A Laboratory Bioassay Method to Assess the Use of Toxic Bait on Anastrepha fraterculus (Weidemann 1830).

The lack of standardization of bioassays for the evaluation of toxic bait toxicity on the South American fruit fly, Anastrepha fraterculus (Weidemann 1830), has led to erroneous interpretations of assay results. The objective of this study was to develop a methodology for the standardization and validation of toxicological tests on A. fraterculus toxic bait using the Success™ 0.02CB formulation (80 mg L-1 of spinosad). Anastrepha fraterculus adults, obtained from larvae reared on an artificial diet, showed higher susceptibility (LT50 = 48.96 h) than adults from larvae reared on cattley guava (LT50 = 53.83 h) and mango fruit (LT50 = 53.55 h). Anastrepha fraterculus adults at the age of five (LT50 = 65.30 h), 15 (LT50 = 59.01 h), and 30 (LT50 = 55.53 h) days presented similar toxicity. The consumption of toxic bait (4.74 mg) increased at 15 days, a fact also observed with insects without food deprivation. In addition, the absence of a food source (artificial diet) with the toxic bait significantly reduced adult mortality time by 7 h (LT50 = 57.42 h). In relation to exposure time, adults exposed to toxic bait for 1 h reduced consumption by 25%; however, they showed the same susceptibility as insects exposed to 2 (LT50 = 55.72 h), 4 (LT50 = 57.64 h), and 8 h (LT50 = 57.76 h). However, with 24 h of food deprivation, they had a higher susceptibility (LT50 = 46.48 h). Five-day-old A. fraterculus adults fed an artificial diet before being deprived of food for 12 or 24 h, then exposed to toxic bait for 4 h in the absence of a food source, are considered optimum conditions to evaluate the toxicity of toxic bait.

Development and reprotuction of Spodoptera eridania on natural hosts and artificial diet / Desenvolvimento e reprodução de Spodoptera eridania em hospedeiros naturais e dieta artificial

Abstract The development and reproductive potential of Spodoptera eridania (Stoll, 1782) (Lepidoptera, Noctuidae) was compared on natural and artificial diets. Its biology was determined under laboratory conditions, providing an artificial diet, leaves of white clover and the peach cultivar 'Chimarrita' and fruits and leaves of the apple cultivar 'Gala'. Larvae of S. eridania could not complete their biological cycle when fed on apple fruits or peach leaves. The artificial diet provided the shortest development time, with a cycle of 28.5±0.14 days from egg to adult and 37.3% total viability. Apple leaves led to a longer development time from egg to adult (62.8±1.22 days) and lower total viability (23%) and white clover provided the highest total viability (54.3%). The results showed that S. eridania can use white clover and apple leaves to develop normally in apple orchards. The reduction of food sources such as white clover used by the larvae results in infestation and damage to fruits from "test bites".

Resumo O desenvolvimento e o potencial reprodutivo de Spodoptera eridania (Stoll, 1782) (Lepidoptera, Noctuidae) foi comparado em dietas naturais e artificial. A biologia de S. eridania foi determinada em condições de laboratório, comparando-se uma dieta artificial com folhas de trevo branco e de pêssego da cultivar 'Chimarrita' e frutos e folhas de maçã da cultivar 'Gala'. As larvas de S. eridania não puderam completar seu ciclo biológico quando alimentadas com frutas de maçã ou folhas de pêssego. A dieta artificial proporcionou o menor tempo de desenvolvimento, com um ciclo completo de 28,5 ± 0,14 dias de ovo a adulto e 37,3% de viabilidade total. As folhas de maçã levaram maior tempo de desenvolvimento de ovo a adulto (62,8 ± 1,22 dias) e menor viabilidade total (23%). O trevo branco apresentou a maior viabilidade total (54,3%). Os resultados mostraram que S. eridania pode usar trevo branco e folhas de maçã para se desenvolver normalmente em pomares de maçã. A redução de fontes alimentares, como o trevo branco usado pelas larvas, resulta em infestação e danos aos frutos através das "mordidas de prova".

Development and reprotuction of Spodoptera eridania on natural hosts and artificial diet.

