Impact of density of Aphis craccivora (Aphididae) on growth and yield of susceptible and resistant cowpea cultivars

Impact of initial density of cowpea aphid Aphis craccivora Koch (Aphididae) at infestation on the growth and yield of aphid-susceptible cowpea cultivar ICV-1 and aphid-resistant cultivar ICV-12, was investigated. Plants at the seedling, flowering and podding stages of development were infested with five aphid densities consisting of 0, 2, 5, 10 and. 20 aphids per plant and maintained for 22 days. Extended leaf heights of plants and aphid counts were recorded at 7, 12, 17 and 22 days after infestation. Two crop growth parameters (biomass duration and leaf area duration), and two plant yield parameters (number of pods per plant and number of seeds per pod) were recorded. Due to the occurrence of parthenogenesis and changes in population dynamics during infestations, aphid densities were converted into cumulative cowpea aphid-days, to facilitate data analyses and interpretation. ANOVA indicated that there was significant (P=s 0.05) difference in aphid-day accumulations between the two cultivars when infested at the seedling stage. Accumulations on cv. ICV-1 were greater than on cv. ICV-12. However, no such differences between the cultivars were detected when plants were infested at flowering and podding stages. Therefore, the seedling stage was used for comparisons of the impact of cowpea aphid-days on the growth and yield parameters of the two cultivars. At the 95% confidence intervals, ICV-12 plants were consistently taller than ICV-1 plants. Infested ICV-1 seedlings showed stunting and other growth deformities which were not observed on ICV-12 plants. Regression analyses revealed substantial reductions in the growth and yield parameters of ICV-1 relative to ICV-12. Overall, cowpea aphid-days provided a convenient and reliable method for studying the aphid population dynamics and the subsequent impact on plant growth and yield performance.     

Probing behaviour of Aphis craccivora Koch on host plants of different nutritional quality

Abstract 1. Reciprocal transfer experiments were undertaken using four different hosts to examine the effects of a change in host at adult moult on the probing behaviour of the cowpea aphid Aphis craccivora Koch.
2. The highest intrinsic rate of increase r _m was achieved by aphids born and reared on cowpea, followed by those born and reared on broad bean, then Larissa, and finally Huia.
3. Mean probing time, time to first probe, number of probes per time allocation, and non-probing time were all examined. Host quality r _m did not affect the instantaneous probability of probing, and aphids that did not find a probing site within 200 s did not settle and did not probe further on that leaf/stem.     

Feeding behaviour of Aphis craccivora (Koch) on cowpea cultivars with different levels of aphid resistance

The feeding activity of Aphis craccivora (Koch) was monitored on cowpea plants of aphid-susceptible (Vita 7) and aphid-resistant (TVu 801) cultivars, using an AC electronic feeding monitoring system. Waveforms corresponding to salivation, phloem ingestion and non-phloem ingestion were observed. Aphids probing on the resistant cultivar showed a significantly reduced ingestion of phloem sap compared with those aphids which fed on the susceptible cultivar. The insect also made more brief and repeated probes on TVu 801. In addition, the duration of non-probing activities and non-phloem ingestion was shorter on the susceptible than on the resistant cultivar.     

Evaluation of selected cowpea varieties for resistance to Aphis craccivora Koch (Homoptera: Aphididae) at the seedling and podding phase

Twelve varieties of cowpea (Vigna unguiculata) were tested at the seedling and podding growth phases for resistance to infestation and damage to Aphis craccivora Koch. Nine of these cowpeas have previously been known to exhibit seedling resistance and the other three, susceptibility to the insect. A. craccivora could not colonise pods of TVu 9930. Pods of Tvu 36 also manifested a high level of resistance to the aphid. The three seedling susceptible varieties proved quite susceptible to A. craccivora at the podding phase. The other varieties were more resistant to the aphid in the seedling phase than in the podding phase.     

Soil pH alters the biological parameters of cowpea aphid Aphis craccivora Koch (Hemiptera: Aphididae) on its host plant Vicia faba

The biotic and abiotic factors including the agricultural implementation can modify soil acidification. We hypothesized that soil pH should as repercussion, alter the plant physiological and physical properties and eventually affect insect herbivores including agricultural pests. This study aimed to evaluate the impact of seven levels of soil pH on the performance of cowpea aphid Aphis craccivora on Vicia faba. Significant relationships between soil pH and growth of host bean seedlings or development and reproduction of the aphid were detected. Data demonstrated significant differences in the total longevity, the pre-reproductive, reproductive, post-reproductive and pre-viviparity periods. Within a suitable range of pH for bean growth between pH 5.3 and pH 7.2, the aphid performance was worse on seedlings growing better, however, under unfavorable extreme pH conditions, plant quality measured as height did not affect the aphids anymore and their performance was uniformly low except the case in pH 8.1 condition in which the best aphid reproduction was observed. The results confirm that soil pH affect the performance of cowpea aphid A. craccivora and also exhibited strong influence on the growth of broad bean plants.     

