Mortality of Fruit Flies (Diptera: Tephritidae) Exposed to Spinetoram Toxic Bait in the Laboratory

Fruit flies (Diptera: Tephritidae) cause significant losses during the production and marketing of horticultural products. Brazilian growers usually adopt full-coverage insecticide spraying to control fruit flies, but toxic bait is a more strategic technique, because reach efficacy and the target surface is the foliage and branches. We provide information regarding the toxicity of spinetoram bait to two fruit fly species in the laboratory as an alternative to organophosphates and the specific spinosad formulation. We tested toxic baits in the laboratory, using commercial hydrolysed corn protein (10% v/v) plus 90 g, 120 g, 150 g and 180 g dilutions of spinetoram 250 WG (commercial product/1,000 litres of water). All toxic baits were compared with an untreated control (only protein) for the adults of females and males of Anastrepha obliqua (Macquart, 1835) and Ceratitis capitata (Wiedemann, 1824) up to 30 hours of exposure. Dry food for adults was included in all dilutions (5% w/v). In addition, we tested the residual effect of toxic baits applied to the leaves of mandarin seedlings. We used the same treatments of the earlier bioassay without dry food, collecting treated leaves and exposing them to C. capitata (medfly) females for 24 hours in the laboratory. Leaves were collected 1, 3, 7, 15 and 30 days after application. Overall, medfly adults were more susceptible to spinetoram baits than A. obliqua. All toxic baits resulted in 100% C. capitata mortality 24 hours after initial exposure, and the toxic bait at 150 g/1,000 L of water resulted in the maximum mortality (96%) in A. obliqua. Except for 90 g of spinetoram bait at 30 days after application, all spinetoram bait concentrations resulted in significantly, more dead C. capitata females than the control over all tested periods in the residual bioassay. At 30 days after application, spinetoram baits at 120 g, 150 g and 180 g resulted in 85%, 87% and 86% mortality in C. capitata, respectively. Spinetoram toxic baits have proven promising for long-term fruit fly management.

Genomic Traces of the Fruit Fly Anastrepha obliqua Associated with Its Polyphagous Nature

Anastrepha obliqua (Macquart) (Diptera: Tephritidae) is an important pest in the neotropical region. It is considered a polyphagous insect, meaning it infests plants of different taxonomic families and readily colonizes new host plants. The change to new hosts can lead to diversification and the formation of host races. Previous studies investigating the effect of host plants on population structure and selection in Anastrepha obliqua have focused on the use of data from the mitochondrial DNA sequence and microsatellite markers of nuclear DNA, and there are no analyses at the genomic level. To better understand this issue, we used a pooled restriction site-associated DNA sequencing (pooled RAD-seq) approach to assess genomic differentiation and population structure across sympatric populations of Anastrepha obliqua that infest three host plants—Spondias purpurea (red mombin), Mangifera indica (mango) of the family Anacardiaceae and Averrhoa carambola (carambola) of the family Oxalidaceae—in sympatric populations of the species Anastrepha obliqua of Inter-Andean Valley of the Cauca River in southwestern Colombia. Our results show genomic differentiation of populations from carambola compared to mango and red mombin populations, but the genetic structure was mainly established by geography rather than by the host plant. On the other hand, we identified 54 SNPs in 23 sequences significantly associated with the use of the host plant. Of these 23 sequences, we identified 17 candidate genes and nine protein families, of which four protein families are involved in the nutrition of these flies. Future studies should investigate the adaptive processes undergone by phytophagous insects in the Neotropics, using fruit flies as a model and state-of-the-art molecular tools.

Mating, but Not Male Accessory Gland Products, Changes Female Response to Olfactory Cues in Anastrepha Fruit Flies

Copulation and/or ejaculate components can alter female physiological state and female post-mating behavior. The objective of the present study was to determine if copulation and male reproductive accessory gland products (MAGs) modify the behavior of female Anastrepha ludens (Loew) and Anastrepha obliqua (Macquart; Diptera: Tephritidae) in response to two stimuli: male-emitted pheromone and oviposition host volatiles. Olfactometry studies revealed that mated females of both A. ludens and A. obliqua have a stronger response for host volatiles compared to unmated females, which have a stronger response for male pheromone. We also examined olfactory responses of females mated to testectomized males who could transfer MAGs but not sperm. In both species, MAGs alone did not cause the change in the olfactory response observed after copulation, unlike what has been found in Ceratitis capitata (Wiedemann). Females mated to testectomized males responded equally to the male sex pheromone or to host volatiles, thus suggesting that the whole ejaculate is needed to elicit the complete behavioral switch in olfactory response. The function of MAGs is still unknown in these two pests of economic importance. The response for host volatiles by mated females has implications for the development of baits and traps that should preferably attract and target this population.

