Laboratory efficacy of mycoparasitic fungi(Aspergillus tubingensis and Trichoderma harzianum) against tropical bed bugs(Cimex hemipterus)(Hemiptera:Cimicidae)

Objective: To test the effectiveness of conidial spore formulations [Aspergillus tubingensis(A.tubingensis) and Trichoderma harzianum(T.harzianum)] against tropical bed bugs, Cimex hemipterus.Methods: Spore formulations were made from two fungal strains, T.harzianum and A.tubingensis.The bed bugs were exposed to the conidial spores placed soaked onto a fabric cloth for 1 h and the mortality counts were recorded daily until 14 days.Results: Mean survival times based on Kaplan–Meier survival analysis showed no significant differences between all the concentrations in both the fungal isolates:T.harzianum and A.tubingensis.However, the evaluation of both the isolates in terms of virulence resulted in low lethal hours in all the concentrations except for the high concentration of A.tubingensis(LT_(50)= 44.629 h) at the conidial exposure of 1 × 10~6 spores/mL.Rapid mortality of the bed bugs was observed from Day 6 to Day 12, ranging from 13% to 90% in all three concentrations of A.tubingensis.With reference to the T.harzianum exposure, the concentration of 1 × 10~4 spores/mL displayed a gradual increase in the percentage mortality of 90 on Day 14.Conclusions: Approaches to the bed bugs treatment should be explored in-depth using a natural biological agent like fungus especially A.tubingensis to reduce this pest population, in order to replace chemical methods.

Morphological and molecular characterization of fungus isolated from tropical bed bugs in Northern Peninsular Malaysia, Cimex hemipterus(Hemiptera: Cimicidae)

Objective:To investigate some morphological and molecular characteristics of fungal parasites isolated from wild tropical bed bug, Cimex hemipterus.Methods: A series of culture methods were used to obtain fungal isolates from i eld-collected bed bugs. Characteristics of the isolates such as colony appearance, mycelial texture and pigmentation were studied to explore their morphology. Isolates were also subjected to a PCRbased genotyping test.Results: There were noticeable dif erences in morphological characteristics among the four isolates. Conidial areas of one isolate were dark green, whereas those of the remaining colonies were olive-green, black or dark brown. Conidia of the dark green isolate were globose, while those of olive-green, black and dark brown isolates were globose to subglobose, globose to spherical and globose to subglobose/i nely roughened, respectively. These morphological specii cities and the molecular analyses showed that the fungal internal transcribed spacer ribosomal region and β-tubulin gene sequences of the isolates shared clade with Trichoderma and Aspergillus sequences.Conclusions: Overall, the new discovery of common pathogens in agricultural i eld developed in live bed bugs storage tank may initiate the use of biological agents in later years.

臭虫击倒抗性基因突变检测及抗性测定

近20多年,臭虫(Cimex spp.)在世界范围内成为常见的卫生害虫,其防治主要采用化学防治,但很多种群发现击倒抗性(Knockdown resistance gene,kdr)基因突变的存在以及抗药性。监测kdr的发生频率以及不同种群对农药的抗性对臭虫有效防治很重要,但我国对臭虫种群的抗药性报道很少。本试验采用点滴法测定了1个温带臭虫Cimex lectularius野外种群对氯虫苯甲酰胺、呋虫胺、吡虫啉、噻虫嗪和高效氯氰菊酯等5种药剂的毒性及抗性水平,使用区分剂量快速鉴定抗性方法对2个温带臭虫和2个热带臭虫Cimex hemipterus种群对高效氯氰菊酯的抗性水平进行了检测,此外用PCR方法检测8个臭虫地理种群(1个温带臭虫实验室种群,1个温带臭虫野外种群和6个热带臭虫野外种群)174个个体的kdr突变频率。点滴法结果表明,5种杀虫剂对温带臭虫的毒性是吡虫啉和呋虫胺>噻虫嗪>氯虫苯甲酰胺和高效氯氰菊酯,测试的野外温带臭虫种群仅对噻虫嗪无明显抗性。热带臭虫2个野外种群对高效氯氰菊酯的抗性均远高于温带臭虫。在温带臭虫的实验室种群中未检测到突变,在野外种群中检测到了V419L和L925I突变,可分为2种基因型类型(A:无突变位点;B:同时有L925I和V419L),而在热带臭虫的6个种群检测到M918I和L1014F突变,只有1种基因型类型,即M918I和L1014F双位点突变。温带臭虫1个野外种群及热带臭虫6个野外种群kdr突变的存在与臭虫对高效氯氰菊酯敏感密切关联。基于kdr基因突变检测结果推测我国臭虫种群广泛存在对拟除虫菊酯的抗性。