1,721,085 research outputs found
The effects of fungicides on non-target mites can be mediated by plant pathogens
No full textField tests are useful for the evaluation of the pesticides' impact in realistic use situations. However, the distinction between the direct and indirect effects of a pesticide is not always possible in field, with consequences on the conclusions about pesticides toxicity. Generalist predatory mites belonging to the Phytoseiidae family are widely considered as non-target organisms in pesticide side-effect evaluations. Plant pathogens of several cultivated plants can be of importance as food resources for various phytoseiids. Pesticides with fungicidal activity may have a direct impact on phytoseiids, but they can also have an indirect effect reducing food availability for predatory mites. Here, we present the results of field experiments performed on grapevine, where we investigate whether the availability of the plant pathogen grape downy mildew has an effect on fungicides impact on the predatory mites Typhlodromus pyri Scheuten and Amblyseius andersoni (Chant). In these experiments we used fungicides characterized by differential selectivity to predatory mites in laboratory: copper compounds, folpet, and mancozeb. Results indicated that the abundance of predatory mites was associated with the plant pathogen foliar symptoms presence. The presence of predatory mites was different among treatments in response of the toxicological traits of a pesticide (direct effects), but also as consequences of differential plant pathogen availability induced by fungicide applications (indirect effects). During the investigation, the variable plant pathogen spread on untreated control determined contrasting results on pesticides effect. We segregated the direct effects from the indirect food resource-mediated effects including a non-toxic reference in the experimental protocols. © 2010 Elsevier Ltd. All rights reserved
Grape downy mildew Plasmopara viticola, an alternative food for generalist predatory mites occurring in vineyards
No full textThe persistence of generalist predatory mites in scarcity or absence of prey is a requirement for successful biocontrol of herbivore mites. Pollen is an alternative food for generalist predatory mites. However, the presence of pollen in vineyards is often limited and thus other food sources should
contribute towards generalist predatory mite persistence. Relationships between the population increases of generalist phytoseiids with late-season spread of grape downy mildew (GDM) Plasmopara viticola have been reported. We testest the hypothesis that GDM could be a suitable food for the predatory mites Amblyseius andersoni and Typhlodromus
pyri. We compared the development times, oviposition rates and life-table parameters of predatory mites feeding on pollen or GDM in the laboratory. GDM supported the survival, development and oviposition of T. pyri and A. andersoni. GDM was a less suitable food source than pollen for both phytoseiid species and was more favorable for A. andersoni than for T. pyri. Implications for conservation biological control in vineyards are discussed
Impiego di formulati diversi a base di Bacillus thuringiensis Berl. nel controllo delle tignole della vite.
No full textEffects of potential food sources on biological and demographic parameters of the predatory mites Kampimodromus aberrans, Typhlodromus pyri and Amblyseius andersoni
No full textKampimodromus aberrans, Typhlodromus pyri and Amblyseius andersoni are generalist predatory mites important in controlling tetranychid and eriophyoid mites in European vineyards. They can persist by exploiting various non-prey foods when their main prey is absent or scarce. A comparative analysis of the effects of various prey and non-prey foods on the life history of these predators is lacking. In the laboratory, predatory mites were reared on herbivorous mites (Panonychus ulmi, Eotetranychus carpini and Colomerus vitis), a potential alternative prey (Tydeus caudatus) and two non-prey foods, i. e. the pollen of Typha latifolia and the mycelium of Grape downy mildew (GDM) Plasmopara viticola. Developmental times, survival, sex ratio and fecundity as well as life table parameters were estimated. Kampimodromus aberrans developed faster on E. carpini, C. vitis or pollen than on P. ulmi and laid more eggs on pollen than on prey. Low numbers of this predator developed on GDM infected leaves. Tydeus caudatus was not suitable as prey for any of the three predatory mites. Kampimodromus aberrans showed the highest intrinsic rate of population increase when fed on pollen. Developmental times of T. pyri on prey or pollen were similar but fecundity was higher on pollen than on P. ulmi. Typhlodromus pyri had higher intrinsic rates of population increase on C. vitis and pollen than on P. ulmi; E. carpini showed intermediate values whereas GDM resulted in the lowest rm values. Development of A. andersoni females was faster on pollen and C. vitis than on P. ulmi and GDM. Fecundity was higher on pollen and mites compared to GDM. Life table parameters of A. andersoni did not differ when predators were fed with prey or pollen while GDM led to a lower rm value. On a specific diet A. andersoni exhibited faster development and higher fecundity than T. pyri and K. aberrans. These findings improve knowledge on factors affecting the potential of predatory mites in controlling phytophagous mites in European vineyards. © 2012 Springer Science+Business Media B.V
