东亚小花蝽(Orius sauteri)成虫对入侵害虫西花蓟马(Frankliniella occidentalis)成虫的捕食作用

为探明东亚小花蝽对西花蓟马的控制效能,开展了东亚小花蝽成虫对西花蓟马成虫的捕食功能反应与寻找效应研究。试验结果表明,在供试温度下,其捕食功能反应符合HollingⅡ型方程。在相同温度下,东亚小花蝽成虫的捕食量随着猎物密度的增加而增大,搜寻效应随着猎物密度的增加而降低。在18～26℃,随着温度的升高,东亚小花蝽成虫对西花蓟马成虫的捕食量增加,而在26～34℃则有相反的趋势。在相同猎物密度条件下,随着东亚小花蝽成虫密度的增大,其平均捕食量逐渐减少,捕食作用率E也相应地降低,捕食作用率E与东亚小花蝽成虫密度P的关系为E=0．5224P^-0.7148,分摊竞争强度,与东亚小花蝽成虫密度P的关系为I=0．9689logP＋0．0763。     

球孢白僵菌对黄瓜代谢产物及西花蓟马取食行为的影响

球孢白僵菌Beauveria bassiana灌根处理黄瓜后,发现西花蓟马Frankliniella occidentalis对叶片危害面积显著低于对照组;为探究产生这一现象的原因,测定黄瓜叶片中防御酶系和次生代谢产物等含量变化,采用直流刺吸电位仪(direct current electrical penetration graph,DC-EPG)分析西花蓟马成虫取食黄瓜叶片的行为.球孢白僵菌对黄瓜灌根后叶片中过氧化氢酶(CAT)、过氧化物酶(POD)和超氧化物歧化酶(SOD)含量均呈上升趋势,其中CAT活性增加最高,增加率为37.26％;丙二醛MDA的含量呈下降趋势;可溶性蛋白、类黄酮的含量增加.DC-EPG显示西花蓟马在经球孢白僵菌处理的黄瓜上,取食时间和次数均低于对照组.结果表明,黄瓜植株经球孢白僵菌处理后防御酶物质增加,进而导致西花蓟马对叶片危害下降,利于对西花蓟马的防治.     

害虫与天敌个体数量比值对天敌竞争作用指数的影响——以茶园花蓟马及其主要天敌为例

为合理保护和利用自然天敌,明确害虫与天敌个体数量比值对天敌竞争作用指数(竞争系数和竞争强度指数)的影响。运用竞争系数分析法、灰色关联度分析法、竞争强度指数分析法和Pearson相关系数法对2020年、2021年三种茶园花蓟马与主要天敌个体数比值对主要天敌竞争作用指数的影响。三种茶园两年数据汇总分析得出,竞争系数和竞争强度指数均值与花蓟马-天敌比值的Pearson相关系数分别为-0.7858和-0.8199;2020年三种茶园数据综合分析得出,竞争系数和竞争强度指数均值与花蓟马-天敌比值的Pearson相关系数分别为-0.7391和-0.7819;2021年三种茶园竞争作用指数与比值的跟随关系不明显,主要是平阳特早茶园9种主要天敌以外的其他天敌影响了竞争作用趋势。综合多种分析结果得出,9种主要天敌的竞争作用指数与花蓟马-天敌比值呈显著负相关,其中三突花蟹蛛(-0.9936)负相关性最显著,鞍型花蟹蛛是高比值组竞争作用指数最高的天敌。研究结果为利用天敌开展花蓟马生物防治提供参考。     

The Mirid Bug Dicyphus tamaninii as a Greenhouse Whitefly and Western Flower Thrips Predator on Cucumber

Dicyphus tamaninii Wagner is a polyphagous predator that also feeds on plants. Its effectiveness against several pests has been tested and good results have been obtained on tomato, but not on cucumber. This paper reports the results of three exclusion cage experiments. The first was carried out to evaluate the effectiveness of D. tamaninii for reducing greenhouse whitefly and western flower thrips populations on cucumber. The second experiment examined the safety of the mirid bug in terms of the potential for damaging cucumber fruits even at very low prey densities. Two predator (3 and 18 insects/plant) and variable prey release rates were used. The predator was able to reduce whitefly populations greatly, even at high initial pest infestation levels, especially at the higher release rate. Western flower thrips populations were maintained at very low densities a few weeks after the predator had been introduced into cages at the two release rates tested. The mirid bug was barely able to reproduce on cucumber in the absence of prey. Mirid feeding punctures on cucumber fruit or yield decrease due to the action of mirids were not observed. The potential of this mirid bug for inoculative and conservation biological control is discussed.     

Propagation of tomato spotted wilt virus in Frankliniella occidentalis does neither result in pathological effects nor in transovarial passage of the virus

The effect of tomato spotted wilt virus (TSWV) on Frankliniella occidentalis Pergande (Thysanoptera; Thripidae) following a 6-hour acquisition access period on infected plants was investigated. No statistically significant differences were observed among viruliferous, non-viruliferous and control thrips with respect to developmental time, reproduction rate and survival. Thrips larvae, exposed or non-exposed to TSWV, developed from egg to adult in 13.1 and 13.2 days, respectively. Exposed females produced an average of 28.3 larvae whereas control thrips produced 22.3 larvae and longevity was 13.4 and 12.5 days, respectively. None of these values were significantly different. Population reproductive statistics, net reproductive rate (R ₀), mean generation time (T) and intrinsic rate of increase (r _m) were calculated from the life fertility tables. R ₀ and r _m were higher for viruliferous thrips as compared to non-viruliferous and non-exposed thrips. Virus transmission studies revealed that viruliferous thrips were able to transmit virus until death and that TSWV was not transovarially transmitted.     

