Penetration of pesticides into the bulb miteRhizoglyphus echinopus (Acari: Acaridae)

Bulb mites,Rhizoglyphus echinopus (Fumoze and Robin), were exposed for 10 min in vials precoated with 23 radiocarbon-labeled pesticides, and the kinetics of penetration were assessed following post-exposure periods of 320 min or 24h, depending upon the compound. With all pesticides, penetration was biphasic and consisted of a rapid initial component (alpha phase) followed by a much slower secondary component. The alpha phase of penetration was analyzed with a linear model, and the entire penetration curve was analyzed with a non-linear model. Correlation analyses of ten mass balance and penetration parameters and partition coefficients yielded 14 combinations that were significant atP<0.05. It was found that compounds with the fastest penetration rates had the highest dosing coefficients and the lowest octanol-water partition coefficients. Thus, fastest penetration was associated with relatively polar compounds such as oxythioquinox, promecarb, methomyl, aldicarb, and chlordimeform, whereas slowest penetration was observed with lipophilic compounds such as DDT, diflubenzuron, di-2-ethylhexyl phthalate, and the pyrethroids. However, the polar formetanate hydrochloride penetrated very slowly and was an exception to this generalization. These results provide a basis for suggesting that pesticide penetration proceeded at a faster rate in bulb mites than in two-spotted spider mites,Tetranychus urticae Koch, in other studies.     

Cholinesterase inhibition in the bulb miteRhizoglyphus echinopus (Acari: Acaridae) in relation to the acaricidal action of organophosphates and carbamates

The 5000-g supernatant fraction of whole-bulb-mite homogenates was shown to possess a cholinesterase (ChE) that hydrolyzed acylcholine esters in the order acetyl>propionyl>butyryl. Acetyl--methylcholine, but not benzoylcholine, also was hydrolyzed as were acetylthiocholine and acetyl--methylthiocholine. No inhibition by excess substrate was observed at cholinester concentrations as high as 30mM. Cholinesterase activity was markedly insensitive to eserine and to certain other carbamates and organophosphates. Only organophosphates of the dimethylphosphate type generally were active ChE inhibitors. It was concluded that the inability of carbamates such as eserine, and organophosphates such as those with alkyl groups larger than dimethyl, to inhibit the bulb-mite ChE was probably a consequence of the nature of the esteratic site. The data suggested that ChE inhibition was likely involved in the toxicity to bulb mites of some of the toxic carbamates and organophosphates, but that it might not be the only mechanism involved, at least with several of the compounds.Contribution from the Missouri Agricultural Experiment Station, Columbia, MO, Journal Series No. 10 924.     

Clofentezine toxicity and fate in the bulb mite Rhizoglyphus echinopus (Acari: Acaridae)

Clofentezine was toxic to bulb mite, Rhizoglyphus echinopus (Fumouze and Robin), eggs and larvae; however, it was not toxic to adults alone or in the presence of piperonyl butoxide. When adults were exposed to radioactive clofentezine, the acaricide was absorbed, metabolized and excreted. After 48 h exposure, 49.8% of the recovered radiocarbon was parent compound with 37.1, 9.1 and 3.6% detected in the container rinse, mite rinse and internal fraction, respectively. Homogenates of adults extensively metabolized clofentezine. The most active fraction was the 12 000 g supernatant plus glutathione followed in decreasing order by the supernatant, supernatant plus NADPH and the whole homogenate, each of which metabolized at least 16% of the acaricide. In the presence of piperonyl butoxide, in vitro metabolism of clofentezine by each of these active fractions was increased approximately 10%. Although it is possible that rapid metabolism could have contributed to the lack of toxicity of clofentezine to bulb mite adults, it is more likely that another major mechanism was involved. Perhaps adult bulb mites lack the sensitive target found in immature mites.     

