Genetic diversity of melon aphids Aphis gossypii associated with landscape features

Despite increasing evidence that landscape features strongly influence the abundance and dispersal of insect populations, landscape composition has seldom been explicitly linked to genetic structure. We conducted a genetic study of the melon aphid, Aphis gossypii, in two counties of Beijing, China during spring migration using samples from watermelon. We performed aphid genetic analysis using restriction site associated DNA sequencing (2b‐RAD) and investigated the relationship between land cover and the genetic diversity. The percentage area of land cover (cropland, vegetable, orchard, grassland, woodland) was quantified in each particular scale (ranging from 0.5 km to 3 km) and was used as a predictor variable in our generalized linear models. We found a moderate level of genetic differentiation among nine sampled populations. Geographic distance and genetic distance were not significantly associated, indicating that geographic location was not a barrier to migration. These nine populations could be clustered depending on their level of genetic diversity (high and low). The genetic diversity (Shannon’s information index) was positively correlated with grassland at the spatial scales of 1 and 2 km and negatively with orchard and vegetable at 0.5 and 1 km. Genetic diversity was best predicted by the grassland + orchard + vegetable model at a spatial scale of 1 km. Based on the method of relative weights, orchard land had the greatest relative importance, followed by grassland and vegetable land, in that order. This study contributes to our understanding of the genetic variation of aphids in agricultural landscapes.     

Role of leaf glandular trichomes of melon plants in deterrence of Aphis gossypii Glover

External characteristics of the leaf epidermis and their effects on behaviour of Aphis gossypii Glover were evaluated in two Cucumis melo L. genotypes, ‘Bola de Oro’ (aphid susceptible) and TGR‐1551 (aphid resistant) in order to explore their role in the early rejection of TGR‐1551 by this aphid. No differential effects of epicuticular waxes on aphid behaviour were observed. The type, distribution and number of trichomes on melon leaves were also studied. Pubescence in melon, measured as the number of non‐glandular trichomes per cm², was not sufficient to prevent aphid settling. However, there was a high density of type I glandular trichomes on leaves of the aphid‐resistant genotype. According to microscopic observations and stain testing, these trichomes store and secrete phenols and flavonoids. Free‐choice tests were conducted to determine the effect of these glandular trichomes on A. gossypii preference, revealing that aphids reject leaf disks of TGR‐1551 from the onset of the experiment. Additional experiments after removal of leaf type I glandular trichome exudates showed that A. gossypii preferred washed TGR‐1551 leaf disks over unwashed disks, while this effect was not observed in experiments using washed and unwashed ‘Bola de Oro’ leaf disks. These results suggest that a high density of glandular trichomes and chemicals secreted by them deter A. gossypii and disturb aphid settling on TGR‐1551.     

不同温度条件对棉蚜、棉长管蚜种间竞争关系的影响

【目的】棉蚜Aphis gossypii和棉长管蚜Acyrthosiphon gossypii是棉花上的共存种,本文拟明确不同恒温条件下两种蚜虫单种和共存时的种群动态、有翅蚜发生及在棉株上的分布情况,探讨温度对两者种间竞争的作用。【方法】棉蚜、棉长管蚜单种、混合初始等蚜量设置,分别置于室内21、24和27℃恒温条件下,系统调查记录各处理种群数量、有翅蚜数量及在棉株上的分布,应用内禀增长率rm、空间分布情况、有翅蚜比例为竞争判别指标。【结果】棉蚜单种种群过程的rm均大于棉长管蚜,共存条件下一种对另一种蚜虫的rm均没有显著影响;棉蚜种群97%以上在叶片活动,棉长管蚜在叶片的比例为55%~75%;同一温度条件,两种共存不影响对方在棉花叶片和茎秆上的分布;棉蚜和棉长管蚜主要分布于棉花中上部。随温度升高,共存种群中棉蚜向棉株下部移动的比例增加,单种和共存种群棉长管蚜趋向于棉株上部移动。同一温度条件下,共存对棉蚜上下分布没有明显影响。21℃和27℃棉蚜的存在对棉长管蚜没有显著影响,但24℃时共存可使棉长管蚜在下部的比例明显增加;随温度的升高,棉蚜有翅蚜比例下降显著,而棉长管蚜无显著变化。【结论】适温范围内,两种蚜虫种间竞争的存在不影响彼此的内在繁殖能力,棉蚜比棉长管蚜具有更强的内在竞争能力;温度对棉蚜在竞争活动空间上的影响不明显,而对棉长管蚜的上下位置的选择有一定作用;种间竞争和种内竞争加速棉蚜有翅蚜的发生。     

