An in vitro feeding assay to test acaricides for control of hard ticks

Animal husbandry could not be practised over large areas of the planet without acaricides. The prevention of tick bite and the transmission of diseases requires the use of pesticides, but this contributes to the development of tick resistance against acaricides. This drives the quest for new molecules that target physiological processes crucial to tick survival. In vivo trials involve multiple repetitions because of inherent variations between host animals, requiring large amounts of test products and ticks. An in vitro alternative should permit the testing of the ability of a product to restrict attachment and feeding by ticks at precise doses. In this paper an in vitro feeding system is described where the European tick Ixodes ricinus L. feeds on blood through a cellulose rayon-reinforced silicone membrane. The membrane Shore hardness is modified to imitate the elastic retraction forces of skin that ensure the closing of tick penetration sites on the membrane to prevent bleeding. Tick attachment (75-100%) is achieved by adding chemical and mechanical stimuli to the membrane. Survival curves for different doses of fipronil and ivermectin tested with the method showed highly reproducible acaricide effects within 5-7 days. Significant effects are recorded down to ppb levels in blood. Standardised tests can be made with blood from the same donor animal or culture medium under the membrane.     

Encounter the poultry red mite resistance to acaricides in Czechoslovak poultry-farming

Poultry red mite susceptibility to permethrin, deltamethrin, tetramethrin, trichlorfon, fenitrothion, carbaryl and DDT, respectively, was screened within the territory of Bohemia by a method of diagnostic doses. The survey indicated widely spread resistance to DDT; in a few cases ineffectivity of permethrin, tetramethrin and trichlorfon, respectively, was also documented.     

Inhibition of oviposition in the cattle tick Boophilus microplus by certain acaricides

Doses of ten acaricides, ranging from 2.5 to 10 μg, induced about 10-60% mortality and inhibited oviposition in engorged Boophilus microplus as well as preventing larval hatching from the eggs. The effects of the acaricides were dose dependent. The efficacy of acaricides in reducing the reproductive potential (inhibition of oviposition × inhibition of hatching/100) was in the following order: dimethoate > dioxathion > naled > diazinon > chlordimeform > carbaryl > trichlorphon > phosphamidon > gamma-HCH > fenitrothion. Most of the acaricides also retarded the oviposition cycle, delaying the peak activity by 4-8 days. The ovarian development in control ticks reached its peak between the 5th and 7th days before decreasing gradually and ceasing completely between the 16-20th days after engorgement. The protein content of the ovaries and the rate of incorporation of [¹⁴C]glycine into the tissues followed a similar pattern. Carbaryl, fenitrothion and naled inhibited these activities. Chlordimeform stimulated [¹⁴C]glycine incorporation and increased the ovarian protein content up to the 13th day before resorption of the oocytes. The eggs from treated ticks were mostly non-viable and contained more protein; those from dioxathion, carbaryl and chlordimeform treatments had a higher dry weight than the control.     

8种杀螨剂对苹果树红蜘蛛田间防效评价

对8种不同作用机理杀螨剂防治苹果树红蜘蛛的效果进行了田间试验。结果表明：三唑锡、炔螨特、哒螨灵、阿维菌素、唑螨酯、螺螨酯、双甲脒、甲氰菊酯均是防治苹果树红蜘蛛的有效药剂,以螺螨酯的总体防效最好。     

两种生测方法对杀螨剂毒力测定结果的影响比较

通过室内生物测定 ,研究了不同测定方法对杀螨剂毒力测定结果的影响 ,明确了应用叶片残毒法测定的药剂对害螨毒力高于玻片浸渍法测定的结果 ,且对不同药剂差异程度不同     

常用杀螨剂与顶孢霉Ahy1菌株的相容性及协同作用

为了筛选与顶孢霉菌株相容的化学杀螨剂,本文采用孢子萌发法和菌丝生长速率法,测定了哒螨灵、虫螨腈和螺螨酯对顶孢霉孢子萌发和菌丝生长的影响及协同效应。结果表明:哒螨灵、甲氰菊酯、四螨嗪、氟虫脲、螺螨酯、虫螨腈、螺虫乙酯在不同浓度下对顶孢霉孢子萌发和菌丝生长均有不同程度的抑制作用,哒螨灵、虫螨腈、螺螨酯与顶孢霉混用对二斑叶螨有一定的协同作用。哒螨灵、虫螨腈、螺螨酯在高浓度下(25μg/mL、0.83μg/mL、60μg/mL),对顶孢霉孢子萌发的抑制率分别为27.67%、27.83%和29.22%,对菌丝生长抑制率分别为20%、18%和18%,抑制作用较低,有较好的相容性;25μg/mL哒螨灵、0.83μg/mL虫螨腈、60μg/mL螺螨酯与含孢量为1×106个/mL顶孢霉复配处理二斑叶螨11d,对二斑叶螨的致死效果明显大于单用顶孢霉的处理,3种药剂与顶孢霉复配剂对二斑叶螨的半数致死时间(LT50)分别为5.38、5.41、5.79d,较单用半数致死时间缩短了4.19、4.16、3.78d,提高了顶孢霉的杀螨速度。     

