运用α-氰代酯荧光底物检测抗性棉蚜羧酸酯酶代谢活性

为了研究抗性和敏感棉蚜Aphis gossypii品系对菊酯类药剂代谢的差异, 本实验合成了溴氰菊酯和高效氯氰菊酯报告荧光底物, 应用这两种底物水解后生成具有荧光化合物的特性,测定了不同品系棉蚜羧酸酯酶的代谢活性。结果表明: 氧化乐果棉蚜抗性和敏感品系羧酸酯酶对溴氰菊酯报告荧光底物的代谢活性分别为10.0和3.4 pmol/min·mg; 对高效氯氰菊酯报告荧光底物的代谢活性分别为4.0和2.4 pmol/min·mg, 抗性品系羧酸酯酶对溴氰菊酯和高效氯氰菊酯报告荧光底物的代谢活性分别为敏感品系的2.9和1.7倍; 溴氰菊酯棉蚜抗性和敏感品系羧酸酯酶对溴氰菊酯报告荧光底物的代谢活性分别为7.6和6.2 pmol/min·mg; 对高效氯氰菊酯报告荧光底物的代谢活性分别为9.3和5.2 pmol/min·mg, 抗性品系羧酸酯酶对溴氰菊酯和高效氯氰菊酯报告荧光底物的代谢活性分别为敏感品系的1.2和1.8倍。这种衍生的报告荧光底物能够用来检测抗性棉蚜羧酸酯酶的水解活性, 表明羧酸酯酶可能参与棉蚜对溴氰菊酯和氧化乐果抗性的形成。     

棉蚜抗氧化乐果品系及敏感品系羧酸酯酶性质的比较

在室内用氧化乐果逐代筛选的棉蚜抗性品系,相对于敏感品系的抗性倍数是17。用α-乙酸萘酯（α-NA）、α-丁酸萘酯（α-NB）、α-磷酸萘酯（α-NP）和β-磷酸萘酯（β-NP）作底物比较研究了氧化乐果抗性和敏感品系棉蚜Aphis gossypii羧酸酯酶的比活力、米氏常数（K_m）和最大反应速度V_max）等有关的动力学常数。以α-NA和α-NB作底物时,抗性品系棉蚜的比活力显著低于敏感品系的;以α-NP和β-NP作底物时,两个品系棉蚜的比活力、K_m和V_max没有明显差异。用α-NA、β-NA作底物染色做酯酶同工酶电泳,抗性品系棉蚜的酯酶同工酶染色比敏感品系棉蚜的浅。     

抗性品系棉蚜乙酰胆碱酯酶和羧酸酯酶的变异

用浸叶法测定了采自我国不同地区(泰安、莱阳、南京、北京和安阳)的棉蚜品系Ⅰ、Ⅱ、Ⅲ、Ⅳ、Ⅴ对久效磷、甲胺磷、抗蚜威和灭多威等杀虫剂的抗性水平,各棉蚜品系对杀虫剂的抗性依次为Ⅴ>Ⅳ>Ⅲ,Ⅱ>Ⅰ。进一步研究表明,Ⅴ和Ⅳ品系棉蚜乙酰胆碱酯酶对杀虫剂的敏感性显著下降,Ⅱ品系次之,Ⅲ和Ⅰ品系接近于敏感品系。Ⅴ和Ⅳ品系乙酰胆碱酯酶的Km值显著下降,表明酶发生了质的变化。不同棉蚜抗性品系的酯酶（全酯酶和羧酸酯酶）活性均显著升高,其中Ⅲ品系的酯酶活力为Ⅱ品系的2倍。Ⅴ品系羧酸酯酶Km值达2460.4 μmol/L,而Ⅳ品系仅为84.4 μmol/L,该两个品系羧酸酯酶发生了质的变化。研究结果表明,不同抗性程度的棉蚜品系均存在代谢抗性和靶标抗性。低抗水平的棉蚜品系,以代谢抗性为主,靶标抗性为辅;中抗水平的棉蚜品系,抑或由于解毒代谢酶的活性显著增强,也可能由于靶标的敏感性显著下降;而高抗水平的棉蚜品系,依赖于代谢抗性和靶标抗性的联合作用。     

Plasticity in biochemical characteristics of cotton aphid,Aphis gossypii Glover in response to different host plants and neonicotinoid pesticides

