Impacts of Climate Change on the Occurrence Degree of Cotton Aphids in Huang-Huai-Hai and Yangtze River Basins

[Objective] The aim was to analyze the impacts of climate change （tem- perature and precipitation） on the occurrence degree of cotton aphids. [Method] Ec- onometric models were established to explore the impacts of climate change on the occurrence degree of cotton aphids based on the observation data from 50 counties in Huang-Huai-Hai and Yangtze River basins in 1991-2010, including variables on the occurrence degree of cotton aphids, temperature and precipitation, and other factors. [Result] There were significant differences in the effects of temperature and precipitation changes on the occurrence degrees of cotton aphid in different growth stages, and even in the same growth stage, the cotton aphids had different responses to the changes of temperature and precipitation in different re- gions. [Conclusion] It should give full consideration to the climatic conditions in dif- ferent periods of different regions, and it should adopt proper measures to control the cotton aphids on the basis of figuring out the occurrence rule of cotton aphid, so as to ensure cotton production.

Occurrence Rule and Forecast Method of Cotton Aphid in Poyang Lake Area in Jiujiang City

[Objective] The aim was to explore occurrence rules and forecast methods of cotton aphid in Poyang Lake Area in Jiujiang City to enrich prediction methods of cotton aphid in the area. [Method] The occurrence rules and influencing factors of cotton aphid in Pengze County in 28 years were analyzed with comparative analysis, correlation analysis and wavelet analysis. Furthermore, a long-term forecast model of occurrence grade of cotton aphid and a short-term forecast model of weather condi- tion suitability were established based on stepwise regression. In addition, a forecast test was conducted in cotton area in the north of Poyang Lake. [Result] The wavelet analysis showed that in recent 28 years, oscillating period at 4 years was significant for the occurrence grade of cotton aphid in the north of Poyang Lake, but insignifi- cant for cotton at seedling stage. The comparative and correlation analyses suggest- ed that occurrence of cotton aphid is of significant correlation with winter climate and weather conditions at middle and short periods. The prediction test indicated that long-term forecast model of occurrence grade of cotton aphid and short-term forecast model of weather condition suitability based on stepwise regression can be made use of in the areas with similar climate. [Conclusion] The research provides theoreti- cal references for prevention against cotton aphid in cotton-planting area.

Weed and insect control affected by mixing insecticides with glyphosate in cotton

Field studies were conducted in 2012 and 2013 to evaluate weed and insect control efficacy with glyphosate at 1 230 g ai（active ingredient） ha^（-1） and the insecticides acephate（728 g ai ha^（-1））,carbosulfan（135 g ai ha^（-1））,endosulfan（683 g ai ha^（-1））,imidacloprid（32 g ai ha^（-1））,or lambda-cyhalothrin（23 g ai ha^（-1））,as well as glyphosate tank-mixed with these insecticides.Four of the most common weeds in cotton,common purslane,false daisy,goosegrass,and lambsquarters,were manually sown in the cotton field and treated with glyphosate alone or in combination with insecticides.Glyphosate efficacy,based on visual estimates of control and weed fresh weight at 21 d after treatment（DAT）,was unaffected by the addition of insecticides.Four weeds were controlled by 93-97%and 86-100%（visual rating） and reduced weed fresh biomass by98-99%and 96-100%with glyphosate alone and its combination with insecticides,respectively.Addition of glyphosate to acephate improved cotton aphid control compared with acephate alone.However,addition of glyphosate to carbosulfan,endosulfan,imidacloprid,or lambda-cyhalothrin did not affect the aphid control when compared with the insecticide alone treatments.These results indicate that cotton producers could potentially integrate weed and insect management strategies by choosing suitable insecticide mixing partners with glyphosate,thereby reducing the application costs without sacrificing the efficacy of the glyphosate or the insecticides.

