Hot Water Treatment for Post-Harvest Disinfestation of Bactrocera dorsalis (Diptera: Tephritidae) and Its Effect on cv. Tommy Atkins Mango

Mango production and trade in sub-Saharan Africa is hampered by direct damage and the high quarantine status of B. dorsalis and the paucity of effective post-harvest phytosanitary treatments. The current study reports the development of a quarantine treatment protocol using hot water to disinfest B. dorsalis and assess its effect on cv. Tommy Atkins mango quality. We first determined the development of the eggs and all larval stages of B. dorsalis in cv. Tommy Atkins mango and used the information to establish a time–mortality relationship of the immature stages after subjecting infested fruits to a regimen of eight, time instances of hot water at 46.1◦ C. Using probit analysis, we estimated the minimum time required to achieve 99.9968% mortality of each stage. Our results indicate that the egg was the least heat tolerant, followed by the first, second, and third instar. The time required to achieve 99.9968% control of the third instar in cv. Tommy Atkins mango (400–600 g) was determined to be 72.63 min (95% Cl: 70.32–74.95). In the confirmatory trials, the hot water treatment schedule of 46.1◦ C/72.63 min was validated, and none of the 59,120 most heat-tolerant individuals treated survived. Further, there were no significant differences between hot water-treated and untreated mangoes recorded in weight loss, fruit firmness, pH, total soluble solids, moisture content, and titratable acidity eleven days post-treatment. These findings demonstrate an effectively optimum post-harvest disinfestation treatment against B. dorsalis in cv. Tommy Atkins mango that should be adopted commercially to facilitate access to profitable but strict export markets globally

Efficacy of hot water treatment for postharvest control of western flower thrips, Frankliniella occidentalis, in French beans

Background: The western flower thrips, Frankliniella occidentalis, is a quarantine pest of French beans that requires phytosanitary treatment to meet quarantine requirements for strict lucrative markets. In this study, the efficacy of hot water treatment against F. occidentalis eggs and its effects on the postharvest physicochemical quality parameters of French beans was evaluated. Results: The immersion time of 8.01 min (95% critical limits CL 7.77–8.24) was predicted by the probit model as the minimum time required to achieve a 99.9968% control level. Confirmatory tests with a large number of F. occidentalis eggs were performed to validate the estimated time to achieve probit-9 control level, and there were no survivors from the 50 103 eggs treated. Likewise, none of the 55 364 eggs exposed to 45 ± 0.2 °C for 7 min (observational time) survived. The effect of the treatment schedule on French beans quality parameters was assessed and there were no differences in weight loss, moisture content, total soluble solids, titratable acidity, pH, and reducing sugars between treated and untreated samples. Conclusion: Our results indicate that hot water treatment (at 45 ± 0.2 °C for a duration of 8.01 min is an effective phytosanitary treatment for the control of Frankliniella occidentalis on French beans, with no significant impact on pods quality. © 2022 Society of Chemical Industry

Optimizing Western Flower Thrips Management on French Beans by Combined Use of Beneficials and Imidacloprid

Western flower thrips (WFT), Frankliniella occidentalis (Pergande), is an important pest of vegetable crops worldwide and has developed resistance to many insecticides. The predatory mites Neoseiulus (=Amblyseius) cucumeris (Oudemans), the entomopathogenic fungus Metarhizium anisopliae (Metsch.), and an insecticide (imidacloprid) were tested for their efficacy to reduce WFT population density and damage to French bean (Phaseolus vulgaris L.) pods under field conditions in two planting periods. Metarhizium anisopliae was applied as a foliar spray weekly at a rate of one litre spray volume per plot while imidacloprid was applied as a soil drench every two weeks at a rate of two litres of a mixture of water and imidacloprid per m(2). Neoseiulus cucumeris was released every two weeks on plant foliage at a rate of three mites per plant. Single and combined treatment applications reduced WFT population density by at least three times and WFT damage to French bean pods by at least 1.7 times compared with untreated plots. The benefit-cost ratios in management of WFT were profitable with highest returns realized on imidacloprid treated plots. The results indicate that M. anisopliae, N. cucumeris, and imidacloprid have the potential for use in developing an integrated pest management program against WFT on French beans.BMZ/GIZ/07.7860.5-001.0