印楝素与脂肪酸甲酯联合使用对豆蚜的防治效果

本文对新疆博州豇豆豆蚜Aphis craccivora (Koch)田间消长规律进行调查,研究了0.3%印楝素与脂肪酸甲酯喷雾助剂联合对豆蚜的防治效果,并对豆蚜天敌消退率进行了调查。结果表明,在博州,豆蚜以卵在苦豆子和苜蓿上越冬,3月下旬至4月初开始孵化,5月上中旬出现有翅蚜在杂草上繁殖蔓延,5月中旬开始迁入棉花上危害,6月中旬陆续迁入豇豆上危害,7月上中旬在豇豆上达到危害高峰时期,7月中下旬慢慢迁入苜蓿地,9月中旬出现性蚜,9月下旬-10月中旬在苜蓿和杂草上产卵越冬。施药后1 d,20%啶虫脒可湿性粉剂1 000倍液对豆蚜的防效最高,达到82.91%; 施药后3 d,20%啶虫脒可湿性粉剂1 000倍液防效仍最高为97.92%;施药后7 d,0.3%印楝素乳油60 mL/667m2+脂肪酸甲酯喷雾助剂1 000倍液防效达97.38%,显著高于其他处理。总体来说,在豇豆豆蚜发生期施用1次0.3%印楝素+脂肪酸喷雾助剂防治豇豆豆蚜,防效好、持效期长,对豇豆及蚜虫天敌安全性较好。     

Suitability of Aphis craccivora (Hemiptera: Aphididae) and Bemisia tabaci (Hemiptera: Aleyrodidae) biotype-B as prey for Chrysopa pallens (Neuroptera: Chrysopidae)

The suitability of Aphis craccivora Koch (Hemiptera: Aphididae) and Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) biotype-B eggs and nymphs as prey for pre-imaginal development and survival, adult longevity, and fecundity of the lacewing, Chrysopa pallens (Rambur) (Neuroptera: Chrysopidae) was evaluated under laboratory conditions at 25±1°C, 50±10% RH and a photoperiod of 16 h L:8 h D. Survival of C. pallens from first instar to adult eclosion was significantly different between the larvae that fed on the two prey species. C. pallens fed on A. craccivora completed development from egg to adult emergence, but those fed on eggs and nymphs of B. tabaci could not complete development, resulting in abnormal pupae and no normal adults emerged. The net reproductive rate (R ₀), intrinsic rate of natural population increase (r _m ), finite rate of increase (λ), mean generation time (T), index of population trend (I), doubling time (DT), and gross reproductive of rate (GRR) of C. pallens that fed on A. craccivora were 201.9 eggs per female, 0.13/d, 1.1/d, 40.1 d, 68.5, 5.2 d, 203.1 eggs per female, respectively. These results could be useful for mass-rearing of C. pallens and for understanding its population dynamics in the field in relation to the availability of different prey species.     

Stylet activity of cowpea aphid (Homoptera: Aphididae) on leaf extracts of resistant and susceptible cowpea cultivars

Electrical penetration graph recordings using direct current (DC-EPGs) were used to analyze aspects of the probing behavior of cowpea aphid,Aphis craccivora Koch, on intact plants and on hexane, ethyl acetate, and methanol extracts of leaves of aphid-resistant (ICV-12) and aphid-susceptible (ICV-1) cultivars of cowpeaVigna unguiculata (L.) Walp. In one set of experiments, recordings were done on plants with or without parafilm wrapping, or on plants painted with raw leaf juice and extracts of the two cultivars. In another study, recordings were done on leaf extracts homogenized in water or in 0.5M sucrose solution and then placed in parafilm membrane sachets. Electrodes were inserted into soil mix for the experiments on potted plants or into extract fractions and raw juice for the membrane feeding experiments on leaf extracts in parafilm sachets. Waveform signals were recorded from resistance fluctuations from interactions between aphids and substrates, and electromotive forces generated within each preparation. ICV-12 plants with or without parafilm wrapping, and ethyl acetate extracts and raw juice of that cultivar significantly (P≤0.05) reduced stylet penetration behavior. Thus, antixenosis as manifested by disruption of aphid stylet activity on host substrates, appeared to be a governing modality of aphid resistance in ICV-12.     

