菜豆田叶螨及天敌复合生态系统群落组成及其主成分分析

【目的】叶螨对贵州省菜豆Phaseolus vulgaris的危害日趋严重,为明确菜豆田叶螨及其天敌群落结构特征,对菜豆田叶螨防治提供依据。【方法】于2013年5月至8月对菜豆田叶螨及其天敌进行系统调查,应用群落特征参数、主成分分析法及评价函数对其群落特征、时间格局及群落稳定性进行了研究。【结果】菜豆田叶螨及天敌共有7目11科21种,其中:叶螨4种,优势种为二斑叶螨Tetranychus urticae Koch;捕食性天敌17种,优势种为南方小花蝽Orius similis Zheng。菜豆叶螨及天敌复合系统群落的多样性和均匀度随着植株的生长不断增加,但在植株生长盛期随着二斑叶螨个体数的剧增而下降,在菜豆生育中后期,由于复合生态系统中物种丰富、个体数发生量大,多样性指数和均匀度指数又呈上升趋势。对各时期复合程度的评价表明,中后期复合程度高,初期和末期复合程度低。【结论】复合系统中捕食性天敌对叶螨的控制作用大,优势种天敌表现出一定的跟随效应。     

巴氏新小绥螨对猎物搜寻能力的研究

巴氏新小绥螨Neoseiulus barkeri(Hughes)是一种多食性捕食螨,主要捕食叶螨和蓟马等。因其捕食范围广,捕食量相对较大,且易人工繁殖,因此,被广泛应用于农业生物防治中。本文利用温室的释放-回收实验研究了巴氏新小绥螨对截形叶螨Tetranychus truncatus和西花蓟马Frankliniella occidentalis(Pergande)的搜寻能力。实验共设3个处理:(1)叶螨为害植株与清洁植株;(2)蓟马虫害植株与清洁植株;(3)蓟马、叶螨混合为害植株与清洁植株。当捕食螨释放于清洁黄瓜植株和虫(螨)害黄瓜植株交替排列的六角结构的中心时,2种害虫(螨)不论是单独危害还是混合危害,巴氏新小绥螨回收比例随着时间的延长逐渐趋于平缓。释放后1 d之内,叶螨、蓟马及混合猎物处理中回收到的捕食螨分别占释放总量的65.25%±1.61%、62.75%±1.31%和81.75%±2.14%,并且虫(螨)害植株上回收到的捕食螨数量明显比清洁植株多,叶螨、蓟马及混合猎物危害植株回收的捕食螨量分别占释放总量的53.5%±5.6%、49.5%±3.6%和74.0%±2.7%。因此,巴氏新小绥螨对这2种猎物及其混合物均有较强的搜寻能力,能够有效定位作物中有猎物的植株。同时对利用一种捕食螨生物防治温室中同时发生的2种害虫(螨)的可能性进行了讨论。     

二斑叶螨为害对菜豆生理指标的影响

二斑叶螨(Tetranychus urticae)是为害菜豆的重要害虫。本文研究了二斑叶螨不同密度和不同时间为害对菜豆各种生理指标的影响。结果表明:在二斑叶螨2头·叶-1的低密度和为害少于5 d的短时期内,菜豆叶片叶绿素a、叶绿素b和叶绿素总含量变化不大,但随着二斑叶螨为害时间的延长和密度的增大,叶绿素含量下降明显增加;总糖和还原糖的含量与二斑叶螨的为害程度关系密切,即为害时间越长、受害程度越严重,还原糖降低幅度越大,总糖的含量则先升高再降低;随着二斑叶螨为害程度的加重,菜豆叶片中全磷、全钾损失显著,全氮含量变化不显著。     

