寄主型和迁飞型棉蚜的交配行为

棉蚜Aphis gossypii Glover种群存在寄主利用和迁飞能力上的明显分化,有棉花型和瓜型、迁飞型和滞留型之分。但是,棉花型与瓜型之间,以及迁飞型与滞留型之间是否能发生交配行为,尚无研究报道。本文在低温和短光照条件下分别诱导棉花型、瓜型、迁飞型和滞留型棉蚜的性蚜,并进行性蚜间的交配行为观察。结果表明,迁飞型和滞留型性蚜间可以发生交配行为,杂交时发生交配行为的个体比率与自交时无显著差异,但是杂交时雄蚜寻找配偶所花的时间要显著长于自交时,并且迁飞型雌蚜(M♀)与滞留型雄蚜(S♂)杂交时的交配持续时间也显著长于自交时。迁飞型和滞留型棉蚜同型交配容易完成,棉蚜的迁飞型和滞留型已在交配行为上产生了一定的分化。棉花型和瓜型棉蚜的性蚜间可以发生交配行为,并且两品系在正交和反交时雄蚜的寻偶时间与交配持续时间均无显著差异。     

棉花型和瓜型棉蚜形态和生态适应力的分化

棉蚜由于长期在同种或同类植物上生活,形成了多种寄主专化型。本研究以室内长期用单一寄主培养的棉花型和瓜型棉蚜为材料,采用形态测定、生命表技术、对寄主的选择性试验,以及接触刺激等方法,研究了两寄主型棉蚜的形态分化和生态适应力的差异。结果表明,瓜型棉蚜的一些形态特征值（如体长）极显著地大于棉花型个体,但是头宽、口针和各腿节的长度与体长的比值却极显著的小于棉花型个体。采用7个形态指标与体长的比值,可将瓜型和棉花型棉蚜区分开来。在24℃和26℃下瓜型蚜的净增殖率（R₀）极显著地高于棉花型蚜。27℃和32℃显著缩短了瓜型蚜的平均世代长度,而对棉花型蚜无影响。棉花型蚜对接触刺激的反应比瓜型蚜敏感。两寄主型蚜对寄主的选择能力表现为瓜型蚜显著强于棉花型蚜。因此,两寄主型棉蚜存在明显的形态和生态适应力的分化。     

用微卫星引物PCR分析棉蚜不同蚜型的DNA多态性

用微卫星引物PCR方法, 对棉蚜Aphis gossypii干母、干雌、孤雌蚜(有翅迁飞孤雌蚜和无翅孤雌蚜)、性母、性雌蚜和雄蚜的DNA多态性进行分析。 结果表明：① 棉蚜的有性蚜型和无性蚜型之间在遗传上有较大的差异; ② 性母与性雌蚜和雄蚜的遗传关系都十分接近,说明同一性母既产性雌蚜,也产雄蚜;③ 干母和干雌的遗传关系很近, 但孤雌蚜已与二者有分化。     

棉花型和黄瓜型棉蚜对寄主植物的适合度

采用寄主转换建立生命表及触角电位 (EAG)方法比较了棉蚜两寄主专化型 (棉花型和黄瓜型 )对不同夏季作物的适合度。结果表明 ,棉花型蚜转到黄瓜上及黄瓜型蚜转接到棉花上均不能正常产仔繁殖和建立种群。两种蚜型均不能在茄子和苋菜上建立种群。黄瓜型蚜能在豇豆上建立种群 ,但棉花型蚜不能 ,表现出两种寄主型棉蚜对夏寄主利用上存在显著差异。受棉蚜为害 12～ 36 h后的黄瓜或棉花植株仍不适合于棉花型或黄瓜型蚜 ,表现出黄瓜型蚜不能在被棉花型蚜为害过的棉株上正常存活和繁殖 ,棉花型蚜也不能在被黄瓜型蚜为害过的黄瓜苗上存活和繁殖。两种寄主型蚜对不同寄主叶片丙酮提取物的触角电位表明 ,黄瓜型蚜对棉花、哈密瓜和马铃薯叶片提取物的反应显著强于棉花型蚜 ,而对黄瓜和甜瓜叶片提取物的反应上两种蚜型差异不显著。文中同时对棉花型和黄瓜型棉蚜产生的生态机制进行了讨论。     

