Manipulation of Gut Symbionts for Improving the Sterile Insect Technique: Quality Parameters of Bactrocera dorsalis (Diptera: Tephritidae) Genetic Sexing Strain Males After Feeding on Bacteria-Enriched Diets.

One environmentally friendly method used to manage Bactrocera dorsalis (Hendel), a key agricultural pest of substantial economic importance, is the sterile insect technique (SIT). Nevertheless, several deficiencies related to this strategy impair the success of the SIT, including the inferior performance of released sterile males compared with wild males, which could be partly solved by the utilization of gut symbionts as probiotic dietary components. In this study, a culture-dependent method was used to isolate and characterize gut-associated bacterial species in adult B. dorsalis genetic sexing strain (GSS) males. In addition, three bacterial isolates from the Enterobacteriaceae family, namely, Enterobacter sp., Morganella morganii, and Moellerella wisconsensis, were used as supplements in larval and adult diets to assess their effects on the life-history traits of irradiated males. Consistent with many previous studies, Enterobacter spp. was shown to be beneficial, with some quality control indices, such as adult size, pupal weight, survival rate under stress and nutritionally rich conditions, and mating competitiveness, being significantly increased, while slight nonsignificant increases in emergence rate and flight ability were observed. Conversely, the M. morganii and M. wisconsensis strains both had negative effects on irradiated male fitness and mating competitiveness. Our results, in combination with those of earlier studies, can contribute to improving the effectiveness of SIT application by enhancing the different aspects of augmentative rearing and biological traits of pests under laboratory rearing conditions.

Tyrosine hydroxylase is crucial for pupal pigmentation in Zeugodacus tau (Walker) (Diptera: Tephritidae).

Tyrosine hydroxylase (TH) is the initial enzyme responsible for cuticle sclerotization and pigmentation in many insect species, but to date, no direct functional studies have focused on TH in Zeugodacus tau. Here, the 3336-bp full-length cDNA of TH was isolated from Z. tau, a notorious horticultural pest infesting fruits and vegetables. qRT-polymerase chain reaction revealed that ZtTH transcripts were highly abundant at the time of pupal tanning and during adult emergence and were expressed in the midgut, integument and head of molting larvae. The pupation and eclosion rates gradually decreased when the 1st-instar larvae were fed diets containing higher concentrations of the TH inhibitor 3-iodo-tyrosine (3-IT). Moreover, pupal weights were significantly decreased, and abnormal uncolored phenotypes were observed after 20 mg/g 3-IT was incorporated into the diet. In addition, the suppression of TH function (mediated by RNA interference) led to a decrease in TH mRNAs and eclosion rates, accompanied by less-pigmented phenotypes. There was a severe impairment of larval-pupal cuticle tanning, leading to pupae with less yellowish pigment or that were completely white and transparent, when we injected 2 µL of 24.4 mM or 73.27 mM 3-IT into 3rd-instar larvae or prepupae. These results suggest that TH is an important enzyme for the normal growth and pupal pigmentation of Z. tau and that TH is a potential gene target for use in the control of Z. tau.

Evaluation of Protein Bait Manufactured From Brewery Yeast Waste for Controlling Drosophila suzukii (Diptera: Drosophilidae).

We evaluated a protein bait based on an enzymatically hydrolyzed beer yeast and two widely used baits including a sugar + vinegar + wine mixture and apple cider vinegar for their ability to trap Drosophila suzukii (Matsumura) in the laboratory and outdoors. The protein bait was a more attractive lure than the other tested baits, with the protein bait capturing significantly more female and male adults at different developmental stages than the other baits. Furthermore, the protein bait with 20% vinegar attracted significantly more adult flies than the other baits, and the protein bait without dilution attracted the most adults. Except for the addition of 0.05% spinosad, increased insecticide content in protein bait reduced its attractiveness to adult flies. Moreover, we found that D. suzukii has a bimodal activity pattern in visiting protein bait, where maximum activity occurs during 8:00-10:00 a.m. and 14:00-16:00 p.m. The antennae and maxillary palpi played an important role in detecting the chemicals emitted from the protein bait, as the number of intact flies that responded to new protein bait was significantly higher than the number of flies without antennae that responded, but almost 15% of defective flies still responded to the protein bait. Our results suggested that the protein bait based on spent brewery yeast could be a promising alternative for D. suzukii population monitoring and for managing this pest when combined with bioinsecticides, providing guidance for using this protein bait as a component of integrated pest management.