In the present investigation an effort was made to realise the role of feeding host plants on some enzymes’ activities. The results showed that the enzymes’ activities were changed in the aphids feeding on different host plants which assist in detoxification of their host metabolites. It is important when the aphids are exposed to insecticides. The results indicated that the measured enzyme activity has significant changes depending on the host plant. It is shown in this study that there are no significant differences between different host plants on esterase activity (p = 0.446); however, there is a significant difference between GSH activity (p = 0.047) but this relationship is not significant on MFO activity (p = 0.417). Among three strains of Ag-PP, Ag-MO and Ag-FA, strain Ag-PP was the most resistant strain against neonicotinoids, and the resistance mechanism was related to metabolic increase in carboxyl esterase activity. The results showed that strain of Ag-MO was the most susceptible strain against neonicotinoids. The result of this investigation also showed that the general esterases might play an important role in conferring or contributing to neonicotinoid resistance in the cotton aphids.     

Assessment of cotton aphids, Aphis gossypii, and their natural enemies on aphid-resistant and aphid-susceptible wheat varieties in a wheat–cotton relay intercropping system

The cotton aphid, Aphis gossypii Glover (Homoptera: Aphididae), is an important cotton pest in northern China, especially in the seedling stage of cotton. After large scale commercial use of transgenic Bt cotton, cotton aphids became one of the most important cotton pests. A 2‐year study was conducted to evaluate the role of four winter wheat varieties that were resistant or susceptible to wheat aphid, Sitobion avenae Fabricius (Homoptera: Aphididae), in conserving arthropod natural enemies and suppressing cotton aphids in a wheat–cotton relay intercropping system in northern China. The results indicated that wheat–cotton intercropping preserved and augmented natural enemies more than a monoculture of cotton. The density of natural enemies in cotton was significantly different among relay‐intercropping fields with different wheat varieties. The highest density of natural enemies and low cotton aphid populations were found in the treatment of cotton in relay intercropped with the wheat variety Lovrin10, which is susceptible to wheat aphid. The lowest density of predators and parasitoids associated with high cotton aphid populations were found with the wheat variety KOK1679, which is resistant to wheat aphid. The results showed that wheat varieties that are susceptible or moderately resistant to wheat aphid might reduce cotton aphids more effectively than an aphid‐resistant variety in the intercropping system by enhancing predators to suppress cotton aphids during the cotton seedling stage.     

抗吡虫啉棉蚜种群对啶虫脒和噻虫胺的交互抗性及相关酶学机理

【目的】通过对乙酰胆碱受体β1亚基突变后的抗吡虫啉棉蚜Aphis gossypii (Glover)种群的继续筛选, 明确该种群的抗性发展规律以及对其他新烟碱类杀虫剂啶虫脒和噻虫胺的交互抗性及相关酶学机理。【方法】采用浸渍法连续对抗吡虫啉棉蚜进行室内筛选、 测定噻虫胺和啶虫脒对抗吡虫啉棉蚜种群的毒力; 选择LC₂₀剂量吡虫啉、 啶虫脒和噻虫胺处理抗性棉蚜, 采用生化分析法测定其体内羧酸酯酶、 谷胱甘肽-S-转移酶和乙酰胆碱酯酶的活性变化, 并观察其生物学特性的变化。【结果】本研究对抗性棉蚜突变种群用吡虫啉继续筛选至75代, 抗性倍数达到72.6倍, RF75停止用药筛选12代（RF₇₅₊₁₂）, 抗性仍达72.0倍。且RF₇₅₊₁₂对噻虫胺和啶虫脒的交互抗性可分别达11.9倍和20.1倍。噻虫胺对抗吡虫啉棉蚜的蜜露分泌和体重的抑制作用均大于吡虫啉和啶虫脒。噻虫胺对RF₇₅₊₁₂的羧酸酯酶、 谷胱甘肽-S-转移酶和乙酰胆碱酯酶均具有明显的抑制作用, 而啶虫脒的抑制作用较小。【结论】结果表明乙酰胆碱受体基因突变棉蚜种群对吡虫啉的抗性水平不仅升高, 且停止用药后其抗性可稳定遗传; 第二代新烟碱类的噻虫胺在抗吡虫啉棉蚜靶标突变种群的治理中具有较大的应用价值。     

Polymorphisms in a carboxylesterase gene between organophosphate-resistant and -susceptible Aphis gossypii (Homoptera: Aphididae)