Mating behaviour of host-specialized and migratory biotypes of the cotton aphid

棉蚜Aphis gossypii Glover种群存在寄主利用和迁飞能力上的明显分化,有棉花型和瓜型、迁飞型和滞留型之分.但是,棉花型与瓜型之间,以及迁飞型与滞留型之间是否能发生交配行为,尚无研究报道.本文在低温和短光照条件下分别诱导棉花型、瓜型、迁飞型和滞留型棉蚜的性蚜,并进行性蚜间的交配行为观察.结果表明,迁飞型和滞留型性蚜间可以发生交配行为,杂交时发生交配行为的个体比率与自交时无显著差异,但是杂交时雄蚜寻找配偶所花的时间要显著长于自交时,并且迁飞型雌蚜(M ♀)与滞留型雄蚜(S♂)杂交时的交配持续时间也显著长于自交时.迁飞型和滞留型棉蚜同型交配容易完成,棉蚜的迁飞型和滞留型已在交配行为上产生了一定的分化.棉花型和瓜型棉蚜的性蚜间可以发生交配行为,并且两品系在正交和反交时雄蚜的寻偶时间与交配持续时间均无显著差异.     

棉花型和黄瓜型棉蚜(Aphis gossypii Glover)的寄主适应性及转移通道

采用寄主转接建立生命表的方法研究了棉花型和黄瓜型棉蚜对不同寄主植物的适应性,以及两寄主型棉蚜是否可通过中间桥梁寄主实现寄主互换的问题。结果表明,两寄主型棉蚜直接互换寄主后,其存活和繁殖力显著下降,表现为棉花型和黄瓜型棉蚜的净增殖率比在原寄主上分别下降980倍和12倍,平均世代寿命缩短5～12d。两寄主型棉蚜均能利用木槿植物,并且适应性没有显著差异。但是两寄主型棉蚜均不能在车前草和大叶黄杨上存活和繁殖后代。西葫芦作物对棉蚜在木槿、棉花和黄瓜寄主上的相互转移起到了重要的桥梁寄主作用。冬寄主木槿上棉蚜可通过甜瓜或西葫芦转移到黄瓜寄主上,棉花和黄瓜上棉蚜也可通西葫芦作物分别转移到黄瓜和棉花作物上,从而形成棉蚜在不同寄主植物间的相互转移通道,造成为害和病毒病的扩张。     

室内人工诱导大豆蚜产生有性世代的研究

【目的】大豆蚜Aphis glycines(Matsumura)是大豆上最重要的害虫之一,短暂的有性阶段是蚜虫种群基因交流的关键环节。通过探索影响大豆蚜产生有性世代的室内人工诱导条件,对研究种群遗传和生态适应机制具有重要意义。【方法】采用豆苗罩笼培养法,在实验室条件下用一定的光温组合处理,测定了处理1代和连续处理3代的大豆蚜各蚜型产生的比率,并且分析了各相关因素的影响。【结果】本试验成功诱导大豆蚜产生无翅孤雌蚜、有翅孤雌蚜、有翅产雄性母和有翅雄性蚜。结果表明,人工诱导雄性母产生的最适条件为15℃,10L︰14D处理3代,雄性蚜产生的最适条件为12℃,10L︰14D处理3代,而15℃,8L︰16D条件下大豆蚜翅型分化率最高。对各相关因子进行方差分析结果表明,温度与光周期互作对有性世代的产生影响最为显著,其次是温度、诱导日龄的单独作用,诱导世代只有和光温条件互作才有显著影响。【结论】在特定的光周期内,温度是大豆蚜有性世代产生的重要因素,同时光温条件组合对此有一定的累积效应,表现为光、温、诱导世代三者交互对有性世代的产生影响显著。     