Cloning of Partial Sodium Channel Gene From Strains of Fenvalerate-Resistant and Susceptible Cotton Aphid(Aphis gossypii Glover)

The strain of fenvalerate-resistant cotton aphids was selected using fenvalerate insecticide in the laboratory, the resistance factor of the strain was 199.54. Three degenerate primers were designed and used to perform PCR amplification. A cDNA encoding partial sodium channel gene was cloned from the fenvalerate-resistant and -susceptible strains. There were two nucleotide acid differences between fenvalerate-resistant strain and -susceptible strain, resulting in an amino acid mutation, Met→Leu. It is predicted that the mutation is related to the cotton aphid resistance to fenvalerate.

Energy Metabolism Pattern in Cotton Aphid, Aphis gossypii Glover （Hem.： Aphididae） Exposure to Neonicotinoids

This study was mainly made on the role of energy revisers in cotton aphid, Aphis gossypii Glover （Hemiptera： Aphididae） countered with imidacloprid and thiametoxam. We measured used energy, available energy and the content of total energy in three strains of cotton aphid which were from very resistant to neonicotinoid, sup to semi-sensitive and sensitive speccies, respectively. It was observed changes in energy resources rate in all of the aphid strains at which each substrate was metabolized under stress. Our findings indicated among energy sources, total lipid in susceptible strain was increased in counter of spraying and it was decreased in resistance and semi sensitive strains. Whereas, total protein was decreased in all of the strains encountering with neonicotiniod stress. Total glycogen was increased significantly in different aphid strains and sugar was decreased in countered of spraying.

Energy Intensity and Fitness Cost of Cotton aphid Exposure to Neonicotinoids

Three populations of Aphis gossypii of distinct susceptibility to neonicotinoids show differences in the accumulation and mobilization of energy reserves, what may allow the production of their defensive tools against two neonicotinoid insecticides without impairing their reproductive performance. Bioassays were also carried out for these aphid populations. According to the results obtained, the Ag-R population showed resistant rate significantly higher than the other two populations. Levels of some biochemical characteristics were determined in the resistant, susceptible and semi susceptible populations of cotton aphid. The results obtained in the assays with biochemical parameters indicated significant differences in activity among the populations, with higher activity in using glycogen in the Ag-R population. The inverse activity trends oft （generation time） and DT （doubling time） in both resistant and susceptible populations, one showing fitness disadvantage without insecticide exposure and the other not showing it, may underlay the mitigation of insecticide resistance physiological costs observed in the Ag-R population.

Tri-Trophic Interactions within Potato Agro-Ecosystem, Qassim, KSA

Tri-trophic interactions between fertilizer applications, cotton aphid (Aphis gossypii Golver) and associated beneficial insects were studied to investigate direct and indirect effects of fertilizers (types and ratios) on potato plants under field and greenhouse conditions, A. gossypii and associated beneficial insects. Fertilizers regimes showed direct impacts on the potato plant phenology and indirect effects on both A. gossypii population and the associated beneficial insects. Our data indicated that potato plants had been influenced by fertilizer elements used within tri-trophic system comprising potato plants, cotton aphid, and certain associated beneficial insects. This demonstrates that a bottom-up interaction is robust and has a particular value in the attraction of beneficial insects towards the potato plant signals due to used fertilizers which can also have a function when plants are attacked by A. gossypii. Yet, flexibility in the use of fertilizers (as chemical cues) is conserved, and that may help beneficial insects to specifically focus on the odor of plants that carry potential plant hosts and avoid plants that are only attacked by non-hosts. These results support the still controversial notion that fertilizer elements, at least in part, help plants to serve as functional signals to attract the enemies of the harmful insects. These observations declare the benefits of the tri-trophic interactions as an ecological phenomenon in particular and the food chain in general. Additionally, this study may be useful to be used as a predictable model with the associated beneficial insects which may have key roles in overall aphid suppression or regulating its population. Impact of fertilizers on potato phenology characteristics and the cotton aphid population density seems to be variable based on types and ratios of the fertilizers. Interfacing the impact of natural enemies (plant-pest-natural enemies) through tri-trophic relationship within the food chain verified to be straightforward way of predicting on the impact of beneficial insects-guild on the cotton aphid population density.