石榴园棉蚜及其天敌之间的关系

采用灰色系统分析方法,分析了对主要害虫棉蚜及其天敌日捕食总量之间关联度,结果表明,棉蚜群落中与其关联度较高的天敌种类依次为肖蛸蛛(0．8607)、中华草蛉(0．8058)、八斑球腹蛛(0．7989)、异色瓢虫(0．7881)和大草蛉(0．7758),与理想天敌日捕食总量间关联度较高的天敌种类为草间小黑蛛(0.8975)、智利小绥螨(0．8132)、龟纹瓢虫(0.7806)和大草蛉(0．7669);与天敌数量间关联度较高的天敌依次为草间小黑蛛(0．8482)、中华草蛉(0．7533)、肖蛸蛛(0．7532)、八斑球腹蛛(0．7411)和大草蛉(0．7116),与理想天敌数量间关联度较高的为草间小黑蛛(0．8461)、智利小绥螨(0．7325)、龟纹瓢虫(0．6983)、大草蛉(0．6815)和中华草蛉(0．6757)．棉蚜垂直生态位和水平生态位的重迭值均>0．9567的天敌有草间小黑蛛、大草蛉和肖蛸蛛;时间生态位重迭值>0．4020的天敌有草间小黑蛛、大草蛉和肖蛸蛛,表明草间小黑蛛、大草蛉、肖蛸蛛等为棉蚜主要天敌优势种。     

Aspects of insecticide resistance in the melon and cotton aphid, Aphis gossypii (Hemiptera: Aphididae)

Strains of the aphid Aphis gossypii, taken from cucumber in UK glasshouses were tested for resistance to pirimicarb, diazinon and heptenophos. Compared to a susceptible strain, resistance factors to diazinon of up to 659 were found in populations collected between 1987 and 1989. Compared to the same susceptible strain, diazinon-resistant populations also showed a reduced response to heptenophos. All field populations tested against pirimicarb were resistant. Host plant preference tests showed that all strains (including stock cultures) tested could readily breed on cotton. However strains originally collected from chrysanthemum did not transfer to cucumber and likewise strains from cucumber would not colonise chrysanthemum. Polyacrylamide gel electrophoresis of four of the aphid strains showed differences in migration rates and intensity of staining of esterase bands. Intensity of staining was correlated with the degree of diazinon resistance.     

DNA‐based discrimination between the sibling species Aphis gossypii Glover and Aphis frangulae Kaltenbach

Abstract Morphologically similar species occur in various groups of insects, including aphid pests. In Europe, Aphis frangulae Kaltenbach and Aphis gossypii Glover (sometimes considered as subspecies) are differentiated usually on the basis of life cycle and host plant. We used a sexual population of A. frangulae collected on the primary host and samples of A. gossypii collected on cucurbits or cotton for the development of molecular markers. DNA sequence data for the gene encoding cytochrome b and for the barcode region of cytochrome oxidase I, as well as a length polymorphism for an intron in the sodium channel para‐type gene discriminated unambiguously between the two taxa. These markers were also used as identification keys for aphids collected on crops belonging to the Solanaceae. The cytochrome b marker differentiates host‐related Aphis gossypii haplotypes, and the para‐type gene intron might be suitable for the resolution of taxonomic problems in other aphid species complexes.     

Influences of fertilization on Aphis gossypii and insecticide usage

Abstract: Fertilization levels for ornamental crops may influence pest population dynamics, crop quality, and pest management strategy. We examined the effect of fertilization on population growth and within‐plant distribution of melon or cotton aphid, Aphis gossypii Glover, on potted chrysanthemum, Dendranthema grandiflora (Tzvelev). In terms of pest management implications, we also investigated the effect of fertilization on the number of insecticide applications needed to control A. gossypii on potted chrysanthemum. Population growth rate of A. gossypii increased with fertilization levels from 0 to 38 ppm N and reached a plateau from 38 to 488 ppm N. Increased fertilization beyond 38 ppm N, 10% of the commercial standard, did not result in higher aphid number. Aphids responded to nutrient availability of plants by distributing themselves in areas with higher level of nitrogen. More aphids were found in the apical and middle strata of the plants than the basal stratum, which had the lowest nitrogen content. Leaf nitrogen content increased with increased fertilization level and was consistently higher in the apical and middle strata than the basal stratum. Increased fertilization from 0 to 375 ppm N did not result in higher number of insecticide applications. All three insecticides (bifenthrin, kinoprene or pymetrozine) were effective in keeping the aphid infestation below a pre‐determined level, five aphids per plant, but pymetrozine required the least number of applications. For chrysanthemum, a fast‐growing crop and heavy utilizer of nitrogen, increased fertilization shortened the time to flowering, which would allow growers to harvest their crop sooner and reduce the time for aphid population growth. Reduction in time to harvest could result in significant reduction of insecticide usage by reducing the time for aphid population growth. As a result, high fertilization together with minimal runoff may be a useful tactic to an integrated pest management (IPM) programme for managing A. gossypii on potted chrysanthemums.     

