Statistics for Spatial Data.

A positive temperature coefficient is the term which has been used to indicate that an increase in solubility occurs as the temperature is raised, whereas a negative coefficient indicates a decrease in solubility with rise in temperature.

Effect of Temperature

Summary 1. Neonicotinoids are now the most widely used insecticides in the world. They act systemically, travelling through plant tissues and protecting all parts of the crop, and are widely applied as seed dressings. As neurotoxins with high toxicity to most arthropods, they provide effective pest control and have numerous uses in arable farming and horticulture. 2. However, the prophylactic use of broad-spectrum pesticides goes against the long-established principles of integrated pest management (IPM), leading to environmental concerns. 3. It has recently emerged that neonicotinoids can persist and accumulate in soils. They are water soluble and prone to leaching into waterways. Being systemic, they are found in nectar and pollen of treated crops. Reported levels in soils, waterways, field margin plants and floral resources overlap substantially with concentrations that are sufficient to control pests in crops, and commonly exceed the LC50 (the concentration which kills 50% of individuals) for beneficial organisms. Concentrations in nectar and pollen in crops are sufficient to impact substantially on colony reproduction in bumblebees. 4. Although vertebrates are less susceptible than arthropods, consumption of small numbers of dressed seeds offers a route to direct mortality in birds and mammals. 5. Synthesis and applications. Major knowledge gaps remain, but current use of neonicotinoids is likely to be impacting on a broad range of non-target taxa including pollinators and soil and aquatic invertebrates and hence threatens a range of ecosystem services.

/pdf/review-an-overview-of-the-environmental-risks-posed-by-hj0ee8p6bs.pdf

REVIEW: An overview of the environmental risks posed by neonicotinoid insecticides

The efficacy of disease resistance genes in plants decreases over time because of the selection of virulent pathogen genotypes. A key goal of crop protection programs is to increase the durability of the resistance conferred by these genes. The spatial and temporal deployment of plant disease resistance genes is considered to be a major factor determining their durability. In the literature, four principal strategies combining resistance genes over time and space have been considered to delay the evolution of virulent pathogen genotypes: cultivars mixture, rotation, landscape deployment, pyramiding. We reviewed this literature with the aim of determining which deployment strategy results in the greatest durability of resistance genes. Although theoretical and empirical studies comparing deployment strategies of more than one resistance gene are very scarce, they suggest that the overall durability of disease resistance genes can be increased by combining their presence in the same plant (pyramiding). Retrospective analyses of field monitoring data also suggest that the pyramiding of disease resistance genes within a plant is the most durable strategy. By extension, we suggest that the combination of disease resistance genes with other practices for pathogen control (pesticides, farming practices) may be a relevant management strategy to slow down the evolution of virulent pathogen genotypes.

/pdf/combining-selective-pressures-to-enhance-the-durability-of-4jl7nu8i1i.pdf

Combining Selective Pressures to Enhance the Durability of Disease Resistance Genes

The soybean aphid, Aphis glycines Matsumura, has become the single most important arthropod pest of soybeans in North America. Native to Asia, this invasive species was first discovered in North America in July 2000 and has rapidly spread throughout the northcentral United States, much of southeastern Canada, and the northeastern United States. In response, important elements of the ecology of the soybean aphid in North America have been elucidated, with economic thresholds, sampling plans, and chemical control recommendations widely adopted. Aphid-resistant soybean varieties were available to growers in 2010. The preexisting community of aphid natural enemies has been highly effective in suppressing aphid populations in many situations, and classical biological control efforts have focused on the addition of parasitoids of Asian origin. The keys to sustainable management of this pest include understanding linkages between the soybean aphid and other introduced and native species in a landscape context al...

Ecology and Management of the Soybean Aphid in North America

Soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), reached damaging levels in 2003 and 2005 in soybean, Glycine max (L.) Merrill, in most northern U.S. states and Canadian provinces, and it has become one of the most important pests of soybean throughout the North Central region. A common experimental protocol was adopted by participants in six states who provided data from 19 yield-loss experiments conducted over a 3-yr period. Population doubling times for field populations of soybean aphid averaged 6.8 d ± 0.8 d (mean ± SEM). The average economic threshold (ET) over all control costs, market values, and yield was 273 ± 38 (mean ± 95% confidence interval [CI], range 111–567) aphids per plant. This ET provides a 7-d lead time before aphid populations are expected to exceed the economic injury level (EIL) of 674 ± 95 (mean ± 95% CI, range 275–1,399) aphids per plant. Peak aphid density in 18 of the 19 location-years occurred during soybean growth stages R3 (beginning pod formation) to R5 (full size pod) with a single data set having aphid populations peaking at R6 (full size green seed). The ET developed here is strongly supported through soybean growth stage R5. Setting an ET at lower aphid densities increases the risk to producers by treating an aphid population that is growing too slowly to exceed the EIL in 7 d, eliminates generalist predators, and exposes a larger portion of the soybean aphid population to selection by insecticides, which could lead to development of insecticide resistance.