棉蚜迁飞型和居留型及其杂交后代飞行特性的比较研究

为了明确棉蚜种群飞行能力发生分化的遗传基础,本文对春季木槿上有翅棉蚜中的起飞个体和不起飞个体分别进行连续4代次和2代次的起飞特性选择。结果表明,棉蚜的起飞比率和起飞角度特性表现出了明显的选择响应,并筛选出了棉蚜的迁飞型(M)和居留型(S)。通过对棉蚜性蚜的诱导,摸索出了棉蚜性蚜交配及卵孵化的条件。对迁飞型(M)、居留型(S)、迁飞型和居留型的正反交后代（M♀×S♂,S♀×M♂）、夏季木槿上的滞留蚜（H）等5类棉蚜的起飞特性进行了比较研究。结果表明,迁飞型和居留型的正反交后代的起飞比率显著高于居留型,且稍高于迁飞型。迁飞型雌蚜与居留型雄蚜的杂交后代的起飞角度显著高于居留型和夏季木槿上的滞留蚜。居留型产生有翅蚜的比率低于迁飞型及其与居留型的正反交后代。棉蚜的起飞角度、起飞比率及有翅蚜产生能力表现出了较强的遗传效应。平均起飞时间虽然表现出迁飞型雌蚜与居留型雄蚜的杂交后代显著短于迁飞型雄蚜与居留型雌蚜的杂交后代及夏季木槿上的滞留蚜,但与迁飞型和居留型之间却无显著差异,表现出棉蚜起飞时间特性的遗传效应不明显。     

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。     

棉蚜寄主专化型及其形成的行为机理

通过生活在甜瓜和棉花上的棉蚜Aphisgossypii Glover的行为,研究棉蚜的寄主专化型及其形成的行为机理。生物学观察显示： 两类棉蚜在寄主植物相互交换以后,定居数显著减少,棉花蚜型棉蚜的繁殖系数及若虫存活率显著下降,说明棉蚜存在甜瓜蚜型和棉花蚜型两种寄主专化型。通过刺探电位技术研究棉蚜的取食行为,以探索其寄主专化型形成的行为机理。结果表明： 甜瓜蚜型棉蚜在棉花上的取食行为容易被中断,但其口针定位韧皮部的能力并没有显著削弱;而棉花蚜型棉蚜在甜瓜上的取食行为受到更大的影响,口针无法顺利定位至韧皮部,并在2 h内根本无法在筛管内取食。生物学观察和EPG取食行为分析都显示： 与甜瓜蚜型棉蚜相比,棉花蚜型棉蚜对寄主的要求更严格-寄主专化程度更高,对寄主的利用率更高。     

Specialized host-plant performance of the cotton aphid is altered by experience

Although distinct host specialization is observed for the cotton-melon aphid (Aphis gossypii Glover) on cotton and cucurbit plants, it is still ambiguous whether the specialization is altered by experience on a novel host plant. Here the performance of cotton and cucurbit-specialized aphids, A. gossypii on novel host plants was studied by a host-selection test and by the life-table method. The two host-specialized aphids cannot survive and establish populations after reciprocal host transfers. They have ability to recognize the host plants on which they were reared, and escape behavior from novel hosts was observed. Interestingly, the cotton and cucurbit-specialized aphids survive and reproduce normally on hibiscus (Hibiscus syriacus), a main overwintering host plant, and host-fidelity of A. gossypii to cucurbit plants is altered by feeding and living experience on hibiscus, which confers the same capacity to use cotton and cucumber on to the cucurbit-specialized population, but host-fidelity to cotton is not altered and the fitness of the cotton specialized population to cucumber is still poorer. A. gossypii from hibiscus has a significant preference for cotton to cucumber in the host-selection process, and none stays on cucumber more than 20 h after transfer. The results presented imply that cucurbit-specialized aphids might not return to an overwintering host plant (hibiscus) in wild fields, so host conservatism to cucurbit plants is maintained. The potential of cucurbit-specialized aphids of A. gossypii to use cotton plants, intermediated by experience on hibiscus, suggests that the specialized host-plant performance of phytophagous insects is not wholly conservative.     

How does the host‐specialized aphid deal with food deficiency?

Aphis gossypii Glover shows obvious host specialization, with cucurbit‐ and cotton‐specialized biotypes or host races in many regions. Because its annual natal host crops senesce earlier the cucurbit‐specialized biotype may suffer food deficiency. The method this biotype uses to overcome this challenge is still poorly understood. In order to understand the potential of the cucurbit‐specialized biotype aphids in host shift and usage, the performance of this biotype on cotton (Gossypium hirsutum), a common but poor quality host plant, was explored in this study. The cucurbit‐specialized aphids could establish populations on cotton only when these plants had at least nine leaves, and subsequent populations developed rather slowly. The presence of whitefly populations on cotton improved the success rate of cucurbit‐specialized aphids. The cucurbit‐specialized aphids were mainly distributed on the older leaves of cotton, with only a few settling on the upper leaves. The cucurbit‐specialized aphids reared on cotton for 40, 54 and 61 days still maintained strong preference for their natal host plant, cucumber (Cucumis sativus), rather than cotton, and their net reproductive rates and intrinsic rates of natural increase were dramatically lower when they were transferred onto new six‐leaf cotton plants or detached leaves. Therefore, we concluded that the cucurbit‐specialized aphids have the potential to utilize mature or whitefly‐stressed cotton plants, but that this feeding experience on cotton did not alter their specialization for cucurbits. Some cotton plants could act as a temporary host for the cucurbit‐specialized aphids to overcome food deficiency arising from senescing cucurbits.     