Resistance to omethoate was suppressible by the hydrolytic enzyme inhibitor SSS-tributyl phosphorotrithioate in a laboratory-selected resistant cotton aphid, Aphis gossypii Glover, strain, suggesting the involvement of hydrolytic enzymes in the detoxification process. The kinetic properties of carboxylesterases from both resistant and susceptible cotton aphids were characterized by four acyl ester substrates: alpha-naphthyl acetate (alpha-NA), alpha-naphthyl butyrate (alpha-NB), alpha-naphthyl phosphate (alpha-NP), and beta-naphthyl phosphate (beta-NP). No significant differences of carboxylesterase activity were found between resistant and susceptible strains by using either alpha-NP or beta-NP as substrates. In contrast, the susceptible A. gossypii exhibited significantly higher activity compared with resistant aphids with either alpha-NA or alpha-NB as substrates. To understand the molecular basis of this esterase-mediated resistance, carboxylesterase genes from both strains were cloned. Two genes share 99.4% identity at the nucleic acid level and 99.2% identity at the amino acid level. The full length of the cDNA opening reading frame is 1581 bp, encoding 526 amino acids. Four amino acid substitutions, Thr210 --> Met210, Asn294 --> Lys294, Gly408 --> Asp408, and Ser441 --> Phe441, were identified in the resistant strain. Probing of Southern blots with the 0.5 kb esterase fragment showed the same banding patterns and intensities with genomic DNA extracts from both resistant and susceptible A. gossypii. Furthermore, the MspI and HpaII fragments are the same in both strains, indicating there is no methylation of sequences detected by the probe. The combined results suggest that the structural gene substitution is likely the molecular basis of the organophosphate resistance in this laboratory-selected cotton aphid strain.     

Differential mRNA expression levels and gene sequences of carboxylesterase in both deltamethrin resistant and susceptible strains of the cotton aphid, Aphis gossypii

Extensive use of insecticides on cotton has prompted resistance development in the cotton aphid, Aphis gossypii (Glover) in China. A deltamethrin‐selected population of cotton aphids from Xinjiang Uygur Autonomous Region, China with 228.59‐fold higher resistance to deltamethrin was used to examine how carboxylesterase conferred resistance to this pyrethroid insecticide. The carboxylesterase activity in the deltamethrin‐resistant strain was 3.67‐, 2.02‐ and 1.16‐fold of the susceptible strain when using α‐naphthyl acetate (α‐NA), β‐naphthyl acetate (β‐NA) and α‐naphthyl butyrate (α‐NB) as substrates, respectively. Carboxylesterase cDNA was cloned and sequenced from both deltamethrin‐resistant and susceptible strains. The cDNA contained 1581 bp open reading frames (ORFs) coding a 526 amino acid protein. Only one amino acid substitution (Val⁸⁷‐Ala) was observed between deltamethrin‐resistant and susceptible strains but it is not genetically linked to resistance by the catalytic triad and signature motif analysis. The real‐time polymerase chain reaction analysis indicated that the resistant strain had a 6.61‐fold higher level of carboxylesterase mRNA than the susceptible strain. The results revealed that up‐regulation of the carboxylesterase gene, not modified gene structure, may be responsible for the development of resistance in cotton aphids to deltamethrin.     

棉蚜抗杀灭菊酯品系的某些生物学特性

1908-1990年抗性监测表明,河南棉区棉蚜Aphis gossypii Glover对杀灭菊酯、氧化乐果和 久效磷的抗性水平明显增长,特别是对杀灭菊酯的抗性已达较高水平。使用杀灭菊酯对敏感棉蚜连续选择8次,棉蚜对杀灭菊酯抗性上升1392.67倍(浸溃法测定),并表现对久效磷和氧化乐果有3-4倍的正交互抗性。对4个不同抗性品系棉蚜的实验种群生命表分析表明,杀灭菊酯抗性棉蚜的适合度并不降低,抗性棉 蚜的繁殖力不表现降低趋势。利用棉田常用8种有机磷、菊酯类和脒类农药的单剂及混剂测定了对高抗棉蚜的毒力水平,DDVP表现对高抗杀灭菊酯棉蚜有较强毒力;脒类和菊酯类农药混配有显著的增效作用, 但与DDVP混用则有拮抗作用。     