Toxicological studies of the carbamates methomyl and bendiocarb in the bulb mite Rhizoglyphus echinopus (Acari: Acaridae)

Methomyl was 15 and 31.3 times more toxic than bendiocarb to bulb mites at the LC50 and LC90 values respectively. However, methomyl (pI50 3.0) was at least 126 times less active than bendiocarb (pI50 5.1) as an inhibitor of bulb mite cholinesterase in vitro. The disparity between the high toxicity of methomyl and its extremely low activity as an inhibitor of mite cholinesterase in vitro indicated that another mechanism was likely involved in its toxic action. Pharmacokinetic studies of methomyl and bendiocarb showed that penetration and metabolism were rapid and that there were no substantial differences in the internal levels of the respective parent carbamates during the 24 h test period. However, volatile radioactive material(s), some of which was carbon dioxide, was produced in appreciably greater amounts from methomyl than from bendiocarb. We speculate that the production of volatiles, such as carbon dioxide, acetonitrile and/or methylamine, may contribute to the toxicity of methomyl to bulb mites. © Rapid Science Ltd. 1998     

Toxicity of organophosphorus insecticides to diazinon-reversely-selected,pesticide-pressure-relaxed and field-resistant strains of bulb miteRhizoglyphus robini (Acari: Acaridae)

Some field strains ofRhizoglyphus robini in Taiwan, developed high multi-resistance to organophosphorus insecticides including diazinon, dimethoate, fenitrothion, malathion, methyl parathion, omethoate, parathion and prothiophos. The organophosphorus resistance of bulb mites remained stable when the pesticide pressure was relaxed. Changes of the susceptibility to several organophosphorus insecticides for a strain after relaxation of selection pressure for 3 and 27 generations were compared. Since susceptible bulb mites could not be found in the field, a reverse selection for susceptibility to diazinon was designed and conducted. Although heterogeneity was observed in the progeny of the mixed populations, the susceptibility of these reversely-selected mites increased slowly. A stable and susceptible strain was obtained after 26 generations of selection.Contribution No. 1412 from Taiwan Agricultural Research Institute.     

食物对刺足根螨生长发育、繁殖及休眠体产生的影响

在(25±1)℃、(95±5)%RH、全黑暗条件下,研究了4种食物对刺足根螨生长发育、繁殖及休眠体产生的影响。结果表明:取食马铃薯、马铃薯淀粉及鱼粉后,刺足根螨能完成世代发育,但其取食滤纸不能完成世代发育;在适宜的温湿度条件下,供试的4种食物对刺足根螨休眠体的产生无影响。     

Biogenic amine degradation by homogenates of the bulb mite,Rhizoglyphus echinopus (Fumouze and Robin) (Acari: Astigmata: Acaridae)

Whole homogenates of bulb mites rapidly metabolized 2-phenylethylamine (PEA) but were appreciably less active against tryptamine, 5-hydroxytryptamine, and dopamine; no degradation of octopamine was detected. The rate of PEA degradation by bulb mites was dependent upon both substrate and homogenate concentrations. PEA degradation was inhibited by pargyline (pI₅₀, 6.7), tranylcypromine (pI_{50 6.2}), and harmaline (pI_{50 4.1}), but not by 5-chloro-2,4-dimethoxyformanilide. These results suggested that PEA metabolism by bulb mite homogenates was catalyzed mainly by Type B monoamine oxidase.Contribution from the Missouri Agricultural Experiment Station, Columbia, MO. Journal Series No. 9777     

Male morph determination in Rhizoglyphus echinopus (Acaridae)

In Rhizoglyphus echinopus (Fumouze and Robin) two male morphs occur: heteromorphs, with a thickened and sharply terminated third pair of legs that serve as a weapon in intrasexual conflicts, and homeomorphs, with unmodified legs. This study investigated the system of male morph determination. No significant heritability of male morph was found, but cues emanating from a dense colony were found to suppress the production of heteromorphs. Developmental plasticity was retained throughout the protonymphal stage. Diet did not influence morph expression, but lowered temperature decreased the proportion of heteromorphs emerging.     

Biology, ecology, and management of the bulb mites of the genus Rhizoglyphus (Acari: Acaridae)

Bulb mites of the genus Rhizoglyphus (Claparède) (Acari: Acaridae) have been identified as pests of many crops and ornamentals in storage, in the greenhouse, and in the field. The most importanthosts are species in the family Liliaceae (e.g. Allium spp.), but bulb mites will often attack otherimportant crops such as potatoes (Solanum sp.) and carrots (Daucus carota). Despite their economicimportance and broad distribution, the systematics of the genus remains in a state of confusion and is inneed of a comprehensive revision. In addition, the field biology and ecology of these mites is not wellunderstood, and methods for sampling, monitoring, and loss assessment are limited. Management of bulbmites is complicated by their short generation time, high reproductive potential, broad food niche,interactions with other pests and pathogens, and unique adaptations for dispersal. Historically, control ofthese acarine pests has relied on the use of synthetic miticides and insecticides, but this option is nowlimited due to documented resistance and withdrawal of registration of some products. Alternativecontrol strategies, including cultural and biological control, have shown limited success, but need to befurther developed and implemented.     

