the choice to parasitize treated and untreated scales they significantly preferred the control ones, and when they were exposed to only treated scaled the parasitism rate was significantly lower only with mineral oil-treated hosts. The significant differences in the susceptibility of the two parasitoid instars highlight the importance of including this aspect in pesticide risk assessment procedures and in the choice of the pesticide and of the treatment timing in the field. Overall, the results indicate potential for integrating A. melinus, both naturally present and artificially released, and these insecticides only by appropriate timing of insecticide spraying and parasitoid releases

Potential for management of Protopulvinaria pyriformis (Cockerell) (Hemiptera: Coccidae) in organic avocado in eastern Sicily, Italy

Organic avocado (Persea americana Mill. (Lauraceae) farming is a growing industry in eastern Sicily, and in this environment Protopulvinaria pyriformis (Cockerell) (Hemiptera: Coccidae) is a key pest. Biological control strategies against this invasive scale are thus crucial for the sustainability of this cropping system. A field trial was performed to record the natural enemy complex in early autumn, and for comparing the efficacy of a paraffinic oil application (Biolid E® at 2L/ha), of the release of adults (1/m2) of the predator Cryptolaemus montrouzieri Mulsant (Coleoptera: Coccinellidae), and of their combined application, i. e. oil spray and after one week predator release. In the pretreatment sampling a high proportion of ovipositing female, 38. 64% of the entire population, was recorded. The natural parasitoid community of P. pyriformis consisted of two primary parasitoids and one facultative hyperparasitoid species. Metaphycus helvolus (Compere) (Hymenoptera: Encyrtidae) accounted for 81% of the parasitoids recovered; Microterys nietneri (Motschulski) (Hymenoptera: Encyrtidae) for 8%, and the secondary parasitoid Pachyneuron muscarum (L. ) (Hymenoptera: Pteromalidae) for 11%. The mean percentage of parasitism recorded was 2. 45%, however, an encapsulation rate of 1. 78% was also observed. Adults and larvae of generalist predators belonging to the genera Scymnus spp, Exochomus spp. (Coleoptera: Coccinellidae) and larvae of Chrysopa spp. (Neuroptera: Chrysopidae) were also noticed actively feeding on immature stages of the soft scale. The number of live scales (N2-oviposting females) was reduced by 54. 16, 55. 73 and 19. 58 % following the oil application, the oil plus predator release and predator alone, respectively. While, in the control plots the number of live scales increased by 23. 4%, and no changes in the presence of natural enemies was recorded in the sprayed plots. The recorded data suggest that any pesticide application should take into account and thus respect the activity of the rich natural enemy assemblage. In addition, artificial releases of C. montrouzieri were not able to effectively control the scale population

Efficacy of sulphur on Tuta absoluta and its side effects on the predator Nesidiocoris tenuis

The South American tomato pinworm, Tuta absoluta (Meyrick), is one of the major pests of tomato crop. Since its detection in the Mediterranean basin, it has been commonly controlled using chemical insecticides. However, inoculation and conservation of predatory mirids, integrated with sprays of selective insecticides, has been demonstrated to be a cost-effective strategy for controlling this pest. In this work, we tested the efficacy of two sulphur formulations, dustable and wettable powder, for controlling T. absoluta on tomato under greenhouse and open-field conditions. In addition, the side effects of both sulphur formulations on the predator, Nesidiocoris tenuis (Reuter), were evaluated under laboratory conditions. Dustable sulphur, applied weekly on tomato seedlings artificially infested with T. absoluta in greenhouse conditions, significantly reduced the infestation levels and was demonstrated to have a repellent effect on oviposition. Wettable sulphur was not effective for controlling T. absoluta populations in both greenhouse and open-field experim ents. In the side effect trials conducted with N. tenuis, only dustable sulphur resulted in being moderately harmful as a fresh residue and slightly harmful as a 7-day-old residue; no effects were recorded exposing the predator to 14-day-old sulphur residues. In contrast, wettable sulphur was classified as harmless to N. tenuis. Our results suggest that the use of sulphur, especially as dustable powder, could be considered as a tool in T. absoluta management strategies, although its side effects on N. tenuis should be taken into account. The implications of these results for the use of sulphur formulations in pest and disease management programmes in tomato crops are discussed

