Aphis gossypii is one of the most economically important agricultural pests that cause serious crop losses worldwide, and the indiscriminate chemical application causes resistance development in A. gossypii, a major obstacle to successful control. In this study, we selected the up-regulated expression gene AgJHAMT, which was enriched into juvenile hormone pathway though transcriptome sequencing analysis of the cotton aphids that fed on transgenic cotton lines expressing dsAgCYP6CY3 (the TG cotton). The AgJHAMT gene was overexpressed in cotton aphids which fed on the TG cotton, and its expression profile during the nymphs was clarified. Then, silencing AgJHAMT could advance the developmental period of cotton aphids by 0.5 days compared with control groups. The T and t values of cotton aphids in the dsJHAMT treatment group (6.88 ± 0.15, 1.65 ± 0.06) were significantly shorter than that of the sprayed H2O control group (7.6 ± 0.14, 1.97 ± 0.09) (P < 0.05), respectively. The fast growth caused by AgJHAMT silencing was rescued by applying the JH analogue, methoprene. Overall, these findings clarified the function of AgJHAMT in the developmental period of A. gossypii. This study contributes to further clarify the molecular mechanisms of delaying the growth and development of cotton aphids by the transgenic cotton lines expressing dsAgCYP6CY3.

Ladybeetles are known beneficial insects, with a long history in augmentative and classical biological control. The ladybeetle Oenopia conglobata (L.) is a natural enemy of many herbivores, particularly aphids. The temperature-dependent development of O. conglobata was studied at six constant temperatures (22.5, 25, 27.5, 30, 32.5 and 35 °C) to understand its development rate and environmental constraints better. Linear and nonlinear (Lactin) models were fitted to the data. In the thermal range from 22.5 to 32.5 °C, the rate of development increased for all stages; 35 °C was lethal for all stages and no eggs hatched. The Tb and K values for the biological cycle (egg–adult) were 8.84 °C and 263.15 DD, respectively. Depending on the model, tmin values for the total development time of the coccinellid ranged from 8.45 to 8.82 °C. The nonlinear model of Lactin estimated the optimum and upper temperature thresholds for the total development time of the ladybeetle to be 33.2 and 35.0 °C, respectively. High R2 values and low residual sum of squares values revealed a good fit to the experimental data for total development and different developmental stages of O. conglobata. The results may contribute to the improvement of practical methods for mass rearing of O. conglobata.

The volatile compounds of crofton weed infested by cotton aphids and sprayed with MeJA were collected and analyzed by the TCT-GC/MS technique. The healthy weeds were controls. Seventeen volatiles identified from crofton weed included green leaf odors, monoterpenes and sequiterpenes, and oxo-compounds. Camphene, 2-carene, α-phellandrene, ρ-cymene, and caryophyllene were the major volatiles and constituted about 77% of the total volatile emissions from the control. In the aphid-infested weeds, no new induced component was found. Among the terpenes, ρ-cymene increased markedly in the infested weeds compared with the control, whereas all sesquiterpenes decreased markedly. Levels of endogenous JA in leaves and young stems of the aphid-infested weeds were markedly higher than in the control, whereas both endogenous SA level and ABA level were not significantly different. MeJA sprayed on crofton weed with the aphid infestation had a similar effect on volatile emissions. It is suggested that JA was one of the most important signals in crofton weed and could regulate the emission of volatile compounds.

Three cryptic species, Aphis gossypii, Aphis glycines, and Aphis rhamnicola sp. nov., are recognized as sharing buckthorn plant, Rhamnus spp. as primary hosts. These aphid species have morphological similarities; however, there are significant genetic differences between the three cryptic species. Based on the high level of genetic divergence and the different secondary host association, we described a new species, Aphis rhamnicola sp. nov., for apterous and alate vivipara, fundatrix, ovipara, and gynopara, including diagnostic key for the host sharing species in the genus Aphis.

