Is the effect of priming plants,and a functional JAR1, negligible on the foraging behaviour and development of a generalist lepidopteran,Helicoverpa armigera?

Theory and recent literature suggest strong effects of induced plant defences in some plant herbivore systems. Few have studied behavioural effects on intact plants. Differences in foraging behaviour as well as weight gain were determined for first instar Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) on Arabidopsis thaliana (L.) Heynh. (Brassicaceae) mutant and wild type plants, non‐primed, or primed by herbivore feeding or methyl jasmonate. The differences in feeding were primarily in the length of feeding time as opposed to the area fed on, feeding location, or frequency. More larvae dispersed from plants after priming by mite feeding than dispersed after caterpillar feeding. Other behavioural activities such as resting were not significantly affected. Early instars gained less weight feeding on ein2 (ethylene insensitive) mutant, but there was no difference in weight gain between larvae feeding on induced and non‐induced plants of the same type. We concluded that there are fitness consequences for neonates of the generalist H. armigera after feeding on induced plant tissues in some cases, and that distinct changes in behaviour are recognisable both at the fine scale and at grosser levels (dispersal). However, these changes are more subtle than might be expected.     

40种植物丙酮提取物对朱砂叶螨的毒杀活性

为推动植物源杀螨剂的研发进程,采用玻片浸渍法测定40种植物丙酮提取物对朱砂叶螨（Tetranychus cinnabrinus）雌成螨的毒杀活性,以期发现具开发潜力的植物资源。结果表明,沙茴香（Ferula bungeana）、盐肤木（Rhus chinensis）、黄连木（Pistacia chinensis）、紫丁香（Syringa oblata）和南方六道木（Abelia dielsii）等5种植物丙酮提取物对朱砂叶螨的毒杀活性较好;毒力测定表明,沙茴香和盐肤木丙酮提取物对朱砂叶螨的毒杀活性最好,LC₅₀分别为0.08 g·mL^-1和0.09 g·mL^-1。可见,沙茴香和盐肤木可作为植物源杀螨剂研发的候选材料,值得进一步研究。     

模拟酸雨对朱砂叶螨寄主植物三月早茄生理生化的影响

以朱砂叶螨的寄主植物三月早茄为对象,研究了不同pH值和不同时间模拟酸雨胁迫下,茄子对酸雨的抵抗、适应能力和营养物质含量变化.结果表明,随酸雨酸度增强,茄叶的过氧化氢酶(CAT)活性、磷和可溶性蛋白含量呈单峰变化趋势;而过氧化物酶(POD)活性、可溶性糖含量呈单谷变化趋势;还原糖含量和超氧化物歧化酶(SOD)活性随酸度增加呈上升趋势;茄叶pH值呈下降趋势,含水量不受酸雨影响.POD对酸雨作用反应迟缓,而SOD、CAT较敏感,其他几项生理指标则对酸雨作用时间反应灵敏.高pH(4.0～5.6)的酸雨刺激茄叶的保护能力增强,促进茄叶的生长发育.由于茄叶内糖含量、磷及可溶性蛋白含量的改变,植物的适口性有所变化,可促进叶螨生长,而在强酸性酸雨(pH＜3.0)胁迫下,植物的生长受到抑制,营养物质含量降低,抑制朱砂叶螨的生长.     

北京地区朱砂叶螨在蔬菜集约化栽培下的种群动态

为了明确集约化栽培管理模式对蔬菜上朱砂叶螨Tetranychus cinnabarinus(Boisduval)的种群数量及动态的影响,2008年在中国农科院蔬菜花卉所塑料棚和露地春、秋茬5种蔬菜上,调查了该螨的种群动态。结果表明,6月中旬春棚的朱砂叶螨种群数量达到高峰期,6月下旬后则明显下降;露地春茬菜豆、茄子、甜椒和黄瓜于6月上旬始见叶螨发生,有螨株率比单株螨量增长迅速,番茄上未发现叶螨。塑料棚和露地秋茬菜豆、茄子和黄瓜上朱砂叶螨发生数量低于13.3头/株,番茄、甜椒寄主上均未发现叶螨为害。分析认为,集约化栽培措施是制约朱砂叶螨种群发生数量的关键因素,降雨和高湿等不良的气象条件也有重要影响。     

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.