西花蓟马的鉴别及其与近缘种的区别

西花蓟马是我国2 0 0 3年在北京新发现的外来入侵害虫,因虫体很小鉴定困难。该文提供了西花蓟马详细的形态鉴别特征,同时给出了与西花蓟马相似的烟蓟马、花蓟马和佛罗里达花蓟马共4种花蓟马的鉴定检索表。     

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.     

防治西花蓟马的病原真菌-白僵菌微菌核的液体培养

微菌核是许多植物病原真菌产生的越冬结构,目前还没有关于白僵菌微菌核的报道。用含不同氮源的介质培养出了2株白僵菌菌株,RSB和SZ21的微菌核。在液体培养条件下,2株菌株不仅能产生典型的芽孢和菌丝,还能产生微菌核。在以玉米粉(RSB和SZ21菌株分别为6.5×102和6.3×102mL-1)为氮源的介质中产生的微菌核浓度高于以大豆粉(RSB和SZ21菌株分别为2.5×102和2.2×102mL-1)为氮源的介质。菌株SZ21产生的芽孢浓度(在以大豆粉和玉米粉为氮源的介质中,分别为17.9×105和7.4×105L-1)高于RSB菌株的芽孢浓度(在以大豆粉和玉米粉为氮源的介质中,分别为14.8×105和6.2×105L-1)。含有硅藻土的微菌核制剂能在真空干燥(<5%湿度)后存活下来,并且对于活力没有显著影响。干燥后的微菌核颗粒在水洋菜培养基上复水和培养后,能够萌发菌丝和产生高浓度的分生孢子。将微菌核颗粒预混到土壤中能引起西花蓟马Frankliniella occidentalis(Pergande)土栖阶段的高死亡率。这是首次报道白僵菌的微菌核的培养,并为用虫生真菌防治土栖昆虫提供了一个新的方法。     

Evaluation of the nematodes Steinernema feltiae and Thripinema nicklewoodi as biological control agents of western flower thrips Frankliniella occidentalis infesting chrysanthemum

In greenhouse studies, we evaluated a commercial formulation of the entomopathogenic nematode Steinernema feltiae and the inoculative release of the thrips-parasitic nematode Thripinema nicklewoodi against western flower thrips (WFT), Frankliniella occidentalis Pergande infesting potted chrysanthemums. Foliar sprays of S. feltiae applied at 1.25-2.5×10³ IJ mL^-1 and 1000 - 2000 L ha^-1 at 3-day intervals alone (targeting feeding stages) or in combination with soil applications (simultaneously treating non-feeding stages in the soil at the same rates) decreased but did not provide adequate control of thrips in flowering plants artificially infested with a dense population. Similar nematode treatments applied for four to five applications at 6-day intervals in two batches of initially clean chrysanthemums failed to prevent unacceptable damage to flowers and leaves from a dense natural infestation within the greenhouse. Although some IJ survived up to 48 h within flowers and flower buds, few nematode-infected thrips (larvae and adults) were recovered. In studies with T. nicklewoodi (which is not amenable for mass production), the inoculative releases of two parasitized hosts per plant enabled the nematode to become established within existing WFT populations under greenhouse conditions. However, relatively poor transmission and slow speed of kill (nematode primarily suppresses populations through host sterilization) prevented low level inoculations being effective over a single crop cycle. Further studies showed that transmission of T. nicklewoodi persisted for nine host generations, infected up to 83% of adult thrips and provided long-term suppression of discrete caged populations, but only after uneconomically high thrips densities had been reached.     

