Tracheal Mite Research Articles

Development of a gel formulation of formic acid for control of parasitic mites of honey bees.

Formic acid has been used in various countries for the control of parasitic mites of honey bees (Apis mellifera), particularly the Varroa mite (Varroa jacobsoni) and the tracheal mite (Acarapis woodi). Its corrosivity and consequent fear of liability have precluded commercial interest in the United States, and its rapid vaporization requires frequent reapplication. We have developed a gel formulation of formic acid which provides controlled release over 2-3 weeks and improves the convenience and safety of handling of formic acid. The strong acidity of formic acid restricts the choice of gelling agents; vegetable gellants such as agar are destroyed, and bentonite clay derivatives do not gel, even with high-shear mixing. Polyacrylamides lead to viscous liquids lacking thixotropic properties. High-molecular-weight poly(acrylic acids) and fumed silicas provided gels with suitable physical characteristics. The poly(acrylic acid) gels were difficult to mix and gave slower and nonlinear release behavior, while the fumed silica gels were easy to prepare and linear in formic acid vaporization.

FEEDING MENTHOL TO HONEYBEES (HYMENOPTERA: APIDAE): ENTRY AND PERSISTENCE IN HAEMOLYMPH WITHOUT CAUSING MORTALITY

Tracheal mites, Acarapis woodi (Rennie) (Acari: Tarsonemidae), are important parasites of honeybees, Apis mellifera L. (Morse and Flottum 1997). They enter the prothoracic tracheae and feed through the walls on haemolymph. Currently, these mites are controlled by applying 50 g of menthol crystals in a perforated bag per hive when ambient temperatures are 15°C or more. Even then, it takes 2 weeks for the menthol to perfuse the hive (Herbert et al. 1988; Wilson et al. 1990). In cold climates, sublimation of menthol is too slow to be effective in controlling mites, especially in spring and fall when control is most needed (Scott-Dupree and Otis 1992).Because menthol fumes enter the bees' trachea and kill the mites therein, it may be possible to kill the mites with menthol that is delivered to them via the haemolymph. Therefore, finding if menthol could become systemic when ingested by bees and it could kill tracheal mites by that route, an ingestible menthol medicament for the bees would hold potential for mite control (Kevan and Kevan 1997).

Pest status and incidence of the honey bee tracheal mite in Finland

Colonies of honey bees (Apis mellifera L.) were surveyed for the presence of the honey bee tracheal mite (Acarapis woodi Rennie) in Finland between 1991 and 1997. Colony background information and winter loss data were obtained from beekeepers who had taken tracheal mite infested samples. A total of 2116 samples from honey bee colonies of 402 beekeepers were investigated. Infestations were found in 8% of the beekeeping operations and in 10% of the samples inspected. In the last years of the survey more than 20% of apiaries were infested. This increase may be partly explained by tracheal mite infestations found in commercial queen-rearing apiaries. A field experiment with colonies infested at different levels showed that colonies in which 20% or more of bees are infested with tracheal mites have an increased risk of dying during the winter under Finnish conditions. This infestation level was found among colonies in 92% of the infested apiaries. Comparison of the tracheal mite prevalence in apiaries with their winter losses indicated that infestations were associated with colony mortality. The results of this survey point to the high pest potential of the tracheal mite in Finland, in contrast to findings on tracheal mites from elsewhere in Europe. Therefore, strategies to prevent further spread of the mite are highly recommended and methods for effective control should be sought.;

Evidence of autogrooming as a mechanism of honey bee resistance to tracheal mite infestation