Insights into wing dimorphism in worldwide agricultural pest and hostalternating aphid Aphis gossypii

Background:The worldwide pest Aphis gossypii has three-winged morphs in its life cycle,namely,winged parthenogenetic female(WPF),winged gynopara(GP),and winged male,which are all produced by a wingless parthenogenetic female(WLPF).Most studies on A.gossypii have focused on WPF,while few have investigated GP and male.The shared molecular mechanism underlying the wing differentiation in the three wing morphs of A.gossypii remains unknown.The wing differentiation of WPF was explored in a previous study.Herein,GP and male were induced indoors.The characters of the body,internal genitals,wing veins,and fecundity of GP and male were compared with those of WPF or WLPF.Compared with WLPF,the shared and separate differentially expressed genes(DEGs)were identified in these three-wing morphs.Results:Newly-born nymphs reared in short photoperiod condition(8 L:16D,18°C)exclusively produced gynoparae(GPe)and males in adulthood successively,in which the sex ratio was GP biased.A total of 14 GPe and 9 males were produced by one mother aphid.Compared with WLPF,the three-wing morphs exhibited similar morphology and wing vein patterns but were obviously discriminated in the length of fore-and underwings,reproductive system,and fecundity.A total of 37090 annotated unigenes were obtained from libraries constructed using the four morphs via RNA sequencing(RNA-Seq).In addition,10867 and 19334 DEGs were identified in the pairwise comparison of GP versus WLPF and male versus WLPF,respectively.Compared with WLPF,the winged morphs demonstrated 2335 shared DEGs(1658 upregulated and 677 downregulated).The 1658 shared upregulated DEGs were enriched in multiple signaling pathways,including insulin,FoxO,MAPK,starch and sucrose metabolism,fatty acid biosynthesis,and degradation,suggesting their key roles in the regulation of wing plasticity in the cotton aphid.Forty-four genes that spanned the range of differential expression were chosen to validate statistical analysis based on RNA-Seq through the reverse transcription quantitative real time polymerase chain reaction(RT-qPCR).The comparison concurred with the expression pattern(either up-or downregulated)and supported the accuracy and reliability of RNA-Seq.Finally,the potential roles of DEGs related to the insulin signaling pathway in wing dimorphism were discussed in the cotton aphid.Conclusions:The present study established an efficiently standardized protocol for GP and male induction in cotton aphid by transferring newly-born nymphs to short photoperiod conditions(8 L:16D,18°C).The external morphological characters,especially wing vein patterns,were similar among WPFs,GPe,and males.However,their reproductive organs were strikingly different.Compared with WLPF,shared(2335)and exclusively(1470 in WLPF,2419 in GP,10774 male)expressed genes were identified in the three-wing morphs through RNA-Seq,and several signaling pathways that are potentially involved in their wing differentiation were obtained,including insulin signaling,starch and sucrose metabolism.

Demographic parameters of cotton aphid, Aphis gossypii Glover （Homoptera： Aphididae） on five cotton cultivars

Life table parameters of the cotton aphid, Aphis gossypii Glover, were estimated on five cotton cultivars （‘ Sealand＇ ,‘Siokra＇ ,＇ Vararnin＇ ,‘ Bakhtegan＇ and ‘ Sahel＇ ）. Demographic parameters of the cotton aphid were assessed at 27.5 ± 1 ℃, 65% ＋ 10% RH and a photoperiod of 14：10 （L： D）h. The shortest developmental time for the nymphal stages was 5.5 days on ‘Siokra＇ and the longest was 6.1 days on‘ Sealand＇. The highest offspring per female was 29.6 on ‘Sahel＇ and the lowest was 15.3 on ‘Sealand＇. The rm values varied from 0.272 on ‘Sealand＇ to 0.382 （day^-1） on ‘Varamin＇. Jackknife estimates of the A. gossypii parameters on these cultivars indicated the greatest developmental rate and fecundity on ‘ Varamin＇ and the poorest on ‘ Sealand＇ cultivar.