西花蓟马或二斑叶螨为害的菜豆对两者间后取食者体内保护酶和解毒酶活性的影响

【目的】害虫取食后会导致植物的防御反应;取食同种植物的不同种害虫其生理适应性可能不同。本研究旨在阐明一种害虫取食后的植物对后取食的另一种害虫虫体酶活性的影响。【方法】采用生化分析法研究了西花蓟马Frankliniella occidentalis 2龄若虫或二斑叶螨Tetranychus urticae雌成螨为害后的菜豆对后取食不同时间下的二斑叶螨第2若螨和雌成螨及西花蓟马2龄若虫和雌成虫体内保护酶[过氧化物酶(POD)、过氧化氢酶(CAT)和超氧化物歧化酶(SOD)]和解毒酶[多功能氧化酶(MFO)、羧酸酯酶(Car E)、谷胱甘肽-S-转移酶(GSTs)和乙酰胆碱酯酶(Ach E)]活性的影响。【结果】二斑叶螨雌成螨取食西花蓟马为害菜豆5 h时,POD,CAT和SOD这3种保护酶的活性均明显高于取食健康植株(P0.01),取食蓟马为害的菜豆18 h时只有POD活性低于取食健康植株(P0.01);二斑叶螨第2若螨取食蓟马为害菜豆后只有CAT活性在5 h时明显高于取食健康植株(P0.01)。二斑叶螨雌成螨取食蓟马为害菜豆5 h时,解毒酶MFO和Car E的活性受到抑制(P0.01),但GSTs和Ach E活性均比取食健康菜豆高(P0.01);取食18 h时,只有MFO的活性变化与5 h不同。第2若螨取食蓟马为害菜豆只有MFO的活性不论在5 h还是18 h时明显高于取食健康菜豆(P0.01)。西花蓟马取食二斑叶螨雌成螨为害菜豆时,雌成虫体内的3种保护酶的活性不论取食5 h还是18 h均明显升高(P0.01),但2龄若虫只有CAT活性在这两个时间段下明显升高(P0.01)。西花蓟马雌成虫取食螨害菜豆5 h时,解毒酶活性的变化同二斑叶螨雌成螨,取食18 h时只有GSTs活性变化状态与取食5 h不同;西花蓟马2龄若虫取食螨害菜豆时除GSTs外解毒酶的活性变化在这两个时间下正好相反。【结论】西花蓟马或二斑叶螨为害的菜豆能诱导后取食的二斑叶螨和西花蓟马产生一系列应激生化反应,且两种害虫成虫体内所有的保护酶和解毒酶活性在5 h时变化状态相同,但在其余时间和虫态下酶活性的变化状态不同。说明这两种昆虫体内保护酶和解毒酶活性的变化既有共性,又与害虫种类、虫(螨)态、取食时间相关,两种害虫对虫害植物的生理适应性不完全相同。     

二斑叶螨的卵和丝网对西花蓟马生长发育和繁殖的影响

为探讨二斑叶螨Tetranychus urticae Koch的卵和丝网对西花蓟马Frankliniella occidentalis(Pergande)的影响,本文研究了西花蓟马分别取食健康菜豆叶片、带二斑叶螨卵的菜豆叶片、带卵+丝网的菜豆叶片3种不同情况下,西花蓟马生长发育、存活和繁殖情况,并获得了其生命参数。结果表明西花蓟马在带二斑叶螨卵的菜豆叶片上发育最快,其未成熟期为11.35 d,明显短于另外两个处理,在带有二斑叶螨卵和丝网的菜豆叶片上成虫获得率最低为63%,西花蓟马在不同处理之间的成虫寿命和繁殖力没有明显的差异;西花蓟马取食3种菜豆叶片的内禀增长率分别为0.1779、0.1827和0.1710。以上结果说明取食二斑叶螨的卵可缩短西花蓟马发育时间,对种群增长有利,二斑叶螨的丝网可降低西花蓟马的存活率。     