The fruit fly Anastrepha obliqua harbors three kingdoms of life in its intestinal tract.

The fruit fly Anastrepha obliqua is an economically important pest for mango fruits in Mexico. The sterile insect technique is used to control this pest; it involves mass production and release of sterile flies to reduce the reproduction of the wild population. As noted in different tephritidae, the performance of sterile males may be affected by the assimilation of nutrients under mass-rearing conditions. In the wild, the fly's life cycle suggests the acquisition of different organisms that could modulate the fitness and physiology of the fly. Therefore, the microorganisms lodged in the gut may be determinative. For A. obliqua, there is no information regarding microorganisms other than bacteria. This study analyzed bacteria, fungi, and archaea communities in the A. obliqua gut through denaturing gradient gel electrophoresis (DGGE) profiles of 16S and 18S ribosomal DNA markers. Besides, 16S sequencing and phylogenetic analysis provided a better description of bacteria and archaea communities. We found that wild flies presented higher microbial diversity than laboratory samples. Phylogeny analyses of wild samples suggest the presence of microbial species related to fructose assimilation while laboratory microbial species suggest the presence of microorganisms leading to a specialized metabolism to process yeast as a result of the consumption of an artificial diet. Here, the archaea kingdom is suggested as an important player in fly metabolism. This is the first report of the intestinal microbial (bacteria, archaea, and fungi) composition of A. obliqua, which will aid in our understanding of the role of microorganisms in the development and physiology of the flies.

Influence of Mineral Particle Films and Biomaterials on Guava Fruits and Implications for the Oviposition of Anastrepha obliqua (Macquart) (Diptera: Tephritidae)

Anastrepha obliqua (Macquart, 1835) is an important pest of tropical fruits, especially Anacardiaceae and Myrtaceae, in the Americas. The objective of this study was to evaluate the influence of mineral films and biomaterials on the coloring of guava fruits (Psidium guajava L.) and implications for the oviposition of A. obliqua. Before the bioassays, color, firmness characteristics, total soluble solids, pH, and titratable acidity were determined to characterize the maturation stage of the fruits. Pieces of guava fruit covered in aluminum foil were immersed in suspensions of mineral particles (Surround® WP kaolin; kaolins 605, 607, 608, and 611; and talc) and biomaterials (chitosan, cassava and potato starch, and guar gum) and distilled water (control). After drying, the fruits were exposed to two A. obliqua pairs for 48 h in choice and non-choice tests, and the numbers of eggs per fruit were counted. Mineral films (Surround® WP kaolin, and kaolins 605, 607, 608, and 611) and biomaterials (cassava and potato starch) interfered with the color of guava (luminosity, chroma, and hue angle), inhibiting the oviposition of A. obliqua. Talc, chitosan, and guar gum did not influence the oviposition of A. obliqua in guava.

Anastrepha ludens (Mexican fruit fly).

A. ludens has a broad host range and is a major pest, especially of citrus and mango (Mangifera indica) in most parts of its range. This species and Anastrepha obliqua are the most important pest species of Anastrepha in Central America and Mexico. It occurs in subtropical areas as far north as southern Texas, thus it may be more of a threat of introduction to other subtropical areas of the world than other species of Anastrepha. It is invasive at least in Panama and has been trapped in California, USA. It is considered an A1 quarantine pest by EPPO.

Anastrepha obliqua (West Indian fruit fly).

A. obliqua is the most important fruit fly pest of mango (Mangifera indica) in the Neotropics and attacks a broad range of other fruits. It is widespread in Mexico, Central and South America and the West Indies. It is invasive in the Lesser Antilles and was temporarily established in Key West, Florida, USA. It should be considered a serious threat to other tropical parts of the world, particularly mango-producing regions. It is considered an A1 quarantine pest by EPPO.