Cross‐resistance of chrysanthemum to western flower thrips,celery leafminer,and two‐spotted spider mite

Chrysanthemum [Chrysanthemum × morifolium Ramat. (Asteraceae)] is one of the economically most important greenhouse ornamentals worldwide. A major constraint in chrysanthemum production is adequate pest management, requiring the use of different tactics, such as improving host plant resistance, in the framework of an integrated pest management (IPM) approach. In this study, we investigated cross‐resistance of chrysanthemum to its three major pests: western flower thrips [Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae)], celery leafminer [Liriomyza trifolii (Burgess) (Diptera: Agromyzidae)], and two‐spotted spider mite [Tetranychus urticae Koch (Acari: Tetranychidae)]. We quantified resistance to each pest by performing greenhouse bioassays with a broad range of chrysanthemum types from commercial germplasm provided by Dutch breeding companies. Considerable variation was detected among the chrysanthemum cultivars in thrips silver damage and growth damage, leafminer damage, measured as number of mines and pupae, and spider mite numbers and damage. We observed significant positive correlations between thrips damage (both silver and growth damage) vs. leafminer numbers (both mines and pupae), and between leafminer numbers (both mines and pupae) vs. spider mite numbers. Our results indicate an overlap in resistance to all three herbivores. The important implications of this result for chrysanthemum breeding are discussed.     

<Emphasis Type="Italic">Wolbachia</Emphasis>-induced cytoplasmic incompatibility in Japanese populations of <Emphasis Type="Italic">Tetranychus urticae</Emphasis> (Acari: Tetranychidae)

Intracellular bacteria of the genus Wolbachia (alpha Proteobacteria) induce cytoplasmic incompatibility (CI) in many arthropod species, including spider mites, but not all Wolbachia cause CI. In spider mites CI becomes apparent by a reduced egg hatchability and a lower daughter:son ratio: CI in haplodiploid organisms in general was expected to produce all-male offspring or a male-biased sex ratio without any death of eggs. In a previous study of Japanese populations of Tetranychus urticae, two out of three green-form populations tested were infected with non-CI Wolbachia strains, whereas none of six red-form populations harbored Wolbachia. As the survey of Wolbachia infection in T. urticae is still fragmentary in Japan, we checked Wolbachia infection in thirty green-form populations and 29 red-form populations collected from a wide range of Japanese islands. For Wolbachia-infected populations, we tested the effects of Wolbachia on the reproductive traits and determined the phylogenetic relationships of the different strains of Wolbachia. All but one green-form populations were infected with Wolbachia and all strains belonged to the subgroup Ori when the wsp gene was used to determine the phylogenetic relationships of different strains of Wolbachia. Six out of 29 red-form populations harbored Wolbachia and the infected strains belonged to the subgroups Ori and Bugs. Twenty-four of 29 infected green-form populations and five of six infected red-form populations induced CI among the hosts. Thus, CI-Wolbachia strains are widespread in Japan, and no geographical trend was observed in the CI-Wolbachia. Although three red-form populations harbored other intracellular bacteria Cardinium, they did not affect host reproduction.     

Acaricidal activity of spinosad and abamectin against two-spotted spider mites

Spinosad is a bioinsecticide with a high degree of selective toxicity towards insects of different orders, but its toxicity towards the two-spotted spider mite (TSSM), Tetranychus urticae Koch (Acari: Tetranychidae) is under debate. In this study, we compared the acaricidal properties of spinosad with the commercial bioacaricide abamectin on the life stages of TSSM. Adulticide and ovicide bioassays were performed on a susceptible laboratory strain using direct spraying of leaf disks with five rates of spinosad (20, 25, 30, 35 and 40 mg/l), five rates of abamectin (0.125, 0.25, 0.5, 1 and 2.5 mg/l), sublethal concentrations or a combination of spinosad and abamectin. Both adulticidal and ovicidal effects of spinosad against T. urticae in the laboratory were apparent, based on morality rates of the adults, reduction of female fecundity and death of offspring. Abamectin was also found to significantly reduce female fecundity and killed offspring when applied directly on the eggs. Interestingly, sublethal concentrations of spinosad reduced female fecundity stronger than abamectin. When a mixture of spinosad and abamectin was applied at LC_50, mortality was 74%, fecundity reduction was comparable to abamectin alone and egg hatching rate was lower than by either compound alone. In conclusion, spinosad was more harmful than abamectin for TSSM life stages and the combined application is recommended.     

