Influence of Parental Age on Reproductive Potential and Embryogenesis in the Pepper Weevil, Anthonomus eugenii (Cano) (Col.: Curculionidae).

The pepper weevil (Anthonomus eugenii Cano) is a devastating pest that inflicts severe damage to pepper crops, leading to substantial economic losses. This study investigated the impact of aging on the reproductive success of the pepper weevil. Pepper weevil-infested fruit were harvested from pepper fields and subsequently transferred into an insect cage to facilitate the emergence of adults. The emerged adults were housed in separate cages and allowed to mature until they reached specified ages: 10 days old (young), 20 days old (middle-aged), and 30 days old (old) individuals. Eggs laid by each age group were carefully collected and incubated under controlled laboratory conditions (28 ± 1.5 °C). Several reproductive variables including the number of eggs laid, the percentage of hatched eggs, and the egg incubation period were recorded for each age group. Embryonic development was also monitored daily using a VHX digital microscope at a magnification of 200×. Differences in developmental stages such as the blastoderm, germ band, gastrulation, segmentation, and appendage formation were observed, and the time span of every stage was recorded. The results show that the 10-day-old weevils laid the most eggs and had the highest hatching rate and the shortest developmental time. The 30-day-old weevils laid the fewest eggs and had the lowest hatching rate and longest developmental time. Thus, the pepper weevil age significantly influenced the fecundity, length of time for each embryonic development stage, hatching rate, and incubation period, and should be considered when studying the reproductive biology of this pest insect. This first report of the effect of aging on the reproductive potential of the pepper weevil should enable pepper growers to adopt cultural practices aimed at reducing the pepper weevil populations, thereby helping to protect their crop from this important pest.

Assessing the sterility and quality of gamma-irradiated pepper weevils, Anthonomus eugenii (Coleoptera: Curculionidae), toward the development of the sterile insect technique.

BACKGROUND: The pepper weevil (PW), Anthonomus eugenii, is an economically significant pest of cultivated Capsicum spp. pepper crops in North America where it remains a challenge to manage because of its cryptic immature life stages. The sterile insect technique (SIT) is a genetic pest management tactic that relies on the release of insects that have been sterilized with ionizing radiation to lower the population reproductive rate. Toward developing an effective PW-SIT program, this study has, for the first time, investigated the effects of gamma irradiation on the sterility and survival of this species. RESULTS: Among the array of doses tested, we found that pupal PW males and females irradiated at 110 Gy produced no adult offspring. Furthermore, females mated with a male irradiated at 110 Gy had high egg sterility (97.3%), and irradiated females nearly completely failed to lay eggs (97.5%). Individuals irradiated at this dose had a shortened lifespan (lethal time to 50% mortality values of 12 and 11 days for males and females, respectively) and quantitatively reduced spontaneous flight activity. The eclosion rate of PW pupae was not significantly reduced by any radiation treatment. CONCLUSION: This study suggests that PWs irradiated at a gamma radiation dose of 110 Gy as pupae could feasibly be used in a PW-SIT program, because both males and females were 100% sterile at this dose. These findings will inform the development of a SIT program that could considerably improve the sustainability and effectiveness of PW management in greenhouse and field pepper crops worldwide. © 2023 His Majesty the King in Right of Canada and The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. Reproduced with the permission of the Minister of Agriculture and Agri Food Canada.

Integrated approach using insecticides in combination with reflective plastic mulch for the management of pepper weevil, Anthonomus eugenii (Coleoptera: Curculionidae).