SUMMARYInfestations of tracheal mites (Acarapis woodi) were measured in honey bees (Apis mellifera) whose autogrooming ability was compromised by having legs or segments of legs amputated. Bees of two stocks, one more resistant (Buck-fast) and one more susceptible to tracheal mite infestation, were tested by performing amputations on uninfested, young (0–24 h) adult bees, exposing the treated bees to mites in infested colonies, then retrieving and dissecting the bees to measure parasitism. In both stocks, bees that had mesothoracic legs amputated had greatly increased mite abundances. However, the relative increase in infestation was greater in resistant bees. Mite infestation increased as more (0 vs. 1 vs. 2) mesothoracic legs were removed. In bees with only one leg removed, mite infestations were greater on the treated side. In subsequent tests with resistant stock bees only, removing the mesotarsi resulted in infestations equalling those found when entire mesothoracic legs were removed, but amputating the four distal mesotarsomeres or the metatarsi resulted in less significant increases. Restraining rather than removing mesothoracic legs also resulted in increased infestation. Young (0–24 h) bees were more affected than older (3–4 day) bees by leg removal, indicating that a factor other than autogrooming accounts for the low susceptibility of older bees to tracheal mites. Together these results are evidence that autogrooming is an important mechanism of protection against tracheal mites, especially in bees known to have genetically-based resistance to the parasite.

Grooming behavior by Apis mellifera L. in the presence of Acarapis woodi (Rennie) (Acari: Tarsonemidae)

The role of grooming behavior by the honey bee, Apis mellifera L., in limiting the infes- tation of, or being elicited by, the parasitic mite Acarapis woodi was investigated. Grooming behaviors examined included allogrooming and the grooming dance that involves self or auto- grooming. Observation hives monitored over 24 h revealed that dancing increased significantly at night while allogrooming decreased. In 32 mite-infested observation hives the percentage of bees infested was positively correlated with allogrooming acts and dances observed. In a third expe- riment, young marked bees were introduced into three hives with 0, 50 and 70 % tracheal mite pre- valence and grooming dances increased significantly in the bees 1-3 d of age in the mite-infes- ted colonies. We postulate that mite movement on young bees elicits the grooming dance. Bees from four different single patrilines that had exhibited different propensities to allogroom or dance were marked and placed into eight mite-infested colonies for 5 d. Dissections of marked bees revealed that the allogrooming line was most susceptible and the dancing line least sus- ceptible to mite infestation. We postulate that the dancing line of bees had a lower threshold for detecting mites on their body resulting in increased dance behavior and autogrooming, which we propose lowered the number of mites that transferred to these bees. This is the first evidence for a mechanism of resistance to the honey bee tracheal mite. © Inra/DIB/AGIB/Elsevier, Paris

Plant Extracts Used for Control of the Parasitic Mites Varroa jacobsoni (Acari: Varroidae) and Acarapis woodi (Acari: Tarsonemidae) in Colonies of Apis mellifera (Hymenoptera: Apidae)

Natural products were evaluated as control agents for the tracheal mite Acarapis woodi (Rennie) and the Varroa mite Varroa jacobsoni (Oudemans) in colonies of the honey bee, Apis mellifera L. Test materials consisted of 1:1 (wt:wt) blends of thymol with cineole, citronellal, or linalool. Two, 25.0-g applications (rate 1) of each blend were applied to colonies infested with Varroa. A 2nd group of Varroa infested colonies received 2 x 12.5 g applications (rate 2). Each application was left in place for 14 d, during which time Varroa mites were collected on, sticky boards placed on the bottom boards of the colonies. At the end of the 28-d treatment period, remaining mites were killed with fluvalinate and collected on sticky boards. Mite mortality in the colonies receiving thymol and cineole was 56.4 and 49.1% for rates 1 and 2, respectively, compared with a natural mite fall of 28.0% in control colonies. Two applications of each blend (rate 1) were applied to colonies infested with A. woodi in September. Mite prevalence values increased 28.3% in control colonies by the following May, but decreased 22.4% in colonies receiving thymol and citronella!. Our results suggest that the presence of brood seriously limits the efficacy of thymol-based control measures when they are applied as fumigants against Varroa. However, these products may be useful against the tracheal mite and may be an important component of an integrated pest management program for Varroa if used when brood levels are low.