Cytopathology, Mode of Aphid Transmission and Search for the Casual Agent of Cotton Bunchy Top Disease

The cytopathological effects of cotton bunchy top (CBT) disease and its mode of transmission by Aphis gossypii Glover (cotton aphid), were studied. CBT infection affected the leaf epidermal layer producing a loose, ruptured and rough surface morphology with many stomata closed and misshapen. Roots of CBT‐infected plants showed reduced growth, small knots and a dark brown appearance. A single aphid per plant was capable of transmitting CBT at 5%, whereas three aphids per plant transmitted CBT to 50% of the cotton seedlings and 20 aphids per plant transmitted the disease agent to 80% of the cotton seedlings. Aphis gossypii acquired CBT after a minimum acquisition access period of 5 min and transmitted the agent after a minimum inoculation access period of 1 h. Both alate and apterous aphids and nymph instars 2, 3 and 4 of A. gossypii transmitted CBT. This preliminary data suggest that A. gossypii transmits CBT in a semi‐persistent manner. Myzus persicae Sulz (green peach aphid) was unable to transmit CBT. A comprehensive attempt to isolate the CBT agent, using a range of virological techniques including double‐stranded RNA extraction, two‐dimensional gel electrophoresis for viroid, circular DNA test, nanovirus polymerase chain reaction (PCR), luteovirus PCR and enzyme‐linked immunosorbent assay, phytoplasma test, nucleoprotein purification and electron microscopy, was unsuccessful, raising the possibility that CBT may be caused by a unique new pathogen.     

Identification of Aphis gossypii Glover (Hemiptera: Aphididae) Biotypes from Different Host Plants in North China

Background

The cotton-melon aphid, Aphis gossypii Glover (Hemiptera: Aphididae), is a polyphagous species with a worldwide distribution and a variety of biotypes. North China is a traditional agricultural area with abundant winter and summer hosts of A. gossypii. While the life cycles of A. gossypii on different plants have been well studied, those of the biotypes of North China are still unclear.

Results

Host transfer experiments showed that A. gossypii from North China has two host-specialized biotypes: cotton and cucumber. Based on complete mitochondrial sequences, we identified a molecular marker with five single-nucleotide polymorphisms to distinguish the biotypes. Using this marker, a large-scale study of biotypes on primary winter and summer hosts was conducted. All A. gossypii collected from three primary hosts—hibiscus, pomegranate, and Chinese prickly ash—were cotton biotypes, with more cotton-melon aphids found on hibiscus than the other two species. In May, alate cotton and cucumber biotypes coexisted on cotton and cucumber seedlings, but each preferred its natal host. Both biotypes existed on zucchini, although the cucumber biotype was more numerous. Aphids on muskmelon were all cucumber biotypes, whereas most aphids on kidney bean were cotton biotypes. Aphids on seedlings of potato and cowpea belong to other species. In August, aphids on cotton and cucumber were the respective biotypes, with zucchini still hosting both biotypes as before. Thus, the biotypes had different fitnesses on different host plants.

Conclusions

Two host-specialized biotypes (cotton and cucumber) are present in North China. Hibiscus, pomegranate, and Chinese prickly ash can serve as winter hosts for the cotton biotype but not the cucumber biotype in North China. The fitnesses of the two host-specialized biotypes differ on various summer hosts. When alate aphids migrate to summer hosts, they cannot accurately land on the corresponding plant.     