寄主植物对朱砂叶螨药剂敏感性及解毒酶活性的短期诱导研究

将继代饲养在菜豆上的朱砂叶螨Tetranychus cinnabarinus(Boisduval)分别转移到黄瓜、甘蓝和茄子上饲养3代后,测定不同寄主植物对叶螨的药剂敏感性及其解毒酶系活性的诱导作用。结果表明,从菜豆上转养到黄瓜、甘蓝和茄子上后,后3个寄主上叶螨种群对阿维菌素的敏感度均有所上升,对联苯菊酯的敏感度有升有降,甘蓝、茄子上的叶螨种群LC50值分别是菜豆种群的0.27倍和0.44倍。各寄主上饲养的朱砂叶螨的解毒酶活性也发生了不同程度的变异,黄瓜种群上MFO、CarE活性均显著高于其它3种寄主,菜豆种群的GST活性显著高于转养的3种寄主,而甘蓝种群的AchE活性是菜豆种群的3.37倍。研究结果表明不同寄主植物短期饲养可改变朱砂叶螨的药剂敏感性及其解毒酶活性,这种改变随寄主不同而异。     

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。     

山楂叶螨危害对海棠叶片POD的影响

以人工接种的方法研究了山楂叶螨(Tetranychus viennensis Zacher)危害初期(9d内)对海棠(Malus zumi)叶片过氧化物酶(POD)的影响。结果表明,随危害时间延长和虫口密度增大,POD活性迅速升高,30头／叶危害9d和60头／叶危害6d时均约达对照的190％;PAGE分析结果显示叶螨危害使海棠叶片产生2种新的POD同工酶,受害植株的未接虫叶片的POD活性同时升高,并出现与接虫叶片相同的PAGE谱带,揭示叶螨危害对海棠叶片POD有系统诱导性。POD的变化可能是受害植株对叶螨危害的一种应激反应。     

截形叶螨雄螨有第二若螨期

雄螨（Ｍａｌｅｍｉｔｅ）是否存在第二若螨期（Ｄｅｕｔｏｎｇｍｐｈ－ｐｅｒｉｏｄ）各种资料说法不一,且国内尚未见这方面的详细报道。笔者于１９９４～１９９７年以截形叶螨ＴｅｔｒａｎｙｃｈｕｓｔｒｕｎｃａｔｕｓＥｈａｒａ为试验材料,对此进行了初步研究,现将结果报告如下。１螨种与试验条件螨种于１９９４年８月在延边大学农学院附近的菜豆上采集,经鉴定后在室内２５℃、１４小时／天光照条件下饲养,供试验用。本试验在自动控制温度（±０．５℃）和光照长度（±０．０１小时／天）的小室内进行。小室大小为１．７ｍ×１．４…     

朱砂叶螨刺吸胁迫对玉米自交系化学防御物质的系统诱导效应

为了探明朱砂叶螨刺吸胁迫对玉米体内化学防御的系统诱导效应,以玉米抗螨性自交系‘H1014168’和感螨性自交系‘H1014591’幼苗为材料,在叶螨刺吸第1叶7 d后,测定了未被刺吸部位(第2叶和根系内)的丁布、总酚、胰蛋白酶抑制剂(TI)和胰凝乳蛋白酶抑制剂(CI)含量.结果表明: H1014168 第2叶和根内的丁布、总酚、TI和CI含量均显著高于健康植株; H1014591 第2叶内4种化学防御物质含量显著高于健康植株,根内TI含量显著高于健康植株,丁布和CI含量与健康植株差异不显著,总酚含量显著低于健康植株.朱砂叶螨刺吸胁迫对玉米体内的丁布、总酚、胰蛋白酶抑制剂和胰凝乳蛋白酶抑制剂的诱导具有系统性,对玉米抗螨性自交系的系统诱导效应强于感螨性自交系.     