棉蚜与其天敌种群分布格局的关系

对棉蚜与其多种天敌在数、时、空方面关系的研究表明,龟纹瓢虫与棉蚜种群数量极相关,两者发生数量高峰期和低谷期均是同步的,龟纹瓢虫对棉蚜种群有明显的控制作用,龟纹瓢虫、草间小黑株及棉蚜种群的三维空间格乙为聚集型,棉蚜和草间小黑蚜个体间互相吸引,龟纹瓢虫个体间互相排斥。     

Comparative efficacy of emulsifiable-oil,wettable-powder,and unformulated-powder preparations of Beauveria bassiana against the melon aphid Aphis gossypii

Aphidicidal efficacy of two formulations of Beauveria bassiana strain GHA conidia, an emulsifiable paraffinic oil dispersion (OD) and a clay-based wettable powder (WP), were compared to unformulated conidia (technical material, TC) in laboratory bioassays with adult melon/cotton aphids. For the initial 24 h post-treatment, aphids were incubated under differing humidity conditions: high (100%) versus 'low' (75 ± 3%) relative humidity (RH), and over the subsequent 6 days, all aphids were incubated under the low RH conditions. Mortality from the OD and TC treatments did not differ significantly under any test conditions, and ANOVA revealed no synergism of B. bassiana activity by the OD carrier ingredients. In contrast, formulation as a WP had a small, but significant, negative impact on B. bassiana efficacy. Mean LC50 across formulations was nearly 6.5-fold higher (3457 vs. 539 conidia/mm²) at low vs. high RH. The OD formulation was significantly more effective than the WP, increasing mortality a maximum of 27 percentage points. There were no significant effects of formulation on probit regression slopes. The equivalent slopes and small differences in efficacy of the OD formulation vs. TC preparation support a hypothesis that oils function primarily as spray stickers and spreaders, increasing the efficiency of spray applications.     

瑞香狼毒素对蚜虫防治的初步试验

以从瑞香狼毒（Stellera chamaejasme L.）中提取获得天然活性物质1,5-二苯基-1-戊酮、1,5-二苯基-2-烯-1-戊酮为主体成分,研制成生物灭蚜剂（LX-1）,对农业上几类重要蚜虫进行了防治应用的初步试验.结果表明,室内对棉蚜和烟蚜的触杀作用24 h 的LC50分别为81.73 mg/L和83.32 mg/L;并利用该制剂对棉蚜、烟蚜和麦蚜进行了田间防治试验,施药后3～5天防效达到峰值,2400倍稀释度下,防效达93%～99%,显示了较好的应用前景.     

Relationship between Aphis gossypii (Homoptera: Aphididae) and sticky lint in cotton

The study was conducted in the northern Texas Rolling Plains in 1999 to define the relationship between number of cotton aphids, Aphis gossypii Glover, and resulting contamination of cotton lint by honeydew. Whole-plot treatments were three furrow irrigation management treatments: cotton grown without supplemental irrigation (dryland), irrigated cotton with last irrigation in mid August, and irrigated cotton with last irrigation in late August. Subplots within each irrigation treatment included an untreated check, a plot treated with lambda-cyhalothrin to stimulate aphid population increase, a plot treated with lambda-cyhalothrin followed by pymetrozine after aphids began to increase, and a plot treated with lambda-cyhalothrin followed by thiamethoxam after aphids began to increase. Cotton aphids were counted on leaves picked from the top and bottom half of the plant. Cotton lint was analyzed for contamination by glucose, fructose, sucrose, and melezitose secreted by cotton aphids, and percentage leaf moisture and nitrogen and leaf sucrose concentrations were determined. The manual sticky cotton thermodetector was used to determine degree of lint stickinesss. There was a significant relationship between thermodetector counts and melezitose contamination on lint, and a melezitose concentration of 90.9 microg/g of lint was associated with a thermodetector count of 10, the threshold for sticky lint problems in textile mills. An equation was developed to estimate melezitose concentration on lint as a function of average numbers of aphids per leaf and the interaction between percentage leaf moisture and nitrogen. The number of aphids per leaf associated with a melezitose concentration of 90.9 microg/g of lint ranged from 11.1 to 50.1, depending on percentage leaf moisture and nitrogen. The threshold for sticky lint problems occurred when aphid numbers ranged between 11.1 and 50.1 per leaf after bolls open.     

