Small-scale intraspecific life history variation in herbivorous spider mites (Tetranychus pacificus) is associated with host plant cultivar.

Life history variation is a general feature of arthropod systems, but is rarely included in models of field or laboratory data. Most studies assume that local processes occur identically across individuals, ignoring any genetic or phenotypic variation in life history traits. In this study, we tested whether field populations of Pacific spider mites (Tetranychus pacificus) on grapevines (Vitis vinifera) display significant intraspecific life history variation associated with host plant cultivar. To address this question we collected individuals from sympatric vineyard populations where either Zinfandel or Chardonnay were grown. We then conducted a "common garden experiment" of mites on bean plants (Phaseolus lunatus) in the laboratory. Assay populations were sampled non-destructively with digital photography to quantify development times, survival, and reproductive rates. Two classes of models were fit to the data: standard generalized linear mixed models and a time-to-event model, common in survival analysis, that allowed for interval-censored data and hierarchical random effects. We found a significant effect of cultivar on development time in both GLMM and time-to-event analyses, a slight cultivar effect on juvenile survival, and no effect on reproductive rate. There were shorter development times and a trend towards higher juvenile survival in populations from Zinfandel vineyards compared to those from Chardonnay vineyards. Lines of the same species, originating from field populations on different host plant cultivars, expressed different development times and slightly different survival rates when reared on a common host plant in a common environment

Effects on Lettuce Yield Parameters and Toxicological Safety Assessment of a Plant-Derived Formulation Based on Rosemary and Eucalyptus Essential Oils

Essential oils from medicinal and aromatic plants are increasingly recognized as a promising class of green molecules for use in crop production. In many cases, the beneficial aspects of a substance are not supported by sufficient toxicological safety testing, even though recent reports suggest that some compounds may be toxic to terrestrial or aquatic non-target species. It is, therefore, essential to investigate the possibility of adverse effects on non-target animals and humans exposed to these substances through the consumption of fruit and/or vegetables. The present study aims to examine the potential effects on yield and quality parameters and investigate the level of in vitro and in vivo toxicity of an Eco-product (EP) based on rosemary and eucalyptus essential oils, to provide a measure for safe use in the agricultural sector. The product was evaluated in lettuce crop production and indicated that one-time application of the EP formula increases yield, activating various secondary metabolism pathways of the plant to cope with oxidative stress. Cytotoxicity assays and in vivo acute oral and dermal toxicity studies suggest that the tested compound does not pose any significant health hazard, and the dissolved product can be classified in Category 5, according to the Globally Harmonized System of Classification and Labelling of Chemicals (GHS)

A critical analysis of the potential for EU Common Agricultural Policy measures to support wild pollinators on farmland

1. Agricultural intensification and associated loss of high‐quality habitats are key drivers of insect pollinator declines. With the aim of decreasing the environmental impact of agriculture, the 2014 EU Common Agricultural Policy (CAP) defined a set of habitat and landscape features (Ecological Focus Areas: EFAs) farmers could select from as a requirement to receive basic farm payments. To inform the post‐2020 CAP, we performed a European‐scale evaluation to determine how different EFA options vary in their potential to support insect pollinators under standard and pollinator‐friendly management, as well as the extent of farmer uptake. 2. A structured Delphi elicitation process engaged 22 experts from 18 European countries to evaluate EFAs options. By considering life cycle requirements of key pollinating taxa (i.e. bumble bees, solitary bees and hoverflies), each option was evaluated for its potential to provide forage, bee nesting sites and hoverfly larval resources. 3. EFA options varied substantially in the resources they were perceived to provide and their effectiveness varied geographically and temporally. For example, field margins provide relatively good forage throughout the season in Southern and Eastern Europe but lacked early‐season forage in Northern and Western Europe. Under standard management, no single EFA option achieved high scores across resource categories and a scarcity of late season forage was perceived. 4. Experts identified substantial opportunities to improve habitat quality by adopting pollinator‐friendly management. Improving management alone was, however, unlikely to ensure that all pollinator resource requirements were met. Our analyses suggest that a combination of poor management, differences in the inherent pollinator habitat quality and uptake bias towards catch crops and nitrogen‐fixing crops severely limit the potential of EFAs to support pollinators in European agricultural landscapes. 5. Policy Implications. To conserve pollinators and help protect pollination services, our expert elicitation highlights the need to create a variety of interconnected, well‐managed habitats that complement each other in the resources they offer. To achieve this the Common Agricultural Policy post‐2020 should take a holistic view to implementation that integrates the different delivery vehicles aimed at protecting biodiversity (e.g. enhanced conditionality, eco‐schemes and agri‐environment and climate measures). To improve habitat quality we recommend an effective monitoring framework with target‐orientated indicators and to facilitate the spatial targeting of options collaboration between land managers should be incentivised

The effects of timing and rate of release on population growth of Phytoseiulus persimilis reared on Tetranychus urticae

