Pesticide Susceptibility of Two Coccinellids (Stethorus punctum picipes and Harmonia axyridis) Important in Biological Control of Mites and Aphids in Washington Hops

The susceptibility of Stethorus punctum picipes (Casey) and Harmonia axyridis Pallas larvae to pesticides used or with potential for use in Washington hops, was examined in laboratory bioassays. All pesticides tested except the miticide, hexythiazox, the insecticides, chlorpyrifos and pirimicarb, and the fungicide, mycobutanil, produced 100% mortality in S. punctum picipes at concentrations equivalent to field rates. The insecticides, pirimicarb, endosulfan, and thiamethoxam were least toxic to H. axyridis. Bifenthrin, diazinon, dimethoate, methomyl, carbaryl, malathion, phosmet, imidacloprid, and chlorpyrifos were highly toxic. The miticides, abamectin and fenpyroximate were highly toxic, milbemectin was moderately toxic but all other miticides tested were non-toxic. All fungicides had low toxicity. Selection and use of pesticides compatible with natural enemies and conservation biological control in Washington hop production is discussed.     

Field evaluation of the effects of the insect growth regulator tebufenozide on entomophagous arthropods and pests of apples

Organophosphate insecticides are very widely used in commercial apple production to control fruit-attacking pests but their broad-spectrum activity constrains biological control of other pests. Compounds with narrow-spectrum activity are therefore desirable. The insect growth regulator (IGR) tebufenozide was compared with another IGR, fenoxycarb, and the organophosphate, azinphos-methyl, in a replicated field trial in the 1994/1995 apple-production season. Vacuum sampling of the tree foliage on five occasions during the growing season showed significantly lower populations of various natural enemies (spiders, lacewings and the specialist mite predator Stethorus spp. adults and larvae) in the azinphos-methyl treatment than in either of the two IGR treatments. The two-spotted mite ( Tetranychus urticae Koch) was most numerous in the azinphos-methyl treatment. In 1995/1996, the entire trial area was placed under a tebufenozide treatment program to determine the extent to which natural enemy populations would recover when broad-spectrum insecticide (azinphos-methyl) use was halted. Populations of polyphagous natural enemies assumed levels broadly equivalent to those observed under IGR treatments the previous year. Numbers of Stethorus spp. were lower than in the 1994/1995 season, possibly because T. urticae (prey) populations were much reduced from the previous season's densities. All three insecticide treatments were equally effective in controlling the lepidopteran pests, codling moth ( Cydia pomonella (L.)), lightbrown apple moth ( Epiphyas postvittana (Walker)) and early season caterpillars (predominantly Helicoverpa punctigera (Wallengren)). Results indicate that tebufenozide provides good control of lepidopteran pests, while allowing the rapid build-up of natural enemies which contribute to control of other pests.     

拟小食螨瓢虫捕食六点始叶螨的初步观察

在室内以六点始叶螨Eotetranychus sexmaculatus(Riley)为猎物观察了拟小食螨瓢虫Stethorusparapauperculus Pang的发育历期、捕食量、捕食作用及干扰效应。研究结果表明:拟小食螨瓢虫取食六点始叶螨时完成一个世代需23.2 d,幼虫1～4龄的捕食量分别为9.5、14.5、19.5、64.2头六点始叶螨成螨;成虫期对六点始叶螨成螨的捕食量高达880.4头,拟小食螨瓢虫对六点始叶螨的捕食作用符合HollingⅡ方程,拟合的模型方程为Na=1.3843 N/(1+0.0231N),日均最大捕食量为43.29头;拟小食螨瓢虫的捕食率与个体间的干扰效应用Hassell-Varley(1959)模型拟合为E=0.4690P-0.5470。     

Impact of temperature and prey density on the predacious capacity and behaviour of Stethorus punctillum Weise

Temperature had various effects on the predacious efficacy of immature and mature stages of the coccinellid predator, Stethorus punctillum on the two-spotted spider mite, Tetranychus urticae. In the case of immature stages, food consumption at the lowest tested temperature (15°C) was significantly higher than that at higher temperatures (25 and 35°C). On the contrary, positive correlation between food consumption and temperature was evaluated in the case of adult predator. Regarding predator responses to different prey density, a high positive correlation between food consumption and prey density was evaluated among 4^th instar larvae of the predator, followed by adult predator, while younger instars did not show reasonable increases with increasing prey densities. These results confirm that larval and adult stages of S. punctillum exhibit “Type II” functional response. In conclusion, the 4^th instar larvae and adult predator are the most preferable stages in winter and summer crops to control T. urticae, respectively.     