Attraction of the specialist parasitoid Cotesia rubecula to Arabidopsis thaliana infested by host or non-host herbivore species

In this study we investigated whether in a two‐choice set‐up the parasitoid Cotesia rubecula (Marshall) (Hymenoptera, Braconidae) distinguishes between volatiles emitted by Arabidopsis thaliana (L.) Heynh. (Brassicaceae) infested with its host, Pieris rapae (L.) (Lepidoptera: Pieridae) and Arabidopsis infested with non‐host herbivores. Four non‐host herbivore species were tested: the caterpillars Plutella xylostella (L.) (Lepidoptera: Plutellidae) and Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae), both chewing insects, the spider mite Tetranychus urticae (Koch) (Acari: Tetranychidae), which punctures parenchymal cells, and the aphid Myzus persicae (Sulzer) (Hemiptera: Aphidoidea), which is a phloem‐feeder. Compared with undamaged plants, C. rubecula females were more attracted to Arabidopsis plants infested by P. rapae, P. xylostella, S. exigua, or T. urticae, but not to plants infested by M. persicae. The parasitoids preferred host‐infested plants to spider mite‐ or aphid‐infested plants, but not to plants infested with non‐host caterpillars (P. xylostella or S. exigua). The data show that when Arabidopsis plants are infested with a leaf tissue‐damaging herbivore they emit a volatile blend that attracts C. rubecula females and the wasps only discriminate between a host and non‐host herbivore when the type of damage is different (chewing vs. piercing). When Arabidopsis is infested with a herbivore that hardly damages leaf tissue, C. rubecula females are not attracted. These results may be explained by differences in the amount of damage and in the relative importance of different signal‐transduction pathways induced by different types of herbivores.     

Interactions between white mealybugs and red spider mites sequentially colonizing coffee plants

Plants under herbivore attack often respond defensively by mounting chemical and physical defences. However, some herbivores can manipulate plant defences to their own benefit by suppressing the expression of induced defences. These herbivore‐induced changes specific to the attacking herbivore can either facilitate or impede the colonization and establishment of a second herbivore. Although recent studies have focused on the effect of multiple herbivory on plant induced response and the third trophic level, few have examined the ecological relevance of multiple herbivores sharing the host. Here, we investigated whether herbivory by the white mealybug Planococcus minor (Maskell) (Hemiptera: Pseudococcidae) or the red spider mite Olygonychus ilicis (McGregor) (Acari: Tetranychidae), two herbivores that peak in coffee plantations during the dry season, may facilitate the colonization and establishment of the other species in coffee plants. Dual‐choice arena tests showed that white mealybugs preferred mite‐infested over uninfested coffee plants as hosts. Fifteen days after the release of 50 first‐instar P. minor nymphs, greater numbers of nymphs and adults were found on mite‐infested than uninfested plants, indicating superior performance on mite‐infested plants. On the other hand, female red spider mites did not show clear preference between uninfested and mealybug‐infested plants and deposited similar numbers of eggs on both treatments. In a no‐choice test, red spider mites performed poorly on mealybug‐infested plants with a smaller number of eggs, nymphs, females and males found in mealybug‐infested plants relative to uninfested plants. Thus, our results indicate that coffee plants are more likely to be infested by the red spider mite before white mealybug, rather than the inverse sequence (i.e. mealybug infestation followed by red spider mites). Our findings are discussed in the context of plant manipulation reported for pseudococcid mealybugs and spider mites.     

The effect of the cassava green mite Mononychellus tanajoa on the growth and yield of cassava Manihot esculenta in a seasonally dry area in Kenya