棉蚜及龟纹瓢虫空间格局的地学统计学研究

应用地学统计学的原理和方法研究了不同时期棉蚜及龟纹瓢虫种群的空间结构和空间生。结果表明,不同时期棉蚜种群的关变异函数曲线皆为球型,其空间格局为聚集型,变程在８．２１￣１０．８１ｍ之间;龟纹瓢虫种群的拟合半变异函数曲线也表现为球型,呈聚集空间格局,空间变程在８．０１￣１４．２５ｍ之间,并与棉蚜种群在数量和空间上有较强的追随关系,说明龟纹瓢虫种群是棉蚜种群的优势种天敌。     

棉蚜在木槿上的扩散迁飞动态

对木槿和棉株上棉蚜自然种群消长动态、扩散及迁飞动态研究表明,木槿上棉蚜两种水平空间格局４月２０ 日～５ 月６ 日一直都是聚集格局,东向方位数量偏多,以株为单位第４ 、第１０ 株偏多,５ 月６ 日后扩散引起了格局变化;天敌中大草蛉与棉蚜数量之间相关,棉蚜与各种天敌总量极相关,天敌对棉蚜种群数量影响程度的顺序关联度显示为龟纹瓢虫＞ 食蚜蝇＞ 大草蛉;４ 月１８ 日～５ 月１６ 日木槿上棉蚜种群增长模型为线性模型;气象因子中前一天的大气相对湿度与木槿上棉蚜成若蚜总有翅率相关显著;大田棉蚜成蚜有翅率与提前２天木槿上棉蚜成蚜有翅率之间极相关．     

棉蚜和草间小黑蛛种群空间格局的地统计学研究

应用地统计学的原理和方法研究了石榴园不同时期棉蚜及草间小黑蛛种群的空间结构和空间相关性．结果表明,不同时期棉蚜种群的半变异函数曲线皆为球型,其空间格局为聚集型,变程在7．33～12．40cm之间;草间小黑蛛种群的拟合半变异函数曲线也表现为球型,呈聚集空间格局,空间变程在6．47～20．88cm之间,并与棉蚜种群在数量和空间上有较强的追随关系,说明草间小黑蛛种群是棉蚜种群的优势种天敌．     

棉蚜在棉株上数量动态的初步研究

棉蚜(Aphis gossypii)是棉花苗期至花铃前期的主要害虫之一。长期以来,由于大量使用化学药物,其抗药性不断增加。为了掌握棉蚜种群数量消长的一般规律,给寻找其他有效的防治方法提供依据,本文对棉蚜实验种群的数量动态与其宿主棉株的关系进行了初步探讨。现将结果报道如下。     

Esterase variation and insecticide resistance in Japanese Aphis gossypii

Nine clones of Aphis gossypii Glover (Homoptera: Aphididae) collected from five localities in Japan were tested for esterase activity and resistance to two insecticides. These clones were classified into six types according to esterase pattern and activity detected by electrophoresis. Three clones with very high esterase activity (Type-1) were moderately resistant to malathion and very highly so to pirimicarb. Of six clones with moderate esterase activity one clone (T-4a) was susceptible to malathion but highly resistant to pirimicarb, whereas five clones (T-2, 3a, 3b and 4b) were susceptible to both insecticides. Thus malathion resistance is positively correlated with high esterase activity, whereas pirimicarb resistance is not necessarily so. It is suggested that high esterase activity plays an important role in resistance to these insecticides but that another mechanism is also responsible for resistance to pirimicarb.

