Movement, toxicity, and persistence of imidacloprid in seedling Tabasco pepper infested with Myzus persicae (Hemiptera: Aphididae)

Application of imidacloprid to the soil in which Tabasco pepper, Capsicum frutescens L., seedlings were growing was highly effective against the green peach aphid, Myzus persicae (Sulzer) (Hemiptera: Aphididae). In just 48 h after the soil drench, aphid numbers on treated plants declined from 292.1 to 33.0 per plant, a reduction of 89%. By 72 and 96 h after the application, the reductions were 97 and 100%, respectively. Reductions in green peach aphid numbers also indicated that imidacloprid readily moved throughout the Tabasco pepper plant. Although, initial green peach aphid reductions at 24 and 48 h after imidacloprid application to soil, were greater on the lower leaves than on the upper leaves, by 72 h toxicity was high throughout the plant. At 48 h, overall green peach aphid reduction on seedlings grown in wet soil was significantly higher than that on plants growing in the drier soil. Regardless of soil moisture or leaf location, no live green peach aphids were detected on treated seedlings after 96 h. After the initial uptake period, toxicity to green peach aphid remained high for 5 wk. Under Tabasco pepper production conditions in Central America, the greatest need for aphid management is just after transplanting. Imidacloprid soil drenches before transplanting should offer the Tabasco pepper producer an extended period of aphid-free production.     

Organic farming-compatible insecticides against the aphid Myzus persicae (Sulzer) in peach orchards

Abstract:  Three products allowed in organic farming (kaolin, mineral oil and insecticidal soap) as alternatives to chemical insecticides, were evaluated for the control of Myzus persicae (Sulzer) in a peach orchard. Their efficacy was compared with the neonicotinoid imidacloprid and an untreated control. The experiment was replicated for 2 years (2003 and 2004). The products were applied once in May every year and aphid infestation was recorded three to four times post-treatment. In 2004, the effect of the products on the predatory coccinellid species was also recorded. In 2003, all four products showed good control with average Abbott's efficiency ranging from 80% to 88%. In the next year, however, the products were less effective and only imidacloprid and kaolin reduced aphid population significantly compared with the untreated control, with an average Abbott's efficiency of 62% and 31%, respectively. This reduced efficiency was attributed to high rainfall occurring post-treatment. Regarding the effects on beneficial coccinellids, only imidacloprid and mineral oil reduced their numbers after application. The results showed that the three alternative products and especially kaolin are promising for aphid control in peach orchards. Kaolin has also low side-effects on beneficials and it could be used in organic peach orchards.     

Insecticidal properties of a Chenopodium-based botanical

The emulsifiable concentrate UDA-245 based on an essential oil extract from Chenopodium ambrosioides variety near ambrosioides, a North American herbaceous plant, was compared with commercially available pesticides for their effectiveness to control green peach aphid, Myzus persicae (Sulzer) (Homoptera: Aphididae), western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), and greenhouse whitefly, Trialeurodes vaporariorium (Westwood) (Homoptera: Aleyrodidae). Side effects on the whitefly parasitoid Encarsia formosa Gahan (Hymenoptera: Aphelinidae) also were determined. With green peach aphid, UDA-245 at 0.5% concentration was significantly more effective than the control (water) treatment in a laboratory bioassay and significantly more effective than neem oil and the control treatment and as effective as insecticidal soap in a greenhouse assay. With the western flower thrips, UDA-245 at 0.5% was significantly more effective than neem oil, insecticidal soap and the control treatment in a laboratory bioassay, whereas in a greenhouse assay, UDA-245 at 1.0% was the only treatment that maintained control of the western flower thrips 2 wk after the last treatment period. UDA-245 at 0.5% (laboratory bioassay) was significantly more effective in managing greenhouse whitefly than neem oil, endosulfan, and the control treatment and as effective as insecticidal soap. Insecticidal soap proved to be toxic to the parasitoid E. formosa (71.9% mortality), whereas UDA-245 at 0.5% was not significantly more toxic than the control (11.2 and 4.6% mortality, respectively). Our results suggest that a greenhouse integrated pest management (IPM) program using a botanical such as UDA-245 could effectively control infestations of major pests present while having a negligible effect on biological control agents.     