四个二斑叶螨地理种群卵对10种杀螨剂的敏感性差异

为了明确二斑叶螨卵对现有杀螨剂的敏感性现状,采用棉苗浸渍法测定了4个二斑叶螨地理种群卵对10种常用杀螨剂的敏感性。结果表明,昌乐和寿光蔬菜大棚内二斑叶螨卵的敏感性明显低于郑州和沂源种群。其中,4个抗性种群对哒螨灵的敏感性均较低,敏感系数从高到低依次为:昌乐(216.02倍)、郑州(112.45倍)、沂源(53.56倍)、寿光(12.74倍)。唑螨酯和螺螨酯对卵的毒力均较高,是防治二斑叶螨卵较好的药剂。     

8种杀螨剂对马铃薯朱砂叶螨的防治效果

为了筛选在西北旱作区针对马铃薯朱砂叶螨的最佳防治药剂, 选择了8种杀螨剂进行两年的田间药效试验。结果表明, 24%螺螨酯悬浮剂(SC)处理下的马铃薯单株块茎数最高, 螨株率最低, 并且叶片SPAD值及光合参数值最高, 8种药剂中, 24%螺螨酯SC、43%联苯肼酯SC、2%阿维菌素SC、11%乙螨唑SC和73%炔螨特乳油(EC)对马铃薯朱砂叶螨防效高于80%, 可作为防治马铃薯朱砂叶螨的药剂。     

4种药剂对茶树螨类的防治效果评价

针对茶园中的茶黄螨和茶橙瘿螨进行4种常用杀螨剂的田间药效试验,筛选出效果好的防治药剂,为有效控制茶树螨类的为害提供防治建议,结果显示:4种药剂对茶黄螨和茶橙瘿螨均有良好的防治效果。     

6种杀螨剂对黄瓜新小绥螨和朱砂叶螨的选择毒力评价

采用叶片残毒法测定了6种田间常用杀螨剂对黄瓜新小绥螨［Neoseiulus cucumeris (Oudemans)］和朱砂叶螨［Tetranychus cinnabarinus (Boisduval)］的毒力,并分析了这几种杀螨剂对这两种螨的选择毒力。结果表明：供试6种杀螨剂中甲氰菊酯与高效氟氯氰菊酯对黄瓜新小绥螨具有较强的毒力,对其成螨的LC50值分别为8.7和6.7 mg/L,且在对两种螨的毒力选择上表现为负向选择性,因此在释放黄瓜新小绥螨协同防治害螨时,需慎重选择使用。6种杀螨剂对两种螨的选择毒力大小依次为：哒螨灵>阿维菌素>炔螨特>毒死蜱>高效氟氯氰菊酯>甲氰菊酯,且哒螨灵对黄瓜新小绥螨的毒力最低,对其成螨的LC50值达到了593.7 mg/L,而阿维菌素对黄瓜新小绥螨成螨的LC50值为90.2 mg/L,对朱砂叶螨成螨的LC50值为17.8 mg/L。哒螨灵和阿维菌素具有较高的正向选择性,表明这两种杀螨剂在利用黄瓜新小绥螨及化学药剂协同防治朱砂叶螨中具有重要的应用价值。     

阿维菌素与其他3种药剂复配对朱砂叶螨的联合作用

室内采用叶片残毒法测定了阿维菌素、丁醚脲、哒螨灵和炔螨特对朱砂叶螨雌成螨的毒力及其复配剂的联合作用。结果表明,以阿维菌素为主干药剂,与其他3种杀螨剂复配对朱砂叶螨雌成螨的增效作用显著,相同浓度下复配剂显著优于各单剂,其中,阿维菌素和丁醚脲(1∶1、1∶49)、阿维菌素和哒螨灵(1∶19、1∶29)、阿维菌素和炔螨特(1∶1、1∶2、1∶4、1∶39)增效作用显著,共毒系数分别为350.9、488.4、465.9、582.5、349.7、350.5、436.1、452.6。阿维菌素与其他3种杀螨剂复配可有效克服或延缓害螨抗性的产生,并且可以提高药效、降低成本,在害螨防治中极具应用前景和开发潜力。     

桔全爪螨田间种群对杀螨剂的敏感性

采用玻片浸渍法测定了不同地区桔全爪螨田间种群雌成螨对四种杀螨剂的敏感性。结果表明,万州种群2005—2006年对四种杀螨剂的LC50均最低,因此视为相对敏感种群。另外4个桔全爪螨田间种群中,长寿种群对炔螨特的LC50最高,2005和2006年分别为162.14和199.30μg/mL,但相对抗性倍数仅为2.82和2.13倍;北碚种群对双甲脒的相对抗性水平最高,2005和2006年LC50分别为111.27和113.94μg/mL,抗性系数分别达到了15.03和5.50倍;南充种群对丁醚脲的相对抗性水平最高,2005和2006年LC50分别为510.91和226.15μg/mL,抗性系数分别为15.25和6.83倍;长寿种群对三唑锡的相对抗性水平最高,2005和2006年LC50分别为171.25和344.87μg/mL,抗性系数分别为6.03和25.35倍。     