Pepper weevil, Anthonomus eugenii Cano, is a serious pest of peppers (Capsicum annuum) in the United States and worldwide. This study evaluated the combined effect of insecticides (thiamethoxam and oxamyl) and reflective mulches (reflective silver on white and reflective silver on black) on pepper weevil suppression and yield increase. This study was conducted under field conditions in Homestead, FL, during the fall 2020, spring 2021, and 2022 growing seasons. The study consists of 2 mulch treatments as the main plots (reflective "silver on white," "white on black") and a bare ground with "no mulch" treatment in fall 2020 and spring 2021, and in spring 2022 with an additional treatment of reflective "silver on black" mulch. We hypothesized that jalapeño pepper grown on either reflective "silver on black" or "silver on white" plastic mulches would have fewer pepper weevil adults, fewer pepper weevil infested fruits, and higher yield than those grown on "white on black" plastic mulch or bare soil. Overall, the number of pepper weevil adults on plants and infested fruits was lower in the fall season compared to the spring season. In the fall 2020 season, the number of adults was not significantly different regardless of insecticide treatment and mulch type. However, infested fruits were higher on the untreated control plots than the treated plots in Fall 2020. Marketable yield was not significantly different among insecticide treatment on the "white on black" and reflective "silver on white" mulches. However, thiamethoxam treated plots had significantly higher yield than on the rest of the treatment on the bare soil with "no mulch." The number of adults was higher in the untreated control plot than the treated plots in spring 2021. The number of infested fallen fruits was not significantly different. However, marketable yield was significantly different among treatments on the "white on black" and reflective "silver on white" mulches in 2021. The treated plots on the reflective "silver on white" mulch produced significantly higher yield than the untreated control plots in 2022. The result of this study suggests that growing jalapeño peppers on reflective plastic mulch ("silver on white") in integration with thiamethoxam or oxamyl has the potential in reducing pepper weevil adult population and increasing yield of jalapeño pepper.

Odorant-Binding and Chemosensory Proteins in Anthonomus eugenii (Coleoptera: Curculionidae) and Their Tissue Expression.

The pepper weevil Anthonomus eugenii is one of the most damaging pests to the pepper crop. To offer alternative management strategies to insecticides, several studies have identified the semiochemicals that are involved in the pepper weevil's aggregation and mating behavior; however, there is no information on its perireceptor molecular mechanism, to date. In this study, bioinformatics tools were used to functionally annotate and characterize the A. eugenii head transcriptome and their probable coding proteins. We identified twenty-two transcripts belonging to families related to chemosensory processes, seventeen corresponding to odorant-binding proteins (OBP), and six to chemosensory proteins (CSP). All results matched with closely related Coleoptera: Curculionidae homologous proteins. Likewise, twelve OBP and three CSP transcripts were experimentally characterized by RT-PCR in different female and male tissues. The results by sex and tissue display the different expression patterns of the AeugOBPs and AeugCSPs; some are present in both sexes and all tissues, while others show expressions with higher specificity, which suggests diverse physiological functions in addition to chemo-detection. This study provides information to support the understanding of odor perception in the pepper weevil.

Effect of Pepper Variety on the Susceptibility of Pepper Weevil Parasitoids.

Anthonomus eugenii Cano (Coleoptera: Curculionidae) is a key pest of cultivated peppers (Capsicum species) in tropical and subtropical America. Here we evaluated the effect of five pepper varieties on the susceptibility of A. eugenii to the parasitoids Bracon sp. (Hymenoptera: Braconidae), Eupelmus cushmani (Crawford) (Hymenoptera: Eupelmidae), and Jaliscoa hunteri Crawford (Hymenoptera: Pteromalidae). Potential parasitism was estimated by comparative analysis of parasitoid ovipositor size and the depth to which host larvae develop inside the fruit. Highest potential parasitism rates were achieved by Bracon sp. and E. cushmani on árbol and habanero peppers (84-99%) while the lowest rates were achieved by J. hunteri on serrano, bell, and jalapeño (7-18%). To validate potential parasitism rates, the actual parasitism rate by Bracon sp. and J. hunteri on three varieties of peppers was assessed. Actual parasitism rates of A. eugenii larvae in árbol were similar for Bracon sp. and J. hunteri (33%), while on bell and jalapeño Bracon sp. achieved 24% and 13% parasitism and J. hunteri achieved 14% and 8%, respectively. In most cases, actual parasitism was lower than estimated potential parasitism, although the latter had a notable predictive power (predicted R2 = 0.84). Results showed that the host was more vulnerable on small-fruited varieties because larvae were closer to the pericarp and could be reached by parasitoid ovipositors; likewise, in varieties with little placenta and seed, some larvae fed in the pericarp, where they were more vulnerable.