Neotropical Entomology最新文献

Seed beetles spend most of their lives within the seeds of host plants belonging to the Fabaceae family. Evidence suggests the cues that mediate pre-oviposition behaviour in Zabrotes subfasciatus (Boheman) are volatile organic compounds (VOCs) emitted by the seeds and suggests differential abilities in environment sensing between sexes. Here, we tested whether VOCs from different legume species trigger different levels of attraction, whether females and males differ in their ability to respond to VOCs, and whether the seeds promoting different behaviours feature singular VOCs. Finally, we tested females' response to selected VOCs from legume seeds with different levels of attraction. Behavioural assays testing the beetles' response to four Fabaceae species allowing varied levels of fitness (Phaseolus vulgaris, Glycine max, Lens culinaris, and Cicer arietinum) and antenna removal assays confirmed volatiles emitted by the seeds act as chemical cues for females and showed the seeds of the tested legume species trigger different levels of attraction. GC-MS analysis revealed the seeds of two of the species at the extreme of the preference hierarchy feature singular VOCs profiles and abundance. One of the differentially expressed VOCs found in higher quantities in P. vulgaris (ethenylbenzene = styrene) and one in C. arietinum (2-ethyl-1-hexanol) mediate opposing behaviours in Z. subfasciatus females. These results suggest host choice in Z. subfasciatus relies upon at least a two-component kairomone-based system: styrene attracts females to P. vulgaris seeds and 2-ethyl-1-hexanol keeps them from choosing C. arietinum as a substrate for oviposition. The system has evolutionary and agricultural relevance because it may allow for "niche" specialisation in seed stores and natural environments and may help develop pest management strategies.

This study analyzed the morphological characteristics of C. brunnea adults that allow for sexual differentiation. Sensilla trichodea, spatulate setae and lanceolate setae were found on the antennae, tarsi and tibiae apex, respectively, with no difference between sexes. Females of C. brunnea have a longer and wider body, as well as a longer fifth urosternite compared to males. The shape of the fifth urosternite allows for sex differentiation in C. brunnea adults.

This study discusses plant-mediated effects of beneficial soil-borne microorganisms on population growth parameters of Spodoptera exigua (Lepidoptera: Noctuidae), a major cotton pest. In particular, we investigated the impact of these microorganisms on oxidative stress, chlorophyll content, and sugar and protein levels in cotton plants, and how these changes in the plant affect the survival, development, reproduction, and ultimately population growth of the pest. A longer preadult period, lower preadult survival rate, and lower reproduction were obtained for the pest cohort feeding on treated plants, which resulted in lower population parameters, i.e., intrinsic growth rate, finite growth rate, and net reproduction rate. The population projection results showed the same trend as the population parameters. These results can be attributed to the changes caused by microorganisms in the treated plants. There was no oxidative stress in the treated plants. Instead, the chlorophyll content in these plants increased, and the protein-carbohydrate ratio decreased. Additionally, we assessed the effects of plant-insect-microorganisms interaction on total glutathione levels, glutathione S-transferase, and esterase enzyme activities in S. exigua. Overall results indicate that beneficial microorganisms tested enhance the plant's ability to defend against the pest. Additionally, the findings from this study provide valuable insights into the complex interplay among plants, microorganisms, and pests, offering potential strategies for incorporating these interactions into pest management practices.

The crop system of soybean (summer)-maize (fall/winter) succession has been adopted widely in the Neotropics. It inadvertently provides food to stink bugs between crops, forming "green-bridges," which favor Diceraeus melacanthus (Dallas) outbreaks. Attempts to control these outbreaks, usually occurring at the end of the soybean cycle and the beginning of the maize cycle, were made by spraying insecticides at the time of soybean desiccation in addition to insecticide seed treatment on maize, but apparently it has been insufficient to provide acceptable control. Therefore, this study was carried out in two consecutive seasons (2016 to 2018) to evaluate different management strategies for the control of D. melacanthus at the end of the soybean cycle and the beginning of the maize cycle, a period of time in which major D. melacanthus outbreaks have been frequently recorded. Late stink bug control (insecticide spray at development stage R7 of soybean) significantly reduced pest populations but left insecticide residue in the soybean grains. Pre-harvest desiccation with and without addition of insecticides (also at R7) also reduced pest populations but negatively impacted soybean yield. Seed treatment on maize numerically reduced the number of stink bugs, without significant difference from maize without seed treatment, but still resulting in higher yield. Thus, we conclude that the best of the here evaluated treatments is the adoption of soybean-IPM (Economic Threshold, ET at levels of two stink bugs/m) during soybean pod development/filling (R3 to R6) to guide insecticide use in addition to maize seed treatment.

The sugar beet flea beetle, Cassida vittata Vill. (Coleoptera: Chrysomelidae), is a major pest in Morocco's sugar beet crops and is primarily controlled with chemical insecticides despite environmental concerns. Our aim was to assess the impact of three biorational insecticides (spinosad at 30-7.5 cc/hL, mineral oil at 2000-250 cc/hL, and potassium salts of fatty acids at 1500-375 cc/hL) and two entomopathogenic fungi (Alternaria murispora and Alternaria destruens applied at 1.0 × 10⁸, 5.0 × 10⁷, and 2.5 × 10⁷ conidia mL^-1) both individually and in combination on C. vittata adults. All treatments were conducted at 25 ± 1 °C, with mortality recorded over 10 days. Conidial germination was highest for A. murispora with mineral oil (98.4%). Alternaria destruens showed consistently high germination across treatments. At 100% concentration, A. murispora + mineral oil and A. destruens + mineral oil treatments achieved 96.67 and 92.00% mortality, respectively. Median survival times (MST) for A. murispora were 6.0 days at 100% concentration, increasing to 10.0 days at lower concentrations, while A. destruens had a consistent 10.0 days MST. LC₅₀ for A. murispora was 1.3 × 10⁷ conidia mL^-1 alone, increasing to 2.2 × 10⁷ with spinosad, but remained 1.7 × 10⁷ with potassium salts of fatty acids. For A. destruens, LC₅₀ was 4.2 × 10⁷ conidia mL^-1 alone, decreasing to 1.5 × 10⁷ with mineral oil, and 3.1 × 10⁷ with potassium salts of fatty acids. Combining A. murispora with mineral oil and potassium salts of fatty acids enhanced efficacy against C. vittata.