The effect of the cassava green mite Mononychellus tanajoa on the growth and yield of cassava Manihot esculenta was studied over a 10-month period in two field trials near Lake Victoria in Kenya. One plot was maintained free of mites by means of acaricide, while the other was artificially infested.The highest population density of M. tanajoa occurred during the dry season. A maximum leaf area index (LAI) of about 2 was reached at the onset of the dry season. The total leaf area of mite infested plants was reduced compared with uninfested plants during the dry spell. During the following rainy season infested plants recovered and attained the same leaf area as uninfested plants. A multiple regression model predicting the leaf area showed that 58% of the seasonal variation could be explained by plant age, soil water, and leaf injury.The net growth rate of infested plants was lower than that of uninfested plants. Maximum values of 21 (infested plants) and 49 (uninfested plants) g m^-2 week^-1 were attained at the onset of the second rainy season. No difference was found between uninfested and infested plants with respect to net assimilation rates per unit leaf area during the dry season. The net assimilation rates reached a maximum almost at the same time as the growth rates, but the infested plants peaked slightly earlier and at a lower level than the uninfested plants. M. tanajoa did not affect the relative allocation of dry matter into stems and storage roots, but the absolute allocation of dry matter declined with increasing mite injury. Thus, after 10 months the dry matter of infested plants was reduced by 29% and 21% for storage roots and stems, respectively, compared with the uninfested plants.     

Effect of the carmine spider mite (Acarida: Tetranychidae) infestation and mechanical injury on the level of ABA in tomato plants

The aim of this study was to determine the changes in the abscisic acid (ABA) content in tomato leaves infested by the carmine spider mite (CSM) (Tetranychus cinnabarinus Boidsuval) and in leaves that were mechanically injured. It was also investigated whether signalling from stressed to non-stressed organs occurred. Tomato plants (Lycopersicon esculentum Mill.) cvs. Romatos and Slonka (with various susceptibility to CSM) were stressed at the stage of first cluster flowering by either CSM feeding (72 hours) or by mechanical puncturing simulated feeding injury by CSM (18 hours). It was found that under control condition the level of ABA differed significantly between cultivars, being always higher in plants of the susceptible cv. Romatos. In response to CSM feeding, the content of ABA in infested organs of the more tolerant plant (cv. Slonka) increased by 95 % but in the susceptible one by 11 % only. ABA content in the organs non-stressed by CSM feeding either increased (Slonka cv.) or decreased (Romatos cv.). In response to mechanical wounding, ABA content in directly injured organs increased but to a lower degree (49 %) and only in Slonka cv.. The same was true for ABA content in non-injured organs of damaged plants of this cultivar. Observed changes in ABA level in non-stressed organs are probably the results of signalling from stressed organs. Plant response measured by changes in ABA level to the stress generated by CSM feeding, was much stronger than merely by mechanical injury.     

Adaptive learning in arthropods: spider mites learn to distinguish food quality

Many herbivorous arthropods have been shown to possess learning capabilities, yet fitness effects of learning are largely unknown. In this paper, we test whether two-spotted spider mites (Tetranychus urticae) learn to distinguish food quality in choice tests, and whether this results in fitness benefits. Food consisted of cucumber plants with one of three degrees of feeding damage: undamaged (no mites), mildly damaged (infested by a mite strain adapted to tomato) and heavily damaged (infested by a mite strain adapted to cucumber). Mites were subjected to one choice test in a greenhouse and three sequential choice tests on leaf disks. Thereafter, individual mite performance was measured as oviposition rate over four days. In the course of the three small-scale choice tests, preference shifted towards less damaged food. The performance tests showed that learning was adaptive: mites learned to prefer the food type that yielded the higher oviposition rate. Interestingly, innate preferences in the greenhouse tests were close to those shown after learning in the small-scale tests. Given that both strains of mites had not experienced cucumber for several years, we hypothesize that the preference in the greenhouse was due to avoidance of mite odours rather than odours of damaged plants. Through its effect on foraging behaviour, adaptive learning may promote the evolution of host plant specialization in herbivorous arthropods.     