The purpose of this study was to determine the effects of the timing and rate of release on the population growth of Phytoseiulus persimilis (Acari: Phytoseiidae) reared on bean plants infested with two-spotted spider mite (TSM), Tetranychus urticae (Acari: Tetranychidae). Dwarf bean plants were infested with TSM and 20 P. persimilis females were introduced on each plant 3, 6, 9 and 12 days following TSM infestation. In another experiment, female P. persimilis were introduced at the rates of 5, 10 and 20 per plant 6 days after TSM infestation. The maximum per capita net population growth (MCPG) of P. persimilis was estimated as the maximum number of mobile stages observed on a plant during the course of the experiment divided by the initial number of females released on that plant. Both the timing and rate of release had a significant effect on the MCPG of P. persimilis. Releasing 20 P. persimilis on day nine resulted in an MCPG of 2.97, whereas releases on day 3, 6 or 12 resulted in MCPG values of less than 1.7. In the rate of release experiment, the highest MCPG (4.4) occurred when five female P. persimilis were released per plant, whereas releasing 10 and 20 predatory mites per plant led to MCPG values of 2.71 and 1.66, respectively. The findings indicate that the productivity of a P. persimilis rearing system may be significantly improved through optimization of the timing and/or rate of release. © 2010 Springer Science+Business Media BV

The effects of timing and rate of release on population growth of Phytoseiulus persimilis reared on Tetranychus urticae

The purpose of this study was to determine the effects of the timing and rate of release on the population growth of Phytoseiulus persimilis (Acari: Phytoseiidae) reared on bean plants infested with two-spotted spider mite (TSM), Tetranychus urticae (Acari: Tetranychidae). Dwarf bean plants were infested with TSM and 20 P. persimilis females were introduced on each plant 3, 6, 9 and 12 days following TSM infestation. In another experiment, female P. persimilis were introduced at the rates of 5, 10 and 20 per plant 6 days after TSM infestation. The maximum per capita net population growth (MCPG) of P. persimilis was estimated as the maximum number of mobile stages observed on a plant during the course of the experiment divided by the initial number of females released on that plant. Both the timing and rate of release had a significant effect on the MCPG of P. persimilis. Releasing 20 P. persimilis on day nine resulted in an MCPG of 2.97, whereas releases on day 3, 6 or 12 resulted in MCPG values of less than 1.7. In the rate of release experiment, the highest MCPG (4.4) occurred when five female P. persimilis were released per plant, whereas releasing 10 and 20 predatory mites per plant led to MCPG values of 2.71 and 1.66, respectively. The findings indicate that the productivity of a P. persimilis rearing system may be significantly improved through optimization of the timing and/or rate of release. © 2010 Springer Science+Business Media BV

Two-spotted spider mite in Cyprus: Ineffective acaricides, causes and considerations

Growers of greenhouse roses in Cyprus have recently reported failures of several acaricides against two-spotted spider mite (Tetranychus urticae Koch). To verify the cause of these failures we evaluated the effectiveness of seven acaricides against two rose and two cucumber spider mite populations in the laboratory. The acaricides included in our study represented the most important mode of action groups registered for use in greenhouses on the island. Label rates of all seven acaricides (abamectin, clofentezine, dicofol, fenbutatin oxide, fenazaquin, propargite and milbemectin - a product under registration) caused close to 100% mortality in the cucumber populations, but significantly lower mortality in the two rose populations. Mortality never exceeded 65% in the first rose population and 20% in the second population for any acaricide, suggesting development of resistance. The higher frequency of acaricide applications in roses and the perennial nature of the crop, that sustains genetically similar populations for long periods of time, may have facilitated the development of resistance. Judicious use of newer acaricides with distinct modes of action as they become registered may help control resistant spider mite populations in roses and other ornamental crops. Additionally, adoption of a mode of action labeling scheme of pesticides and training of growers on alternation of products will facilitate long term sustainable spider mite management in Cypriot agriculture. © Springer-Verlag 2008

Two-spotted spider mite in Cyprus: Ineffective acaricides, causes and considerations

Growers of greenhouse roses in Cyprus have recently reported failures of several acaricides against two-spotted spider mite (Tetranychus urticae Koch). To verify the cause of these failures we evaluated the effectiveness of seven acaricides against two rose and two cucumber spider mite populations in the laboratory. The acaricides included in our study represented the most important mode of action groups registered for use in greenhouses on the island. Label rates of all seven acaricides (abamectin, clofentezine, dicofol, fenbutatin oxide, fenazaquin, propargite and milbemectin - a product under registration) caused close to 100% mortality in the cucumber populations, but significantly lower mortality in the two rose populations. Mortality never exceeded 65% in the first rose population and 20% in the second population for any acaricide, suggesting development of resistance. The higher frequency of acaricide applications in roses and the perennial nature of the crop, that sustains genetically similar populations for long periods of time, may have facilitated the development of resistance. Judicious use of newer acaricides with distinct modes of action as they become registered may help control resistant spider mite populations in roses and other ornamental crops. Additionally, adoption of a mode of action labeling scheme of pesticides and training of growers on alternation of products will facilitate long term sustainable spider mite management in Cypriot agriculture. © Springer-Verlag 2008