---

Variations de l'activité estérase et résistance aux insecticides chez des Aphis gossypii japonais

Résumé L'activité estérase et la résistance aux insecticides ont été examinées chez 9 clones de A. gossypii, récoltés dans 5 sites du Japon. Ces clones ont été groupés en 6 types suivant le comportement et l'activité de l'estérase mis en évidence par électrophorèse. 3 clones ont présenté une activité estérase très élevée (type 1) et des résistances, moyenne pour le malathion et très élevée pour le pirimicarbe. Parmi les 6 clones ayant une activité estérase modérée, un clone (T-4a) était sensible au malathion mais très résistant au pirimicarbe, tandis que les 5 autres clones (T-2, 3a, 3b et 4b) étaient très sensibles aux deux insecticides. Ainsi, la résistance au malathion présente une forte corrélation avec une activité estérase élevée, sans qu'il n'en soit nécessairement de même pour la résistance au pirimicarbe. Une hypothèse est émise suivant laquelle l'activité estérase élevée joue un rôle important dans la résistance à ces deux insecticides, mais qu'un autre mécanisme intervient aussi dans la résistance au pirimicarbe.

     

棉蚜飞行行为与卵巢发育的关系

采用高空黄盆诱蚜、卵巢解剖、体型测量及起飞角度测定方法研究了南京地区棉蚜飞行行为与卵巢发育间的关系。结果表明 ,5月份高空诱蚜的卵巢小管数与个体大小间成显著正相关 ,而木槿上有翅蚜的体长与卵巢小管数间相关不显著。棉蚜起飞角度的大小与卵巢小管数目呈显著的负相关 ,棉蚜的最大起飞角度为 4 4°左右。     

十一星瓢虫对枸杞棉蚜的捕食作用研究

十一星瓢虫Coccinella undecimpunctata Linnaeus是青海省柴达木地区的一种重要捕食性天敌。为明确其对枸杞棉蚜Aphis gossypii Glover和枸杞木虱Poratrioza sinica Yang et Li.两种主要枸杞害虫的嗜好性,开展了捕食选择性试验,发现当两种害虫共存时,瓢虫成虫更喜食棉蚜。为进一步探究十一星瓢虫对枸杞棉蚜的捕食能力,测定了瓢虫各龄幼虫和成虫在不同棉蚜密度下的捕食量、寻找效应以及种内干扰、自身密度对捕食作用的影响。结果表明：十一星瓢虫各虫态对棉蚜的捕食功能反应均符合Holling-Ⅱ功能反应模型,种内干扰、自身密度对捕食量的影响分别符合Hassell干扰效应模型和Watt模型。十一星瓢虫1~4龄幼虫及成虫对枸杞棉蚜的日最大理论捕食量分别为18.94、44.29、81.57、145.27和126.48头;在一定空间、相同瓢蚜比条件下,瓢虫同一虫态个体间存在种内干扰效应,以1龄幼虫受干扰最大,干扰常数为1.1803。此外,瓢虫自身密度对其捕食作用产生一定影响,以4龄幼虫和成虫尤甚,竞争参数分别为0.7948、0.6848。本研究可为今后更高效地利用青海高原本地十一星瓢虫资源提供理论依据。     

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。     

Blockage of stylet tips as the mechanism of resistance to virus transmission by Aphis gossypii in melon lines bearing the Vat gene

Aphis gossypii is the main virus vector in muskmelon crops. The melon gene Vat confers resistance to non‐persistent virus transmission by this aphid. The mechanism of this resistance is not well understood, but no relationship has been detected between resistance and the probing behaviour of aphids on resistant plants. Results presented here suggest that temporary blockage of aphid stylet tips preventing virus particle release may explain the resistance conferred by Vat gene. We performed experiments in which viruliferous aphids were allowed to probe different sequences of resistant (Vat‐bearing) and/or susceptible melon plants. The results demonstrated that A. gossypii inoculates Cucumber mosaic virus (CMV) efficiently in susceptible plants having previously probed resistant plants, showing that the resistance mechanism is reversible. Furthermore, the infection rate obtained for susceptible plants was the same (25%) regardless of whether the transmitting aphid had come directly from the CMV source or had subsequently probed on resistant plants. This result suggests that virus is not lost from stylet to plant during probing of resistant plants, supporting the temporary blockage hypothesis. We also found that the ability of Myzus persicae to transmit CMV is noticeably reduced after probing on resistant plants, providing evidence that this aphid species also responds to the presence of the Vat gene. Finally, we also found that in probes immediately after virus acquisition M. persicae inoculates resistant plants with CMV more efficiently than susceptible plants, perhaps because the Vat gene product induces increased salivation by this aphid.