The effects of two aphidophagous predators, the larvae of Chrysoperla carnea and adults of Adalia bipunctata, on the spread of cucumber mosaic virus (CMV) transmitted in a non-persistent manner by the cotton aphid Aphis gossypii were studied under semi-field conditions. Natural enemies and aphids were released inside insect-proof cages (1 m ×1 m ×1 m) with a central CMV-infected cucumber plant surrounded by 48 healthy cucumber seedlings, and the spatiotemporal dynamics of the virus and vector were evaluated in the short and long term (1 and 5 days) in the presence and absence of the natural enemy. The spatial analysis by distance indices methodology together with other indices measuring the dispersal around a single focus was used to assess the spatial pattern and the degree of association between the virus and its vector. Both natural enemies significantly reduced the number of aphids in the CMV-source plant after 5 days but not after 1 day. The CMV transmission rate was generally low, especially after 1 day, due to the limited movement of aphids from the central CMV-source plant, which increased slightly after 5 days. Infected plants were mainly located around the central virus-infected source plant, and the percentage of aphid occupation and CMV-infected plants did not differ significantly in absence and presence of natural enemies. The distribution patterns of A. gossypii and CMV were only coincident close to the central plant. The complexity of multitrophic interactions and the role of aphid predators in the spread of CMV are discussed.

A 2-year study in a vegetable-growing area (Tori, Hla Avamé) in Benin has shown that the invasive aphid parasitoid Lysiphlebus testaceipes (Cresson) was attacked by three species of native hyperparasitoids. On several occasions, hyperparasitoids emerged from more than 90% of the mummies collected. The dominating hyperparasitoid was Syrphophagus africanus (Gahan). Two species in the genera Pachyneuron (Pteromalidae) and Aphanogmus (Ceraphronidae), respectively, were also recorded as hyperparasitoids. Charipinae hyperparasitoids were lacking. The only aphid host present at Hla Avamé was Aphis gossypii Glover, a dominating species in vegetable agroecosystems in Benin.

The influence of solitary versus group rearing on the development and survival of the three-striped ladybird beetle Brumoides suturalis (Fabricius) was studied using two aphid species, Acyrthosiphon pisum (Harris) and Aphis gossypii Glover, as diet. Rearing pattern (solitary or group) had no significant influence on the success of rearing, but prey species did. While immature stages developed faster on A. pisum, the survival of early instars was higher on A. gossypii. Diet had no effect on pupal survival.

The population dynamics, development of gonads, takeoff and flight behaviour of Aphis gossypii Glover were investigated in order to test whether there was variation of migratory ability in the spring population. Field surveys showed that not all the aphids overwintering on hibiscus migrated to the secondary host plants, and the host-alternating and host-specific life-cycle forms coexisted in Nanjing, China. Substantial variation in flight capacity of winged individuals, development of gonads and takeoff behaviour were found within the spring population. The frequency distribution of flight duration and the number of ovarioles per individual alatae exhibited two peaks, representing the migratory and sedentary genotypes, respectively. Significant response to directional selection on takeoff behaviour demonstrated the additive genetic component of this variation. Selection for ‘takeoff’ individuals caused a significant increase in takeoff angle from 39.8° in the first selection to 68.7° in the fifth; and, hence, screened out the migratory genotype (M), while selection for the sedentary individuals increased the rate of non-takeoffs significantly, and screened out the sedentary genotype (S). The reciprocal cross, M♀×S♂, produced hybrid offspring performing significantly steeper takeoff angles compared with those from the cross S♀×M♂, suggesting the presence of a maternal effect. On the other hand, takeoff rate was ranked as M♀×S♂=S♀×M♂>M>S, involving no sex-linkage and maternal effect. The coexistence of host-alternating and host-specific life-cycle forms of A. gossypii on the primary host has, as deduced from the present studies, a genetic basis.

The study of intraspecific variation with respect to host plant utilization in polyphagous insects is crucial for understanding evolutionary patterns of insect-plant interactions. Aphis gossypii (Glover) is a cosmopolitan and extremely polyphagous aphid species. If host plant species or families constitute selective regimes to these aphids, genetic differentiation and host associated adaptation may occur. In this study, we describe the genetic structure of A. gossypii collected in six localities in Tunisia on different vegetable crops, on citrus trees and on Hibiscus. The aim was to determine if the aphid populations are structured in relation to the host plants and if such differentiation is consistent among localities. The genetic variability of A. gossypii samples was examined at eight microsatellite loci. We identified only 11 multilocus genotypes among 559 individuals. Significant deviations from Hardy-Weinberg equilibrium, linkage disequilibria and absence of recombinant genotypes, confirmed that A. gossypii reproduces by continuous apomictic parthenogenesis. Genetic differentiation between localities was not significant, whereas a strong differentiation was observed between host plant families (0.175<FST<0.691). The great majority of aphids exhibited one of three predominant multilocus genotypes that were repeatedly and respectively associated to the three plant families, Cucurbitaceae, Solanaceae and Rutaceae, demonstrating host specialization in A. gossypii. These specialized genotypes were simultaneously found with other clones on Hibiscus, suggesting that this perennial host could act as a refuge plant between two vegetable crop seasons.