Within-plant distribution of cotton aphids, Aphis gossypii Glover (Hemiptera: Aphididae), in Bt and non-Bt cotton fields

Knowledge of the vertical and horizontal distribution of Aphis gossypii Glover (Hemiptera: Aphididae) on genetically modified cotton plants over time could help optimize decision-making in integrated cotton aphid management programs. Therefore, the aim of the present study was to determine the vertical and horizontal distribution of A. gossypii in non-transgenic Bt cotton and transgenic Bt-cotton over time during two cotton seasons by examining plants throughout the seasons. There was no significant interaction between years and cotton cultivar treatments for apterous or alate aphids. Considering year-to-year data, analyses on season-long averages of apterous or alate aphids showed that aphid densities per plant did not differ among years. The number of apterous aphids found per plant for the Bt transgenic cultivar (2427 apterous aphids per plant) was lower than for its isoline (3335 apterous aphids per plant). The number of alate aphids found per plant on the Bt transgenic cultivar (12.28 alate aphids per plant) was lower than for the isoline (140.56 alate aphids per plant). With regard to the vertical distribution of apterous aphids or alate aphids, there were interactions between cotton cultivar, plant age and plant region. We conclude that in comparison to non-Bt cotton (DP 4049), Bt cotton (DP 404 BG (Bollgard)) has significant effects on the vertical, horizontal, spatial and temporal distribution patterns of A. gossypii, showing changes in its distribution behaviour inside the plant as the cotton crop develops. The results of our study are relevant for understanding the vertical and horizontal distribution of A. gossypii on Bt cotton cultivar (DP 404 BG (Bollgard)) and on its isoline (DP 4049), and could be useful in decision-making, implementing controls and determining the timing of population peaks of this insect.     

Special Plant Species Determines Diet Breadth of Phytophagous Insects: A Study on Host Plant Expansion of the Host-Specialized Aphis gossypii Glover

Host specialization is a ubiquitous character of phytophagous insects. The polyphagous population is usually composed of some subpopulations that can use only a few closely related plants. Cotton-melon aphids, Aphis gossypii Glover exhibited strong host specialization, and the cotton- and cucurbits-specialized biotypes had been clearly identified. However, the experimental work that addressed the roles of plant species in determining diet breadth of phytophagous insects is rare. In the present study, we took the artificial host transfer method to assess the role of two special plants, zucchini Cucurbita zucchini L. and cowpea Vigna unguiculata (Linn.) Walp, in regulating diet breadth of cotton- and cucurbits-specialized A. gossypii collected from cotton and cucumber fields and reared separately on the native host plant for ten years. The results showed that the cotton-specialized aphids did not directly use cucumber whereas the cucurbits-specialized did not use cotton regardless of the coexistence or separation of cotton and cucumber plants. Neither of the cotton- and cucurbits-specialized aphids could use capsicum Capsicum annuum, eggplant Solanum melongenahttp://en.wikipedia.org/wiki/Carolus_Linnaeus, tomato Solanum lycopersicum, maize Zea mayshttp://en.wikipedia.org/wiki/Carl_Linnaeus, and radish Raphanus sativus, however, both of them could use zucchini and cowpea. Moreover, the feeding experience on zucchini led the cotton-specialized aphids to use cucumber well and finally to be transformed into the cucurbits-specialized biotype. The short-term feeding experience on cowpea resulted in the diet breadth expansion of the cucurbits-specialized aphids to use cotton. On the other hand, the diet breadth expansion of the cucurbits- and cotton-specialized aphids was only realized by different species of plant. It concluded that the special host plant did induce the conversion of feeding habits in the cotton- and cucurbits-specialized aphids, and consequently broke the host specialization. The plant species is an underlying factor to determine the diet breadth of phytophagous insects.     

Presence of two host races of Aphis gossypii Glover (Hemiptera: Aphididae) collected in Turkey

The aphid, Aphis gossypii, is a primary pest of citrus, cotton, cucurbits and greenhouse‐grown vegetables in Turkey and throughout Europe. There is some previous empirical data suggesting that host‐adapted genotypes of this aphid exist which may in fact be host‐races. To determine if host races of A. gossypii are indeed present in the eastern Mediterranean region of Turkey, reciprocal host transfer experiments and life table analyses were performed with multiple asexual lineages (= clones) of the aphid collected from different hosts. The collection hosts included citrus, cucumber, eggplant, okra, sweet pepper and cotton. Aphid developmental times on the host from which the aphid was originally collected (= collection or natal host) were shorter (5.2–6.0 days) and had a higher intrinsic rate of population growth (r_m = 0.25–0.44) than the 6.6–7.3 days required when the aphid was reared on a non‐original collection host (= non‐collection host or non‐natal host) and had r_m = 0.03–0.30. Total immature mortality of the cotton clone, especially in the first nymphal stage, was high (51–100%) with low r_m (0–0.03) on cucumber, citrus and sweet pepper. Aphid populations transferred from citrus, eggplant and okra to cotton (r_m = 0.29–0.30) did not differ significantly in their performance from that of the cotton population on cotton (r_m = 0.34), whereas that from sweet pepper and cucumber populations (r_m = 0.22–0.24) were significantly lower. These data have allowed us to separate A. gossypii into two distinct biological groups: (a) a ‘generalist’ population obtained from cucumber, sweet pepper, citrus, eggplant and okra which exhibited statistically better development on cotton; versus (b) a population from cotton which, by comparison on reciprocal hosts, developed poorly on non‐natal hosts except on eggplant. Development of the cotton clone on cucumber and okra was not improved after four successive generations on the non‐natal host. The good development of A. gossypii from eggplant and cotton on these reciprocal hosts suggests that these particular clones were similar, if not identical, host races.     