利用冷冻切片对球孢白僵菌侵染西花蓟马过程的观察

为探索球孢白僵菌对西花蓟马的侵染,研究球孢白僵菌在西花蓟马体表和虫体内的侵染过程,采用冷冻切片与HE染色技术,对被球孢白僵菌侵染的西花蓟马成虫进行组织切片及HE染色。结果表明,接菌4 h,体表粘附的孢子开始萌发,8-12 h芽管继续伸长并出现穿透体壁。18 h虫菌体出现在西花蓟马体内,球孢白僵菌成功侵入西花蓟马体内。之后,西花蓟马体内虫菌体、菌丝明显增多,各组织器官均受到感染,消化道、肌肉组织等发生病变。     

Increased damage by western flower thrips Frankliniella occidentalis in chrysanthemum intercropped with subterranean clover

Suppressive effects of intercropping on Frankliniella occidentalis (Pergande) infestations have been reported in several crops. However, this study demonstrates that in year-round chrysanthemum, Dendranthema grandiflora Tzvelev, undersowing with subterranean clover, Trifolium subterraneum L., results in an increased thrips feeding damage. In a pot experiment, performed with chrysanthemum plants (cultivars Reagan and Tiger) grown with or without subterranean clover, significantly more leaves with silver and growth damage were found in the chrysanthemum plants with subterranean clover in comparison with the monocropped chrysanthemum plants. Similarly, the degree of deformation of leaf perimeter and leaf surface was higher in the top leaves of the intercropped chrysanthemum plant. In the soil experiment (only performed with Tiger and plants were grown in the soil in the greenhouse) intercropped chrysanthemum plants suffered a higher feeding damage as well. Analysis of the relation between silver or growth damage and the thrips pressure demonstrates that at similar thrips pressure in the intercropped chrysanthemum plants suffered significantly more damage. The higher thrips pressure in the intercropped chrysanthemum only explains the differences in damage partly. Changes in the reaction of chrysanthemum plants to thrips feeding or in the behaviour of the thrips, mediated by the presence of the non-host crop, are discussed. Our explanation is that chrysanthemum plants grown with clover are more susceptible to thrips feeding than monocropped plants. We conclude that undersowing with clover does not contribute to reduce damage by F. occidentalis in year-round chrysanthemum. Also, the influence of crop diversification on a pest cannot be foreseen until the specific characteristics of each individual crop – pest system are studied.     

Host age and pathogen exposure level as factors in the susceptibility of the house fly,Musca domestica (Diptera: Muscidae) to Beauveria bassiana

Adult house flies, Musca domestica L., of four ages, <1, 3, 7, and 14 day post-eclosion, were exposed to three strains of Beauveria bassiana (P89, L90 and 447). Flies were exposed to moistened filter paper treated with either a low (1.57×10⁴ conidia/cm²) or high (1.57×10⁵ conidia/cm²) concentration of each fungal strain for 6 h. Strain 447 was superior to the two house fly-derived B. bassiana strains in inducing host infection and mortality. Significant spikes in infection and mortality occurred as early as 5 days post-exposure with higher concentration exposures acting more quickly. Few differences were observed in either infection or mortality among the four fly age classes. On Day 10 post-exposure, 77% of the high-concentration, 447-exposed flies were infected, compared with only 24% of the flies from the P89 low-concentration exposure. Potential applications of these results in integrated house fly management programs are discussed.     

A new Y-tube olfactometer for mosquitoes to measure the attractiveness of host odours

The behavioural responses of flying western flower thrips (Frankliniella occidentalis Pergande) (Thysanoptera: Thripidae) to the colour yellow and the odour anisaldehyde were examined. In a wind tunnel, upwind flight by female thrips was common in an airflow of 0.11 m s^–1 but was impeded at 0.22 m s^–1. In the absence of anisaldehyde, flying female thrips exhibited an oriented response towards a yellow cue in the wind tunnel at a wind speed of 0.11 m s^–1. The main response of females to anisaldehyde in the wind tunnel was flight inhibition. There was no evidence of an odour-induced visual response, an odour-induced anemotactic response or chemotaxis by female thrips to anisaldehyde in wind tunnel bioassays, but chemokinesis was implicated. With a matrix of yellow or black water traps with and without anisaldehyde in a greenhouse sweet pepper crop, yellow traps with anisaldehyde caught more thrips adults than yellow traps without anisaldehyde, black traps with anisaldehyde and black traps without anisaldehyde (1.3, 28 and 721 times for males respectively and 2.4, 9 and 117 times for females, respectively). Differences between respective traps were statistically significant in almost all cases. Trapping experiments using a centre-baited trap design to reduce the interaction of anisaldehyde between baited and unbaited traps were undertaken in tomato and sweet pepper greenhouse crops. When the spatial distribution of the thrips adult population within the greenhouse was taken into account, yellow water traps with anisaldehyde caught between 11 and 15 times more female and 3 and 20 times more male F. occidentalis adults than yellow traps without anisaldehyde.     