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% (LC₅₀) 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 LC₄₀ 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 A. gossypii; it may be useful for implementation in IPM programs against this aphid pest.     

基于模糊识别和刺探电位技术鉴定小麦种质资源抗蚜性

利用田间抗蚜性鉴定模糊识别技术,结合室内刺探电位(EPG)植物抗性鉴定技术,比较分析了不同遗传背景的小麦种质资源的抗蚜性,为筛选新型小麦抗蚜种质材料提供依据。2年田间抗蚜性鉴定结果表明: 小偃麦多表现为中抗或低抗,而小黑麦多为中感或低感。选取抗性性状稳定且抗性级别不同的小偃麦21(中抗)、小偃麦22(低抗)、小黑麦31(中感)和小黑麦32(低感)进行麦长管蚜取食行为分析。对非刺探波(Np)、刺探波(P)、电势落差(Pd)、水溶性唾液分泌波(E1)、韧皮部取食波(E2)、细胞机械阻碍波(F)和木质部取食波(G)等基本波形的分析显示,麦长管蚜在小偃麦上首次开始刺探的时间显著长于小黑麦,且在小偃麦上的E1波的持续时间显著大于小黑麦;麦长管蚜在小偃麦21上的F波和小偃麦22上Np波的持续时间最长,在小黑麦31上的P波和小黑麦32上的G波的持续时间最长。以E1、F和Np波的持续时间为指标,基于刺探电位的小麦种质资源抗性水平鉴定结果与田间鉴定结果基本一致。因此,使用EPG技术筛选抗蚜小麦材料时,建议采用E1、F和Np波作为评价小麦抗性水平的指标。小偃麦21、22对麦长管蚜的抗性水平较高,可作为小麦抗蚜育种的种质材料。     

Phloem specific aphid resistance in Cucumis melo line AR 5: effects on feeding behaviour and performance of Aphis gossypii

The feeding behaviour, excretion rate, and life history traits of the cotton-melon aphid, Aphis gossypii (Glover) (Homoptera, Aphididae), were measured on a resistant melon, Cucumis melo L., breeding line, AR 5. The site of resistance detection by the aphids was determined using the electrical penetration graph (EPG) technique. EPG recordings showed that resistance is expressed within the host plant, rather than on its surface, because the time to first stylet penetration was not significantly different between AR 5 and the closely related susceptible breeding line, PMR 5. EPG patterns associated with stylet pathway activities of the aphids were not significantly different between the resistant and susceptible lines. Significant behavioural differences were observed only after stylets contacted phloem sieve elements. On AR 5, the duration of salivation after sieve element puncture (waveform E1) was significantly longer, and the number of aphids showing phloem sap ingestion (waveform E2) was significantly reduced. We conclude that the resistance mechanism producing the effects seen in this study acts within the phloem sieve elements. Monitoring of excretion rates on the two genotypes showed that aphid feeding was delayed and greatly reduced on the resistant genotype. Comparisons of aphid life history traits and population development between host plant genotypes showed that the effects of resistance act throughout aphid development and are highly effective at slowing down population increase.     

Efficacy of three plant essential oils,Azadirachta indica (Adr. Juss.), Eucalyptus camaldulensis (Dehn.) and Laurus nobilis (L.) on mortality cotton aphids,Aphis gossypii Glover (Hem: Aphididae)

The cotton aphid, Aphis gossypii Glover (Hem: Aphididae), is one of the most injurious pests of fruits, vegetables and ornamental plants worldwide, both outdoor and indoor. Currently, the main method of control of this pest is through application of pesticides which is mostly accompanied by the resistance of the pest against pesticide(s). The resurgence of resistant aphid populations brings about further contamination of foodstuff and environment. Essential oils obtained from the aerial parts of plants may have the potential to be an alternative to synthetic pesticides, since they have been demonstrated to possess a wide range of bioactivities against insects and mites. So, the aim of the current study was to investigate the effect of essential oils extracted from three different plants namely: Azadirachta indica Adr. Juss. (Meliaceae), Eucalyptus camaldulensis Dehn. (Myrtaceae) and Laurus nobilis L. (Lauraceae) against A. gossypii. The LC₅₀ values of essential oils of A. indica, E. camaldulensis and L. nobilis against A. gossypii were 1.96, 2.28 and 3.16?μl L^?1 air, respectively. This shows that A. indica possesses the highest lethal activity whereas L. nobilis the lowest. These data suggest that essential oils of all the three plants have the potential to be employed in the pest management programmes designed for a control of A. gossypii under greenhouse conditions.     

