Economic thresholds of Thrips palmi (Thysanoptera: Thripidae) for eggplants in a greenhouse
Thrips palmi Karny has recently been implicated in damage to eggplant fruits. This thrips causes cosmetic scars on and deforms fruits, thus lowering their market value. To investigate the relationship between the density of thrips and the resulting damage, experimental plots with initial release densities of 0, 20, 40, 70, and 100 adults thrips per plot were established under greenhouse conditions. Thrips density (for flower sampling = x1; for sticky trap = x2) was monitored using flower sampling and blue sticky trap counts, and was found to be directly related to the proportion of damaged-fruits (y) and the reduction in fruit yield: significant relationships were found for the flower samples (y = 1.2261x1 − 0.6232, r2 = 0.8582) and for the trap catches (y = 11.667 ln(x2) − 9.5, r2 = 0.8896). The proportion of damaged fruits that could be tolerated from an economic perspective, based on the cost of controlling the thrips population chemically and the market value of the fruit, was 6.67–11.76 %; this translated into economic thresholds of 1.05–1.5 adults and/or larvae of T. palmi per flower or 4.91–10.17 adults T. palmi per four-day sticky card count.
Commodity risk assessment of Momordica charantia fruits from Thailand
Abstract The European Commission requested the EFSA Panel on Plant Health to prepare and deliver risk assessments for commodities listed in Commission Implementing Regulation (EU) 2018/2019 as ‘High risk plants, plant products and other objects’. Momordica fruits originating from countries where Thrips palmi is known to occur qualify as high‐risk plants. This Scientific Opinion covers the introduction risk for T. palmi posed by fruits of Momordica charantia L. imported from Thailand, taking into account the available scientific information, including the technical information provided by the Department of Agriculture of Thailand. The risk mitigation measures proposed in the technical dossier from Thailand were evaluated taking into account the possible limiting factors. An expert judgement is given on the likelihood of pest freedom taking into consideration the potential pest pressure in the field, the risk mitigation measures acting on the pest in the field and in the packing house, including uncertainties associated with the assessment. For T. palmi on M. charantia fruits from Thailand, an expert judgement is given on the likelihood of pest freedom following the evaluation of the risk mitigation measures acting on T. palmi, including any uncertainties. The Expert Knowledge Elicitation indicated, with 95% certainty that between 9,496 and 10,000 M. charantia fruits/10,000 will be free from T. palmi.
Effects of plant density and late-season defoliation on yield of field beans
Effects of stand density and late-season defoliation by Mexican bean beetles, Epilachna varivestis Mulsant, on three yield components of beans were estimated from field studies conducted during 1983 and 1984 in four fields of pinto beans in northeastern Colorado. Number of beans per plant, mean weight of a bean, and mean weight of beans per plant were calculated for 100 samples per field, and regressed against three independent variables: plant density, percentage of defoliation, and density × defoliation interaction. Results of the analyses showed that plant density negatively affected number of beans per plant and weight of beans per plant, but not average weight of a bean. Responses were not linear; slope decreased at higher densities. Defoliation negatively affected all three yield variables. Average weight of a bean was linearly related to defoliation. Number of beans per plant and weight of beans per plant showed linear responses above a threshold level of defoliation. A piecewise regression model indicated that yields were not affected by defoliation until levels reached approximately 19% foliage loss. Laboratory consumption studies were conducted to determine age-specific damage potential for Mexican bean beetles and two occasional defoliators of pinto beans, saltmarsh caterpillars, Estigmene acrea (Drury), and yellow woollybears, Spilosoma virginica (F.). Insect consumption potentials and field studies of yield responses to defoliation were used to estimate threshold densities.