球孢白僵菌分生孢子乳悬剂对甘蓝上桃蚜的田间控制效果

利用液-酵法生产球孢白僵菌(Beauveria bassiana)SG8702菌株的分生孢子粉,配制成含孢量为10^10个.ml^-1的孢子乳悬剂Ⅰ,在此基础上按1％(W／V)的比例舔加10％砒虫琳可湿性扮剂而得孢子乳悬剂Ⅱ．于2001年7月对两种孢子乳悬剂在云南昆明进行了自然条件下甘蓝上桃蚜(Myzus persicae)的田间小区(5．5m×4．8m)药效试验,各3个浓度(含孢量分别为10^7、10^6及10^5个·ml^-1常规喷雾处理,重复设清水喷雾对照,重复3次,随机区组排列．在喷菌后连续28d的田间蚜虫密度定期抽样调查中,乳悬剂Ⅱ的1000倍稀释液喷雾有效抑制了蚜虫数量增长,喷后策7—28天防效始终在90％以上．乳悬剂Ⅰ的相同稀释液喷雾对桃蚜的控制略逊于乳悬剂Ⅱ,但喷后第7天的相对防效也达到85％,此后维持防效70％以上达两周,策24天和28天才分别降至64．4％和52．6％．用含孢量10^6和10^5个·ml^-1的菌液喷雾,乳悬剂Ⅰ仍表现出明显的控蚜效果,而舔加微量砒虫琳的乳悬剂Ⅱ的控蚜效果总是优于同一浓度下的乳悬剂Ⅰ,昆明地区夏季温和而多小雨的气候有利于孢子乳悬剂发挥作用．     

寄主植物对烟蚜药剂敏感性及相关酶活性的影响

以甘蓝、烟草和桃树上的饲养的烟蚜Myzus persicae（Sulzer）种群为研究材料,分别测试了其对吡虫啉、丁硫克百威和氰戊菊酯这3种杀虫剂的敏感性。结果表明,桃树上的烟蚜种群敏感性最高,其次为烟草种群,甘蓝种群最低。测试了在3种不同寄主上饲养的烟蚜种群的羧酸酯酶、乙酰胆碱酯酶和谷光甘肽-s-转移酶的比活力,这3种酶均表现为甘蓝种群最高,其次为烟草种群,桃树种群最低。     

Effect of papaya trunk angle on infestation by white peach scale,Pseudaulacaspis pentagona (Hemiptera: Diaspididae)

Two papaya (Carica papaya L.) seedlings growing in one planting hole often results in angular or non-vertical growth of the trees. Data on trunk angularity, or leaning, (deviation from the vertical line of reference) and white peach scale, Pseudaulacaspis pentagona Targioni-Tozzetti (Hemiptera: Diaspididae), densities on paired papaya trees were collected approximately 1 year after infestation of a papaya field was discovered. Paired trees showed a significantly higher degree of leaning than single trees. White peach scale densities were significantly higher on tree trunks with a greater departure from vertical in paired comparisons. Therefore, paired tree planting practices may facilitate the development of economic infestations of white peach scale populations in papaya orchards.     

STUDIES ON SELECTIVE TOXICITY OF SIX INSECTICIDES BETWEEN GREEN PEACH APHID AND LADYBIRDS

Abstract  The selective toxicity of six kinds of insecticides, including imidacloprid, imidacloprid + synergist (SV1), fenvalerate, endosulfan, methomyl and dimethoate, between the green peach aphid ( Myzus persicae Sulzer) and two species of ladybirds ( Coccinella septempunctata Linnaeus and Propylaea japonica Thunbery), was investigated in the laboratory. The reults showed that both imidacloprid WP and imidacloprid + synergist (SVl) EC possessed the highest toxicity to the aphids. Between C. septempunctata and M. persicae and between P. japonica and M. persicae , the selective toxicity ratios (STRs) of imidacloprid WP, imidacloprid+ synergist (SV1) EC and endosulfan EC were 37.6 and 13.0, 9.84 and 7.75, 54.0 and 7.28 respectively. All of them showed rather high selective toxicity. The STRs of fenvalerate EC, dimethoate EC and methomyl EC were all very low, ranging from 0.02 to 0.21, indicating their low degree of safety to the two species of ladybids. The results demomarated that imidacloprid WP and imidacloprid + SVl EC not only had rather high toxicity to the aphids, but also reduced strikingly the reproduction rate and fecundity of the survival aphids. Insecticides can induce the relative fitness of insects decrease. Among the six insecticides tested with M. persicae , the following were insecticides and the order of induction was: imidacloprid + SV1 imidacloprid endosulfan methomyl fenvalerate > dimethoate.     