热应激和吡虫啉对大豆蚜hsp70和hsc70基因mRNA表达的影响

【目的】昆虫在高温或农药的胁迫下,通过高效表达热休克蛋白(HSP)等建立应激自我保护机制。本研究为从转录组水平上认识大豆蚜Aphis glycines在热应激和吡虫啉胁迫下hsp70和hsc70 mRNA表达分子机制,进而寻找自我保护应激反应中的薄弱环节,为大豆蚜的生物防治提供理论基础。【方法】采用同源克隆、RACE技术和实时荧光定量PCR等方法研究不同热激时间和热激后不同恢复时间及不同吡虫啉浓度对大豆蚜4龄若虫hsp70和hsc70的表达影响。【结果】37℃热激后,大豆蚜4龄若虫中hsp70表达量先上调,1 h时升至对照组的10.36倍（P<0.05）,然后逐渐下降。同样热激后恢复时间的长短对大豆蚜若蚜中hsp70的表达具有显著影响。热激处理后,大豆蚜若蚜中hsp70立即大量表达,表达量为对照组的8.78倍（P<0.05）,随后表达量下降至对照组水平,而hsc70的表达量并没有显著变化（P>0.05）。大豆蚜若蚜受吡虫啉的胁迫时,其hsp70和hsc70的表达量受吡虫啉的浓度及胁迫的时间的影响,呈现先升高后下降的趋势,具有明显的短期效应。【结论】吡虫啉诱导大豆蚜hsp70和hsc70表达量的上调;而热胁迫对hsp70和hsc70 mRNA具有不同的表达模式,高温可以诱导hsp70的表达,但对hsc70没有明显的诱导作用。     

Subsocial behaviour in Oniticellus cinctus (Coleoptera, Scarabaeidae): effect of the brood on parental care and oviposition

ABSTRACT. In Oniticellus cinctus (F.) the nest chambers each contain about twenty brood balls. Females enlarge the brood balls during the egg and larval stages and remain in the chamber for the whole period of brood development (1 month); they then make a new nest after 1 week. The presence of the brood releases parental care and ensures that the mother remains in the nest: she repairs defects in the brood balls and the nest, and expels other O. cinctus females. A new ball is formed around a naked O. cinctus larva, but larvae of other species are killed. In addition, the brood inhibits oviposition: removal (or addition) of brood balls stimulates (or inhibits) egg laying. In inhibited ovarioles, existing follicles are resorbed and production of new ones ceases. Control of clutch size by the brood is an adaptation to the nest structure and life history of O. cinctus. It may have an important role in the reproductive strategy of other insects with parental care.     

Effects of temperature on biology and life table parameters of the Asian citrus psyllid, Diaphorina citri Kuwayama (Homoptera: Psyllidae)

The development, survivorship, longevity, reproduction, and life table parameters of the Asian citrus psyllid, Diaphorina citri Kuwayama were evaluated at 10°C, 15°C, 20°C, 25°C, 28°C, 30°C and 33°C. The populations reared at 10°C and 33°C failed to develop. Between 15°C and 30°C, mean developmental period from egg to adult varied from 49.3 days at 15°C to 14.1 days at 28°C. The low‐temperature developmental thresholds for 1st through 5th instars were estimated at 11.7°C, 10.7°C, 10.1°C, 10.5°C and 10.9°C, respectively. A modified Logan model was used to describe the relationship between developmental rate and temperature. The survival of the 3rd through 5th nymphal instars at 15–28°C was essentially the same. The mean longevity of females increased with decreasing temperature within 15–30°C. The maximal longevity of individual females was recorded 117, 60, 56, 52 and 51 days at 15°C, 20°C, 25°C, 28°C and 30°C, respectively. The average number of eggs produced per female significantly increased with increasing temperature and reached a maximum of 748.3 eggs at 28°C (P<0.001). The population reared at 28°C had the highest intrinsic rate of increased (0.199) and net reproductive rate (292.2); and the shortest population doubling time (3.5 days) and mean generation time (28.6 days) compared with populations reared at 15–25°C. The optimum range of temperatures for D. citri population growth was 25–28°C.