Improving the Control of Tetranychus urticae on Edible Glasshouse Crops Using a Specialist Coccinellid ( Stethorus punctillum Weise) and a Generalist Mite ( Amblyseius californicus McGregor) as Biocontrol Agents

Current glasshouse biological control practice relies on regular prophylactic introductions of one or two 'best' species of natural enemy. Whilst this is effective for much of the time, occasional failures occur due to factors such as differences in response to seasonal changes in environmental conditions and/or host plant effects. This study looks at the predatory behaviour of a specialist coccinellid, Stethorus punctillum Weise, and a generalist mite, Amblyseius californicus McGregor (which predate on the two-spotted spider mite, Tetranychus urticae ) in order to assess how they responded to temperatures and relative humidities typical of glasshouse conditions on four edible crop plant species. Activity (distance covered, time spent walking, walking speed, angular velocity, and turning rate) was recorded at 20, 25 and 30 o C and at relative humidity (RH) levels of 33, 65 and 90%, on tomato, pepper, aubergine and cucumber leaves, and analysed using video-computer techniques. The results show that the activity of S. punctillum significantly increased at higher temperature levels. Host plant species also strongly influenced the performance of the predator, with it being most active on pepper and tomato and least active on aubergines. RH had no significant influence. The activity and predation by A. californicus increased at low humidity levels, especially in terms of time spent moving and number of prey killed. Temperature levels had no significant influence, but host plant species strongly influenced the performance of the predator, which was most active on pepper, and least active on aubergines. Further research was conducted with semi-field trials to investigate the efficacy in controlling TSSM with different combination of predators. When contrasting the commercially available predatory mite Phytoseiulus persimilis , used alone, compared with its use in a treatment with a combination of predator species, there was a stronger decrease in TSSM numbers on the crop plants in the latter treatment.     

朱砂叶螨对三种杀螨剂的抗性选育与抗性风险评估

为评价朱砂叶螨Tetranychus cinnabarinus对3种杀螨剂的抗性风险,在实验室抗性品系选育基础上,应用数量遗传学中的域性状分析法,研究了朱砂叶螨北碚种群对甲氰菊酯、阿维菌素和哒螨灵3种杀螨剂的抗性现实遗传力,并对3种药剂在不同杀死率下抗性发展的速率进行了预测。结果表明：分别单一连续汰选16代后,朱砂叶螨对甲氰菊酯、阿维菌素的抗性倍数分别达26.54和4.51倍,对哒螨灵表现为敏感性降低（抗性倍数为1.16倍）;朱砂叶螨对甲氰菊酯、阿维菌素和哒螨灵的抗性现实遗传力分别为0.2472,0.1519和0.0160。在室内选择条件下,杀死率为50%～90%时,要获得10倍抗性,甲氰菊酯仅需要13～6代,阿维菌素需要约21～10代;哒螨灵需要约197～89代;在田间选择,三种药剂都将需要更长的时间。抗性筛选16代结果表明,抗性风险较高的是菊酯类的甲氰菊酯,其次是生物源农药阿维菌素,杂环类的哒螨灵抗性风险较小。试验结果可为朱砂叶螨抗性治理提供参考。     

智利小植绥螨密度对朱砂叶螨产卵能力的影响

智利小植绥螨是朱砂叶螨的专性捕食者。本研究在室内,研究了智利小植绥螨密度对朱砂叶螨存活及生殖的影响。智利小植绥螨对朱砂叶螨存活干扰结果表明:干扰后24 h各处理朱砂叶螨的死亡率均显著高于对照,且死亡率随干扰密度增大而提高,10头捕食螨/叶碟处理高达76.67%,为对照处理的14.38倍。但是干扰48 h后对叶螨存活影响不大。对朱砂叶螨产卵干扰结果表明:干扰后各时间段朱砂叶螨单雌产卵量均随智利小植绥螨干扰密度的增加而降低。干扰24 h后,除1头捕食螨/叶碟处理与对照差异不显著外,其他各处理均与对照有显著差异。干扰48 h后,10头捕食螨/叶碟处理的叶螨单头产卵量是2.80粒,仅为对照的28.5%。但是干扰96h后,除10头捕食螨/叶碟处理与对照差异显著外,其余各处理与对照均差异不显著。本研究还分析了干扰对96 h内朱砂叶螨单雌总产卵量影响,处理5头/叶碟和10头/叶碟均显著低于对照,并且10头/叶碟显著低于5头/叶碟;1头/叶碟和3头/叶碟与对照相当,但是均显著高于10头/叶碟。结果显示,智利小植绥螨密度对朱砂叶螨有较强的生殖干扰作用,并且捕食螨密度越大,干扰作用越强,后代增殖潜能越小。     