Toxicity of Seven Monoterpenoids to Tracheal Mites (Acari: Tarsonemidae) and Their Honey Bee (Hymenoptera: Apidae) Hosts When Applied as Fumigants

Laboratory bioassays were conducted to characterize the acute toxicity of 7 monoterpenoids to tracheal mites, Acarapis woodi (Rennie), and their honey bee, Apis mellifera L., hosts. Citral, thymol, carvacrol, a-terpineol, pulegone, d-limonene, and menthol were applied as fumigants to mite-infested honey bees. Thymol and menthol were the most toxic compounds to honey bees, and a-terpineol was the least toxic. Menthol, citral, thymol, and carvacrol were more toxic to tracheal mites than to honey bees. Pulegone, d-limonene, and a-terpineol were more toxic to honey bees than to tracheal mites. Menthol was 18.9 times more toxic to tracheal mites than to honey bees at the LCso concentrations; however, as the concentration increased, bee mortality increased more rapidly than mite mortality, and men­ thol was only 5.7 times more toxic at the LCgo concentrations. Probit regressions for bee and mite mortality were parallel for citral and thymol. Citral and thymol were 2.9 (2.5-3.3) and 2.0 (1.0-3.6) times more toxic to tracheal mites, respectively, at all concentrations estimated.

Micro-organisms associated with tracheal mite-infested honey bees

SUMMARYThe possible association of bacteria or fungi with honey bees (Apis mellifera) infested with tracheal mites (Acarapis woodi) was investigated. Methods and procedures were developed for sampling, dissecting and processing samples. One thousand tracheae and 250 haemolymph samples were obtained from 500 honey bees from 12 infested and 12 uninfested outdoor and indoor overwintered colonies during January to March, 1994. Few micro-organisms were cultured from internal bee tissues, whereas numerous and diverse bacteria and fungi were cultured from the exterior surfaces of tracheal mite-infested and uninfested honey bee thoraces and heads. No specific bacterial or fungal associations with tracheal mite-infested bees were found. The bacteria and fungi isolated from samples are listed.

Guanine visualization: a new method for diagnosing tracheal mite infestation of honey bees

La presence de guanine (2-amine-6-oxypurine), purine qui est le principal produit final du metabolisme azote chez les acariens mais n'est present qu'a l'etat de traces dans les excretions des abeilles, a ete utilisee comme test biologique pour diagnostiquer l'infestation des trachees de l'abeille par l'acarien Acarapis woodi (Rennie). Les abeilles infestees ont ete homogeneisees dans des solutions acides ou basiques. Les cellules ont ete dechirees aux ultrasons puis centrifugees. Le surnageant a ete etale sur des plaques pour chromatographie en couche mince avec les marqueurs de guanine appropries et visualise en lumiere UV (fig 1). Dans un test preliminaire, la comparaison des resultats de la methode classique (dissection de 100 abeilles) et de la methode de visualisation de la guanine sur les memes abeilles prises individuellement, a montre que les deux methodes donnaient des resultats identiques quel que soit le taux d'infestation (nul, moyen ou fort) (fig 2). La methode de la guanine n'a pas pu mettre en evidence de facon nette les infestations debutantes. Les valeurs d'ACAREX®, produit commercial mis au point pour detecter la presence d'acariens de la poussiere domestique par lecture de la guanine, etaient trop grossieres pour diagnostiquer l'acarien des trachees. On a compare trois types d'essais (la methode du disque thoracique, la methode ELISA et la methode de la guanine) sur 13 echantillons de 170 acariens chacun (tableau I). La concordance entre les resultats, bonne sur le plan qualitatif mais seulement moyenne sur le plan quantitatif, indique que la methode de la guanine pourrait etre utilisee pour etablir la presence d'A woodi. Les avantages et inconvenients de cette nouvelle methode sont discutes.