Genetic diversity is an important attribute of populations, essential for understanding the ecological and evolutionary processes affecting them and assessing their health status. In Hymenoptera, such as eusocial bees, colony management can influence genetic diversity in both natural and managed populations. Management can impact admixture, increasing the number of alleles due to colony displacement and decreasing the number of alleles in natural populations due to colony extraction. In this study, we analyzed genetic diversity in natural and managed colonies as well as in drone congregations of Scaptotrigona mexicana (Guérin), to assess genetic diversity, patterns of genetic structure and gene flow, and the presence of diploid males. We identified three distinct genetic groups: Northern, Central, and Southern. Although genetic differentiation and limited gene flow among genetic groups were evident, we detected significant gene flow from wild to managed populations, suggesting that natural populations can be an important reservoir of genetic diversity. The highest genetic diversity was found in the Northern group, composed of managed localities. This is likely due to the introduction of new alleles through to colony translocation. Notably, some loci exhibited more than three alleles in localities where all analyzed individuals were from the same colony, indicating possible polyandry in the species. We also detected diploid males, which suggests inbreeding and/or inefficient mechanisms for their elimination from the colony. Our results provide an initial assessment of genetic diversity in both natural and managed populations, as well as in drone congregations of S. mexicana.

The Meliponini tribe is the most diverse group of social bees, thriving across tropical regions. Breeding stingless bees (meliponiculture) holds significant ecological and economic value. In meliponaries, multiple species often share small foraging areas, a scenario less common in natural environments. Due to deforestation, stingless bees face a diminishing availability of natural nesting sites, which are often found in hollow tree trunks. Consequently, meliponaries serve as a crucial nesting resource. In this study, we examined whether Melipona scutellaris and Tetragonisca angustula share pollen resources when reared closely together in high-density nest environment at the RCCO Meliponary in Aldeia, Camaragibe, and Pernambuco, which could potentially lead to competition. Our findings indicate that these bee species utilize different pollen sources, being Araceae type 1, Mimosoideae type 1, Asteraceae type 1, and Myrtaceae type 1 the most important for differentiating between groups. Their daily activity periods outside the nest differ, leading to varying responses to changes in temperature and humidity. The results suggest that competition for pollen resources may not be a significant issue between the two bee species in such situations.

This study addresses the challenge of predicting Dalbulus maidis (DeLong & Wolcott) (Hemiptera: Cicadellidae) density in cornfields by developing an artificial neural network (ANN). Over two years, we collected data on meteorological variables (atmospheric pressure, air temperature, dew point, rainfall, relative humidity, solar irradiance, and wind speed), plant age, and density of D. maidis in cornfields located in two Brazilian biomes (Atlantic Forest and Brazilian Tropical Savannah). Out of 1056 ANNs tested, the neural network featuring a 30-day time lag, six neurons, logistic activation, and resilient propagation demonstrated the lowest root mean squared error (0.057) and a high correlation (0.919) with observed D. maidis densities. This ANN exhibited an goodness of fit in low-density (Atlantic Forest) and high-density (Brazilian Tropical Savannah) scenarios for D. maidis. Critical factors influencing D. maidis seasonal dynamics, including corn plant age, rainfall, average air temperature, and relative humidity, were identified. This study highlights the potential of the ANN as a promising tool for precise predictions of pest seasonal dynamics, positioning it as a valuable asset for integrated pest management programs targeting D. maidis.

Aedes aegypti transmits the arboviruses that cause dengue, zika, and chikungunya. Entomopathogenic fungi are beneficial microorganisms that can be incorporated into current strategies against mosquitoes of public health concern. This study molecularly identified the Metarhizium anisopliae CG 153 isolate and evaluated its virulence against larvae, pupae, and adults (both males and females) of Ae. aegypti. Different concentrations of conidia were used (1 × 10^4-8 conidia mL^-1). Larval and pupal survival was monitored daily for seven and three days, respectively, while adults were monitored for 15 days. The efficacy of M. anisopliae sensu stricto was concentration-dependent, with higher concentrations achieving better results, demonstrating greater virulence against larval and adult stages of Ae. aegypti. The fungus reduced the larval survival by 95,5% (1 × 10⁸ con.mL^-1), 94,4% (1 × 10⁷ con.mL^-1), 78,9% (1 × 10⁶ con.mL^-1), 62,2% (1 × 10⁵ con.mL^-1), and 41,1% (1 × 10⁴ con.mL^-1) after seven days. Adults also showed susceptibility to the fungus, with no observed difference in susceptibility between males and females. Over 15 days of monitoring, adult survival rates ranged from approximately 6.7% to 72%. Pupae exhibited lower susceptibility to the fungus across different concentrations, with survival rates ranging from approximately 87.8% to 100%. This study highlights the high effectiveness of M. anisopliae CG 153 against both Ae. aegypti larvae and adults (male and female) under controlled conditions, suggesting its promising potential for further evaluation and application in field conditions.