Seasonal variation strongly influences insect communities, particularly in seasonally dry ecosystems where climatic conditions and resource availability fluctuate markedly throughout the year. We investigated inter- and intraseasonal variation in the species richness and composition of beetle (Coleoptera) trophic guilds in a tropical montane semiarid region of Brazil. Beetles were sampled with pitfall traps during 2 periods of the dry season and 2 periods of the rainy season. Species richness and composition of the overall assemblage and of detritivorous, herbivorous, and predatory guilds were evaluated using generalized linear mixed effects models and multivariate analyses. Seventy-one species belonging to 14 families and 43 genera were recorded. Most species occurred during the rainy season, particularly during its onset. Species composition differed markedly between the beginning and the end of the rainy season, indicating pronounced intraseasonal turnover, whereas little variation was observed within the dry season. Seasonal responses differed among trophic guilds. Detritivorous beetles were concentrated mainly at the beginning of the rainy season, herbivorous beetles exhibited a broader temporal distribution extending into the dry season, and predatory beetles showed high species turnover during the rainy season despite relatively stable richness. These results demonstrate that beetle trophic guilds respond differently to temporal variation in environmental conditions and resource availability. Intraseasonal climatic fluctuations contribute substantially to temporal turnover, emphasizing the importance of considering both inter- and intraseasonal variation to understand beetle community dynamics in seasonally dry ecosystems.
Tetranychus truncatus Ehara (Acari: Tetranychidae) is one of the major economically important mite pests of numerous plant species. The predatory mite Amblyseius longispinosus (Evans) (Acari: Phytoseiidae) has been successfully used in biological control programs. This study evaluated the contact toxicity activities of ethanol extracts from 5 plants—Cymbopogon nardus (L.) Rendle, Ocimum basilicum L., Ocimum sanctum L., Andrographis paniculata (Burm.f.) Nees, and Stemona tuberosa Lour.—against T. truncatus and A. longispinosus. The ethanol plant extracts revealed different toxicity activity against T. truncatus and A. longispinosus. At concentrations of 7–9% (w/v), Cy. nardus and S. tuberosa extracts showed significant direct contact toxicity against T. truncatus adults, resulting in mortality rates of 64.00–70.67 and 51.33–55.00%, respectively, at 3 d after treatment. Application of 3–9% concentrations of Cy. nardus, 5–9% concentrations of O. basilicum and O. sanctum, and 9% concentrations of A. paniculata to T. truncatus eggs reduced egg viability, with >50% unhatched eggs 4 d following treatment. Concentrations of 5–9% of Cy. nardus and O. sanctum extracts were moderately toxic to A. longispinosus in residual contact toxicity, with mortality ranging from 22.67–34.67 and 22.67–29.33%, respectively, at 3 d after exposure. Based on our findings, extracts of Cy. nardus and T. tuberosa show promise as botanical acaricides for controlling T. truncatus adults, whereas extracts of Cy. nardus, O. basilicum, O. sanctum, and A. paniculata may be effective for the control of T. truncatus eggs. Furthermore, Cy. nardus and O. sanctum extracts negatively affected A. longispinosus.
Pealius kufriensis Dubey is a newly recorded species to China, which was originally described from Western Himalaya, India, by Dubey and Singh in 2021. It was collected from Phoebe sheareri (Lauraceae) in Zhejiang Province. The puparium of Pealius kufriensis is redescribed and illustrated by line art, photomicrographs, and scanning electron microscope photographs. Puparia closely resemble Pealius rubi Takahashi in setation and vasiform orifice, but the 2 species differ in subdorsal and abdominal setae. Leaves from which the specimens were collected were infested with 300 to 400 puparia per leaf. Sooty mold had grown in the sap deposited by the pests, thus, reducing photosynthetic activity in the leaves. The known distribution of Pealius kufriensis is in China (Zhejiang) and India. Host plants are reportedly Phoebe sheareri (Lauraceae) and Rubus ellipticus Smith (Rosaceae). This represents the first record of Pealius kufriensis in China and on Phoebe sheareri. All specimens are deposited in the Insect Collection of Zhejiang Agriculture & Forestry University (Lin'an, Zhejiang, China).
The pear psylla, Cacopsylla chinensis (Yang and Li) (Hemiptera: Psyllidae), is 1 of the most widespread and serious pests of commercial pear orchards in China. Development of effective strategies to control C. chinensis is critical for devising a sustainable integrated pest management (IPM) program. Identification of cultivars with natural resistance is included among these measures. In this study, we compared the resistance of 2 endemic cultivars of Pyrus bretschneideri Rehder (i.e., BHXS and BSL) and 2 introduced cultivars of P. communis L. (i.e., CB and CRB) to C. chinensis based on antixenosis and antibiosis under laboratory, field, and semifield conditions. The results indicated that infestations on the P. bretschneideri cultivars were significantly higher than those on the P. communis cultivars. The numbers of both summer adults and eggs were significantly higher on BSL (or BHXS) than on CB (or CRB). Although the differences in nymphal survival rate were not found prior to Day 21, the population age structure index at 14 d postinfestation was significantly higher on BSL and BHXS than on CB and CRB. Both P. communis cultivars had lower fitness and negative effects on host choice, oviposition of summer adults, and survival and development of nymphs. These introduced pear varieties may be selected as new scions, high grafting rootstocks, or a source of resistant genes in breeding programs. Their contributions can be significative in providing available materials and methods for use in IPM programs.
The fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), is the most significant pest of maize (Zea mays L.) worldwide. However, in regions where insecticides are not applied, damage and yield losses caused by this pest are not always substantial. One hypothesis to explain this phenomenon is the role of natural control. This study was conducted to identify the key mortality factors affecting immature stages of S. frugiperda under field conditions. Field and greenhouse experiments were conducted in Texcoco, State of Mexico, in 2021. The Davis scale was used to assess S. frugiperda damage on maize plants. Under field conditions, egg mortality ranged from 38% to 44%, primarily due to predation and wind-induced detachment. Larval survival in the field reached approximately 6%, with a parasitism rate of 12.5% (Campoletis sonorensis (Cameron): 9.5%; Winthemia occidentis Reinhard: 3%). In contrast, larval survival on greenhouse-grown maize was 49.7%. Pupal mortality in the field ranged from 31% to 63%, largely attributed to predation by ants of the genus Solenopsis. Regarding plant damage, in greenhouse trials with 100 S. frugiperda larvae released on 25 plants, 100% of plants exhibited damage (Davis levels 4-7). In contrast, only 5-9% of field-grown plants were affected, all below level 7. These findings indicate that biotic and abiotic factors significantly influence S. frugiperda mortality in agroecosystems without insecticide use, underscoring the importance of natural control in regulating pest populations.
