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Phenacoccus solenopsis Tinsley is a pest that poses a significant threat to agricultural crops, especially cotton, and is now widely distributed across many regions worldwide. In this study, we performed a meta-analysis on the collected experimental data and found that within the suitable temperature range, the survival rate of P. solenopsis increases with rising temperatures, indicating that climate plays a decisive role in its distribution. Using the MaxEnt model this study predicted that under three future climate scenarios (SSP1–2.6, SSP3–7.0, and SSP5–8.5), the distribution of P. solenopsis will expand and move towards higher latitudes. Climate change is the primary factor influencing changes in pest distribution. We conducted a meta-analysis of P. solenopsis, including seven independent studies covering 221 observation results, and examined the impact of temperature ranging from 18 °C to 39 °C on the developmental cycle of P. solenopsis. As the temperature rises, the development cycle of P. solenopsis gradually decreases. Additionally, by combining the MaxEnt model, we predicted the current and potential future distribution range of P. solenopsis. The results show that under future climate warming, the distribution area of P. solenopsis in China will expand. This research provides a theoretical basis for early monitoring and control of this pest’s occurrence and spread. Therefore, the predictive results of this study will provide important information for managers in monitoring P. solenopsis and help them formulate relevant control strategies.

Phenacoccus solenopsis Tinsley is a highly invasive pest threatening global cotton production and numerous cultivated crops. The sterile insect technique (SIT), based on γ-ray irradiation, offers a sustainable and eco-friendly alternative to chemical controls for managing pests. This study aimed to determine the optimal developmental stage and radiation dose to induce sterility in P. solenopsis. Male pupae aged 5 days demonstrated the highest tolerance to irradiation among all tested age groups. These 5-day-old male pupae were irradiated with 20, 40, 60, and 100 Gy and mated with unirradiated females, and the effects on mating rate, oviposition stage, egg number, egg hatchability, male adult lifespan, and female sex ratio were assessed. Sterility was effectively induced by 60 Gy in males without compromising their mating competitiveness in the parental (F0) generation. Moreover, sterility traits were inherited by descendants, leading to a progressive decline in population size across the F1 and F2 generations. Therefore, a 60 Gy dose was identified as optimal for suppressing P. solenopsis in field settings. These findings establish a theoretical foundation for implementing SIT as a regional pest management strategy for P. solenopsis.

Aenasius arizonensis (Girault) (Hymenoptera: Encyrtidae) is an important solitary endoparasitoid of mealybug, Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae). Studies on seasonal and biological interactions between host and parasitoid are important to optimize the mass production and field release of high-quality females. We investigated the influence of different crop seasons viz., pre-monsoon, monsoon and post-monsoon and host stages viz., three nymphal instars (1st, 2nd and 3rd) and adult stage of P. solenopsis on the development, longevity, fecundity and sex ratio of its parasitoid, A. arizonensis. A. arizonensis female parasitized all life stages of its host except the 1st instar nymphs. Only males emerged from parasitized 2nd instar nymphs, while the sex ratio in the later host instars was strongly female-biased. The adult host stage was most suitable for A. arizonensis in terms of shorter development time, while the 3rd instar nymphal stage was most suitable with respect to higher fecundity, proportion of adults emerged and more females in the progeny. Among different seasons, post-monsoon season (September–October) with temperature (25 to 29 °C) and relative humidity (68 to 73%) was most suitable for the overall fitness of the parasitoid. The findings of this study have implications in designing mass rearing of this parasitoid and devising an effective biological control strategy for P. solenopsis on cotton.

The mealybug species Phenacoccus solenopsis (P. solenopsis) has caused much agricultural damage since its recent invasion in China. However, the source of this invasion remains unclear. This study uses molecular methods to clarify the relationships among different population of P. solenopsis from China, USA, Pakistan, India, and Vietnam to determine the geographic origin of the introduction of this species into China. P. solenopsis samples were collected from 25 different locations in three provinces of Southern China. Samples from the USA, Pakistan, and Vietnam were also obtained. Parts of the mitochondrial genes for cytochrome oxidase I (COI) were sequenced for each sample. Homologous DNA sequences of the samples from the USA and India were downloaded from Gen Bank. Two haplotypes were found in China. The first was from most samples from the Guangdong, Guangxi, and Hainan populations in the China and Pakistan groups, and the second from a few samples from the Guangdong, Guangxi, Hainan populations in the China, Pakistan, India, and Vietnam groups. As shown in the maximum likelihood of trees constructed using the COI sequences, these samples belonged to two clades. Phylogenetic analysis suggested that most P. solenopsis mealybugs in Southern China are probably closely related to populations in Pakistan. The variation, relationship, expansion, and probable geographic origin of P. solenopsis mealybugs in Southern China are also discussed.

Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae) an invasive mealybug on cotton is primarily controlled by conventional insecticides. An endoparasitoid Aenasius arizonenesis (Girault) (Hymenoptera: Encyrtidae) is a potential biocontrol agent of this pest. We assessed the susceptibility in field populations of P. solenopsis and A. arizonensis to commonly used insecticides: profenofos, imidacloprid and thiodicarb . Reproductive traits of the parasitoid and Environmental Risk Assessment (ERA) parameters viz., Reduction coefficient, Descriptive analysis, Risk Index (RI), Selectivity ratio and Hazard quotient were measured to assess the direct and indirect effects of these insecticides on the parasitoid. Probit analysis revealed heterogeneity in the insecticide resistance development for both the cotton mealybug and its parasitoid. The field populations of P. solenopsis exhibited resistance to profenofos (18.87–59.86 folds) and thiodicarb (20.07 folds) and susceptibility to imidacloprid. Development of resistance to profenofos was observed in field populations of A. arizonensis . Exposure to lethal doses of imidacloprid and profenofos caused a reduction in parasitization (19–23%) and adult emergence (62–69%) of the parasitoid. Profenofos, thiodicarb and imidacloprid were found to be hazardous, non-selective and harmful to the endoparasitoid, A. arizonensis. There is an urgent need for optimizing insecticide applications for sustainable management of this invasive mealybug in cotton.

The cotton mealybug, Phenacoccus solenopsis , has established itself as an invasive insect pest worldwide. It causes structural and physiological damage to various crops and can cause substantial financial losses in their production. The successful reproduction of this pest under a wide range of conditions is a key to its success. Despite this, the morphology of its genitalia, genital sensilla, and wax-producing dermal pores has received little attention, with little descriptions of their ultrastructure. By investigating those features with SEM, the present study revealed considerable new insights into the identification of the nymphal and adult stages of P. solenopsis . In addition, the description of the ultrastructural genital morphology of the immature stages of P. solenopsis has revealed characteristics that facilitate their discrimination. Trilocular pores were observed on both sides of the body, while the quinquelocular pores were distributed only on the ventral surface in both the first and second nymphal instars. The adult male is characterized by two pairs of waxy caudal filaments surrounded by clusters of 55 to 60 stellate pores, and each pregenital segment bears a pair of stellate pores composed of 4 or 5 peripheral loculi. Sensilla trichodea and numerous microtrichia are present on the pregenital segments. The penile sheath bears three subtypes of sensilla basiconica and also campaniformia, whereas the style bears three subtypes of sensilla campaniformia. The findings of this study could assist in the identification of the adult and nymphal stages of P. solenopsis , and also provide insights into the structures found on the genitalia of the adult male that possibly have an important role in mating events and copulatory behavior. Furthermore, these findings were able to contribute to better understanding the functional morphology of P. solenopsis .

The intricate evolutionary dynamics of endosymbiotic relationships result in unique characteristics among the genomes of symbionts, which profoundly influence host insect phenotypes. Here, we investigated an endosymbiotic system in Phenacoccus solenopsis, a notorious pest of the subfamily Phenacoccinae. The endosymbiont, “Candidatus Tremblaya phenacola” (T. phenacola PSOL), persisted throughout the complete life cycle of female hosts and was more active during oviposition, whereas there was a significant decline in abundance after pupation in males. Genome sequencing yielded an endosymbiont genome of 221.1 kb in size, comprising seven contigs and originating from a chimeric arrangement between betaproteobacteria and gammaproteobacteria. A comprehensive analysis of amino acid metabolic pathways demonstrated complementarity between the host and endosymbiont metabolism. Elimination of T. phenacola PSOL through antibiotic treatment significantly decreased P. solenopsis fecundity. Weighted gene coexpression network analysis demonstrated a correlation between genes associated with essential amino acid synthesis and those associated with host meiosis and oocyte maturation. Moreover, altering endosymbiont abundance activated the host mechanistic target of rapamycin pathway, suggesting that changes in the amino acid abundance affected the host reproductive capabilities via this signal pathway. Taken together, these findings demonstrate a mechanism by which the endosymbiont T. phenacola PSOL contributed to high fecundity in P. solenopsis and provide new insights into nutritional compensation and coevolution of the endosymbiotic system.

Mealybugs of the genus Phenacoccus attack a wide variety of crops, fruits, vegetables, ornamentals and weeds but cotton is the prime target. In current investigations, two trials were carried out under semi-field and field conditions for two consecutive years to investigate the compatibility of native predators, Chrysoperla carnea larvae and adults of Brumus suturalis and the exotic predator Cryptolaemus montrouzieri with neem oil for the control of Phenacoccus solenopsis during 2018–2019 and 2019–2020. The assessments were based on mealybug control (scale 0–9) and the percent recovery of predators. Both native predators, C. carnea and B. suturalis showed better control of the mealybug under semi-field and field conditions over the control and were also recovered at the end of the trials during both the study years which proved the conservation and colonization capability of the predator to local conditions. In contrast, the exotic predator, C. montrouzieri proved to be the most efficient predator of P. solenopsis under semi-field conditions, however, it failed to establish under field conditions and control the mealybug populations. No recoveries were made of the predator in either of the treatments under field conditions. The maximum reduction in the population of mealybug was noticed in the insecticide-treated plants. The present study showed that the application of neem oil followed by the release of C. carnea larvae and B. suturalis adults can be swapped to synthetic insecticides for the safer management of mealybug.