应用酶标仪动力学方法监测棉蚜的抗药性

用酶标仪动力学测定法对3个抗性水平不同的棉蚜品系（R1、R2和R3）和1个敏感品系（S）的羧酸酯酶进行了研究,S、R1、R2和R3品系对α-乙酸萘酯（α-NA）的平均比活力分别为57．10、1171．69、1236．14和3293．00μmol·mgpro－1·min-1（分光光度计终点测定法）和38．24、85．27、198．14和762．25mOD·min－1·aphid-1（酶标仪动力学法）。终点测定法结果显示出不同品系间最大相差达60倍;酶标仪动力学测定法研究表明,4个棉蚜品系羧酸酶活性与其抗药性程度显著相关。通过对这两种方法的比较,酶动力学方法的测定结果更可靠。     

USING FILTER PAPER TEST FOR DETECTING INHIBITORY FREQUENCY OF ORGANOPHOSPHATE TO ESTERASES IN COTTON APHIDS, APHIS GOSSYPII (GLOVER)

Abstract The individual esterase activity which is measured by filter paper test (FPT) method may determine the resistance of cotton aphids Aphis gossypii (Glover) against organophosphorus (OP) insecticides. For testing accurately resistant level caused by different insecticides, we applied FPT method for measuring inhibitory action of methyl-parathion, monocrotophos and omethoate to α-NA esterase of individual cotton aphids, and compared the inhibitory frequencies of these three insecticides to susceptible population (BCA) and resistant population (GCA). Results showed that their inhibitory frequencies of the susceptible population were evidently higher than that of the resistant population. The inhibitory rate of α-NA esterase in F1 generation individual cotton aphids by monocrotophos was low when the cotton aphid population had been treated in advance with monocrotophos, but it got to 75%-90% when the cotton aphid population had been untreated in advance with monocrotophos. Besides, the differences in esterase activity were not obvious between them. In same region when cotton aphids were treated with insecticides the inhibitory frequency of esterases in individual by the insecticides was lower than counterparts in individual cotton aphids which were not treated with insecticides. All these demonstrated that inhibitory frequency of α-NA esterase in individual cotton aphids by OP insecticides could be used as a technique of forecasting pest resistance.     

棉蚜啶虫脒抗性种群交互抗性和增效剂增效作用的研究

【目的】明确棉蚜Aphis gossypii Glover啶虫脒抗性品系与其它杀虫剂的交互抗性现状以及增效剂的增效作用,为延缓和治理棉蚜对啶虫脒的抗性提供依据。【方法】采用单头反选育和群体汰选的方式,获得了棉蚜啶虫脒敏感和抗性品系;采用叶片药膜法测定了13种杀虫剂对啶虫脒的交互抗性以及增效剂对啶虫脒的增效作用。【结果】经过室内棉蚜敏感和抗性品系的筛选,获得了相对抗性倍数为82.33倍的棉蚜啶虫脒抗性品系。棉蚜啶虫脒抗性品系的交互抗性谱的研究表明,交互抗性倍数小于5的药剂为:吡蚜酮,甲基阿维菌素;交互抗性倍数在5~10倍的药剂为:噻虫嗪,联苯菊酯,毒死蜱,马拉硫磷,丙溴磷,辛硫磷;交互抗性倍数在10~15倍的药剂为:硫丹,阿维菌素,高效氯氰菊酯,三唑磷,氧化乐果;交互抗性倍数大于1 5倍的药剂为:吡虫啉。增效剂实验表明,TPP和PBO在啶虫脒敏感品系中增效作用不明显,但在抗性品系中增效作用显著。在啶虫脒抗性品系中的增效比为1.77、1.61,在啶虫脒敏感品系中的增效比为1.02、1.03。DEM在啶虫脒抗性、敏感品系中的增效作用均不明显,增效比为1.04、1.02。TPP和PBO对啶虫脒有很好的增效作用。以室内棉蚜敏感品系(LC_(50)为0.180 mg/L)为基础,对新疆各主要棉区的棉蚜种群进行了啶虫脒药剂的抗性调查,结果表明新疆各主要棉区棉蚜对啶虫脒的相对抗性倍数为6.1~22.0倍。【结论】由此说明新疆主要棉区棉蚜对啶虫脒具有一定的抗性风险,生产中可以利用无交互抗性的吡蚜酮和甲基阿维菌素来治理抗性棉蚜种群。     

