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In the current study, we investigated the functional response of Harmonia axyridis adults and larvae foraging on Acyrthosiphon pisum nymphs at temperatures between 15 and 35 °C. Logistic regression and Roger's random predator models were employed to determine the type and parameters of the functional response. Harmonia axyridis larvae and adults exhibited Type II functional responses to A. pisum, and warming increased both the predation activity and host aphid control mortality. Female and 4th instar H. axyridis consumed the most aphids. For fourth instar larvae and female H. axyridis adults, the successful attack rates were 0.23 ± 0.014 h -1 and 0.25 ± 0.015 h -1 ; the handling times were 0.13 ± 0.005 h and 0.16 ± 0.004 h; and the estimated maximum predation rates were 181.28 ± 14.54 and 153.85 ± 4.06, respectively. These findings accentuate the high performance of 4th instar and female H. axyridis and the role of temperature in their efficiency. Further, we discussed such temperature-driven shifts in predation and prey mortality concerning prey-predator foraging interactions towards biological control.

Synthetic chemical pesticides can enhance crop yields but also have undesired effects. Alternative 'botanical insecticides' may also have non-target effects on pollinators and biocontrol services. Employing action thresholds (ATs) can reduce pesticide (whether synthetic or botanical) use compared to fixed-interval applications. Here the azadirachtin-based botanical formulation NeemAzal and a neem seed extract (NSE) were evaluated in field spraying trials alongside commonly-used synthetics (Voliam Flexi [chlorentraniliprole plus thiamethoxam] and imidacloprid) in developing ATs for the regular and cosmopolitan cauliflower pests Brevicoryne brassicae, Plutella xylostella and Spodoptera litura. We considered the size of the S. litura larvae infesting the crop in order to derive ATs. ATs per plant were higher for NeemAzal (0.55 larvae for P. xylostella and 3 larvae for large-sized S. litura) than for Voliam Flexi (0.30 larvae for P. xylostella and 0.80 larvae for S. litura) but were similar for B. brassicae (50 individuals). Higher ATs when using azadirachtin were associated with the diverse modes of action of botanicals, for instance NeemAzal and NSE deterred oviposition of S. litura. Although the exact values of ATs are likely to have regional limits, our approach can be applied for determining ATs against common lepidopteran and aphid pests in many other vegetable crop agro-ecosystems.

Wheat being staple food of Pakistan is constantly attacked by major wheat aphid species, Schizaphis graminum (R.), Rhopalosiphum padi (L.) and Sitobion avenae (F.). Due to concern on synthetic chemical use in wheat, it is imperative to search for alternative environment- and human- friendly control measures such as botanical pesticides. In the present study, we evaluated the comparative role of neem seed extract (NSE), moringa leaf extract (MLE) and imidacloprid (I) in the management of the aphid as well as the yield losses parameters in late planted wheat fields. Imidacloprid reduced significantly aphids infestation compared to the other treatments, hence resulting in higher yield, particularly when applied with MLE. The percentages of yield increase in I+MLE treated plots over the control were 19.15-81.89% for grains per spike, 5.33-37.62% for thousand grain weight and 27.59-61.12% for yield kg/ha. NSE was the second most effective control measure in suppressing aphid population, but the yield protected by NSE treatment over the control was comparable to that by imidacloprid. Population densities of coccinellids and syrphids in the plots treated with NSE-2 were higher than those treated with imidacloprid in two out of three experiments during 2013-14. Low predator density in imidacloprid-treated plots was attributed to the lower availability of prey aphids. The efficacy of NSE against aphids varied depending on degree of synchronization among the application timing, the activity of aphids, crop variety and environmental conditions. Despite that, we suggested NSE to be a promising alternative botanical insecticide compared to the most commonly recommended imidiacloprid. Further studies should consider the side effects of biopesticides on non-target organisms in order to provide better management practices in the field.

Weather extremes can have profound impact on plant physiology. The altered physiology of stressed plant can also modify trophic interactions in that plant environment. Aphids are important pests of wheat crop causing direct or indirect injury to the crop. The pest is routinely managed through use of insecticides. Insecticides due to their toxic effects are mostly not desired for use on food crops. Thus, alternative approaches such as biological and cultural control are more desirable. This research explores irrigation stress impacts on wheat aphids, predators, and yield characteristics under field conditions. The wheat crop was stressed at any of the tillering, booting, heading or grain formation stages by skipping irrigation during entire length of each stage. Unstressed wheat enjoyed irrigation at all four stages. Schizaphis graminum (Rondani) was the most abundant aphid species and coccinellids, the most abundant predators. S. graminum was least on unstressed or tillering stressed wheatbut was the most on wheat stressed at booting, heading, and grain formation stages. Irrigation stress reduced chlorophyll contents (5-25%) and wheat yield (kg/ha) (6-31%) when compared with unstressed wheat. The irrigation stress changed coccinellid abundance and predator-prey ratio. Altered plant physiology and a weaken plant defense under irrigation stress attracted feeding by more aphids which resultantly reduced chlorophyll amount. The abundant prey attracted more predation in the stressed wheat. The aphids and predator's preference change under irrigation stress are clear in our findings. We also discuss tri-trophic effects and implications of current study toward wheat aphid control. [ABSTRACT FROM AUTHOR]

Pest management strategies relying on biocontrol agents may be altered by climate change because temperature regulates biological rates from individuals to populations. We investigated predation and development of Harmonia axyridis foraging on Acyrthosiphon pisum at four different temperatures (15, 20, 25, and 30 °C). Age-stage, two-sex life table analysis of the predator was conducted. Computer projections based on bootstrap percentile confidence intervals were used for assessment of population growth and predation parameters. H. axyridis development and predation varied across temperature. Development was much slower at 15 °C than at warmer temperatures. Pre-adult stage mean duration was 41.25 d at 15 °C, but this decreased to 28.67, 18.35, and 13.23 d at 20, 25, and 30 °C, respectively. The intrinsic rate of increase was 0.0805 d−1 at 15 °C, but this increased to 0.1009, 0.1324, 0.1813 d−1 at 20, 25, and 30 °C, respectively. The mean generation time (T) was 71.96 d at 15 °C, which decreased to 54.68, 42.64 and 29.96 d at 20, 25, and 30 °C, respectively. The highest intrinsic rate of increase (r) and finite rate of increase (λ) were obtained at 30 °C, while the highest fecundity occurred at 15 °C with 743.68 eggs/female. The net predation rates (C 0) were 4445.28, 4299.30, 3602.18, and 2624.20 aphids at 15, 20, 25, and 30 °C, respectively. Population and predation projections were proportional to temperature. These results are useful for modelling the population response of H. axyridis to climate change and tailoring IPM strategies to altered climates. [Display omitted] • Effect of four constant temperatures was assessed on the predation and life table parameters of H. axyridis fed on A. pisum. • The predator could develop, survive, and reproduce across all tested temperatures (15–30 °C). • The intrinsic rate of increase and finite rate of increase were highest at 30 °C. • The mean generation time and pre-adult stage were shortest at 30 °C. • The net predation rate decreased with warming temperatures. [ABSTRACT FROM AUTHOR]