中国嗜木螨属一新纪录种记述(蜱螨亚纲:粉螨科)

本文记述在江西省安义县米糠中采集到的嗜木螨属Caloglyphus一中国新纪录种:卡氏嗜木螨Caloglyphus caroli ChannaBasavanna 8L Krishna Rao,1982。     

Two new species of the genus Tyrophagus (Acari: Acaridae)

Two new species of Tyrophagus Oudemans, 1924, are described. One species, T. Savasi , has been discovered in several habitats of economic importance. It closely resembles T putrescentiae (Schrank) and T. neiswander Johnston & Bruce. The second, T. rebertsonae , has so far been discovered in only two, soil and tree bark. It differs from other species of Tyrophagus by a number of character. Both new species have pigmented 'eyespots' on the prodorsal shield. A new character used to differentiate these species is the shape of the sclerotized neck of receptaculum semins.
The position of the new species in three commonly used keys to adults of the genus Tyrophagus is indicated     

A new genus and species of mite (Acari: Acaridae) from Mexico

Comerinia chuetolamina gen. & sp. nov. was collected from a cargo of dried Daphnia imported to Britain from Mexico. Females can be distinguished from all others described in the family Acaridae in that setae 14, 15 and d5 are flattened dorsoventrally over most of the basal half. This region appears blade-like, bearing numerous strong pectinations along the ventral side. Males may be recognized by a series of characters, some of which reflect a close relationship with Forcellinia Ouds., 1924 and others with Tyrophagus Ouds., 1924. The position of the new genus in a commonly used key to adults of the family Acaridae is indicated.     

Thermal acclimation in the grain miteAcarus siro (Acari: Acaridae)

Grain mites reared on wheat germ at 21±1°C and 85% r.h. were treated (acclimated) as adults at 0, 14, 28 or 33°C for 1 or 4 days. Fecundity, longevity and numbers of F₁ females and males produced were compared. A treatment of 1 day was enough to acclimateAcarus siro and change the studied developmental parameters. Acclimation always lowered fecundity but the magnitude of the effect was dependent upon the temperature regime. The number of males and females emerging differed greatly among various temperature regimes; however, the sex ratio of emerged adults remained in most instances quite constant.     

腐食酪螨有效积温的研究

腐食酪螨 Tyrophagus putrescentiae(Schrank) ,是世界性仓储物品和食用菌重要害螨 ,也是人体皮炎、体内螨病及螨性过敏的主要病原。本文研究了该螨的有效积温。经测定 ,腐食酪螨全世代的发育始点为 8.38± 1.5 1℃ ,有效积温为 2 2 1.72日度 ;卵、幼螨、第一若螨和第二若螨的发育始点分别为 10 .4 7± 2 .31℃、8.0 9± 2 .36℃、9.0 9± 1.16℃和 10 .5 9± 1.73℃ ,有效积温分别为 4 1.79日度、5 8.0 6日度、36 .2 7日度和 39.5 3日度。     

Energy budget of the grain mite,Acarus siro (Acari: Acaridae)

Immature individuals ofAcarus siro L. ingest a total of 0.1408 J of food energy, 58.5% of which is consumed by the deutonymph, 27.1% by the protonymph and only 14.1% by the larva. The total ingestion is much greater (2.8169 J±0.0981se). Much energy, 0.7031 J±0.0231se, is used for egg production, which is concentrated in the first 20 days of adult life. Assimilation efficiency during this period varies from 63 to 71%. Most energy ingested between the 20th and 40th days of adult life is used in biomass production, and biomass increases significantly up to th 30th day. Afterwards, old individuals expend a large amount of assimilated energy on respiration due to the increased cost of maintenance.Present address: Biology Dept., LB 8042, Georgia Southern University, Statesboro, GA 30460, U.S.A.     