Host‐associated differentiation and evidence for sexual reproduction in Iranian populations of the cotton aphid,Aphis gossypii

Phytophagous insects with wide host ranges often exhibit host‐associated genetic structure. We used microsatellite analysis to assess the population structure of the cotton aphid, Aphis gossypii Glover (Hemiptera: Aphididae), a serious pest on many economically important crops worldwide. We sampled aphids from five host plant species in Iran and detected strong population subdivision, with an overall multilocus F_ST of 0.191. The matrix of pairwise F_ST values indicated that differentiation between populations collected from different hosts was significantly stronger than between populations from the same hosts. Host‐associated differentiation was further supported by Bayesian clustering analyses, which grouped all samples from cotton together with aubergine, and all samples from cucumber together with pumpkin and hibiscus. This adds to the growing body of evidence that many seemingly generalist aphids are in fact an assemblage of host‐specialized lineages. Although we detected a clear genetic signature of clonal reproduction, the genotypic diversity of A. gossypii in Iran is much higher than in other parts of the world. Particularly samples from cotton exhibited a surprisingly high genotypic diversity, suggesting that many lineages on this host are cyclical parthenogens that engage in regular bouts of sexual reproduction.     

Interspecific Associations between Cycloneda sanguinea and Two Aphid Species (Aphis gossypii and Hyadaphis foeniculi) in Sole-Crop and Fennel-Cotton Intercropping Systems

Aphids cause significant damage to crop plants. Studies regarding predator-prey relationships in fennel (Foeniculum vulgare Mill.) and cotton (Gossypium hirsutum L.) crops are important for understanding essential ecological interactions in the context of intercropping and for establishing pest management programs for aphids. This study evaluated the association among Hyadaphis foeniculi (Passerini) (Hemiptera: Aphididae), Aphis gossypii Glover (Hemiptera: Aphididae) and Cycloneda sanguinea (L.) (Coleoptera: Coccinellidae) in cotton with coloured fibres, fennel and cotton intercropped with fennel. Association analysis was used to investigate whether the presence or absence of prey and predator species can indicate possible interactions between aphids and ladybugs. Significant associations among both apterous and alate H. foeniculi and C. sanguinea were observed in both the fennel and fennel-cotton intercropping systems. The similarity analysis showed that the presence of aphids and ladybugs in the same system is significantly dependent on the type of crop. A substantial amount of evidence indicates that the presence of the ladybug C. sanguinea, is associated with apterous or alate A. gossypii and H. foeniculi in fennel-cotton intercropping system. We recommend that future research vising integrated aphid management taking into account these associations for take decisions.     

Alatae production and population increase of aphid vectors on virus-infected host plants

Summary Zucchini yellow mosaic virus (ZYMV) and Aphis gossypii Glover are two components of a recently identified plant-parasite system that provides an excellent opportunity to study interrelations between a virus and a vector that share the same host, but have no direct physiological interaction. In a field experiment we documented numbers of alate and apterous A. gossypii on healthy Cucurbita pepo and on plants inoculated with virus 0, 7, 14, and 21 days before aphid infestation. When plants were inoculated and infested simultaneously, more than twice as many alatae were produced after 20 days of colony growth than on any other treatment. This indicates that properties unique to the early stages of viral infection somehow stimulated wing formation. Because it is spread by the activities of alatae, virus dispersal would be greater as a result of these properties. Developmental rate, total numbers of aphids, and numbers of alatae and apterae decreased as the time between virus inoculation and aphid colonization increased.