山楂叶螨、苹果全爪螨及其捕食性天敌生态位的研究Ⅰ——时间与空间生态位

统计分析表明两种叶螨间生态位重叠值较大、各自生态位宽度较大。两种叶螨的时动空间生态位与各自种群消长曲线相一致,显示了它们对资源有相似要求以及“逐步扩散整树危害”的取食危害方式。它们的生态位分离表现在叶片正、反面及叶片反面的某些小“领域”上。苹果全爪螨更喜欢分布在树冠上层和外层。统计和模糊分析都表明草蛉和小花螨与两种叶螨的时间同步和空间同域性较强,捕食螨与叶螨的时间生态位重叠较小,而空间生态位重叠较大。天敌与叶螨间的时空生态位重叠以及天敌食谱生态位宽度结合分析有助于合理评价天敌的控制作用。     

The use of fecundity, lobe biometry and the RAPD-PCR technique in order to compare strains of Tetranychus sp.

In Belgium, recently two new red carmine forms of Tetranychus sp. have appeared on tomato crops in glasshouses and in maize crops. These forms maintain their red colour even during summer and on other host plants such as French bean. Our aim was to establish their status and to compare them with strains of Tetranychus urticae and Tetranychus cinnabarinus. A strain of Tetranychus kanzawai, a distant relative of the same genus, was used as a control. The five strains tested were characterized by their own demographic parameters, probably because of a longseparated evolution on different host plants. The white eye strain of T. urticae was differentiated from the four other strains by scanning electron microscopy studies of the dorsal integument folds. An investigation using the random amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR) showed T. cinnabarinus as a distinct group. However, the mixing of the individuals of the four other strains raises the question of the role of hybridization and host plant selection in the evolution of the Tetranychus complex. Exp Appl Acarol 22: 649–666 © 1998 Kluwer Academic Publishers     

Neoseiulus fallacis: dispersal and biological control of Tetranychus urticae following minimal inoculations into a strawberry field

In three separate tests, 100 adult female Neoseiulus fallacis (Garman) (plus immatures) were released at five point locations across 1.6-m rows of strawberries to control twospotted spider mites, Tetranychus urticae Koch. Beginning in April, during 6–12 weeks, predators controlled pests locally and dispersed downwind by 20–30 m. Up to 100 m² around each release point was colonized, and the entire 2.5 ha field was covered by predators by September. Distances dispersed by N. fallacis were similar within and across rows, suggesting that dispersal was primarily by aerial rather than by ambulatory means. Factors that affected dispersal were temperature, wind direction, density of spider mites, and mowing and flailing of foliage. An exponential model of dispersal was fitted to the data. On average, the area dispersed by N. fallacis doubled every 70 degree-days. From these results, a strategy of minimum release is suggested. To establish N. fallacis over a field in a single season, ca. 100 adult females per 1–2 m of row can be released before 1 July, after T. urticae have achieved 2–5 female adults per leaf. Releases should be 50 m apart and to the upwind side of the field. Selective sprays may be needed to suppress spider mites until predators gain control and disperse over the field.     

Laboratory and glasshouse evaluation of entomopathogenic fungi against the two-spotted spider mite, Tetranychus urticae (Acari: Tetranychidae), on tomato, Lycopersicon esculentum