Stage-Related Defense Response Induction in Tomato Plants by Nesidiocoris tenuis

The beneficial effects of direct predation by zoophytophagous biological control agents (BCAs), such as the mirid bug Nesidiocoris tenuis, are well-known. However, the benefits of zoophytophagous BCAs’ relation with host plants, via induction of plant defensive responses, have not been investigated until recently. To date, only the females of certain zoophytophagous BCAs have been demonstrated to induce defensive plant responses in tomato plants. The aim of this work was to determine whether nymphs, adult females, and adult males of N. tenuis are able to induce defense responses in tomato plants. Compared to undamaged tomato plants (i.e., not exposed to the mirid), plants on which young or mature nymphs, or adult males or females of N. tenuis fed and developed were less attractive to the whitefly Bemisia tabaci, but were more attractive to the parasitoid Encarsia formosa. Female-exposed plants were more repellent to B. tabaci and more attractive to E. formosa than were male-exposed plants. When comparing young- and mature-nymph-exposed plants, the same level of repellence was obtained for B. tabaci, but mature-nymph-exposed plants were more attractive to E. formosa. The repellent effect is attributed to the signaling pathway of abscisic acid, which is upregulated in N. tenuis-exposed plants, whereas the parasitoid attraction was attributed to the activation of the jasmonic acid signaling pathway. Our results demonstrate that all motile stages of N. tenuis can trigger defensive responses in tomato plants, although these responses may be slightly different depending on the stage considered

Tested insecticides.

<p>* The maximum label rate for tomato with a volume of 1000L ha^-1of insecticide solutions were applied.</p><p>Tested insecticides.</p

Statistics from the multifactorial ANOVA used to analyze (A) the percentages of parasitoids found dead after 3 days of exposure to insecticides (mortality), (B) the total numbers of eggs laid (reproduction) and (C) the numbers of host larvae killed (biocontrol) by each <i>Bracon nigricans</i> female during the three days following the insecticide exposure.

<p><i>P</i> values indicates in bold are those significant at <0.05 level.</p

Sublethal effects on reproduction.

<p>Means (± SEM) of number of eggs laid in three days by each tested <i>Bracon nigricans</i> female previously exposed for three days to residues at three constant temperatures. Columns bearing the same letter (upper case letters: within the same temperature regime; lower case letters: within the same tested insecticide) are not significantly different (<i>P</i>>0.05; ANOVA with LSD post hoc test for multiple comparisons).</p

Combined Non-Target Effects of Insecticide and High Temperature on the Parasitoid <i>Bracon nigricans</i>

<div><p>We studied the acute toxicity and the sublethal effects, on reproduction and host-killing activity, of four widely used insecticides on the generalist parasitoid <i>Bracon nigricans</i> (Hymenoptera: Braconidae), a natural enemy of the invasive tomato pest, <i>Tuta absoluta</i> (Lepidoptera: Gelechiidae). Laboratory bioassays were conducted applying maximum insecticide label rates at three constant temperatures, 25, 35 and 40°C, considered as regular, high and very high, respectively. Data on female survival and offspring production were used to calculate population growth indexes as a measure of population recovery after pesticide exposure. Spinetoram caused 80% mortality at 25°C and 100% at higher temperatures, while spinosad caused 100% mortality under all temperature regimes. Cyantraniliprole was slightly toxic to <i>B</i>. <i>nigricans</i> adults in terms of acute toxicity at the three temperatures, while it did not cause any sublethal effects in egg-laying and host-killing activities. The interaction between the two tested factors (insecticide and temperature) significantly influenced the number of eggs laid by the parasitoid, which was the lowest in the case of females exposed to chlorantraniliprole at 35°C. Furthermore, significantly lower <i>B</i>. <i>nigricans</i> demographic growth indexes were estimated for all the insecticides under all temperature conditions, with the exception of chlorantraniliprole at 25°C. Our findings highlight an interaction between high temperatures and insecticide exposure, which suggests a need for including natural stressors, such as temperature, in pesticide risk assessments procedures.</p></div