Screening for attractants compatible with entomopathogenic fungus Metarhizium anisopliae for use in thrips management

Several thrips attractants were screened for compatibility with Metarhizium anisopliae (Metchnikoff) Sorokin (Hypocreales: Clavicipitaceae) and a subset of these for attraction to Megalurothrips sjostedti Trybom  (Thysanoptera: Thripidae). Conidial germination and germ tube length of M. anisopliae were used as  indicators of its compatibility with thrips attractant. Conidial germination and germ tube length differed significantly according to volatiles of different attractants. The highest conidial germination (76.5±3.5%) and longest germ tube length (130.3±13.4 μm) were recorded in the control, followed by methyl anthranilate (63.8±3.8%; 103.8±8.4 μm), cis-jasmone (61.8±5.9%; 93.8±14.4 μm) and  transcaryophyllene (57.7±6.5%; 96.3±15.5 μm) which were found compatible with M. anisopliae. A  Pearson correlation test indicated a significant positive correlation between conidial germination and germ tube length (r =0.6; P<0.0001). The attraction of M. sjostedti to selected thrips attractant also varied significantly among the attractants. Under field conditions, methyl anthranilate was equally attractive to M. sjostedi as Lurem-TR and could be recommended as a thrips attractant that can be combined with M. anisopliae in autoinoculation devices for potential control of M. sjostedti.Key words: Semiochemicals, conidial germination, germ tube length, Megalurothrips sjostedti, attraction,persistence, field

Temperature-dependent phenology of Plutella xylostella (Lepidoptera: Plutellidae): Simulation and visualization of current and future distributions along the Eastern Afromontane

There is a scarcity of laboratory and field-based results showing the movement of the diamondback moth (DBM) Plutella xylostella (L.) across a spatial scale. We studied the population growth of the diamondback moth (DBM) Plutella xylostella (L.) under six constant temperatures, to understand and predict population changes along altitudinal gradients and under climate change scenarios. Non-linear functions were fitted to continuously model DBM development, mortality, longevity and oviposition. We compiled the best-fitted functions for each life stage to yield a phenology model, which we stochastically simulated to estimate the life table parameters. Three temperature-dependent indices (establishment, generation and activity) were derived from a logistic population growth model and then coupled to collected current (2013) and downscaled temperature data from AFRICLIM (2055) for geospatial mapping. To measure and predict the impacts of temperature change on the pest's biology, we mapped the indices along the altitudinal gradients of Mt. Kilimanjaro (Tanzania) and Taita Hills (Kenya) and assessed the differences between 2013 and 2055 climate scenarios. The optimal temperatures for development of DBM were 32.5, 33.5 and 33ÊC for eggs, larvae and pupae, respectively. Mortality rates increased due to extreme temperatures to 53.3, 70.0 and 52.4% for egg, larvae and pupae, respectively. The net reproduction rate reached a peak of 87.4 female offspring/female/generation at 20ÊC. Spatial simulations indicated that survival and establishment of DBM increased with a decrease in temperature, from low to high altitude. However, we observed a higher number of DBM generations at low altitude. The model predicted DBM population growth reduction in the low and medium altitudes by 2055. At higher altitude, it predicted an increase in the level of suitability for establishment with a decrease in the number of generations per year. If climate change occurs as per the selected scenario, DBM infestation may reduce in the selected region. The study highlights the need to validate these predictions with other interacting factors such as cropping practices, host plants and natural enemies.Peer reviewe

In situ nitrogen mineralization and nutrient release by soil amended with black soldier fly frass fertilizer