A scientific note on the current low levels of honey bee tracheal mite in southern Spain

A scientific note on the current low levels of honey bee tracheal mite in southern Spain

Influence of resistant honey bee hosts on the life history of the parasite Acarapis woodi

Non-infested, young adult honey bees (Apis mellifera L.) of two stocks were exposed to tracheal mites (Acarapis woodi (Rennie)) in infested colonies to determine how divergent levels of susceptibility in host bees differentially affect components of the mite life history. Test bees were retrieved after exposure and dissected to determine whether resistance is founded on the reduced success of gravid female (foundress) mites to enter the host tracheae, on the suppressed reproduction by foundress mites once established in host tracheae or on both. Cohorts of 30–60 bees from each of ten resistant colonies and eight susceptible colonies were tested in eight trials (three to five colonies per stock per trial) having exposure durations of 4, 9 or 21 days. The principal results were that lower percentages of resistant bees than of susceptible bees routinely became infested by foundress mites, individual infested susceptible bees often had more foundress mites than individual infested resistant bees did and mite fecundity was similar in both host types. The infestation percentage results corresponded well with similar results from a prior field test of these stocks and, thus, suggest that the bioassay is useful for assessing honey bee resistance to A. woodi.

Life History of the Honey Bee Tracheal Mite (Acari: Tarsonemidae)

Data on the seasonal reproductive patterns of the honey bee tracheal mite, Acarapis woodi (Rennie), were obtained by dissecting host honey bees, Apis mellifera L., at intervals during their life span. Mite reproduction normally was limited to 1 complete generation per host bee, regardless of host life span. However, limited egg laying by foundress progeny was observed. Longer lived bees in the fall and winter harbored mites that reproduced for a longer period than did mites in bees during spring and summer. Oviposition rate was relatively uniform at ≈0.85 eggs per female per day during the initial 16 d of adult bee life regardless of season. In all seasons, peak mite populations occurred in bees ≈24 d old, with egg laying declining rapidly beyond day 24 in spring and summer bees but more slowly in fall and winter bees. Stadial lengths of eggs and male and female larvae were 5, 4, and 5 d, respectively. Sex ratio ranged from 1.15:1 to 2.01:1, female bias, but because males are not known to migrate they would have been overestimated in the sampling scheme. Fecundity was estimated to be ≈21 offspring, assuming daughter mites laid limited eggs in tracheae before dispersal. Mortality of adult mites increased with host age; an estimate of 35 d for female mite longevity was indirectly obtained. Daughter mites began dispersing when infested bees were ≈13 d old, and mite dispersal peaked when infested bees were 15—25 d old. The mating behavior of tracheal mites is described.

Host-seeking behaviour of tracheal mites (Acari: Tarsonemidae) on honey bees (Hymenoptera: Apidae)

The behaviour of the endoparasitic tracheal mite, Acarapis woodi (Rennie) on honey bees (Apis mellifera L.) is a challenge to observe because of its small size. Through a microscope, we videotaped this mite's movement on young bees, dead bees and bees exposed to vegetable oil. Previous studies have shown that solid vegetable oil decreases mite infestations in a bee colony. We hypothesized that the oil alters mite behaviour to the detriment of the parasite, thus helping to safeguard the host. Habitat-seeking behaviour, identified as necessary for mites to locate a new host environment, was disrupted on both dead and oil-treated bees. Questing behaviour, which is associated with transfer between hosts, increased significantly on the dead and oily bees. The behaviours of mites were significantly different between all three treatments (x 2=494.96, p<0.001 on dead bees and x 2=851.11, p<0.001 on oily bees). Both questing and seeking behaviours were significantly different on each of the thoracic treatments (F 2,66=7.88, p<0.001 and F 2,66=21.28, p<0.001) and mite questing behaviour was not altered between males and females on live or oily bees (F 1,22=0.25, p<0.62), but habitat seeking was (F 1,22=7.42, p<0.012). The male questing and habitat-seeking behaviours were observed. We conclude that oil-treated bees gained protection from habitat-seeking mites because the normal behaviour of the mites seeking an oviposition site is interrupted.