The development and reproductive potential of Spodoptera eridania (Stoll, 1782) (Lepidoptera, Noctuidae) was compared on natural and artificial diets. Its biology was determined under laboratory conditions, providing an artificial diet, leaves of white clover and the peach cultivar 'Chimarrita' and fruits and leaves of the apple cultivar 'Gala'. Larvae of S. eridania could not complete their biological cycle when fed on apple fruits or peach leaves. The artificial diet provided the shortest development time, with a cycle of 28.5±0.14 days from egg to adult and 37.3% total viability. Apple leaves led to a longer development time from egg to adult (62.8±1.22 days) and lower total viability (23%) and white clover provided the highest total viability (54.3%). The results showed that S. eridania can use white clover and apple leaves to develop normally in apple orchards. The reduction of food sources such as white clover used by the larvae results in infestation and damage to fruits from "test bites".

Bioassay Method for Toxicity Studies of Toxic Bait Formulations to Ceratitis capitata (Diptera: Tephritidae).

The development of appropriate methodologies for bioassays is of paramount importance to study the methodological factors that may interfere in the experimental design. Thus, laboratory bioassays have become increasingly important for the determination of data that are realistic and replicable. The objective of the study was to develop a bioassay methodology with the ready-to-use toxic bait Success™ 0.02CB, 96 mg L-1 of spinosad, in adults of Ceratitis capitata (Wiedemann) as a study model. The insect origin (laboratory population, LT50 = 11.16 h), time of toxic bait supply (4 h, LT50 = 16.85 h), food deprivation (12 h, LT50 = 15.55 h), and the adult age (5 days, LT50 = 35.31 h) of C. capitata showed higher susceptibility and a shorter LT50 lethal time to the Success™ 0.02CB toxic bait. However, the absence or presence of a food source (LT50 ≈ 31.17 h) during the bioassay did not affect the susceptibility of C. capitata. Further, adults of C. capitata who were deprived and in the absence of a food source (artificial diet) had higher consumption of toxic baits (mg) during treatment exposure. The use of a 12-h deprivation period, toxic baits offered for 4 h, and absence of an artificial diet for adults of C. capitata at 5 days of age during the bioassay are considered adequate for evaluating formulations of toxic baits under laboratory conditions.

Susceptibility and Interactions of Drosophila suzukii and Zaprionus indianus (Diptera: Drosophilidae) in Damaging Strawberry.

Drosophila suzukii (Matsumura) has been recently detected causing damage to strawberries in Brazil. Infestation in strawberry culture has often been observed jointly with the presence of Zaprionus indianus Gupta. This study investigated the susceptibility of strawberries at three ripening stages to infestation of D. suzukii and Z. indianus and their interaction. In the laboratory, strawberries cv. Albion at different ripening stages (green, semi-ripe and ripe) were exposed to D. suzukii and Z. indianus for 24 h in choice and no-choice bioassays. Additionally, we evaluated the effects of mechanical damage incurred artificially or by D. suzukii oviposition on Z. indianus infestation. In no-choice bioassay, there were no significant differences in fruit susceptibility to D. suzukii infestation at different ripening stages. However, in choice bioassay, D. suzukii adults preferred to oviposit on R fruit. The presence of mechanical damage did not increase susceptibility of fruit to D. suzukii oviposition. For Z. indianus, there was greater susceptibility of R fruit in relation to SR and G fruit in both the choice and no-choice bioassays. There was a significant and positive interaction of mechanical damage and damage caused by D. suzukii to R fruit and infestation by Z. indianus, which was not observed in SR and G fruit. Although infestation of Z. indianus is related to attack damaged or decaying fruit, this work shows that this species has the ability to oviposit and develop in healthy strawberry fruit with and increased infestation level when the fruit has damage to its epidermis.

Seasonal Life Cycle of Linepithema micans (Forel) (Hymenoptera: Formicidae) in Vineyards.

Linepithema micans (Forel) is considered to be the main ant species responsible for the spread of Eurhizococcus brasiliensis (Wille), a soil scale that damages vine plants in southern Brazil. In this work, the seasonal life cycle of L. micans was evaluated in vineyards to define the most appropriate time for the application of toxic baits for control. Ant nests were transported to the laboratory in plastic bags, and individual ants were separated into groups of eggs, larvae, pupae, workers, males, and queens, recording the number of individuals per colony. The seasonal life cycle of L. micans in the vineyards began in spring with the deposition of eggs by queens. During the warm months of the year (spring and summer), it was possible to observe nests consisting primarily of eggs and pupae. During the autumn and winter months, the colonies were composed predominantly of larvae and a reduction in eggs was observed. Because the main control strategy targets the larval stage of the insect, the application of toxic baits for the control of L. micans must be performed during the winter.