Predicting Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae) populations and associated grain damage in smallholder farmers’ maize stores: A machine learning approach

Prostephanus truncatus is a notorious pest of stored-maize grain and its spread throughout sub-Saharan Africa has led to increased levels of grain storage losses. The current study developed models to predict the level of P. truncatus infestation and associated damage of maize grain in smallholder farmer stores. Data were gathered from grain storage trials conducted in Hwedza and Mbire districts of Zimbabwe and correlated with weather data for each site. Insect counts of P. truncatus and other common stored grain insect pests had a strong correlation with time of year with highest recorded numbers from January to May. Correlation analysis showed insect-generated grain dust from boring and feeding activity to be the best indicator of P. truncatus presence in stores (r = 0.70), while a moderate correlation (r = 0.48) was found between P. truncatus numbers and storage insect parasitic wasps, and grain damage levels significantly correlated with the presence of Tribolium castaneum (r = 0.60). Models were developed for predicting P. truncatus infestation and grain damage using parameter selection algorithms and decision-tree machine learning algorithms with 10-fold cross-validation. The P. truncatus population size prediction model performance was weak (r = 0.43) due to the complicated sampling and detection of the pest and eight-week long period between sampling events. The grain damage prediction model had a stronger correlation coefficient (r = 0.93) and is a good estimator for in situ stored grain insect damage. The models were developed for use under southern African climatic conditions and can be improved with more input data to create more precise models for building decision-support tools for smallholder maize-based production systems.     

Motion Perception Using Analog VLSI

Motion perception is arguably a fundamental mechanism used by natural species to accomplish a number of tasks, such as navigating freely in an unknown environment. Traditional motion perception methods tend to be computationally intensive, requiring powerful computers and large memories. However, by copying biological mechanisms, such as elementary motion discrimination at the early stages of the visual processing paths, it should be possible to build small and efficient motion perception systems. This paper describes the manner in which a simple motion perception model based on the insect visual system has been implemented using mixed analog/digital VLSI. The device has been fabricated in a 2 micron double metal, double polysilicon process, and comprises 61 photo-detectors, and associated analog and digital circuitry. While not entirely successful in that component mismatches hamper the detection of dark-to-bright changes in contrast, the results clearly show the feasibility of using such a device in autonomous control systems.     

Insect sex pheromones

The half-lives (t _1/2) for evaporative loss ofn-alkyl andn-alkenyl acetates from rubber septa were determined at temperatures varying from 15 to 35 °C. The changes int _1/2 with temperature gave high correlations with the equation, Int _1/2 = H/RT+y _o where H is the heat of vaporization,R is the gas constant,T is the absolute temperature, andy _o is a constant. Half-lives changed dramatically with temperature and the degree of change with temperature increased with increasing molecular weight. For mixtures, component ratios changed with temperature, but the degree was modest. At 20 °C there was a 7.5-fold ratio oft _1/2 between members of the homologousn-alkyl orn-alkenyl acetates differing by two carbon atoms. The large change int _1/2 with temperature and with number of carbon atoms is a consequence of the thermodynamic relationships and the temperature range of pheromone usage. Therefore, a similar degree of change inf _1/2 with temperature and number of carbon atoms will apply to other formulations of the same type (those in which the rate of evaporation is first order). The values oft _1/2 at 20 °C mainly agreed very well with those reported previously at room temperature. However, our previously reported values for pentadecyl and hexadecyl acetate were revised. Half-lives were shown to depend on the vapor pressure of a compound in the formulation substrate, but not on the vapor pressure of the pure compound.Mention of a commercial or proprietary product does not constitute an endorsement by the USDA.     

Sensitization to Sitophilus granarius in selected suburban population of South Poland

Storage insects may cause occupational allergies in humans. The identification of the prevalence of IgE reactions were measured from protein fractions prepared from multiple life stage of granary weevil Sitophilus granarius [SG] is reported. Sera of 30 patients from a suburban population of Upper Silesia (South Poland) were tested for the presence of IgE antibodies to antigens from larvae, pupae and adults of both sexes of the beetle. To identify protein fractions containing potential allergens, proteins collected from four life stages of granary weevil were fractionated by SDS-PAGE and probed with anti-human, anti-IgE monoclonal antibodies. The proteins were fractionated by SDS PAGE and identified by Western blot. The patients’ antibodies against particular antigens were identified using anti-human anti-IgE monoclonal antibody. The conducted immunological analysis showed the existence of many protein fractions for each life stage of SG which give positive reactions with IgE antibodies. The largest number of allergenic potential fractions was shown in pupae (60 protein fractions) while the smallest amount was shown in larvae (44 protein fractions). Summarizing, the obtained results suggest the existence of many protein fractions with an allergenic potential multiple life stages of SG. This indicates that all developmental stages of SG may be a serious source of antigens and potential risk factors for the exposed persons.     