European monitoring of resistance to insecticides in Myzus persicae and Aphis gossypii (Hemiptera: Aphididae) with special reference to imidacloprid

The susceptibility to several insecticides of 16 and 8 strains of Myzus persicae Sulzer and Aphis gossypii Glover, respectively, received from different European countries in 2001 was investigated. Most of the strains were derived from places known for their aphid resistance problems to conventional insecticides before imidacloprid was introduced. In many regions and agronomic cropping systems imidacloprid has been an essential part of aphid control strategies for a decade, and therefore the susceptibility of aphid populations to imidacloprid using FAO-dip tests and diagnostic concentrations in a leaf-dip bioassay was checked. Additional insecticides tested were cyfluthrin (chemical class: pyrethroid), pirimicarb (carbamate), methamidophos and oxydemeton-methyl (organophosphates). Diagnostic concentrations (LC99-values of reference strains) for each insecticide were established by dose response analysis using a new leaf-disc dip bioassay format in 6-well tissue culture plates. Virtually no resistance to imidacloprid in any of the field-derived populations of M. persicae and A. gossypii was detected. In contrast, strong resistance was found to pirimicarb and oxydemeton-methyl, and to a lesser extent also to cyfluthrin. Two strains of A. gossypii exhibited reduced susceptibility to imidacloprid when tested directly after collection. However, after maintaining them for six weeks in the laboratory, the aphids were as susceptible as the reference strain. The diagnostic concentration of methamidophos did not reveal any resistance in M. persicae, but did so in four strains of A. gossypii.     

几种药剂对桃蚜和两种瓢虫的毒力选择性研究

在室内分别测定了吡虫啉,吡虫啉＋增效剂,氰戊菊酯,硫丹、乐果和灭多威6种杀虫剂对桃蚜Myzus persicae Sulzer,七星瓢虫Coccinella septempunctata Linnaeus和龟纹瓢虫Propylea japonica(Thunbery)的毒力,比较了药剂在桃蚜和两种瓢虫之间的选择毒力比值（STR）,以及药剂之间选择性差异,研究了桃蚜对不同药剂相对适合度,结果表明：吡虫啉＋增效剂（SVI）和吡虫啉对桃蚜的毒力均很高,LC50分别是4628mg/L和0．9535mg/L,吡虫啉在七星瓢虫和桃蚜之间,龟纹瓢虫和桃蚜之间的STR值分别是37．6和13．0,吡虫啉＋增效剂的STR分别是9．84和7．75,硫丹的SR分别是54．0和7．28,都表现出显的毒力选择性,而氰戊菊酯,乐果和灭多威的STR值均很小（0．02－0．21）,不仅对桃蚜毒力低,而且对两种瓢虫也不安全,用吡虫啉和吡虫啉＋SV1的LC50浓度处理桃蚜,其存活个体的产仔率和单雌产仔量明显减少,与其它药剂处理相比,显降低了桃蚜的相对适合度,六种杀虫剂处理的桃蚜种群,其相对适合度大小排列为：乐果EC（0．92）＞氰戊菊酯EC（0．67）＞灭多威EC（0．66）＞硫丹EC（0．51）＞吡虫啉WP（0．40）＞吡虫啉＋增效剂（SV1）EC（0．18）,由此证明,吡虫啉不仅对桃蚜毒力高,对天敌瓢虫杀伤力小,而且对桃蚜种群有持续控制作用。     

Sublethal effects of selected insecticides on fecundity and wing dimorphism of green peach aphid (Hom., Aphididae)

Effects of sublethal concentrations (LC₂₅) of six insecticides (imidacloprid, rotenone, fenvalerate, abamectin, pirimicarb and azadirachtin) on fecundity and wing dimorphism of the green peach aphid, Myzus persicae (Sulzer), were studied both under laboratory and greenhouse conditions. In the laboratory, aphid reproduction reduced by 44.29% and 54.01% when rotenone and abamectin treatments were applied at sublethal dose, respectively, and sublethal fenvalerate application resulted in markedly lower average reproduction per female per day compared with control. Reproductive duration of aphid treated with abamectin significantly decreased by 44.19%. But in the greenhouse, there were no evident differences in the aphid fecundity and reproductive duration between treatments and control. Life‐table parameters also demonstrated that the six insecticides at sublethal doses did not stimulate the aphid reproductive potential. In the laboratory, after being exposed to sublethal doses of imidacloprid and fenvalerate, the proportions of alate progeny in aphid progeny were significantly higher than that of the control. In the greenhouse, percentages of alate offspring from the mother aphids treated with imidacloprid, fenvalerate and abamectin increased pronouncedly compared with control. Mortality rates of offspring in the nymphal stages from adults treated with insecticides revealed no significant changes between laboratory and greenhouse. The developmental time in days of the offspring varied in all treatments. Mechanisms of insecticide‐induced resurgence are discussed.     

