Side effects of insecticides on aphidius rhopalosiphi (Hym.: Aphidiidae) In laboratory

Compatibility of insecticides and fungicides with the zoophytophagous mirid predator Nesidiocoris tenuis

Nesidiocoris tenuis (Reuter) (Hemiptera: Miridae) is an effective predator of multiple pests of vegetable crops, such as thrips, mites, aphids, whiteflies, leafminers. It is mass-reared and released for augmentative biocontrol programs mainly aimed at controlling whiteflies and Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) in greenhouses and open field. We evaluated the lethal and sublethal toxicity upon N. tenuis adults of label doses of three insecticides (pyriproxyfen, spirotetramat, cypermethrin) and seven fungicides (benomyl, chlorothalonil, copper oxychloride, cyazofamid, fluopicolide + propamocarb hydrochloride (FPH), penconazol, trifloxystrobin) commonly used in various crops. Two exposure routes were tested: (i) contact with dry residues of insecticides or fungicides on tomato sprouts and (ii) multiple exposure to these chemicals via topical sprays on adults which foraged on treated sprouts; and fed on treated eggs of Ephestia kuehniella (Zeller) (Lepidoptera: Pyralidae) simultaneously. Mortality and reproductive capacity were investigated as indicators of lethal and sublethal effects on N. tenius. The tested insecticides and fungicides were all classified as harmless when predator was exposed only to the dry residues of each. However, the multiple exposure to either cypermethrin, benomyl, chlorothalonil, copper oxychloride or trifloxystrobin caused significant mortality of N. tenuis adults. Cypermethrin also significantly reduced its reproductive capacity. Interestingly, N. tenuis produced a higher number of progeny when exposed to fungicides penconazol and FPH in both exposure scenarios. Overall, findings suggest that the two insecticides, pyriproxyfen and spirotetramat but not cypermethrin, and all tested fungicides can be considered compatible with N. tenuis.

Efficacy of a long-lasting bifenthrin-treated net against horticultural pests and its compatibility with the predatory mite Amblyseius swirskii and the parasitic wasp Eretmocerus mundus

BACKGROUND

Insecticide-treated nets (ITNs) have been investigated recently for their use in agriculture. Depending on the insecticide, the hole size and the way they are produced, these nets can target different pests and therefore they could be interesting options for use in integrated pest management (IPM). As the information on their compatibility with beneficial fauna is practically negligible, in this work we have tested the compatibility of an experimental bifenthrin long-lasting insecticide-treated net (LLITN) with Amblyseius swirskii and Eretmocerus mundus, important natural enemies of whiteflies and thrips, under laboratory, semi-field and commercial greenhouse conditions.

RESULTS

In the laboratory, the treated net was very deleterious to adults of both natural enemies, after 72 h exposure. However, in choice tests with Y-tubes, both natural enemies were neither attracted nor repelled by the treated net and no short-term mortality was detected in individuals that had crossed it. No deleterious effects on the E. mundus beneficial capacity were detected in semi-field trials. In field trials, the LLITN proved to be compatible with A. swirskii while decreasing pest densities.

CONCLUSIONS

Bifenthrin LLITN studied could be a valuable method for reducing pest population infestations in IPM programmes while being compatible with biocontrol agents. © 2017 Society of Chemical Industry.

Sublethal impact of paraquat on the life span and parasitic behavior of Diaeretiella rapae M'Intosh

This study focuses on assessing the impact of sublethal doses of paraquat on the survival, the emergence, the life span and the parasitic behavior of Diaeretiella rapae M'Intosh (Hymenoptera: Braconidae). The impact of sublethal doses was measured at room temperature using different densities of the cabbage aphid Brevicoryne brassicae. The results reveal that the field dose of paraquat caused 100% mortality in D. rapae. The percentage emergence of D. rapae decreased from 80.5% in the control group to 71.5% when treated with the lowest concentration of paraquat. Similarly, the life span of parasitoids that emerged from the mummy treated with paraquat also decreased significantly. Oviposition capability and ovipositor thrusting frequency of D. rapae also treated with sublethal dose paraquat decreased significantly along with a shortened patch residence time in the foraging area.

Effects of organic-farming-compatible insecticides on four aphid natural enemy species

BACKGROUND

The toxicities of pyrethrins + rapeseed oil, pyrethrins + piperonyl butoxide (PBO), potassium salts of fatty acids and linseed oil were assessed in the laboratory on the parasitic wasp Aphidius rhopalosiphi (Destefani-Perez), the ladybird Adalia bipunctata (L.), the rove beetle Aleochara bilineata (Gyll.) and the carabid beetle Bembidion lampros (Herbst.). The methods selected were residual contact toxicity tests on inert and natural substrates.

RESULTS

Both the pyrethrin products led to 100% mortality in the adult parasitic wasps and ladybird larvae on glass plates and plants. The pyrethrins + PBO formulation was toxic for B. lampros on sand and natural soil, but the pyrethrins + rapeseed oil formulation was harmless for this species. Insecticidal soaps were harmless for all these beneficial species. None of the tested products significantly affected the parasitism of the onion fly pupae by A. bilineata.

CONCLUSION

The results indicated the potentially high toxicity of natural pyrethrins for beneficial arthropods. Although this toxicity needs to be confirmed in field conditions, the toxicity levels obtained in the laboratory were similar to or higher than those of several synthetic insecticides known to be toxic in the field. Insecticidal soaps could be considered as an alternative for aphid control in organic farming in terms of selectivity.

A multi-step bioassay to assess the effect of the deltamethrin on the parasitic wasp Aphidius ervi

Insecticides are widely used for crop protection. Effectiveness of pesticides and beneficial arthropods in an Integrated Pest Management (IPM) program requires a full understanding of how specific pesticides alter natural enemy effectiveness. This may require evaluation of chemicals at different life stages of the insect considered, on different physiological and behavioural components, and also on population dynamic components such as recolonization capacities after a pesticide treatment. Aphidius ervi Haliday (Hymenoptera: Braconidae) is an aphid parasitoid commonly used for the biological control of aphid populations. In this work, our aim was to assess the effects of deltamethrin (pyrethroid) treatments on this parasitoid using a multi-step bioassay. We evaluated its effects on parasitoid emergence, adult survival and longevity, and host searching. Two exposure methods were used, topical and spray, to evaluate impact of the deltamethrin field rate (6.25ga.i./ha) and also to compare the methods of exposure. A four-armed olfactometer was used to investigate effect of deltamethrin on host searching behaviour. When applied at the rate of field exposure, deltamethrin reduced the adult longevity but not the rate of emergence from mummies. Effects varied between the two exposure methods. Two indices were defined: the "population survival index" to measure capacity of parasitoids to recolonize a treated field and the "reproductive potential" to estimate the reduction in reproduction as a function of longevity decrease. These indices predicted effects of deltamethrin on A. ervi in terms of mortality and reduction of recolonization capacities. However, adults that survived residual exposure to deltamethrin retained their ability to orient to host odours. The implications of results in IPM and interest of the methodology used are both discussed.