The effect of chrysanthemum leaf trichome density and prey spatial distribution on predation of Tetranychus urticae (Acari: Tetranychidae) by Phytoseiulus persimilis (Acari: Phytoseiidae)

The effect of plant architecture, in terms of leaf hairiness, and prey spatial arrangement, on predation rate of eggs of the spider mite, Tetranychus urticae Koch, by the predatory mite Phytoseiulus persimilis Athias-Henriot was examined on cut stems of chrysanthemums. Three levels of leaf hairiness (trichome density) were obtained using two different chrysanthemum cultivars and two ages within one of the cultivars. The number of prey consumed by P. persimilis was inversely related to trichome density. At low prey densities (less than ten eggs per stem), prey consumption did not differ in a biologically meaningful way between treatments.The effect of prey spatial arrangement on the predation rate of P. persimilis was also examined. Predation rates were higher in prey patches on leaves adjacent to the release point of P. persimilis, but significantly greater numbers of prey were consumed in higher density prey patches compared to low density patches. The predators exhibited non-random searching behaviour, spending more time on leaves closest to the release point. The implications of these findings for biological control and predator-prey dynamics are discussed

Demographic effects of pesticides on biological control of Pacific spider mite (Tetranychus pacificus) by the western predatory mite (Galendromus occidentalis)

The western predatory mite, Galendromus occidentalis (Nesbitt) (Acari: Phytoseiidae), is a predator of Pacific spider mite, Tetranychus pacificus McGregor (Acari: Tetranychidae), in California vineyards. We evaluated the effects of six pesticides on biological control of T. pacificus on grape plant microcosms in a two-way design: presence and absence of G. occidentalis crossed with presence and absence of pesticide. The insecticide imidacloprid did not affect T. pacificus population growth rate, but it led G. occidentalis populations close to extinction. As a result, T. pacificus populations grew significantly higher in microcosms with release of G. occidentalis and treated with imidacloprid than with G. occidentalis alone. The fungicide wettable sulfur significantly decreased T. pacificus population growth rate but it did not affect G. occidentalis. Consequently, T. pacificus populations were significantly lower in microcosms with release of G. occidentalis and treated with wettable sulfur than with G. occidentalis alone. The insecticide buprofezin had no effect on T. pacificus population growth rate. Although buprofezin did not impact the ability of G. occidentalis to suppress T. pacificus, it negatively affected G. occidentalis population growth rate. The fungicides trifloxystrobin and tebuconazole and the insecticide methoxyfenozide had no influence on T. pacificus or G. occidentalis population growth rates. Furthermore, none of the pesticides affected the sex ratio of G. occidentalis, but buprofezin, methoxyfenozide and trifloxystrobin affected its stage structure. Our study demonstrates that simultaneous testing of the demographic effects of pesticides on pests and natural enemies is essential for a full assessment of pesticide impacts on biological control. © 2008 Elsevier Inc. All rights reserved

Demographic effects of pesticides on biological control of Pacific spider mite (Tetranychus pacificus) by the western predatory mite (Galendromus occidentalis)

The western predatory mite, Galendromus occidentalis (Nesbitt) (Acari: Phytoseiidae), is a predator of Pacific spider mite, Tetranychus pacificus McGregor (Acari: Tetranychidae), in California vineyards. We evaluated the effects of six pesticides on biological control of T. pacificus on grape plant microcosms in a two-way design: presence and absence of G. occidentalis crossed with presence and absence of pesticide. The insecticide imidacloprid did not affect T. pacificus population growth rate, but it led G. occidentalis populations close to extinction. As a result, T. pacificus populations grew significantly higher in microcosms with release of G. occidentalis and treated with imidacloprid than with G. occidentalis alone. The fungicide wettable sulfur significantly decreased T. pacificus population growth rate but it did not affect G. occidentalis. Consequently, T. pacificus populations were significantly lower in microcosms with release of G. occidentalis and treated with wettable sulfur than with G. occidentalis alone. The insecticide buprofezin had no effect on T. pacificus population growth rate. Although buprofezin did not impact the ability of G. occidentalis to suppress T. pacificus, it negatively affected G. occidentalis population growth rate. The fungicides trifloxystrobin and tebuconazole and the insecticide methoxyfenozide had no influence on T. pacificus or G. occidentalis population growth rates. Furthermore, none of the pesticides affected the sex ratio of G. occidentalis, but buprofezin, methoxyfenozide and trifloxystrobin affected its stage structure. Our study demonstrates that simultaneous testing of the demographic effects of pesticides on pests and natural enemies is essential for a full assessment of pesticide impacts on biological control. © 2008 Elsevier Inc. All rights reserved