Forty isolates of entomopathogenic fungi from six genera were assessed against the two-spotted spider mite, Tetranychus urticae, in a single dose, direct application laboratory bioassay on tomato leaflets. Only three isolates caused greater mortality than the control: these were Metarhizium anisopliae 442.99, Hirsutella spp. 457.99, and Verticillium lecanii 450.99. These isolates were assessed in a multiple dose bioassay, together with three isolates cultured from commercial biopesticides as follows: Beauveria bassiana 432.99 (cultured from 'Naturalis-L', Troy Biosciences, Phoenix, TX, USA); Hirsutella thompsonii 463.99 (cultured from 'Mycar', Abbott Laboratories USA); and V. lecanii 19.79 (used in 'Mycotal' Koppert BV, The Netherlands). Beauveria bassiana 432.99, H. thompsonii 463.99, M. anisopliae 442.99, and V. lecanii 450.99 were all pathogenic to T. urticae in this bioassay. In addition, it was found that the mortality caused by B. bassiana 432.99 and Naturalis-L was increased when the mites were exposed to tomato leaflets sprayed previously with conidia suspensions, compared to spraying the mites directly. In a glasshouse experiment, sprays of B. bassiana 432.99, H. thompsonii 463.99, M. anisopliae 442.99, V. lecanii 450.99 and Naturalis-L reduced T. urticae populations in a tomato crop grown according to commercial practice. Naturalis-L reduced T. urticae numbers by up to 97%. In a second glasshouse experiment, single sprays of Naturalis-L and the acaricide fenbutatin oxide (Torq) were compared as supplementary treatments to release of the predatory mite, Phytoseiulus persimilis. Supplementary sprays of fenbutatin oxide reduced the numbers of T. urticae nymphs (80% reduction), while Naturalis-L reduced numbers of T. urticae adults, nymphs and eggs (98% reduction in all three cases). It is concluded that Naturalis-L has the potential to be used against T. urticae on glasshouse tomato crops.     

Imaginal induction of diapause in several 'adult-female diapausing' spider mites

Abstract. The possibility of imaginal induction of diapause in adult female spider mites is suggested in Stigmaeopsis miscanthi. Here, several spider mites are studied to investigate the generality of this phenomenon. The existence of imaginal induction of reproductive diapause is established in Stigmaeopsis longus, two forms of S. miscanthi and Tetranychus kanzawai adult females. The females that develop under diapause-averting (long days and 18 °C) conditions are induced to diapause under short-daylength conditions at 18 °C after moulting to the adult stage. However, the adult females of Tetranychus urticae never diapause under these conditions.     

The effect of a liquid seaweed extract from Ascophyllum nodosum (Fucales,Phaeophyta) on the two-spotted red spider mite Tetranychus urticae

This paper presents evidence from an initial trial in favor of claims that the liquid seaweed extract of Ascophyllum nodosum, marketed in the UK as Maxicrop, can reduce numbers of the two-spotted red spider mite Tetranychus urticae on crop plants. Seven applications of Maxicrop Triple over 20 days significantly suppressed the population build-up of two-spotted red spider mites on treated strawberry plants (Fragaria sp. var. Redgauntlet) raised under high polythene tunnels as compared to untreated controls.     

Absorption and cannibalism: do phytoseiids conserve egg resources when prey densities decline rapidly?

The number of eggs oviposited or left in the opisthosomas of dead mites (total eggs) was assessed for Metaseiulus occidentalis (Nesbitt), Neoseiulus fallacis (Garman), Typhlodromus pyri Scheuten or Amblyseius andersoni Chant when each was caged with either (1) no Tetranychus urticae Koch, (2) only odours of T. urticae, (3) ten eggs of M. occidentalis or (4) ten nymphs of M. occidentalis (T. pyri for M. occidentalis). The total eggs for the no prey versus odour tests did not differ within species; the levels were the greatest for N. fallacis > T. pyri > A. andersoni > M. occidentalis. Among treatments, egg means did not differ for M. occidentalis but they did for N. fallacis and T. pyri and similar trends were seen for A. andersoni. Egg means were usually less for mites held with ten predator nymphs than mites held with ten predator eggs or with no prey. Were adult females with nymphs absorbing rather than ovipositing their eggs or dying with them in their opisthosomas? Activity levels (walking) for adult females were no more for mites held with nymphs versus no food. The data indicated that interference by nymphs was not increasing the energy use of females and thus reducing egg levels. However, tests with ten nymphs, one egg and no adult female had egg losses from nymphal predation that could account for fewer eggs in cage tests. Overall, no evidence for absorption was found. If it occurs, it must be among younger eggs or mites exposed to less rapid prey losses than were the mites tested here; in addition, other stimuli may cause absorption. The total eggs in sticky-tape tests were greatest for N. fallacis > M. occidentalis > T. pyri > A. andersoni. Cage versus stick-tape data differed most for M. occidentalis because of cannibalism. All four mites cannibalized eggs but M. occidentalis did most rapidly and extensively. When starved, it laid all of its eggs before the other three species did. Such behaviours may enhance survival of M. occidentalis when prey become scarce.