Effects of quantitative and qualitative differences in volatiles from host‐ and non‐host‐infested maize on the attraction of the larval parasitoid Cotesia kariyai

Cotesia kariyai Watanabe (Hymenoptera: Braconidae) is a specialist larval parasitoid of Mythimna separata Walker (Lepidoptera: Noctuidae). Cotesia kariyai wasps use herbivore‐induced plant volatiles (HIPVs) to locate hosts. However, complex natural habitats are full of volatiles released by both herbivorous host‐ and non‐host‐infested plants at various levels of intensity. Therefore, the presence of non‐hosts may affect parasitoid decisions while foraging. Here, the host‐finding efficiency of naive C. kariyai from HIPVs influenced by host‐ and non‐host‐infested maize [Zea mays L. (Poaceae)] plants was investigated with a four‐arm olfactometer. Ostrinia furnacalis Guenée (Lepidoptera: Crambidae) was selected as a non‐host species. One unit (1 U) of host‐ or non‐host‐infested plant was prepared by infesting a potted plant with five host or seven non‐host larvae. In two‐choice bioassays, host‐infested plants fed upon by different numbers of larvae, and various units of host‐ and non‐host‐infested plants (infestation units; 1 U, 2 U, and 3 U) were arranged to examine the effects of differences in volatile quantity and quality on the olfactory responses of C. kariyai with the assumption that volatile quantity and quality changes with differences in numbers of insects and plants. Cotesia kariyai was found to perceive quantitative differences in volatiles from host‐infested plants, preferring larger quantities of volatiles from larger numbers of larvae or plants. Also, the parasitoids discriminated between healthy plants, host‐infested plants, and non‐host‐infested plants by recognising volatiles released from those plants. Cotesia kariyai showed a reduced preference for host‐induced volatiles, when larger numbers of non‐host‐infested plants were present. Therefore, quantitative and qualitative differences in volatiles from host‐ and non‐host‐infested plants appear to affect the decision of C. kariyai during host‐habitat searching in multiple tritrophic systems.     

Impact of the erineum strain of <Emphasis Type="Italic">Colomerus vitis</Emphasis> (Acari: Eriophyidae) on the development of plants of grapevine cultivars of Iran

The present experiment was aimed at determining the influence of the grape erineum strain of Colomerus vitis (GEM) (Acari: Eriophyidae) on responses of local grapevine cultivars. GEM was applied at five density levels to each of five cultivars, i.e. Shahani, Sahebi Uroomie, Khalili Bovanat, Rishbaba and Sezdang Ghalat (listed from early to late grape ripening). The experiment was performed in a full factorial design (12 replicates each) and effects of the mite on the relative content of leaf chlorophyll, internode and cane length, leaf area and weight, number and size of the erinea, and percentage of leaves with erinea were investigated. Also mite density on leaves and in buds was assessed. Data were analyzed with a two-way ANOVA followed by Tukey’s test to separate means among treatment levels and cultivars. The relative content of chlorophyll (expressed in Spad units) in infested leaves was reduced along with an increase in mite density and it was shown to be highly significant at the two higher mite density levels for Khalili Bovanat, Rishbaba and Sezdang Ghalat; Shahani and Sahebi Uroomie leaves appeared to be less affected by mite infestation. The highest mite density treatment displayed a strong correlation with weight (positive correlation) and size (negative correlation) of the leaves of four cultivars; leaves of Sahebi Uroomie appeared to be less affected. The reduced internode length was weak in infested plants. Most infested plants produced shorter canes and their lengths appeared to have a strong negative correlation with the highest mite density in four cultivars; canes of Sahebi Uroomie did not appear affected. At the highest mite density, canes of Khalili Bovanat and Sahebi Uroomie displayed the most and the least shortening effects, respectively. The percentage of leaves with erinea, as well as the number of erinea per leaves and the diameter of erinea increased along with the mite population density. The mite densities in buds (April 2014) and on leaves with erinea (in November 2013) were higher at the highest treatment level in the medium-late (Rishbaba) and late ripening (Sezdang Ghalat) cultivars, than in the early and early-medium ripening ones. Almost all data collected in the current experiment allowed the conclusion that Sahebi Uroomie and Shahani were less affected than the other cultivars (Khalili Bovanat, Rishbaba and Sezdang Ghalat).     