Role of supplemental foods and habitat structural complexity in persistence and coexistence of generalist predatory mites
Full text linkPlant traits can influence the interactions between herbivore arthropods and their natural enemies. In these interactions generalist predators are often present, preying on herbivores and also on other arthropods in the same trophic guild. Variation in the strength of intraguild predation (IGP) may be related to habitat structural complexity and to additional resources outside the narrow predator-prey relationship. In this paper we study the food web interactions on grape, which involves two generalist predatory mites. We evaluated the effects of grape powdery mildew (GPM) as supplemental food, and habitat structural complexity provided by domatia. The inoculation of GPM resulted in higher predatory mite densities and reduced the negative impact of unfavorable leaf structure for one species. Access to domatia was the main factor in promoting population abundance and persistence of predatory mites. Access to domatia and GPM availability favored the coexistence of predatory mites at a low density of the intraguild prey. Our findings suggest that structural and nutritional diversity/complexity promote predatory mite abundance and can help to maintain the beneficial mites - plants association. The effect of these factors on coexistence between predators is influenced by the supplemental food quality and relative differences in body size of interacting species
Integrated pest control in viticulture in north-eastern Italy. 2. Grape moths and leafhoppers.
No full textThe effect of insecticides on the non-target predatory mite Kampimodromus aberrans: Laboratory studies
No full textThe side-effects of pesticides on predatory mites have been investigated at various levels and international teams (e.g., the IOBC/wprs Working Group "Pesticides and beneficial organisms") have selected a few species of predatory mites occurring in Central and Northern Europe as representative for such studies. Key biocontrol species occurring in Southern Europe have received much less attention. Kampimodromus aberrans is the most important predator of herbivorous mites in South-European vineyards treated with selective pesticides. The impact of pesticides on K. aberrans populations has been studied in field conditions whereas few toxicological tests have been conducted in the laboratory because of difficulties in rearing this species. A method for rearing K. aberrans in the laboratory has recently been set up allowing toxicological studies to be conducted. In this paper, a toxicological method to assess the effects of pesticides on K. aberrans is described and the effects of insecticides frequently used in European vineyards on two K. aberrans strains are reported. These strains were collected from vineyards treated with organophosphates. Insecticides characterized by different modes of action were selected for trials. Among these, etofenprox and spinosad were classified as harmful to predatory mites. Chlorpyrifos reduced predatory mite fecundity, and was classified as moderately harmful for both strains. The toxicity of thiamethoxam and flufenoxuron varied with the strain (low to moderate). Indoxacarb and methoxyfenozide appeared to be harmless or slightly harmful. Implications of this study for adopting IPM tactics with a reduced risk for K. aberrans are discussed. © 2013 Elsevier Ltd
Single and combined releases of biological control agents against canopy- and soil-dwelling stages of Frankliniella occidentalis in cyclamen
No full textFrankliniella occidentalis is a major pest in agriculture. Problems with its control are mainly due to pupation in the soil and resistance to insecticides. Biological control agents (BCA) can be used against thrips pests as an alternative to conventional insecticides. We evaluated the effectiveness of a number of BCA for control of F. occidentalis in cyclamen under greenhouse conditions. Three BCA (Amblyseius swirskii, Neoseiulus californicus and Orius laevigatus) were applied to the canopy and two (Macrocheles robustulus and Steinernema feltiae) to the soil in single and combined releases. Results showed that applications of predatory mites and nematodes achieved good control of F. occidentalis. Unsatisfactory control was obtained using O. laevigatus. The use of nematodes determined the extinction of thrips, but with a delay. The combination of nematodes in the soil and predatory mites in the canopy caused a more prompt reduction of thrips in flowers
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