Aphis gossypii Glover is a polyphagous aphid pest with a worldwide distribution. However, there is evidence that on a global scale the name A. gossypii is being applied to a number of forms with different life cycles and/or host-plant associations. Morphometric variation of A. gossypii samples from crops and non-cultivated plants in many parts of the world was examined, to determine whether this variation is correlated with the hosts from which the aphids originated. Samples of A. gossypii were collected from Cucurbitaceae and Malvaceae in Europe, and from Compositae in various parts of the world. Morphometric data for 13 parameters measured from 97 clonal lineages (728 specimens) and 27 field-collected samples (313 specimens) were analysed by a series of canonical variates analyses, using the field sample/clonal lineage as grouping factor. Clonal lineages were reared on a common host in controlled conditions to standardize the effect of host and environment on morphology. The analyses provided a clear morphometric separation of the aphids originating from Compositae and those collected on Cucurbitaceae and Malvaceae, regardless of the geographical origin of the aphids and the host plant on which they were reared. This indicates that within A. gossypii there are two widely distributed host races or subspecies with different plant family associations. The taxonomic implications are discussed.

Studies on the population dynamics of Aphis gossypii Glover carried out on cotton in the Tadla area over a 3-year period showed two periods of rapid resurgence: June-July and September, with the highest density reached in the latter month accompanied by considerable indirect economic loss. The resurgence of Aphis gossypii populations on cotton depends mainly on the date and the density of contamination flights. The evolution and other factors responsible for the variations in the population dynamics are discussed.

Aphis gossypii is one of the major pests of cucumber grown in greenhouses in the coastal areas of Morocco. A population dynamics study showed that A. gossypii populations might reach very high levels in June, causing economic damage to cucumber. The proliferation of A. gossypii on cucumber arises mainly from infestations by flying winged adults. Factors regulating the fluctuation of population of the species are discussed.

In this study, Coccinella septenipnnctata was efficient in controlling Aphis gossypii populations on cucumber in the greenhouse. This efficiency was a function of the predator/prey ratio and the initial aphid density at the time of release of the predator. Prey density had a large influence on the fecundity and establishment of this coccinellid in the greenhouse.

The host plant spectrum of Aphis gossypii Glover (Hemiptera:Aphididae) was assessed from 1991 to 1994 in the cotton-growing zone of northern Cameroon. The aphid is generally present on cotton (Gossypium hirsutum L.) and okra (Abelmoschus esculentus (L.) Moench) during the rainy season. During the dry season on the other hand, A. gossypii is observed on a very wide range of plants (63 families, 192 genera and 302 species). During this season, all types of plants, especially legumes, dry-season crops and various types of trees, are colonised. From the representativeness of the sampled plant species within the cotton zone of Cameroon, it is concluded that a part of the A. gossypii population survives the dry season in the Sudano-Sahelian African zone, thus forming numerous reservoirs scattered among plants and in very varied habitats.

The functional response in terms of prey consumption and numerical response in terms of number of eggs laid by individual female adult predators of Coccinella transversalis Fab. and Cheilomenes (Menochilus) sexmaculatus Fab. (Coccnellidae: Coleoptera) at varied prey (Aphis gossypii Glover) (Aphididae: Homoptera) densities were investigated under laboratory conditions. The feeding rate by individual predators increased at increased prey densities, with both the coccinellids showing the Type II functional response. One hundred percent prey consumption was observed up to an initial prey density of 50 and 20 for Co. transversalis and Ch: sexmaculatus respectively. The fecundity of Co. transversalis increased at higher prey densities, but that of Ch. sexmaculatus remained unchanged.