Spider mite (Acari: Tetranychidae) mitochondrial COI phylogeny reviewed: host plant relationships,phylogeography, reproductive parasites and barcoding

The past 15 years have witnessed a number of molecular studies that aimed to resolve issues of species delineation and phylogeny of mites in the family Tetranychidae. The central part of the mitochondrial COI region has frequently been used for investigating intra- and interspecific variation. All these studies combined yield an extensive database of sequence information of the family Tetranychidae. We assembled this information in a single alignment and performed an overall phylogenetic analysis. The resulting phylogeny shows that important patterns have been overlooked in previous studies, whereas others disappear. It also reveals that mistakes were made in submitting the data to GenBank, which further disturbed interpretation of the data. Our total analysis clearly shows three clades that most likely correspond to the species T. urticae, T. kanzawai and T. truncatus. Intraspecific variation is very high, possibly due to selective sweeps caused by reproductive parasites. We found no evidence for host plant associations and phylogeographic patterns in T. urticae are absent. Finally we evaluate the application of DNA barcoding.     

不同生长时期黄花蒿提取物对朱砂叶螨的生物活性

选用不同生长时期(4、5和6月)黄花蒿的根、茎、叶,采用30℃～60℃石油醚、60℃～90℃石油醚、乙醇、丙酮和水溶剂等溶剂,用顺序和平行提取方法获得81种提取物,测定其对朱砂叶螨的生物活性,同时,将81种提取物分别稀释至5mg.ml-1,测定其对朱砂叶螨的触杀毒力。结果表明:在杀螨活性方面,黄花蒿的杀螨活性随植株的生长呈增加的趋势,总体表现为6月>5月>4月。6、5和4月黄花蒿叶的丙酮平行提取物活性最强,5mg.ml-1浓度处理48h对朱砂叶螨的校正死亡率为74%～86%,它们对朱砂叶螨的致死中浓度(LC50)分别为0.84、0.94和1.38mg.ml-1;处理浓度为5mg.ml-1时,它们的致死中时(LT50)分别为24.61、27.63和37.23h。     

温度对拟小食螨瓢虫捕食皮氏叶螨成螨功能反应的影响

在5个温度(16℃、20℃、24℃、28℃和32℃)条件下,测定了拟小食螨瓢虫雌成虫对皮氏叶螨成螨的捕食功能反应。结果表明,在试验温度范围内,各温度下的功能反应均能用Holling圆盘方程(Ⅱ型)拟合,但各温度间功能反应的参数存在差异。以瞬时攻击率和捕食处理时间为评价指标,在16℃～28℃,拟小食螨瓢虫雌成虫对皮氏叶螨成螨的捕食效能随温度的上升而提高,28℃时达到最高,此时的瞬时攻击率和捕食处理时间分别为0.5899和0.0169d。温度上升至32℃时,捕食效能略为下降,此时的瞬时攻击率和捕食处理时间分别为0.5740和0.0184d,与28℃时的瞬时攻击率和捕食处理时间差异不显著。表明较高温度有利于拟小食螨瓢虫发挥对皮氏叶螨成螨的控制作用。在试验的密度和温度范围内,以三次多项方程描述了在不同猎物密度和温度组合下拟小食螨瓢虫雌成虫对皮氏叶螨成螨的捕食作用,以软件Surfer8.0生成了皮氏叶螨成螨密度和温度组合下的拟小食螨瓢虫雌成虫捕食量模拟值等值线图。同时,还对拟小食螨瓢虫在热带作物害虫生物防治中的应用潜力进行了讨论。     