/pdf/economic-threshold-for-soybean-aphid-hemiptera-aphididae-2pxnidkvwg.pdf

Economic threshold for soybean aphid (Hemiptera: Aphididae)

Soybean aphid, Aphis glycines Matsumura, is now widely established in soybean, Glycine max L., production areas of the northern United States and southern Canada and is becoming an important economic pest. Temperature effect on soybean aphid fecundity and survivorship is not well understood. We determined the optimal temperature for soybean aphid growth and reproduction on soybean under controlled conditions. We constructed life tables for soybean aphid at 20, 25, 30, and 35°C with a photoperiod of 16:8 (L:D) h. Population growth rates were greatest at 25°C. As temperature increased, net fecundity, gross fecundity, generation time, and life expectancy decreased. The prereproductive period did not differ between 20 and 30°C; however, at 30°C aphids required more degree-days (base 8.6°C) to develop. Nymphs exposed to 35°C did not complete development, and all individuals died within 11 d. Reproductive periods were significantly different at all temperatures, with aphids reproducing longer and producing more progeny at 20 and 25°C than at 30 or 35°C. Using a modification of the nonlinear Logan model, we estimated upper and optimal developmental thresholds to be 34.9 and 27.8°C, respectively. At 25°C, aphid populations doubled in 1.5 d; at 20 and 30°C, populations doubled in 1.9 d.

https://bioone.org/journals/Journal-of-Economic-Entomology/volume-97/issue-3/0022-0493(2004)097[0854:DOSAHA]2.0.CO;2/Demography-of-Soybean-Aphid-Homoptera-Aphididae-at-Summer-Temperatures/10.1603/0022-0493(2004)097[0854:DOSAHA]2.0.CO;2.pdf

Demography of Soybean Aphid (Homoptera: Aphididae) at Summer Temperatures

Soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), is the primary pest of soybean, Glycine max L., in the north central region. After more than a decade of research and extension efforts to manage this pest, several consensus management recommendations have been developed for sustainable and profitable soybean production. A summary of integrated pest management (IPM) tactics for soybean aphid are discussed, including cultural, genetic, economic, and chemical controls. To date, sampling and timely foliar insecticides are routinely recommended to protect yield and delay genetic resistance to insecticides. Host plant resistance is a new tool that can regulate populations and reduce the reliance of insecticides to control soybean aphid. A combination of these management tools also will reduce overall production costs and minimize negative environmental effects such as human exposure, and mortality of beneficial insects and other animals.

/pdf/management-recommendations-for-soybean-aphid-hemiptera-42s60f82g7.pdf

Management Recommendations for Soybean Aphid (Hemiptera: Aphididae) in the United States

Efficacy of Thiamethoxam to Suppress Soybean Aphid Populations in Minnesota Soybean

The multicolored Asian lady beetle, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), has become a popular study organism due to its promise as a biological control agent and its potential adverse, non-target impacts. Behavioral and ecological research on H. axyridis, including examinations of its impacts, could benefit from non-destructive or non-disruptive sexing techniques for this coccinellid. External morphological characters were evaluated for H. axyridis (succinea color form) sex determination in laboratory and field studies. The shape of the distal margin of the fifth visible abdominal sternite accurately predicted H. axyridis sex for all beetles examined. Males consistently had a concave distal margin, while females had a convex distal margin. In addition, pigmentation of the labrum and prosternum were both significantly associated with H. axyridis sex; males had light pigmentation and females had dark pigmentation. Labrum and prosternum pigmentation increased from light to dark with decreasing rearing temperature and increasing time after adult eclosion for females. Male pigmentation was only affected by a decrease in rearing temperature. Validation through in-field collections indicated that these predictors were accurate. However, labrum pigmentation is a more desirable character to use to determine sex, because it is more accurate and easily accessible. Therefore, we recommend using labrum pigmentation for in-field sex determination of H. axyridis. Implications of this diagnostic technique for applied and basic research on this natural enemy are discussed.

https://bioone.org/journals/Journal-of-Insect-Science/volume-7/issue-10/031.007.1001/A-Simple-Method-for-In-Field-Sex-Determination-of-the/10.1673/031.007.1001.pdf

Brian P. McCornack

Papers

Economic threshold for soybean aphid (Hemiptera: Aphididae)

Demography of Soybean Aphid (Homoptera: Aphididae) at Summer Temperatures

Management Recommendations for Soybean Aphid (Hemiptera: Aphididae) in the United States

Efficacy of Thiamethoxam to Suppress Soybean Aphid Populations in Minnesota Soybean

A Simple Method for In-Field Sex Determination of the Multicolored Asian Lady Beetle Harmonia axyridis