The searching behaviour of two coccinellid predators, Coccinella transversalis Fab. and Cheilomenes (Menochilus) sexmaculatus Fab. at different hunger levels and larval stage was studied on eggplant infested with Aphis gossypii Glov. Females of both predators required more prey to return to a state of complete satiation. As the period of starvation increased, more aphids were consumed by both the beetles, reaching a maximum at 24 h starvation. In first, second, third and fourth instars of both the predators, the searching time and the number of eggplant leaf veins visited increased with increasing hunger levels. A high positive correlation between searching time and hunger level of tested predators was obtained.

Five insecticides and three mixtures were tested on the cotton flea beetle (CFB), Podagricapuncticotis (Weise), the spiny bollworm (SBW), Earias insulana (Boisd.), and the cotton aphids (CA), Aphis gossypii (Glov.). The relative potency (in terms of LD50 and or LC50) for CFB followed this order: endosulfan + dimethoate > endosulfan + chlorpyrifos > dimethoate > fenvalerate > endosulfan > endosulfan + amitraz > amitraz. The LCS0 values ranged from 12. 0–1150 ppm. For SBW, the following order was obtained: fenvalerate > endosulfan + dimethoate, endosulfan + chlorpyrifos > endosulfan > dimethoate > chlorpyrifos > endosulfan + amitraz > amitraz. LC50 ranged between 0.35 and 3388 ppm. With regard to CA endosulfan + chlorpyrifos > endosulfan + dimethoate > endosulfan + amitraz > chlorpyrifos > endosulfan > fenvalerate > dimethoate > amitraz.

In general, C A was relatively tolerant to most tested insecticides when compared with the other two pests. The SBW was the most susceptible.

Commercial cotton growing in the Sudan dates from 1867. At present, about 400,000 ha of various cotton cultivars are grown under different irrigation systems. The production of this main cash crop has been faced with a multitude of entomological and pathological problems, some of which were tackled through the adoption of specific cultural practices or enforcement of legislative regulations.

When cotton treatment with synthetic organic insecticides was initiated in the mid 1940s against Empoasca lybica de Berg, the impressive preliminary results have encouraged over-reliance on chemical control at the expense of other measures. This rather limited approach of control strategy has contributed partially to the appearance of new pests in damaging levels e.g. Heliothis armigera (Hbn.), Bemisia tabaci (Genn), Aphis gossypii (Glov) and Spodoptera littoralis. The principal measure for their control is insecticide application.

The cost of crop protection soared to ten-fold during the last 20 years. The annual number of sprays applied to cotton increased from one to seven sprays. To overcome the ever increasing use and high costs of pesticides on cotton growing, the Agricultural Research Corporation undertook intensive research programmes to find answers to major crop protection problems. Since 1978 researchers are directing their efforts towards the development and implementation of integrated pest management strategies to include cultural and legislative measures, as well as the use of more selective insecticides.

In the present work, influence of food plants on different life table parameters of the parasitoid Trioxys indicus Subba Rao and Sharma was studied as affected through its host Aphis gossypii Glover. Age-specific survival of T. indicus on aphids bred on Lagenaria vulgaris was greater (7 days) than on Luff a cylindrica and Cucurbita maxima (4 days). The net fecundity rate, total reproductive period, intrinsic rate of natural increase, intrinsic rate of total fecundity and weekly multiplication rate of T. indicus fed on L. vulgaris was higher than on other cucurbit food plants. Doubling time of the parasitoid fed on L. vulgaris was lower than on other food plants, whereas the mean generation time of the parasitoid on L. vulgaris was slightly higher than on L. cylindrica but lower than on Cajanus cajan and C. maxima. All these measurements (considered indices of fitness of the entomophages) indicated that population growth pattern of T. indicus fed on L. vulgaris is faster than those fed on other food plants.

Spatial pattern of distribution of populations of three insect species, namely, Amrasca biguttula biguttula (Ishida), Bemisia tabaci (Genn.) and Aphis gossypii Glov. was studied in Upland cotton (Gossypium hirsutum L.) at an interval of 13–15 days during July, August and September in Punjab. The populations were found to be aggregated from the beginning of season upto 25 August in jassid nymphs, 12 August in whitefly adults and the end of season in apterous aphids. Environmental heterogeneity at low population in July and innate behaviour at high population were responsible for the aggregated dispersion in each of the three homopterans. Based on these observations the appropriate number of samples required to be drawn for population studies were determined which varied with change in pest density in each case.