The aetiology and development of damage in young fruit trees infested with fruit tree red spider mite, Panonychus ulmi (Koch)

Infestations of fruit tree red spider mite, Panonychus ulmi (Koch) altered the growth of young plants of plum and apple. At first, damage to the leaves from mite feeding did not affect their photosynthetic rates. The effects on other processes depended on the density of the infestation. Densities of 1–2 mites/cm² of leaf decreased the rate of shoot extension of Brompton plum, but about 0.5 mite/cm² increased it. Less dense infestations apparently caused no damage. The rate of growth of the leaf area of a plant relative to that of the mite population on it determined changes in the mite density, and therefore the effects of infestation. The growth of the root system was decreased before that of the shoots. Later, when some leaves were severely damaged photosynthesis was decreased. The onset and severity of this phase probably depended on the number of mites and days of feeding on individual leaves. The later-formed leaves were smaller, and sometimes fewer on infested plants. Some plants were infested with too low a density of mites to decrease shoot extension, but grew less in dry weight because of decreased photosynthesis later in the season. The initial effects are ascribed to an imbalance in the growth controlling substances caused by feeding. Radioactivity was detected in the growing regions of plants remote from mature leaves on which ¹⁴C-labelled mites were confined.     

Olfactory responses of Neoseiulus cucumeris (Acari: Phytoseiidae) to odors of host plants and Frankliniella occidentalis (Thysanoptera: Thripidae)�Cplant complexes

We studied the olfactory responses of Neoseiulus cucumeris (Acari: Phytoseiidae) to odors from eggplant (Solanum melongena L.), pepper (Capsicum aunuum), and tomato (Solanum lycopersicum), three host plants, and their complexes with different treatments (undamaged, mechanically damaged, infested, pre-infested) in an olfactometer. The results showed that N. cucumeris preferred the odors of undamaged eggplant, pepper, and tomato to clean air. N. cucumeris preferred the volatiles from eggplant infested with Frankliniella occidentalis (Thysanoptera: Thripidae) over undamaged, mechanically damaged, and pre-infested with F. occidentalis eggplant volatiles. The same results were observed with pepper and tomato. N. cucumeris adults preferred the odors of undamaged eggplant and tomato to undamaged pepper. Similarly, same results were observed with mechanically damaged eggplant, pepper, tomato, and same plants pre-infested with F. occidentalis. Compared with odors of tomato infested with F. occidentalis, N. cucumeris adults significantly responded to odors of eggplant and pepper infested with F. occidentalis. There was no significant difference of N. cucumeris in making choice between eggplant infested with F. occidentalis and pepper infested with F. occidentalis.     

Effects of cultivar and irrigation management on population growth of the twospotted spider mite Tetranychus urticae on greenhouse ivy geranium

Greenhouse experiments were conducted to determine whether different ivy geranium cultivars and different irrigation frequencies influenced population growth of the twospotted spider mite (TSM), Tetranychus urticae. Results showed that mite numbers at harvest (about 4 weeks after plants were artificially infested) were very low on 'Sybil Holmes', but significantly higher on 'Amethyst 96'. Irrigation frequency of ivy geraniums had no measurable effect on TSM populations over a range in which water was applied when pot weight dropped 15, 30 or 45% from container capacity. However, the most frequently irrigated plants (15% treatment) produced as much or more growth than plants that received less water. These plants also had the lowest incidence of oedema. There was no significant interaction between water management and host plant resistance, implying the difference in host plant resistance to TSM between the two cultivars should remain constant, at least within the range of the irrigation frequencies studied. Our findings suggest that growers can take advantage of plant resistance to TSM on ivy geranium cultivars of current commercial importance, and that watering practices can be adjusted to optimize plant production without affecting pest populations.