Abstract The cotton or solenopsis mealybug, Phenacoccus solenopsis (Tinsley, 1898) (Hemiptera: Pseudococcidae), infests various host plants in Egypt. A study was conducted to observe the incidence of mealybugs and the possible influences of meteorological variables and plant age on the insect population of maize (single-hybrid 168 yellow maize cultivar) plants in Esna district, Luxor governorate, Egypt, in two consecutive seasons (2021 and 2022). P. solenopsis infested maize plants from the 3rd week of June to harvest, and had three peaks of seasonal incidence/season namely; in the 1st week of June in the 3rd/4th week of July, and the 2nd week of August. Similarly, there were three peaks in the percent of infestations per season. In the first season, the average population density of P. solenopsis per sample was 174.04 ± 16.93 individuals, and in the second season, 156.72 ± 14.28 individuals. The most favorable climate for P. solenopsis population increase and infestation occurred in August in the first season and in September in the second season, while June was less suitable in both growing seasons (as estimated by weekly surveys). The combined effects of weather conditions and plant age are significantly related to the estimates of P. solenopsis populations, with an explained variance (E.V.) of 93.18 and 93.86%, respectively, in the two seasons. In addition, their influences explained differences in infestation percentages of 93.30 and 95.54%, respectively, in the two seasons. Maize plant age was the most effective factor in determining changes in P. solenopsis population densities in each season. The mean daily minimum temperature in the first season and mean daily dew point in the second season were the most important factors affecting the percent changes in infestation. However, in both seasons, the mean daily maximum temperature was the least effective variable in population and infestation variation. This study paves the way for monitoring and early detection of mealybugs in maize; as well as the optimal climatic conditions for its development. Resumo A cochonilha do algodão ou solenopsis, Phenacoccus solenopsis (Tinsley, 1898) (Hemiptera: Pseudococcidae), infesta várias plantas hospedeiras no Egito. Um estudo foi conduzido para observar a incidência de cochonilhas e as possíveis influências de variáveis meteorológicas e da idade da planta na população de insetos de plantas de milho (cultivar de milho amarelo 168 híbrido único) no distrito de Esna, província de Luxor, Egito, em duas temporadas consecutivas (2021 e 2022). P. solenopsis infestou plantas de milho desde a terceira semana de junho até a colheita, e teve três picos de incidência/estação sazonal, a saber: na primeira semana de junho, nas terceira e quarta semanas de julho e na segunda semana de agosto. Da mesma forma, ocorreram três picos na percentagem de infestações por estação. Na primeira temporada, a densidade populacional média de P. solenopsis por amostra foi de 174,04 ± 16,93 indivíduos, e na segunda temporada, 156,72 ± 14,28 indivíduos. O clima mais favorável ao aumento populacional e à infestação de P. solenopsis ocorreu em agosto na primeira época e em setembro na segunda época, enquanto junho foi menos adequado em ambas as épocas de cultivo (conforme estimado por inquéritos semanais). Os efeitos combinados das condições climáticas e da idade das plantas estão significativamente relacionados com as estimativas das populações de P. solenopsis, com variância explicada (E.V.) de 93,18 e 93,86%, respectivamente, nas duas estações. Além disso, suas influências explicaram diferenças nos percentuais de infestação de 93,30 e 95,54%, respectivamente, nas duas épocas. A idade da planta de milho foi o fator mais eficaz na determinação das mudanças nas densidades populacionais de P. solenopsis em cada estação. A temperatura mínima diária média na primeira época e o ponto de orvalho médio diário na segunda época foram os fatores mais importantes que afetaram as alterações percentuais na infestação. Porém, em ambas as estações, a temperatura máxima média diária foi a variável menos eficaz na variação populacional e de infestação. Este estudo abre caminho para o monitoramento e a detecção precoce de cochonilhas no milho, bem como as condições climáticas ideais para o seu desenvolvimento.

Phenacoccus solenopsis Tinsley (Hemiptera, Pseudococcidae) is an invasive mealybug globally, having originated in North America. During routine rearing of this pest in a plant nursery in Karbala, Iraq in June 2023, three species of parasitoid wasps (Hymenoptera, Chalcicoidea) emerged from the mealybug colonies, or were extracted as pupae from parasitised mealybugs. They were identified using both morphology and DNA sequencing as Aenasius arizonensis (Girault), Cheiloneurus nankingensis Li and Zu (Encyrtidae), and Marietta pictus (André) (Aphelinidae). The latter two species represent new country records for Iraq. All three species are diagnosed and illustrated below, with summaries of their distributions and biology. The importance of having databases available of barcodes and other diagnostic sequence data is emphasised in the context of biological control programmes.