Anatomy and ultrastructure of the reproductive systems ofAcarus siro (Acari: Acaridae)

Anatomy and ultrastructure of the female and male reproductive system inAcarus siro L. were investigated by light and electron microscopy. The female system consists of paired ovaries of nutrimentary type in which oogonia and oocytes are connected by bridges with a large central cell. The oviducts empty into the uterus, which passes into preoviporal duct lined bycuticle, and opening as a longitudinal slit (oviporus). An elongated accessory gland composed of one type of secretory cell is located along each oviduct. The copulatory opening occurs at the posterior margin of the body and leads, via the inseminatory canal, to the receptaculum seminis, consisting of the basal and saccular part. Both inseminatory canal and basal part of receptaculum seminis are lined by cuticle, whereas the wall of the sac is formed by cells covered only by long, numerous microvilli. The basal part of the receptaculum seminis joins the ovaries via two lumenless transitory cones.The male reproductive system contains paired testes, in which spermatogonia tightly surround the central cell. The proximal part of the paired vasa deferentia serves as a sperm reservoir, while the distal one has a glandular character. An unpaired, cuticle-lined ejaculatory duct opens into the apex of the aedeagus. The single accessory gland is located asymmetrically at the level of, or slightly posterior to, coxae IV.The structure of the genital papillae, which are topographically related to the genital opening in both sexes, is also briefly described.     

Toxicity of Acaricides to the Bulb Mite Rhizoglyphus Echinopus (Acari: Acaridae)

Using a continuous exposure technique, the toxicity of 35 compounds to the bulb mite, Rhizoglyphus echinopus (Fumouze and Robin) was examined after 48 h. Sixteen acaricides yielded an LC₅₀ of <1.0 mg cm². The highest toxicity was exhibited by cyclodiene GABA antagonists (dieldrin, endrin and aldrin), some organophosphate (chlorpyrifos, diazinon and azinphosethyl) and carbamate (carbofuran) anticholinesterases and a thiazolidine flubenzimine. Oxythioquinox, fenazaflor, fenazaquin and amitraz were less toxic than the cyclodienes, organophosphates and carbamates. The sodium channel agonists (DDT and pyrethroids) and several specific acaricides with other modes of action were inactive (LC₅₀ >11.0 mg cm^-2).     

Effects of alternating temperatures onAcarus siro L. (Acari: Acaridae)

Fecundity, longevity and survival to adulthood ofAcarus siro (L.) at constant and alternating temperatures were compared. Both fecundity and longevity were affected by alternating temperatures but the effect of the frequency of alternations was not significant. Significantly higher fecundity and longer life spans were recorded at constant temperatures of 14 and 21°C than at 28°C or at alternating temperature regimes. Alternating temperature regimes in comparison to constant regimes did not significantly change the number of males and females surviving to adulthood or the sex ratio. However, the lowest number of adults surviving was recorded when temperatures were changed every 12 h and the highest at a constant temperature of 14°C.     

Amplification of single bulb mites by nested PCR: Species-specific primers to detect Rhizoglyphus robini and R. setosus (Acari: Acaridae)

A major problem of using molecular amplicons for DNA amplification in mite systematics is that sufficient template cannot always be acquired from an individual mite. To solve this problem, we developed a nested PCR for DNA amplification of single Rhizoglyphus robini and R. setosus bulb mites. A dilution up to 10⁵ of the DNA from a single egg, larva, nymph or adult contained enough templates for amplification of the target ribosomal region. However, the use of specific primers in the second PCR is necessary to reduce the generation of non-target DNAs from symbiotic organisms. Identification of bulb mites collected from seven sampling locations in Taiwan or of bulb mites that were used in simulated experiments in the presence of host plant tissues was unambiguous with specific PCR primers.     

常用杀虫杀螨剂对腐食酪螨的毒力测定

采用药膜法和玻片浸渍法分别测定了14种常用杀虫杀螨剂对腐食酪螨雌成螨和卵的毒力。结果表明:各药剂对雌成螨都有一定作用,但对卵没有杀伤效果。其中,对雌成螨毒力最高的为杀螨多,LC50为0.2568 mg.L-1;毒力最低的为敌敌畏,LC50为320.4793 mg.L-1。