Tritrophic interactions between cabbage cultivars with different resistance and fertilizer levels,cruciferous aphids and parasitoids under field conditions

Tritrophic interactions involving cabbage Brassica oleracea var. capitata cultivars +/- fertilizer, Brevicoryne brassicae (Linnaeus) and Myzus persicae (Sulzer), and the parasitoids Diaeretiella rapae (M'cIntosh) and Aphidius sp. were conducted in 1998 and 1999. Brevicorne brassicae was the dominant aphid species on all cultivars +/- fertilizer, except for some treatments in late season 1998. Ruby Ball (red-leaved with antixenosis factors for B. brassicae alates) +/- fertilizer was consistently less colonized by aphids in early stages of plant growth, although only significantly so compared with Derby Day (green-leaved, susceptible to aphids) without fertilizer for B. brassicae and Minicole (green-leaved with antibiosis factors for B. brassicae) with fertilizer for M. persicae. In early 1999, only B. brassicae was present and no significant differences between cultivars were seen. In the mid to late season 1998, the highest aphid infestations were usually found on Derby Day, although only significantly so for B. brassicae, in some treatments. In 1999, higher aphid infestations were observed on Derby Day in mid to late season and some significant differences were found for M. persicae as well as for B. brassicae. In both years, Ruby Ball had the greatest mummy:aphid ratios early season, with no consistent difference between the other cultivars. Later in the season, mummy:aphid ratios were generally highest on Minicole. Parasitism differed in seasonal occurrence and relative abundance. Diaeretiella rapae mummies were found earlier than Aphidius sp. There was evidence of a beneficial interaction between the degree of plant resistance and biological control in early to mid season.     

How does winter pruning affect peach tree–Myzus persicae interactions?

Winter tree pruning is a cultural practice known to modify vegetative growth, which is likely to affect the development of pests. However, it has been poorly addressed as a cultural control method for diminishing the population levels of the green peach aphid, Myzus persicae (Sulzer) (Homoptera: Aphididae), in peach [ Prunus persica (L.) Batsch (Rosaceae)] orchards. In this study, we conducted a 2-year, on-station experiment to evaluate how winter pruning affects peach– M. persicae interactions, by examining tree vegetative growth, aphid population dynamics, and crop yield and fruit quality. We collected data under an insect-proof shelter on adult peach trees submitted to various levels of pruning and artificially infested with aphids. Our results showed that pruning enhanced shoot growth due to the proportion of growing shoots, which increased exponentially (10–60%), whereas the growth rate of growing shoots was not affected. The degree of infestation of peach trees increased with increasing pruning intensity. This effect was mainly due to the increase of the proportion of growing shoots, on which aphids developed better than on rosettes. In turn, the higher the aphid infestation, the higher the aphid-induced shoot-tip damage, leaf curling, and leaf fall that disturbed the growth of growing shoots. However, aphids did not considerably reduce fruit quality at harvest. They did not affect fresh fruit weight, and the refractometric index (indicator of sugar content) was reduced by only 3–4%. The relevance of winter pruning as a cultural method for pest control in orchards conducted under integrated fruit production guidelines is discussed.     

植物挥发性物质对蚜虫性信息素诱蚜效果的影响(英文)

本研究首先是在不同的寄主植物中利用蚜虫性信息素进行田间诱蚜实验。结果表明寄主植物影响性信息素田间诱蚜的种类和效果。在桃园 ,以蚜虫性信息素荆芥内酯和荆芥醇为性诱剂的水盆诱捕器 ,诱到 3种蚜虫的雄蚜 ,分别是桃蚜、桃粉大尾蚜和莲缢管蚜。其中 ,桃蚜占绝大多数 ,且还被性信息素的单一组分植物提取的荆芥内酯所吸引。麦田中诱到的雄蚜为麦二叉蚜。苹果园中诱到的雄蚜是绣线菊蚜和梨中华圆尾蚜 ,且性信息素诱捕器中的数目远多于对照诱捕器。据田间诱蚜实验结果推测 ,荆芥内酯和荆芥醇对桃粉大尾蚜有吸引作用 ,荆芥内酯可能是绣线菊蚜和梨中华圆尾蚜性信息素的一个组分。另外进行的田间实验表明寄主植物挥发性物质对蚜虫性信息素诱蚜效果有影响 ,当荆芥内酯诱捕器同时释放桃叶挥发物时 ,诱到的桃蚜雄蚜数量明显增加。触角电位记录实验也表明桃蚜雄蚜对桃叶挥发物和桃芽挥发物有反应。     