Selection of promising fungal biological control agent of the western flower thrips Frankliniella occidentalis (Pergande)

Aims: Larval stages of Frankliniella occidentalis are known to be refractory to fungal infection compared with the adult stage. The objective of this study was to identify promising fungal isolate(s) for the control of larval stages of F. occidentalis. Methods and Results: Ten isolates of Metarhizium anisopliae and eight of Beauveria bassiana were screened for virulence against second‐instar larvae of F. occidentalis. Conidial production and genetic polymorphism were also investigated. Metarhizium anisopliae isolates ICIPE 7, ICIPE 20, ICIPE 69 and ICIPE 665 had the shortest LT₅₀ values of 8·0–8·9 days. ICIPE 69, ICIPE 7 and ICIPE 20 had the lowest LC₅₀ values of 1·1 × 10⁷, 2·0 × 10⁷ and 3·0 × 10⁷ conidia ml^?1, respectively. Metarhizium anisopliae isolate ICIPE 69 produced significantly more conidia than M. anisopliae isolates ICIPE 7 and ICIPE 20. Internally transcribed spacers sequences alignment showed differences in nucleotides composition, which can partly explain differences in virulence. Conclusion: These results coupled with the previous ones on virulence and field efficacy against other species of thrips make M. anisopliae isolate ICIPE 69 a good candidate. Significance and Impact of the Study: Metarhizium anisopliae isolate ICIPE 69 can be suggested for development as fungus‐based biopesticide for thrips management.     

House fly (Musca domestica) (Diptera: Muscidae) mortality after exposure to commercial fungal formulations in a sugar bait†

House flies are pests of medical and veterinary importance. They are known to be susceptible to fungal conidia presented in sugar baits. The purpose of this study was to evaluate the potential for commercial formulations of entomopathogenic fungi to be used as bait for fly control. Differences in sporulation by product were found. Current formulations may influence fly feeding on baits, but because formulations may protect conidia. Additional research into more attractive formulations is warranted.     

Beauveria bassiana for the control of Sunn Pest (Eurygaster integriceps) (Hemiptera: Scutelleridae) and aspects of the insect's daily activity relevant to a mycoinsecticide

A series of investigations was carried out at ICARDA during April-June 2004 and May-June 2005 to investigate the use of the entomopathogenic fungus Beauveria bassiana to control Eurygaster integriceps and to determine aspects of the insect's biology that could be relevant to control with the fungus. Application in 2004 of an oil-based formulation of B. bassiana showed distribution of the spray decreasing from the top of the wheat to the bottom, although the proportion of tillers with coverage at the base was still 80%. Seventy percent of Sunn Pest had received direct hits, with the highest amount on the dorsal surface, followed by the ventral surface, then the legs and antennae. Mortality of field-treated, then laboratory-maintained insects, ranged from 47.6% for insects exposed only to the B. bassiana spray, 74.2% for unsprayed insects exposed to treated wheat and 86.4% for insects receiving direct spray and being exposed to treated wheat. Some field results demonstrated mortality. Mortality assessments following the 2005 treatments were conducted solely in the field, there was no apparent effect upon Sunn Pest numbers. The majority of studies on Sunn Pest biology were carried out on untreated insects outside the trial plots. Different assessment methods resulted in varying estimates of adults and juveniles in the field. The numbers of Sunn Pest found and the proportion of these at the top of the wheat crop, declined after early morning and increased again in the early evening, suggesting sheltering deeper in the crop or in the soil during the middle part of the day. Mobility and location of marked insects was followed in micro-plots and by mark and recapture studies, demonstrating a range of activities, from movement around the crop for a number of metres, including contact with numerous tillers to almost total immobility; Sunn Pest generally avoided movement on the soil. The potential for Sunn Pest control with a mycoinsecticide and how Sunn Pest behaviour is relevant to a mycoinsecticide application are discussed.