瑞香狼毒根提取物对山楂叶螨的生物活性

采用不同的生物活性测定方法比较了瑞香狼毒(Stellera chamaejasme L.)根部4种不同溶剂提取物的杀螨活性。结果表明,瑞香狼毒根提取物对山楂叶螨(Tetranychus viennensis Zacher)有很好的触杀和内吸活性。在触杀活性测试中,石油醚提取物和氯仿提取物的杀螨活性最高;在内吸作用中,乙醇、氯仿和石油醚提取物的杀螨活性均较高,杀螨效果显著。在对石油醚提取物的不同溶剂萃取物进行生物活性追踪测定中发现,石油醚萃取物和氯仿萃取物具有较高的生物活性,浓度为0.6 g.L-1,山楂叶螨的24 h校正死亡率分别达到93.22%和79.66%。     

Interactions of two natural enemies of Tetranychus evansi, the fungal pathogen Neozygites floridana (Zygomycetes: Entomophthorales) and the predatory mite, Phytoseiulus longipes (Acari: Phytoseiidae)

Tetranychus evansi is an exotic pest of Solanaceous crops in Africa discovered in Zimbabwe in 1979. Two natural enemies, the predatory mite Phytoseiulus longipes and the fungal pathogen Neozygites floridana are important causes of mortality in T. evansi populations in Brazil. The first part of this study assessed the effects of N. floridana on predation and oviposition of P. longipes fed on N. floridana infected T. evansi and T. urticae. No N. floridana hyphal bodies were found in P. longipes after this feeding, demonstrating that N. floridana is not pathogenic to P. longipes and does not affect its oviposition. The second part of the study investigated the time spent on searching for and consuming of eggs on leaf discs with and without N. floridana capilliconidia. Both the searching and the feeding time on the first egg were similar on leaf discs with and without capilliconidia. When P. longipes was offered the choice of feeding on eggs on leaf discs with or without capilliconidia, the numbers of eggs consumed were not different. The only N. floridana effect observed on P. longipes was reduced egg predation. In addition, increased time spent grooming on leaf discs with capilliconidia was observed. P. longipes was efficient in removing most capilliconidia attached to the body through self-grooming behavior. This suggests that although the predator did not avoid areas with capilliconidia, it detected and removed most capilliconidia attached to the body. Increased grooming may account for the lower egg predation rates.     

三唑锡亚致死浓度对土耳其斯坦叶螨运动速率的影响

【目的】通过研究三唑锡亚致死浓度LC10、LC20及致死中浓度LC50对土耳其斯坦叶螨Tetranychus turkestani运动速率的影响,为杀螨剂对土耳其斯坦叶螨在行为学方面影响提供科学依据,并将此作为评价药剂的作用机理的理论依据。【方法】采用叶片浸渍法,明确致死中浓度和亚致死浓度,使用LC-100昆虫行为记录仪对土耳其斯坦叶螨在受到三唑锡亚致死浓度LC10、LC20和LC50刺激下其运动速率进行记录,观察其运动速率在三唑锡不同浓度、不同天数、不同时间段的变化规律。【结果】在三唑锡不同亚致死浓度作用下,第1天到第3天的10:00―12:00,其运动速率比对照低,从第3天10:00―12:00期间到第5天20:00―22:00期间,其运动速率与对照没有显著性差异。在相同亚致死浓度作用下,第1天10:00―12:00期间,土耳其斯坦叶螨的运动速率显著高于15:00―17:00期间和20:00―22:00期间,而在第3天和第5天的3个时间段,对土耳其斯坦叶螨的运动速率没有显著影响。当作用的时段不同时,LC10第1天10:00―12:00显著高于第3天和第5天,而LC20、LC50在10:00―12:00没有显著性差异。三种浓度的第1天15:00―17:00显著低于第3天和第5天。第3及第5天20:00―22:00没有显著性差异。【结论】总体来看,3唑锡亚不同致死浓度对土耳其斯坦叶螨的运动速率影响受浓度、时间影响,浓度越高土耳其斯坦叶螨运动速率越慢;随着时间延长,农药亚致死浓度对土耳其斯坦叶螨的运动速率基本没有影响。