Comparison of bioassay techniques for determining baseline susceptibilities to imidacloprid for green apple aphid (Homoptera: Aphididae)

The susceptibility of a clone of green apple aphid, Aphis pomi (De Geer), to the neonicotinyl insecticide imidacloprid was determined by direct and indirect bioassay techniques. Aphid numbers were assessed on potted apple seedlings treated with various concentrations of imidacloprid, adults were dipped in test solutions as per the Food and Agriculture Organization protocol, or nymphs and adults were reared on treated apple leaf disks. Effective concentrations required to kill half of the test population (EC50) varied depending on the bioassay technique, ranging from as low as 0.064 ppm for first instars reared for 3 d on treated leaf disks to 1.79 ppm for adult apterae dipped in solutions of imidacloprid and held for 24 h on clean leaf disks. When imidacloprid was directly applied to aphids, mortality continued to increase over 3 d, but the difference was not statistically significant between day 2 (1.36 ppm) and day 3 (1.19 ppm). Toxicity of neonicotinyls to aphids is expressed rather slowly and primarily after oral ingestion. The effect of imidacloprid on reproduction of green apple aphid was also assessed for adult apterae reared on treated leaf disks. Contrary to previous reports, our results demonstrated that imidacloprid does not have a direct negative effect on the reproductive physiology of this species. Negative effects can mostly be attributed to the antifeedant activity of this compound and the protracted time to death. The results of this study contribute to a better understanding of the most suitable techniques for assessing aphid mortality after exposure to these new insecticides and provides a baseline susceptibility to imidacloprid for green apple aphid.     

褐带蚜小蜂产卵器刺入对寄主桃蚜存活、生长发育和繁殖力的影响

[目的]褐带蚜小蜂Aphelinus maculatus是2016年的中国新纪录种,是桃蚜Myzus persicae的重要寄生蜂之一.为科学评估褐带蚜小蜂对桃蚜的控制作用,研究了褐带蚜小蜂产卵器刺入对寄主桃蚜存活、生长发育和繁殖力的影响.[方法]培养皿中用油菜叶单头饲养、每天记录被褐带蚜小蜂产卵器刺入1次的桃蚜存活数...     

Control of woolly aphid, Eriosoma lanigerum (Hausmann) (Hemiptera: Pemphigidae) on mature apple trees using insecticide soil-root drenches

Abstract Woolly aphid, Eriosoma lanigerum , is an important pest of apples that infests both the aerial and root parts of the tree. Root colonies are protected from the pesticide sprays applied during the growing season and the climatic effects of winter. Consequently, root colonies are a major source of aerial re-infestation in the following spring. Imidacloprid, the first of a new group of insecticides from the chloronicotinyl family, is known to provide excellent control of woolly aphid on trees up to 7-years-old when applied as a root soil drench. This study compared the effects of a single application of chlorpyrifos, imidacloprid, pirimicarb or vamidothion, applied as a root drench over four growing seasons. A soil wetting agent was added to each chemical to improve soil saturation and penetration. Imidacloprid provided excellent control of woolly aphid on the trees that were 17-years-old at the start of the study and continued to do so for four seasons. Pirimicarb appeared to offer some suppression of woolly aphid during the first season but not in subsequent seasons, while chlorpyrifos and vamidothion failed to control woolly aphid in any season. The potential role for imidacloprid in IPM programs is discussed.     

