Establishment Probability of Anastrepha grandis and Zeugodacus cucurbitae (Diptera: Tephritidae) in Brazilian Semiarid Based on Thermal Requirements

The quarantine pests, Anastrepha grandis (Macquart) and Zeugodacus cucurbitae (Coquillett), are economically important for the fruit fly-free area in Brazilian semiarid, an area in which they are not yet present. Therefore, the objective of this study was to assess the probability of establishment of A. grandis and Z. cucurbitae based on the estimate number of generations in different climatic regions of the Brazilian semiarid. For scenarios of future projections, it was estimated the number of generations with increase of 1°C (low radiative forcing scenario) and 4°C (high radiative forcing scenario) in the air temperature. Finally, we also estimate the quarantine period to eliminate the invading population of cucurbit fruit flies in Brazilian semiarid. For this, the average historical air temperature of 32 semiarid municipalities was used and the biology data of fruit flies (thermal threshold of development and thermal constant) were used. The fruit flies are able to present several generations per year in Brazilian semiarid. Anastrepha grandis can present from 7.99 (Sergipe) to 9.66 (Piauí) generations. The melon fly Z. cucurbitae may present from 31.25 (Sergipe) to 40.66 (Piauí) generations. The estimation of species multiplication is accentuated in any season, with greater amplitude in spring and summer. The municipalities of Piauí, Ceará, and Rio Grande do Norte presented the highest estimates of fruit fly generations. The increase of air temperature in a future scenario may favor the quarantine pests, A. grandis and Z. cucurbitae, in Brazilian semiarid. In conclusion, the species A. grandis and Z. cucurbitae can be established in Brazilian semiarid, with particular concern for the fruit fly-free area.

Threshold Concentration of Limonoids (Azamax) for Preventing Infestation by Mediterranean Fruit Fly (Diptera: Tephritidae)

This study identified the threshold concentration of limonoids for the complete inhibition of oviposition of Ceratitis capitata (Wiedemann) in grapes 'Itália.' Choice and no-choice experiments with the insect were performed. The three no-choice bioassays were conducted following a completely randomized design with 18 treatments (three densities of insects [one, two, or three females]×five concentrations of limonoids and control) and 20 replicates. In a free choice bioassay, two fruits per cage (a treatment grape and a control) were provided for ovipositing. Three densities of insects (one, two, or three females) were used, with 15 replicates. Bioassays were conducted at 25±2°C, 60±10% relative humidity, and a photoperiod of 14:10 (L:D) h. The inhibition of oviposition of C. capitata was concentration dependent, with infestation occurring at lower concentrations of azadirachtin (+3-tigloylazadirachtol) and complete inhibition occurring at concentrations at or exceeding 100 ppm azadirachtin (+28.5 ppm of 3-tigloylazadirachtol), maintaining protective effects even at the most densely populated treatment (three females per fruit). When the pest had a free choice of host grapes (treatment vs. control), severe inhibition was observed at concentrations≥50 ppm azadirachtin (+14.3 ppm of 3-tigloylazadirachtol). We conclude that a threshold concentration of 100 ppm azadirachtin (+28.5 ppm of 3-tigloylazadirachtol) is capable of preventing grape infestation. This concentration is likely to provide a reliable level of protection, as the experimental population density of three females per fruit usually does not occur in the field and wild flies usually have more host options.

Neem derivatives are not effective as toxic bait for tephritid fruit flies

Neem derivatives have been widely touted as replacements for pesticides. A feasible replacement of synthetic insecticides in the management of fruit flies could be to use neem products in baits. This study evaluated the bioactivity of neem (Azadirachta indica A. Juss) derivatives in bait for adults of Anastrepha fraterculus (Wiedemann) and Ceratitis capitata (Wiedemann). The estimated LCs50 values for A. fraterculus and C. capitata were 7,522 ppm (18.40 ppm of azadirachtin) and 1,368 ppm (3.35 ppm of azadirachtin), respectively, using an aqueous extract of neem seeds in bait after 10 d of experimentation. No significant differences in the mortality of A. fraterculus and C. capitata adults exposed to baits made from different extracts and neem oil were observed after 3 h or 2 or 6 d; differences among the treatments were observed only on the 10th day of the evaluation. We conclude that neem derivatives applied as a bait spray over citrus plants did not demonstrate a toxic effect on A. fraterculus and C. capitata. The reasons for the low efficacy of the neem bait on Tephritid fruit flies are discussed.