Comparative resistance in Buckfast and Canadian stocks of honey bees (Apis mellifera L.) to infestation by honey bee tracheal mites (Acarapis woodi (Rennie))

The results of bioassay and colony evaluation demonstrated that British and Texas Buckfast honey bee stocks had one-third to one-half the mean prevalence and abundance of tracheal mites as Canadian standard stock, indicating that Buckfast stocks are less susceptible to tracheal mites than Canadian standard stock. Hybrid Canadian and Buckfast stocks exhibited resistance characteristics similar to only one of their parental stocks, suggesting the colony has an unknown effect on the expression of a bee's resistance to mites. A high correlation (rs=0.66) between abundance values from the bioassay and colony evaluations indicates that the bioassay can be used to screen bees for mite resistance.

Practical science—research helping beekeepers 1. Tracheal mites

Because they are easily cultured, economically important, and endlessly fascinating, honey bees are the most well-known and well-researched insects in the world. They interest beekeeper and scientist alike, and although the aims of the two groups differ, their respective activities complement each other. We can thank practical-minded beekeepers for inventing beekeeping equipment, working out basic beekeeping techniques, accumulating untold hours of natural observations, and identifying applied research needs. And we can thank generations of scientists who have pieced together bee biology, disease etiologies and treatments, parasitology, genetics and breeding. Clearly, the relationship between beekeepers and bee scientists is mutually beneficial.

Attractiveness of CO2and Synthetic honey bee (Apis MelliferaL.) (Hymenoptera: Apidae) cuticular hydrocarbons to the honey bee tracheal mite,Acarapis woodi(Rennie) (Acari: Tarsonemidae)

Abstract Despite the devastation caused by the honey bee tracheal mite, Acarapis woodi, over its range, it is difficult to detect and little is known about what attracts the mite to its host. Based on previous studies of tracheal mites and of other blood sucking arthropods, we developed bioassay procedures to study the attractiveness of CO2 and of honey bee cuticular hydrocarbons to dispersing tracheal mites. The CO2 assay consisted of a three-choice test between streams of air, a CO2 /air mix, and a no-gas control. Air was chosen most frequently overall. Weighted scores were calculated based on the strength and frequency of response, and in this case the CO2 /air mixture was favored. Known hydrocarbon mixtures and hexane extracts of bees were applied to pipecleaners and inserted into small test hives. No tracheal mites were recovered from any of these, failing to support other studies that found these substances to be attractive in the lab. The results are discussed in relation to what is known about the...

Evaluation of Four Seed-Derived Oils as Controls for Acarapis woodi (Acari: Tarsonemidae) in Colonies of Apis mellifera (Hymenoptera: Apidae)

Four seed-derived oils were evaluated in field trials as control agents for the parasitic tracheal mite,Acarapis woodi (Rennie), in colonies of the honey bee, Apis mellifera (L.). Seventy-one honey bee colonies infested with the tracheal mite were each assigned to 1 of 4 treatment groups or to a control group. Treatments were peanut, soybean, sunflower, or canola oil, delivered as patties after blending with confectioner sugar (2 parts sugar/l part oil [wt:wt]). All 5 groups had similar mite prevalence values (proportion of infested bees) and parasite load scores (a measure of the number of mites per bee) before initiating treatment. Each colony received five 500-g patties delivered approximately every 14 d starting on 16 September 1992 and continuing until 1 December 1992. Mite prevalence values, parasite load scores, and colony weight gains (an indicator of honey production) were measured the following spring. Average mite prevalence values obtained on 4 and 5 May 1993 in the treated groups ranged from 0.015 to 0.027, compared with 0.094 in the control group. The mite prevalence value in each treatment group was less than the mite prevalence value in the control group. Similar differences were observed for parasite load scores. Differences in colony weight gains among the 5 groups were not significant.