Comparison of feeding behaviour of two Brassica pests Brevicoryne brassicae and Myzus persicae on wild and cultivated brassica species

Feeding behaviour of the specialist Brassicae aphid, Brevicoryne brassicae (L) (cabbage aphid) and the generalist, Myzus persicae, (Sulzer) (peach potato aphid) was monitored electronically on the susceptible cauliflower, Brassica oleracea var. botrytis cv Newton Seale, and a range of 17 Brassica species, B. carinata, B. juncea, B. nigra, B. macrocarpa, and B. villosa var. drepanensis and cultivated brassica varieties, B. oleracea, B. campestris and B. napus. Aphids, monitored for 10 h on the underside of leaves, performed recognisable feeding behaviour on all brassica species. The main differences in feeding behaviour, between M. persicae and B. brassicae, on the susceptible cauliflower Newton Seale, were fewer probes, shorter times to initially reach the phloem but longer times to establish sustained phloem ingestion and the longer times spent, by M. persicae, in xylem ingestion.Feeding behaviour on the range of brassica species tested indicated that generalist and specialist aphids are influenced differently by the host plant. A longer time spent in xylem ingestion was again the major difference in the feeding behaviour of the two aphids. In addition, rejection of passive phloem ingestion, by M. persicae, was not related so closely to increased time spent in non probing activities, as for B. brassicae. This observation indicates that M. persicae does not generally accept or reject brassica species due to the presence of phagostimulants, such as glucosinolates at the leaf surface or along the stylet pathway, unless the concentration is very high. Differences in feeding strategies employed by generalist and specialist aphids on the same plants are discussed.     

Evaluation of artificial diets for rearing Aphis glycines (Hemiptera: Aphididae)

Artificial aphid diets have been previously developed for the pea aphid, Acyrthosiphon pisum (Harris), and the green peach aphid, Myzus persicae (Sulzer). The ability to rear aphids on an artificial diet allows for selectively adding or subtracting compounds from an aphid's food source to determine the effect on fecundity and longevity. Five diets previously developed for the green peach aphid and the pea aphid were tested for their suitability for rearing soybean aphid, Aphis glycines Matsumura. The best diet, originally developed for the green peach aphid and based on the amino acid profile of young potato plants, allowed 12 generations of soybean aphids to develop. For all diets tested, aphid fecundity, and longevity were greatly reduced in comparison with aphids reared on soybean, Glycine max (L.) Merr., plants or on detached soybean leaves. In addition, mean developmental time was significantly longer for aphids reared on artificial diets.     

The toxicity of peach tree roots

Summary The HCN content of peach plants and the effect of this and other substances formed from peach root residues on growth of peach trees and on soil microorganisms were investigated. Peach root bark contained appreciable amounts of HCN. HCN was released from live roots after mechanical injury. Benzaldehyde and KCN were toxic to rooted peach trees in the greenhouse and they inhibited respiration of peach root tips. A similar suppression of respiration was caused by benzoic acid, mandelonitrile, and water extracts of peach root bark incubated in peach and non-peach soils. Extracts from peach soil caused greater inhibition to respiration of peach root tips than extracts from non-peach soil.KCN, mandelonitrile, benzaldehyde, peach root bark, and amygdalin reduced the total micro-organism, actinomycete, pythium, and pathogenic nematode population of an old peach soil.     

Time and concentration dependent interactions of Beauveria bassiana with sublethal rates of imidacloprid against the aphid pests Macrosiphoniellasanborni and Myzus persicae

A series of laboratory bioassays with each consisting of low, medium and high concentration treatments of the fungal biocontrol agent Beauveria bassiana alone or supplemented with an increasing sublethal rate of imidacloprid were conducted to quantify the fungal and chemical interactions on chrysanthemum aphid Macrosiphoniella sanborni (0.01‐0.05 a.i. μg mL^?1) and green peach aphid Myzus persicae (0.05‐0.5 a.i. μg mL^?1). During one week after exposure to a 1 mL spray onto a 95 cm² area in a Potter Spray Tower, M. sanborni was either more susceptible to B. bassiana or more sensitive to imidacloprid than M. persicae. The time–concentration–mortality (TCM) responses of each aphid species in each of five bioassays fit well to a TCM model, indicating a strong dependence of the fungal and chemical interactions on both concentration and post‐spray time. Adding imidacloprid to B. bassiana sprays at the rates of 0.025–0.05 μg mL^?1 against M. sanborni or 0.1–0.5 μg mL^?1 against M. persicae significantly enhanced or accelerated the fungal action. Based on the LC₅₀ or LC₉₀ estimates and their variances determined by the fitted TCM relationships for each aphid species, the relative potencies of an imidacloprid‐inclusive bioassay over those with B. bassiana alone or together with a lower sublethal rate ranged from a few to hundreds of times and varied over days after spray. These results suggest an alternative tactic for practical control of the aphid pests by a combined formulation or application of B. bassiana and imidacloprid and manage aphid resistance to the chemical insecticide.