Global attractivity of the predator-prey system for cotton aphid and seven-spot ladybird beetle with stage structure

It is well known that the cotton aphid is the major pest in cotton fields of Northwest China, and seven-spot ladybird is an important natural enemy among the various possi- ble natural enemies of cotton aphid. In order to increase the applications of population dynamics in integrated pest management and control the cotton aphids biologically, we need to understand the population dynamics of cotton aphid and their natural enemies. A delay predator prey system on cotton aphid and seven-spot ladybird beetle are pro- posed in this paper. Based on the comparison theorem and an iterative method, we investigate the global attra^tivity of the equilibrium points which have important bio- logical meanings. Furthermore, some numerical simulations were carried out to illustrateand expand our theoretical results, in which a conjecture to generalize the well-known Theorem 16.4 in H. R. Thiemes book was put forward, which was taken as the open problem. The numerical simulations show coexistence of periodic solution, confirming the theoretical prediction.

Lethal, sublethal and transgenerational effects of the novel chiral neonicotinoid pesticide cycloxaprid on demographic and behavioral traits of Aphis gossypii （Hemiptera： Aphididae）

Aphis gossypii Glover （Hemiptera： Aphididae） is a key pest in cotton crops, notably owing to its increasing resistance to commonly used pesticides. Such resistance prompts for the development of integrated pest management （IPM） programs that include novel pesticides being effective against the aphid. In the present study, we assessed lethal and sublethal effects of cycloxaprid, a novel chiral neonicotinoid pesticide developed in China, on A. gossypii. The lethal concentration at 50% （LCs0） value of cycloxaprid on A. gossypii was estimated, using the dipping method, at 7.73 mg/L. The impact of a sublethal concentration （LC10） and a lethal concentration （LC40） of cycloxaprid on A. gossypii population growth and feeding behavior （using electrical penetration graph technique [EPG]）, and its transgenerational effect were further assessed. Adult longevity and fecundity significantly decreased after exposure to LEa0 or LC10 of cycloxaprid. Cycloxaprid with sublethal concentrations （especially LC40） had negative effects on phloem ingestion by A. gossypii. Additionally, the offspring of the adults exposed to LC40 of cycloxaprid had shorter nymphal development duration and adult longevity than the control, and those from LC10 and LC40 treatments had lower adult fecundity and net productive rate. We demonstrated that cycloxaprid is a pesticide showing both lethal and sublethal activities, and transgenerational effects on,4. gossypii; it may be useful for implementation in IPM programs against this aphid pest.

Coinfection of the secondary symbionts,Hamiltonella defensa and Arsenophonus sp.contribute to the performance of the major aphid pest,Aphis gossypii(Hemiptera:Aphididae)

Bacterial endosymbionts play important roles in ecological traits of aphids.In this study,we characterize the bacterial endosymbionts of A.gossypii collected in Karaj,Iran and their role in the performance of the aphid.Our results indicated that beside Buchnera aphidicola,A.gossypii,also harbors both Hamiltonella defensa and Arsenophonus sp.Quantitative PCR(qPCR)results revealed that the populations of the endosymbionts increased throughout nymphal development up to adult emergence;thereafter,populations of Buchnera and Arsenophonus were diminished while the density of H.defensa constantly increased.Buchnera reduction caused prolonged development and no progeny production.Furthermore,secondary symbiont reduction led to reduction of the total life span and intrinsic rate of natural increase as well as appearance of the deformed dead offspring in comparison with the control insects.Reduction of the secondary symbionts did not affect parasitism rate of the aphid by the parasitic wasp Aphidius matricariae.Together these findings showed that H.defensa and Arsenophonus contributed to the fitness of A.gossypii by enhancing its performance,but not through parasitoid resistance.