Predicting impact of climate change on habitat suitability of guava fruit fly, Bactrocera correcta (Bezzi) using MaxEnt modeling in India

Maximum entropy (MaxEnt) modeling was used to predict impact of climate change on habitat suitability of guava fruit fly, Bactrocera correcta in India. It is a polyphagus pest on a wide variety of fruit crops. Future prediction of potential habitat of B.correcta was done for the year 2050 and 2070 with RCP 2.6, RCP 4.5, RCP 6.0 and RCP 8.5 climate scenarios. The model preformed better than random with an average test AUC value of 0.75 of 100 replicate tests run. Under the present and future climatic conditions, the model predicted high habitat suitable category for B. correcta in the areas of south-western coastal (Kerala, Karnataka, Tamilnadu, Maharashtra and Gujarat) part of India by 2050 and 2070. Presently absolute unsuitable areas of Indian sub-continent are projected to be slightly suitable for B. correcta by 2070 due to increase in temperature coupled with decrease in cold stress. The predictive modeling approach presented here provides an outline for future risk of B.correcta in India under climate change scenarios, which can be used for its better management strategies.

Influence of adult diet and exposure to methyl eugenol in the mating performance of Bactrocera correcta

The Guava fruit fly Bactrocera correcta is serious pest attacking Dragon fruit (Hylocereus undatus and Hylocereus polyrhizus ). The study on the impact of (i) Protein in adult diet on sexual maturity of Guava fruit fly; (ii) Methyl eugenol (ME) feeding on sterilized male of Guava fruit fly; and (iii) Longevity of sterilized males and females feeding on different diets. All those trials were conducted for both sterile males and laboratory flies reared at Plant Protection Research Institute, Hanoi, Viet Nam. The initial results showed that the first age of sexual maturation of laboratory reared females are 7 days old and 8 days old when fed on a mix diet of hydrolyzed yeast: sugar (1:4) and only sugar diet, respectively. Four days after emergence, females on hydrolyzed yeast fed diet died. The highest percentage of mating for the period of 20 first days after emergence was recorded 7.19% at 11 days old of flies fed on sugar; 40.08% at 10 days old of flies fed on hydrolyzed yeast and sugar. The longevity of sterilized males was 30.7 days, 28.1 days and 3.2 days as feeding on mix of hydrolyzed yeast: sugar, sugar only and hydrolyzed yeast alone, respectively. Likewise, the longevity of females was 32.5 days on hydrolyzed yeast: sugar diet, 30.5 days on sugar only diet and 3.7 days on hydrolyzed yeast only diet. The percentage of sterile males feeding on ME at 3 days old was only 5% and reached 40% at 8 days old with feeding times of 44 seconds and 4 minutes 27 seconds respectively.

Highly variable COI haplotype diversity between three species of invasive pest fruit fly reflects remarkably incongruent demographic histories

Distance decay principles predict that species with larger geographic ranges would have greater intraspecific genetic diversity than more restricted species. However, invasive pest species may not follow this prediction, with confounding implications for tracking phenomena including original ranges, invasion pathways and source populations. We sequenced an 815 base-pair section of the COI gene for 441 specimens of Bactrocera correcta, 214 B. zonata and 372 Zeugodacus cucurbitae; three invasive pest fruit fly species with overlapping hostplants. For each species, we explored how many individuals would need to be included in a study to sample the majority of their haplotype diversity. We also tested for phylogeographic signal and used demographic estimators as a proxy for invasion potency. We find contrasting patterns of haplotype diversity amongst the species, where B. zonata has the highest diversity but most haplotypes were represented by singletons; B. correcta has ∼7 dominant haplotypes more evenly distributed; Z. cucurbitae has a single dominant haplotype with closely related singletons in a ‘star-shape’ surrounding it. We discuss how these differing patterns relate to their invasion histories. None of the species showed meaningful phylogeographic patterns, possibly due to gene-flow between areas across their distributions, obscuring or eliminating substructuring.

Chemical Compounds from Female and Male Rectal Pheromone Glands of the Guava Fruit Fly, Bactrocera correcta

The guava fruit fly, Bactrocera correcta, is one of the major pests affecting mango (Mangifera indica) and guava (Psidium guajava) production in China. The compound β-caryophyllene was identified from the rectal gland extracts of wild B. correcta males and was demonstrated to be a more specific and potent male lure than methyl eugenol (ME) for B. correcta. In order to find potential additional pheromone attractants for the monitoring and mass-trapping of this fruit fly, a series of chemical and behavioral assays were conducted in this study. Ten compounds were identified from the rectal glands of virgin B. correcta females. These compounds consisted of five major compounds (i.e., ethyl dodecanoate, ethyl tetradecanoate, ethyl (E)-9-hexadecenoate, ethyl hexadecanoate, and ethyl (Z)-9-octadecenoate) in high quantities, and other compounds (i.e., octanal, N-(3-methylbutyl) acetamide, (Z)-9-tricosene, ethyl octadecanoate, and ethyl eicosanoate) in trace amounts, while virtually no compounds were found in male rectal glands. The bioassays indicate that female rectal gland extracts are attractive to virgin females and males. Furthermore, a cyclical production of the five major compounds was found, recurring at roughly 10-d intervals with peaks in 10–13-, 25-, and 35-d-old females. Collectively, these results will contribute to the understanding of pheromone communication in B. correcta and may provide important information for improving existing monitoring and control methods for this pest.