7种药剂对柑橘全爪螨的室内毒力及田间防效

柑橘全爪螨是重要的柑橘害虫之一, 对多种化学农药已产生抗性。为合理选择防治药剂, 更好地防治该害虫, 本研究选择7种药剂采用改进浸叶法对柑橘全爪螨雌成螨进行了室内毒力测定, 并参照农药田间药效试验准则开展了田间药效试验。研究结果表明, 7种药剂对柑橘全爪螨的毒力从大到小依次为乙唑螨腈(0.818 mg/L)、丁氟螨酯(4.645 mg/L)、印楝素(4.878 mg/L)、氟啶胺(16.844 mg/L)、哒螨灵(21.167 mg/L)、乙螨唑(69.834 mg/L)、螺虫乙酯(417.089 mg/L)。乙唑螨腈和丁氟螨酯的速效性好且持效期长, 对柑橘全爪螨的防效显著高于其他供试药剂, 可作为防治的首选药剂。此外, 氟啶胺对柑橘全爪螨也有较高的毒力和防效, 作为一种广谱高效的保护性杀菌剂, 可在防治柑橘病害的同时防治害螨, 病虫兼治。     

Monitoring the gravitational reflex of the ectoparasitic mite Varroa destructor: A novel bioassay for assessing toxic effects of acaricides

We investigated the effect of several acaricides on Varroa destructor by monitoring the rhythmic expansion of the sternum, followed by a strong flexion of the legs, initiated when the mite was placed in a dorsal side-down position, as an indication of a mite’s vitality. The pulses generated by the force of the rhythmic expansions had an average duration of 3.11 s, force (amplitude) of 73 μN, and frequency of 0.228 Hz. These parameters remained constant for the first 10 h of recording, whilst significant changes occurred after 15 h. The rhythmic sternal expansion is an indication of a Varroa mite’s gravitational reflex, or attempt to return to an upright position; this reflex is observed in all invertebrates and vertebrates. The sternal expansion can be recorded for over 20 h, or for as long as the Varroa mite remains alive, and the expansion stops as soon as the mite is placed in a normal, upright position. Proper function of the chain of proprioceptors, interneurons, motorneurons, neuromuscular junctions, and muscles of Varroa is required for the initiation and maintenance of such a behavioural motor pattern. Any deleterious effect of synthetic chemicals or natural compounds (acaricides) may have a direct effect on one or more of these links, thereby disturbing or even inhibiting the reflex. Topical application of 1.81 × 10⁻³ mg/mite of amitraz completely inhibited the gravitational reflex within 60–70 min for all mites tested. The volatile acaricides formic acid (13.83 mg), thymol crystals (250 mg), and Apiguard® (1000 mg) eliminated the reflex within 10–35 min. This bioassay, based on the gravitational reflex, could be a useful tool for accurate assessment of the acaricidal action of numerous compounds under laboratory conditions, saving money and time necessary to conduct field trials.     

The effectiveness of various acaricides against resistant and susceptible carmine spider mites

Two colonies of the carmine spider mite,Tetranychus cinnabarinus (Boisd.), were raised on beans in the laboratory. One originated from roses in a greenhouse which had received acaricidal treatments, and the other fromViola odorata L. in a garden where no pesticides had been used. Laboratory evaluation indicated that the greenhouse strain was highly resistant to dicofol (Kelthane) and bromopro-pylate (Neoron), moderately resistant to propargite (Omite), and slightly resistant to cyhexatin (Plictran); in the garden strain, there was no resistance to any of these acaricides. On a strain of carmine spider mites which was identified and defined as resistant, several acaricides were evaluated in the laboratory for their contact toxicity to the mite by the slide dip method, and for their contact plus stomach toxicity by exposing the mites to sprayed leaves. Some of these acaricides were later tested in the field on two undetermined populations. Cyhexatin, triazophos (Hostathion), fentrifanil (PP-199) and R-28627 killed more than 90% of the mites by both methods and were effective in the field. NC-13292 was an ovicide only. Proclonol (R-8284) had a good effect in the slide dip method but was not so effective in the leaf exposure test. The compounds tested were phytotoxic to rose foliage only, but triazophos burned all the crops tested.     

Francisella tularensis from ixodid ticks in Czechoslovakia

A total of 26,478 ixodid ticks (935 pools) were examined by intracerebral inoculation of suckling mice. Six species of ticks were tested: Ixodes ricinus (23,470 individuals), I. trianguliceps (12), Haemaphysalis punctata (831), H. concinna (39), Dermacentor reticulatus (69) and D. marginatus (2,057). The ticks were collected largely by flagging vegetation, a substantial minority (4%) from animals. Three strains of Francisella tularensis were isolated, one each from I. ricinus (males, district Breclav, southern Moravia), D. reticulatus (males, district Breclav) and D. marginatus (engorged females collected from sheep in Roznava district, eastern Slovakia). D. marginatus and D. reticulatus represent new vector species for Czechoslovakia.