取食不同寄主植物对棉蚜后代抗药性的影响

测定了5种药剂对棉蚜Aphis gossypii抗氰戊菊酯、吡虫啉品系和敏感品系取食棉花、黄瓜和石榴的后代的毒力,并对它们的后代体内乙酰胆碱酯酶和羧酸酯酶的比活力做了初步探索。结果表明,氰戊菊酯抗性品系取食棉花比取食黄瓜的后代对氰戊菊酯的抗性大76.4倍,对灭多威、氧乐果、硫丹和吡虫啉的抗性也大0.5～4.6倍;取食石榴的后代对5种药剂的抗性介于取食棉花和黄瓜的之间。吡虫啉抗性品系的测定结果与氰戊菊酯抗性品系基本一致。敏感品系取食黄瓜比取食棉花的后代对5种药剂的敏感性更高。3个品系取食不同植物的后代相比,其体内乙酰胆碱酯酶的比活力,取食棉花的为取食黄瓜的2.4～2.8倍;羧酸酯酶的比活力,取食棉花的为取食黄瓜的1.8～2.4倍。证明棉蚜的抗性和敏感品系取食的寄主植物不同,可引起对药剂敏感性的变化。乙酰胆碱酯酶和羧酸酯酶活力的变化均是引起这种变化的重要因素。     

棉花抗蚜性与苯丙氨酸解氨酶活性的关系

为探讨苯丙氨酸解氨酶活性与棉花抗蚜性的关系,在室内人工接蚜危害和田间自然蚜群2种条件下,测定不同抗蚜性棉花品种受棉蚜Aphis gossypii Glover危害后叶片的PAL活性。结果表明:未受棉蚜危害时,抗、感品种PAL活性无明显差异;棉蚜危害胁迫棉花PAL活性升高,抗蚜品种受到棉蚜危害诱导所产生的PAL活性远比感蚜品种高。田间有蚜株率与棉花叶片苯丙氨酸解氨酶活性的呈显著的负相关关系。研究说明PAL酶活性对棉花的抗蚜性有一定的影响。     

Field evaluation of resistance to pyriproxyfen in Bemisia tabaci (B biotype)

We determined effects of aerial sprays of the insect growth regulator pyriproxyfen on sweetpotato whitefly, Bemisia tabaci (Gennadius) (B biotype), in Arizona cotton (Gossypium spp.) fields. We measured survival for males and females from a susceptible strain and a laboratory-selected resistant strain, as well as for hybrid female progeny from crosses between the strains. Insects were exposed directly to pyriproxyfen sprays in the field or indirectly in the laboratory by rearing them on sprayed leaves collected from the field. In all tests, survival was higher for the resistant strain than the susceptible strain, but did not differ between sexes in each strain. Survival to the adult stage did not differ between eggs and nymphs directly exposed to sprays. For susceptible and hybrid individuals, survival was lower on leaves collected the day of spraying than on leaves collected 2 wk after spraying. In contrast, survival of resistant individuals did not differ based on the timing of exposure. Dominance of resistance to pyriproxyfen depended on the type of exposure. Resistance was partially or completely dominant in direct exposure bioassays and on leaves collected 2 wk after spraying (h > 0.6). Resistance was partially recessive on leaves collected the day of spraying (mean h = 0.34). Rapid evolution of resistance to pyriproxyfen could occur if individuals in field populations with traits similar to those of the laboratory-selected strain examined here were treated intensively with this insecticide.     

INSECTICIDE RESISTANCE OF COTTON APHID IN NORTH CHINA

Abstract  The cotton aphid ( Aphis gossypii Glover) is one of the most important pests infesting cotton in the cotton areas of North China. Since 1953 organophosphorus insecticides such as parathion and systox have been used to control the aphids for keeping up good yield of cotton. After several years. the concentration and the amount of spray were increasing in the field. In the early 1980's highly effective pyrethroid insecticides such as decis and sumicidin were largely imported into China. When first used 2. 5% decis emulsion was diluted in the ratio from 1:10000 to 1: 12000. However in 1985 the resistance of cotton aphid to pyrethroids increased by 171 times in general, 3230 times in some cotton fields. Thus it has prompted us to investigate the mechanism of resistance to insecticides and to search for the strategy to control the resistant aphids.
Experiments showed that the use of synergists including SV₁ (O, O-diethyl, O-phenyl phos-phorothionate) and PB has given evidence indicating mixed function oxidases (MFO). α-NA esterases and α-NA carboxylesterase are involved in the formation of resistance. The results also showed that the sensitivity of AChE to paraoxon in resistant aphids was lower than that in susceptible aphids.
Experiments showed that SV₁ was particularly synergistic to organophosphorus or pyrethroid insecticides and had played an excellent role in overcoming the resistance of cotton aphids to insecticides.     