New innovations in agricultural biotech: Consumer acceptance of topical RNAi in rice production

To test the market viability of a non-GMO topical RNAi insect control, we conducted a Willingness-To-Pay (WTP) survey in the USA, Canada, Australia, France, and Belgium to elicit whether consumers need a premium or discount for: (1) a hypothetical GMO rice variety using the Bacillus thuringiensis (Bt) gene for insect control; and (2) a hypothetical non-GMO rice variety using topical RNAi spray for insect control. The survey was designed based on a Multiple Price List (MPL) format where respondents selected their preferred insect control technology; i.e., conventional, GMO Bt, or non-GMO RNAi, at different prices. Participants' responses were analyzed using an interval regression model to generate WTP premiums and discounts for each country with control variables for demographic influences. Further, we asked consumers their Willingness-To-Consume (WTC) food produced with GM and RNAi technologies respectively and evaluated WTC differences using a McNemar matched pairs test in each country. The results from our study clearly show that: (1) consumers in the USA, Canada, Australia, and France still require a discount for rice produced with topical RNAi compared to conventionally-produced rice (p < 0.05), (2) consumers in the USA, Canada, Australia, France, and Belgium would need an additional 30–40% discount to purchase Bt rice over rice produced with topical RNAi (p < 0.05), and (3) consumers in all countries were more willing to consume rice produced with non-GM RNAi than with GM Bt technology (p < 0.05). These findings suggest consumers differentiate among biotechnology solutions and consumers may prefer topical RNAi insect control to transgenic GMO insecticides.     

Prevalence and diversity of Wolbachia bacteria infecting insect pests of stored products

Wolbachia are common bacterial symbionts of insects. Because infections of these bacteria can alter the reproduction and biology of the host, there is interest in the potential use of Wolbachia to control populations of pest species. To advance this research, we screened 38 species (88 populations from 16 countries) of stored-product insect pests for Wolbachia infections. Infections were detected in nine species of Coleoptera (Anobiidae – Lasioderma serricorne (Fabricius), Stegobium paniceum (Linnaeus); Curculionidae – Sitophilus oryzae (Motschulsky), Sitophilus zeamais Motschulsky; Dermestidae – Attagenus unicolor (Brahm), Dermestes lardarius Linnaeus; Silvanidae – Oryzaephilus mercator (Fauvel), Oryzaephilus surinamensis (Linnaeus); Tenebrionidae – Tribolium confusum Jaquelin Du Val), one species of Hymenoptera (Trichogrammatidae – Trichogramma deion Pinto & Oatman), and one species of Lepidoptera (Pyralidae – Ephestia kuehniella Zeller). Phylogenetic analyses based on wsp gene sequences identified all Wolbachia isolates as members of Supergroups A or B. Additional sequences for the genes gatB, coxA, hcpA, fbpA and ftsZ were obtained for use in multilocus sequence typing (MLST) to identify the sequence types to which the isolates belonged. Our results identify five new Wolbachia-insect associations and support previous findings that infections of Wolbachia in stored-product insect pests are members of Supergroups A or B.     

Diet-derived vicilins detected in eggs laid by a double-mated female Callosobruchus maculatus originate from nuptial gifts donated by both male partners

The eggshell and the cement that attaches the eggs of the seed-beetle Callosobruchus maculatus to the seeds of cowpea (Vigna unguiculata) contain vicilins, the main storage protein found in seeds. These proteins are derived from both males and females, which originally sequester them during the larval phase from their seed hosts. In this test, females received vicilin from different males during mating as a seminal nuptial gift, and transmitted this sequestered blend of proteins to the eggs. The presence of vicilin in the cement and eggshell was demonstrated by light microscopy and Western blotting. Quantification using ELISA showed that the concentration of vicilin from seminal vesicles of a virgin male is approximately double that measured following the first copula to a virgin female, suggesting that the investment of vicilin by the males is very important. This is the first demonstration showing that at least two different males can make a direct contribution of a sequestered protein which is used in oogenesis.     

Extraction and characterisation of protein fractions from five insect species

Tenebrio molitor, Zophobas morio, Alphitobius diaperinus, Acheta domesticus and Blaptica dubia were evaluated for their potential as a future protein source. Crude protein content ranged from 19% to 22% (Dumas analysis). Essential amino acid levels in all insect species were comparable with soybean proteins, but lower than for casein. After aqueous extraction, next to a fat fraction, a supernatant, pellet, and residue were obtained, containing 17–23%, 33–39%, 31–47% of total protein, respectively. At 3% (w/v), supernatant fractions did not form stable foams and gels at pH 3, 5, 7, and 10, except for gelation for A. domesticus at pH 7. At 30% w/v, gels at pH 7 and pH 10 were formed, but not at pH 3 and pH 5. In conclusion, the insect species studied have potential to be used in foods due to: (1) absolute protein levels; (2) protein quality; (3) ability to form gels.