Diapause induction in the thrips predatorAmblyseius cucumeris [Acarina: phytoseiidae] under greenhouse conditions

The predatory miteAmblyseius cucumeris (Oudemans) is an important biological control agent for thrips in commercial greenhouses, but its effectiveness in fall and winter is limited by reproductive diapause induced under short day conditions. Influence of photoperiod and temperature on diapause induction was investigated to provide information for successful management of the predator. Under 8∶16 (L∶D) photoperiods and 22°C photophase temperatures, diapause incidence was inversely related to scotophase temperature, decreasing from 100% diapause at 15°C to no diapause at 21°C. In continuous darkness, diapause was induced by thermoperiods of 20∶10 and 22∶17 and 22∶17 but not 25∶15°C (T∶C) (8h thermophase). Critical daylength for inducing diapause under 22∶17°C (T∶C) was 12.45 h, which was consistent with the trend in diapause incidence in mites collected from an established greenhouse population September to November. MostA. cucumeris diapaused only when exposed to diapause inducing conditions throughout their juvenile development and none stopped laying eggs when transferred from nondiapause to diapause inducing conditions as adults. After 14 generations of genetic selection for a nondiapause strain, diapause incidence was 33.3%.      

Oral toxicity of Photorhabdus toxins against thrips species

The oral toxicity of excretion products of several Photorhabdus and Xenorhabdus strains was tested on two thrips species: Frankliniella occidentalis and Thrips tabaci. Out of 46 Photorhabdus isolates and six Xenorhabdus isolates only six North American P. temperata isolates were toxic to the thrips species. After 7 days of drinking from P. temperata supernatant a mortality of 90% could be reached. Thrips were also killed after sucking from leaves covered with the toxins. Toxins have a negative effect on thrips fecundity. Possibilities of using P. temperata in the control of thrips will be discussed.     

Effects of sub-lethal cold stress on the Western Flower Thrips, Frankliniella occidentalis

In order to establish in a new geographical area, introduced insects must be able to survive any period of adverse conditions such as a temperate winter and be capable of subsequent development to adulthood and/or reproduction. However, this aspect of insect overwintering and cold tolerance has been poorly studied. At high latitudes, Frankliniella occidentalis is typically associated with artificially heated glasshouses, but has some ability to tolerate low temperatures and may survive winter field conditions for short periods, or for longer periods of time during mild winters. The effects of overwintering on the viability of survivors are, however, unknown. In this study, acute and chronic cold exposure regimes were imposed on first instar larvae and adult female Western Flower Thrips, after which the longevity, development and reproductive capacity of the survivors were monitored and compared to those of non-stressed individuals. Survival of cold exposure did not affect subsequent survivorship of immature or adult insects, though cold treated larvae took approximately two days longer to reach adulthood than untreated individuals (at 20°C, 18L:6D). Chill treatment of adult females significantly reduced their rate of reproduction (from 1.45 to 0.93 larvae day^-1), reproductive lifespan (from 13.3 to 9.2 days) and as a result, total reproductive output (from 20.4 to 10.8 larvae), compared to control females. Acute exposure resulted in non-significant decreases of the same parameters. The relevance of the above effects to overwintering of F. occidentalis is discussed.     

Winter and spring abundance of Frankliniella spp. and Thrips tabaci Lindeman (Thysan., Thripidae) on weed host plants in Turkey

Abstract:  The species composition of thrips and abundance of three pestiferous thrips species, Frankliniella occidentalis (Pergande), Thrips tabaci Lindeman and Frankliniella intonsa (Trybom) (Thysan., Thripidae) on weed species during winter and spring time were studied in vegetable production and polycultured areas in the eastern Mediterranean region of Turkey in years 2002 and 2003. Of a total of 61 543 thrips extracted from 8933 samples collected, 77% were adults. F. occidentalis was collected from all of 49 weed species sampled and F. intonsa was detected on 18 plant species between May and June. T. tabaci was collected from 42 of a total of 49 weed species. Immature thrips were extracted from 42 of a total of 49 weed species. Four weed species of a total 35 weed species sampled between April and May in the sampling areas hosted 63% of larvae and approximately 50% of F. occidentalis collected. A total of 23 thrips species was recorded from weeds sampled in this study. F. occidentalis accounted for 83% of a total 47 640 adult thrips collected and followed by low rates of T. tabaci and F. intonsa (9 and 1%, respectively). Melanthrips spp. accounted for 3.54% of total numbers of adult thrips. Flower-inhabiting thrips species and T. tabaci were most abundant on weeds between April and May when the number of weed species in bloom was greatest, then decreased to low levels after May. Most pestiferous thrips on weeds species were collected from vegetable production areas. F. occidentalis was the predominant thrips comprising over 80% in most months in the vegetable grown area. In polycultured area, the composition of adult thrips shifted monthly. While Melanthrips was the more prevailing thrips by rates 53% in February and 81% in March, F. occidentalis was the predominant thrips with 60 to 62% in spring, respectively.     

GROWTH, REPRODUCTION AND FIELD POPULATION DYNAMICS OF FRANKLINIELLA BISPINOSA (THYSANOPTERA: THRIPIDAE)

Abstract Frankliniella bispinosa was reared at five constant temperatures using pollen of Typha domingensis as food. At 15°C, 37.5 days are required for completing the life cycle and the adult females survived for about 30 days. The immature stage and the female longevity were significantly reduced when temperature increased and they were only 9.2 and 3.9 days, respectively, at 35°C. The maximal number of eggs (123.2/female) were laid at 25°C, as compared with 29.5, 42.1, 11.6 eggs per female, respectively, at 15°C, 20°C and 30°C. F. bispinosa occurs on Bidens pilosa flowers all the year round in south Florida. However, the population is more abundant from mid-March to early April.