The impact of Meu1-mediated resistance in tomato on longevity, fecundity and behavior of the potato aphid, Macrosiphum euphorbiae

The effect of the tomato resistance gene, Meu1, on feeding, longevity, fecundity and developmental rate of the pink biotype of the potato aphid, Macrosiphum euphorbiae (Thomas) (Hemiptera, Aphididae), was determined using nearly isogenic tomato (Lycopersicon esculentum Mill, Solanaceae) lines. Aphid mortality was significantly higher on resistant plants, with 60% of the aphids dying by the 4th day of exposure. By the 10th day, all the aphids on the resistant plants were dead whereas 100% of the aphids on susceptible plants were alive. Meu1-mediated resistance resulted in significantly decreased fecundity with a ten-fold decrease in the net fertility rate (4.5 and 45.7 progeny per aphid on resistant and susceptible tomato, respectively). A qualitative analysis showed that honeydew was produced by aphids on resistant and susceptible plants, suggesting that aphids initiate feeding on both plant types. However, significantly lower quantities of honeydew were present when aphids were caged on resistant plants. There were also significant differences in aphid location on resistant and susceptible leaves. Experiments evaluating behavior in less than 24 h showed that aphids left resistant leaves after relatively short exposure (3–6 h). Aphids transferred from resistant to susceptible tomato at intervals between 3 h and 24 h resumed feeding as evidenced by presence of honeydew. Although the mechanism by which Meu1-mediated resistance operates is not yet known, our data suggest that resistance factors act rapidly after initiation of feeding and that lower fecundity and longevity are related to reduction in aphid feeding.     

棉蚜对寄主的选择及寄主专化型研究

采用叶片选择法,生命表及EPG技术研究了棉蚜对寄主植物的选择和专化性,结果表明,棉花上生长的棉蚜对棉花,西葫芦和西瓜叶片均具有强选择性,而对黄瓜和南瓜选择性弱,西瓜,南瓜和黄瓜上生长的棉蚜对其原寄主选择性强,而对棉花选择性弱,棉花上的棉蚜转接到黄瓜和南瓜上,其存活率和繁殖力极低,棉蚜的取食行为在黄瓜和马铃薯,黄瓜和棉花之间存在明显的寄主专化型,黄瓜与棉花上的棉蚜相互转接均难成功,而黄瓜和马铃薯上的棉蚜转移具有不对称性。     

Sublethal effects of insecticides on the intrinsic rate of increase of cotton aphid

Insecticides are often implicated in causing outbreaks of the cotton aphid, Aphis gossypii (Glover) (Homoptera: Aphididae), through stimulation of reproduction. In this study we report the sublethal effects of dosages of bifenthrin, acephate, carbofuran or pyriproxifen on cotton aphid reproduction. We could not detect any increase or decrease in the intrinsic rate of increase of cotton aphids exposed to bifenthrin, acephate or carbofuran. However, we did detect some increases in the net reproductive rate of aphids treated with bifenthrin justifying further investigation of the effect on reproduction by this insecticide. Trends based on simple linear regression models suggest that sublethal dosages of bifenthrin or carbofuran have a negative impact on aphid population growth as dosages increase. These data suggest that stimulation of reproduction by these insecticides probably does not play a major role in cotton aphid outbreaks or resurgence. Pyriproxyfen is a juvenoid currently used for control of whiteflies in cotton. It demonstrated significant activity towards cotton aphid reared on treated cotton in our bioassays. Pyriproxyfen caused sterility in most aphids exposed to dosages exceeding 1 ppm, and reduced aphid longevity by approximately 50%. However, it did not appear to greatly influence the reproductive potential or longevity of reproductively mature aphids. A field study indicates that pyriproxyfen affects cotton aphid population structure and may have potential in managing cotton aphid outbreaks. Modifying aphid population structure and growth through the use of juvenoids such as pyriproxifen may prove to be an effective proactive approach to pest control without adversely impacting beneficial organisms or causing pest resurgence.