Field Test of Resistance to Acarapis woodi (Acari: Tarsonemidae) and of Colony Production by Four Stocks of Honey Bees (Hymenoptera: Apidae)

Characteristics of four stocks of honey bees, Apis mellifera L., were evaluated in colonies managed commercially for honey production at three U.S. locations―one north-central location (Iowa) and two south-central locations (Mississippi, Texas). Stocks were compared for 1 yr beginning in October 1991 to determine the levels of infestation by tracheal mites, Acarapis woodi (Rennie), and to ascertain survival rates, levels of honey production, and sizes of adult and brood populations. Test stocks were ARS-Y-C-1 ( A. mellifera carnica Pollman, imported from Yugoslavia), Buckfast (imported from the United Kingdom), Survivor (developed from colonies in a Louisiana apiary believed to have had severe tracheal mite infestation), and Unchallenged (developed from a feral Louisiana population never exposed to tracheal mites). Stocks initially were represented by 15-20 colonies at each location. After an initial inoculation of mite-infested bees in the autuinn, infestation percentages increased more markedly in the susceptible (Survivor and Unchallenged) stocks than in the resistant (ARS-Y-C-1 and Buckfast) stocks. Mean infestation percentages in the resistant stocks remained <15% and thus were below levels associated with economic damage. Mean infestation percentages in susceptible stocks ranged from 13 to 95% at each site during the final 6 mo of the study Numbers of mites per infested bee differed between stocks in 4 of 21 samples; mite numbers tended to be greatest in Survivor bees and least in Buckfast bees. Mortality increased more rapidly among susceptible colonies than among resistant colonies as infestation increased in 1992. Honey production was greatest by Buckfast, intermediate by Survivor, and least by Unchallenged and ARS-Y-C-l colonies. Differences in population sizes of adult bees and brood occurred in approximately half of samples taken in spring and autumn; Survivor and Buckfast colonies were most populous. Stock characteristics showed no interaction of genotype with environment, i.e., location. Our results support the feasibility of an approach using genetically regulated resistance to manage problems caused by tracheal mites.

Controlling Tracheal Mites (Acari: Tarsonemidae) in Honey Bees (Hymenoptera: Apidae) with Vegetable Oil

Field experiments conducted between 1991 and 1993 demonstrated that treating colonies of honey bees, Apis mellifera L., continuously with vegetable oil depressed populations of tracheal mites Acarapis woodi (Rennie). In 1992-1993, continuous exposure to oil patties, with or without the antibiotic Terramycin, produced significant control of mites. Five of 11 untreated (control) colonies perished. None of the oil-pattytreated colonies died, and only two of 10 colonies treated with Terramycin patties expired. Oil patties were made from a combination of solid vegetable oil (shortening) and white sugar, with or without the addition of the antibiotic. Two oil patty treatments during the summer of 1991 failed to prevent mite population increases in bees by that fall.

Distribution of the tracheal mite, Acarapis woodi, among the mesothoracic tracheal trunks of the honey bee, Apis mellifera

The selection of honey-bee tracheal trunks by host-seeking tracheal mites, Acarapis woodi, was examined in 307 samples of worker honey bees. The number of bees with 0, 1, and 2 infested tracheal trunks was determined for each sample and compared to an expected distribution based on the assumption that the probability that a tracheal trunk is infested is the same for all tracheal trunks. A Monte-Carlo simulation technique was employed to evaluate the significance of the test statistic. Observed distributions of bees with 0, 1, and 2 infested tracheal trunks were found to differ significantly from the expected distributions in 74 of the 307 samples. There were more uninfested bees and bilaterally infested bees than expected in all 74 cases. Further analysis revealed that the left and right tracheal trunks were equally likely to be infested.