Black soldier fly frass fertilizer (BSFFF) is effective on crop performance, but information on nitrogen mineralization and nutrient release capacity of soils amended with BSFFF is lacking. This study utilized field incubation experiments to investigate the ammonification, nitrification, microbial populations, and quantities of nutrients released by soils amended with BSFFF and commercial organic fertilizer (SAFI) for a period equivalent to two maize cropping seasons. The paper provides a detailed breakdown and analysis of results. BSFFF has a high potential to supply adequate nutrients for optimal crop production. Higher population of soil bacteria and fungi underline its potential for improving biological soil fertility.Norwegian Agency for Development CooperationNetherlands Organization for Scientific ResearchWOTRO Science for Global Development (NWO-WOTRO)Rockefeller Foundatio

Insights in the global genetics and gut microbiome of black soldier fly, hermetia illucens : implications for animal feed safety control

This study delineates genetic variability and unravels gut microbiome complex of wild-collected and domesticated BSF populations from six continents using mitochondrial COI gene and 16S metagenomics. Alpha-diversity showed that the Kenyan and Thailand populations had the highest and lowest microbe diversity, respectively; while microbial diversity assessed through Bray Curtis distance showed United States (Maysville) and Netherlands populations to be the most dissimilar. The 16S data depicted larval gut bacterial families with economically important genera that might pose health risks to both animals and humans. To minimize risk of pathogen contamination along the insect-based feed value chain, this study recommends pre-treatment of feedstocks.Netherlands Organization for Scientific ResearchWOTRO Science for Global Development (NWO-WOTRO)Australian Centre for International Agricultural Research (ACIAR)Rockefeller Foundatio

Virulence and horizontal transmission of Metarhizium anisopliae by the adults of the greenhouse whitefly Trialeurodes vaporariorum (Hemiptera: Aleyrodidae) and the efficacy of oil formulations against its nymphs

The pathogenicity of dry conidia and fungal suspensions of 16 entomopathogenic fungal isolates (10 Metarhizium anisopliae and six Beauveria bassiana) was evaluated against adults and second instar nymphs of the greenhouse whitefly, Trialeurodes vaporariorum respectively. All the tested isolates were pathogenic to T. vaporariorum and caused mortality of 45–93% against the adults and 24–89% against the nymphs. However, M. anisopliae strains showed higher virulence to both developmental stages as compared to B. bassiana strains. The three most virulent isolates that caused high mortalities in adults were M. anisopliae ICIPE 18, ICIPE 62 and ICIPE 69, with cumulative mortalities of 82, 91 and 93%, and median lethal times (LT50) of 5.20, 5.05 and 4.78 days, respectively. These isolates were further assessed for spore acquisition and retention by the adult insects at 0, 24, 48 and 72 h after exposure to dry conidia spores. There was no significant difference among isolates on their acquisition by the insects, although the effect of time on the number of spores retained by each insect was significant. For M. anisopliae ICIPE 62 and ICIPE 69, spore number was significantly higher immediately after exposure at 0 h than at 24, 48 and 72 h, whereas for M. anisopliae ICIPE 18, the spore number remained constant for all the days. The infected “donor” insects were able to horizontally transmit the acquired spores to uninfected “recipient” insects causing high mortality rates in both donor and recipient groups. Metarhizium anisopliae ICIPE 7, ICIPE 18 and ICIPE 62 were the most virulent isolates against the nymphs in aqueous formulation during the first screening with >80% mortality. However, in 2% (v/v) oil formulations at 1 108 conidia/ml, canola formulated ICIPE 62, ICIPE 18 and olive formulated ICIPE 18 were the most effective, resulting in 87.8, 88.1 and 99.4% nymphal mortalities respectively and with lower LT50. Oil formulations significantly enhanced the efficacy and virulence of the isolates against the nymphs compared to aqueous formulations.The German Academic Exchange Service (DAAD) through African Regional Postgraduate Programme in Insect Science (ARPPIS) of icipe. The icipe core funding provided by UK’s Foreign, Commonwealth and Development Office (FCDO); Swedish International Development Cooperation Agency (Sida); the Swiss Agency for Development and Cooperation (SDC); the Federal Democratic Republic of Ethiopia; and the Government of the Republic of Kenya.http://www.cell.com/heliyonam2022Forestry and Agricultural Biotechnology Institute (FABI)Zoology and Entomolog