Improving climate suitability for Bemisia tabaci in East Africa is correlated with increased prevalence of whiteflies and cassava diseases

Projected climate changes are thought to promote emerging infectious diseases, though to date, evidence linking climate changes and such diseases in plants has not been available. Cassava is perhaps the most important crop in Africa for smallholder farmers. Since the late 1990's there have been reports from East and Central Africa of pandemics of begomoviruses in cassava linked to high abundances of whitefly species within the Bemisia tabaci complex. We used CLIMEX, a process-oriented climatic niche model, to explore if this pandemic was linked to recent historical climatic changes. The climatic niche model was corroborated with independent observed field abundance of B. tabaci in Uganda over a 13-year time-series, and with the probability of occurrence of B. tabaci over 2 years across the African study area. Throughout a 39-year climate time-series spanning the period during which the pandemics emerged, the modelled climatic conditions for B. tabaci improved significantly in the areas where the pandemics had been reported and were constant or decreased elsewhere. This is the first reported case where observed historical climate changes have been attributed to the increase in abundance of an insect pest, contributing to a crop disease pandemic

The influence of soil type and moisture on pupal survival of Bactrocera tryoni (Froggatt) (Diptera: Tephritidae)

Larvae of the Queensland fruit fly, Bactrocera tryoni, pupate in the soil, but the influence of soil variables on B. tryoni pupal mortality is not known. For other tropical tephritid species, soil moisture has been identified as a major pupal mortality factor. In the laboratory, we tested the effects of soil moisture and soil type on pupal survival through a factorial experiment which used three soil types (loamy sand, loam, sandy clay) and seven soil moisture levels (0%, 10%, 25%, 50%, 75%, 90% and 100%). Minor, but significant, differences in pupal mortality were observed between the soil types, but the most significant factor affecting pupae was extremes of soil moisture. Eighty-five percent pupal mortality occurred at 0% soil moisture and 30% mortality at 100% soil moisture: very low levels of mortality occurred at all intermediate levels. We detected a significant interaction between soil type and moisture level but cannot explain it. In a follow-up experiment, we demonstrated that prepupal wandering larvae of B. tryoni could discriminate between different moisture levels, with significantly greater pupation in loam soil at 75% soil moisture than at either 0% or 100% soil moisture. Results are used to modify a pupal mortality/soil moisture equation used in a recently published DYMEX model of B. tryoni population dynamics

Data from unsprayed fields

Experimental data (egg predation) from unsprayed fields from season 2015/201

Better outcomes for pest pressure, insecticide use, and yield in less intensive agricultural landscapes

Increasing crop field sizes and decreasing seminatural area is believed to lead to increased pest pressure and insecticide use due to earlier and frequent pest immigration and fewer natural enemies. However, after decades of research on how landscape simplification affects pest pressure in crops, there is conflicting evidence. We show that smaller fields surrounded by landscapes with 20 to 30% seminatural area had delayed and reduced pest immigration and spraying while producing the highest yields. These findings reveal a previously untested link sequence starting from agricultural intensification through pest immigration and dynamics, to insecticide use and yield. Moreover, fine temporal analyses provide unique understanding of how these effects change over time and potential explanation for the inconsistencies in the literature.Agricultural systems have been continuously intensified to meet rising demand for agricultural products. However, there are increasing concerns that larger, more connected crop fields and loss of seminatural areas exacerbate pest pressure, but findings to date have been inconclusive. Even less is known about whether increased pest pressure results in measurable effects for farmers, such as increased insecticide use and decreased crop yield. Using extensive spatiotemporal data sampled every 2 to 3 d throughout five growing seasons in 373 cotton fields, we show that pests immigrated earlier and were more likely to occur in larger cotton fields embedded in landscapes with little seminatural area (<10%). Earlier pest immigration resulted in earlier spraying that was further linked to more sprays per season. Importantly, crop yield was the lowest in these intensified landscapes. Our results demonstrate that both environmental conservation and production objectives can be achieved in conventional agriculture by decreasing field sizes and maintaining seminatural vegetation in the surrounding landscapes.The anonymized data and R code data have been deposited in Figshare (https://figshare.com/articles/dataset/AI_pests_insecticides_yield_csv/12062370, https://figshare.com/articles/journal_contribution/R_code_for_all_models/12072105, and https://figshare.com/articles/journal_contribution/R_code_for_all_Figures/12072108). All other study data are included in the article and/or SI Appendix

Pitfall data 2016_2017

Pitfall data, season 2016/201

Data from camera recordings

Pest egg removal data recorded by digital cameras, season 2016/2017

A Behavioral Justification for Escalating Punishment Schemes

The standard two-period law enforcement model is considered in a setting where individuals usually, but not exclusively, commit crimes only after comparing expected costs and benefits. Where escalating punishment schemes are present, there is an inherent value in keeping a clean criminal record; a person with a record may unintentionally become a repeat offender if he fails to exert self-control, and be punished more severely. If the punishment for repeat offenders is sufficiently high, one may rationally forgo the opportunity of committing a profitable crime today to avoid being sanctioned as a repeat offender in the future. Therefore, partial deterrence can be achieved at a very low cost through the use of escalating penalties, providing a behavioral justification for punishing repeat offenders more severely

Baseline <i>Helicoverpa</i> preferences and seasonal availability for different habitat types.

<p>Baseline <i>Helicoverpa</i> preferences and seasonal availability for different habitat types.</p

A native with a taste for the exotic: weeds and pasture provide year-round habitat for Nysius vinitor (Hemiptera: Orsillidae) across Australia, with implications for area-wide management

While pest management tends to focus on pests that are already present in crops, non-crop hosts may play a crucial role in supporting pest populations outside the crop growing season. Non-crop hosts may allow pest populations to persist throughout the year, build-up and colonise crops after emergence. Here, we assess the hosts of the Rutherglen bug, Nysius vinitor Bergroth, which is a polyphagous native insect pest of growing economic importance in Australia. We conducted a literature review on the occurrence of N.\ua0vinitor on crop and non-crop hosts and analysed field survey data on N.\ua0vinitor abundance from two independent field studies in three agricultural regions of Australia. We differentiated between juvenile (nymph) and adult stages to consider the function of plants as reproduction sites. The literature review resulted in reports of N.\ua0vinitor on 44 crop species from 18 plant families. Pigweed Portulaca oleracea and capeweed Arctotheca calendula were the most cited weed hosts. In the field study, N.\ua0vinitor was primarily found on exotic weeds and grasses within pastures, Lucerne and degraded native vegetation remnants. While N.\ua0vinitor was found on a total of 16 weed plant families, juvenile stages of N.\ua0vinitor were most often observed on fleabane (Conyza spp.), goosefoot Chenopodium pumilio (Amaranthaceae) and plants of the Asteraceae family, indicating that these are important host plants for N.\ua0vinitor reproduction. Grasses appear to be an important but understudied host plant group; citations in the literature do not reflect the extent to which N.\ua0vinitor was found on grasses in the field. In contrast, the field survey indicated that very few native plant species supported N.\ua0vinitor, which was consistent across regions and confirms findings from the literature review. Our findings suggest that exotic weeds and grasses (but not native plants) play a key role in supporting N.\ua0vinitor populations in Australian agricultural landscapes. Reducing exotic weeds in pastures and non-crop habitats may limit breeding opportunities of N.\ua0vinitor and may be an important component in the area-wide management of this polyphagous pest