食螨瓢虫自然种群基地建立的研究

腹管食螨瓢虫Stethorus siphonulus Kapur是福建省柑桔全爪蠕(红蜘蛛)Panonychus eitri MeGregor的优势种天敌,控制作用显．已在我省柑桔产区大面积应用成功。为了使柑桔全爪蠕生物防治持续发展,古螨瓢虫自然种群基地的建立至关重要．本将多年来在闽清白中柑桔场、福建农业大学金山柑桔园、福州北郊峙头柑桔场、长泰柑桔园等地进行食螨瓢虫自然种群基地建立的研究,进行总结报道。     

Effect of temperature on intrinsic rates of natural increase (rm) of a coccinellid and its spider mite prey

The intrinsic rate of natural increase(r_m) is useful to estimate the populationgrowth potential of insects and mites, whichmay help predict the outcome of pest-naturalenemy interactions. This study was conductedto determine how 12 constant temperatureregimes between 10–38 °C (± 0.5 °C) may differentially affect ther_m of the McDaniel spider mite, Tetranychus mcdanieli McGregor (Acarina: Tetranychidea), a common pest of raspberry, andits coccinellid predator, Stethoruspunctillum Weise (Coleoptera: Coccinellidae). Tetranychus mcdanieli survived tomaturity in the 14–36 °C range, comparedto the 14–32 °C range for S.punctillum. Survival above 24 °Cremained high for the spider mite, butdecreased markedly for the coccinellid. Tetranychus mcdanieli's range forreproduction was similar to its survival range,but S. punctillum failed to reproduce at14 °C and reproduced only poorlyat 16 °C. Offspring production peakedat 24 °C for both T. mcdanieli(average 152 eggs per female), and S.punctillum (280 eggs per female). At alltemperatures suitable for reproduction, femalelongevity of the coccinellid was greater thanthe spider mite, which was characterized byearlier/faster reproduction than thecoccinellid. As temperature increased, ther_m followed a typical asymmetricaldome-shape pattern, with maximum values of0.196 d^–1 and 0.385 d^–1at 30 °C and 34 °C, for S.punctillum and T. mcdanieli,respectively. For each species, ther_m-temperature relation was successfullymodelled using a curvilinear regressionequation previously shown to predictdevelopment rate. In both species, thedevelopment rate response to temperature has amajor influence on the temperature-r_mrelationship. In the 16–32 °C rangesuitable for population growth of both species,the r_m of T. mcdanieliwas 1.9 (30 °C) to 8 (16 °C) times greaterthan S. punctillum. These growthpotential ratios are consistently in favor ofthe prey, suggesting a limitation of thecoccinellid with respect to its capacity totrack T. mcdanieli populations. However,under short season conditions, the inferiorreproductive dynamics of S. punctillum'svs. spider mite prey should not have aprevailing influence in determining impact, andmay be compensated by high voracity incombination with a strong aggregativeresponse.     

温度对深点食螨瓢虫实验种群的影响

在５种温度下观察了深点食螨瓢虫各虫态的生长发育及成虫产卵的情况,由此拟合了各虫态的发育速率和温度的关系模型,求出了各阶段的发育起点温度和有效积温,组建了４种温度下的实验种群繁殖特征生命表,并算出了内禀增长能力、稳定年龄组配、瞬时出生率和瞬时死亡率等参数值。     

福建省食螨瓢虫区系及地理分布

食螨瓢虫Stethorus spp.是世界上许多果树和经济作物叶螨的一类重要天敌。本文通过对采自福建省28个县、市约3000号食螨瓢虫成虫标本的整理,解剖雄外生殖器制片标本约800张,共鉴定出福建省食螨瓢虫9种,其中4种是福建新记录,包含1种中国大陆新记录和一未定名种。除福建北部和西北部以深点食螨瓢虫Stethorus punctillum Weise为优势种外,其余全省广大地区,以腹营食螨瓢虫片S.siphonulus Kapur和广东食螨瓢虫S.cantonensis Pang为优势种,本文记述了这9个种的分布和寄主,并对福建省食螨瓢虫区系及地理分布作初步分析。     

Prey mediated effects of Bt maize on fitness and digestive physiology of the red spider mite predator Stethorus punctillum Weise (Coleoptera: Coccinellidae)

The present study investigated prey-mediated effects of two maize varieties expressing a truncated Cry1Ab, Compa CB (event Bt176) and DKC7565 (event MON810), on the biology of the ladybird Stethorus punctillum. Although immuno-assays demonstrated the presence of Cry1Ab in both prey and predator collected from commercial maize-growing fields, neither transgenic variety had any negative effects on survival of the predator, nor on the developmental time through to adulthood. Furthermore, no subsequent effects on ladybird fecundity were observed. As a prerequisite to studying the interaction of ladybird proteases with Cry1Ab, proteases were characterised using a range of natural and synthetic substrates with diagnostic inhibitors. These results demonstrated that this predator utilises both serine and cysteine proteases for digestion. In vitro studies demonstrated that T. urticae were not able to process or hydrolyze Cry1Ab, suggesting that the toxin passes through the prey to the third trophic level undegraded, thus presumably retaining its insecticidal properties. In contrast, S. punctillum was able to activate the 130 kDa protoxin into the 65 kDa fragment; a fragment of similar size was also obtained with bovine trypsin, which is known to cleave the protoxin to the active form. Thus, despite a potential hazard to the ladybird of Bt-expressing maize (since the predator was both exposed to, and able to proteolytically cleave the toxin, at least in vitro), no deleterious effects were observed.