Social Apoptosis in Varroa Mite Resistant Western Honey Bees (Apis mellifera)

Honey bees are eusocial animals that exhibit both individual and social immune responses, which influence colony health. This is especially well-studied regarding the mite Varroa destructor Anderson and Trueman (Parasitiformes: Varroidae), a parasite of honey bee brood and disease vector. Varroa was introduced relatively recently to Apis mellifera L. (Hymenoptera: Apidae) and is a major driver of the catastrophic die-off of honey bee colonies in the last decade. In contrast, the original host species, Apis cerana Fabricius (Hymenoptera: Apidae) is able to survive mite infestations with little effect on colony health and survival. This resilience is due in part to a newly identified social immune response expressed by developing worker brood. Varroa infested female A. cerana brood experience delayed development and eventually die in a process called ‘social apoptosis’. Here, an individual’s susceptibility to Varroa results in colony level resistance. We tested for the presence of the social apoptosis trait in two Varroa resistant stocks of A. mellifera (Pol-line and Russian) with different selection histories and compared them to a known Varroa-susceptible stock (Italian). We assessed the survival and development of worker brood reared in either highly or lightly infested host colonies, then receiving one of three treatments: uninfested, experimentally inoculated with a Varroa mite, or wounded to simulate Varroa damage. We found that response to treatment was only differentiated in brood reared in lightly infested host colonies, where experimentally infested Russian honey bees had decreased survival relative to the mite-susceptible Italian stock. This is the first evidence that social apoptosis can exist in Western honey bee populations.     

Understanding the Enemy: A Review of the Genetics,Behavior and Chemical Ecology of Varroa destructor,the Parasitic Mite of Apis mellifera

Varroa destructor (Mesostigmata: Varroidae) is arguably the most damaging parasitic mite that attacks honey bees worldwide. Since its initial host switch from the Asian honey bee (Apis cerana) (Hymenoptera: Apidae) to the Western honey bee (Apis mellifera) (Hymenoptera: Apidae), Varroa has become a widely successful invasive species, attacking honey bees on almost every continent where apiculture is practiced. Two haplotypes of V. destructor (Japanese and Korean) parasitize A. mellifera, both of which vector various honey bee-associated viruses. As the population of Varroa grows within a colony in the spring and summer, so do the levels of viral infections. Not surprisingly, high Varroa parasitization impacts bees at the individual level, causing bees to exhibit lower weight, decreased learning capacity, and shorter lifespan. High levels of Varroa infestation can lead to colony-wide varroosis and eventually colony death, especially when no control measures are taken against the mites. Varroa has become a successful parasite of A. mellifera because of its ability to reproduce within both drone cells and worker cells, which allows populations to expand rapidly. Varroa uses several chemical cues to complete its life cycle, many of which remain understudied and should be further explored. Given the growing reports of pesticide resistance by Varroa in several countries, a better understanding of the mite’s basic biology is needed to find alternative pest management strategies. This review focuses on the genetics, behavior, and chemical ecology of V. destructor within A. mellifera colonies, and points to areas of research that should be exploited to better control this pervasive honey bee enemy.     

Hygiene-Eliciting Brood Semiochemicals as a Tool for Assaying Honey Bee (Hymenoptera: Apidae) Colony Resistance to Varroa (Mesostigmata: Varroidae)

Despite numerous interventions, the ectoparasitic mite Varroa (Varroa destructor Anderson and Trueman [Mesostigmata: Varroidae]) and the pathogens it vectors remain a primary threat to honey bee (Apis mellifera Linnaeus [Hymenoptera: Apidae]) health. Hygienic behavior, the ability to detect, uncap, and remove unhealthy brood from the colony, has been bred for selectively for over two decades and continues to be a promising avenue for improved Varroa management. Although hygienic behavior is expressed more in Varroa-resistant colonies, hygiene does not always confer resistance to Varroa. Additionally, existing Varroa resistance selection methods trade efficacy for efficiency, because those achieving the highest levels of Varroa resistance can be time-consuming, and thus expensive and impractical for apicultural use. Here, we tested the hypothesis that hygienic response to a mixture of semiochemicals associated with Varroa-infested honey bee brood can serve as an improved tool for predicting colony-level Varroa resistance. In support of our hypothesis, we demonstrated that a mixture of the compounds (Z)-10-tritriacontene, (Z)-8-hentriacontene, (Z)-8-heptadecene, and (Z)-6-pentadecene triggers hygienic behavior in a two-hour assay, and that high-performing colonies (hygienic response to ≥60% of treated cells) have significantly lower Varroa infestations, remove significantly more introduced Varroa, and are significantly more likely to survive the winter compared to low-performing colonies (hygienic response to <60% of treated cells). We discuss the relative efficacy and efficiency of this assay for facilitating apiary management decisions and selection of Varroa-resistant honey bees, as well as the relevance of these findings to honey bee health, pollination services, and social insect communication.     

Integrated Pest Management Control of Varroa destructor (Acari: Varroidae), the Most Damaging Pest of (Apis mellifera L. (Hymenoptera: Apidae)) Colonies

Varroa destructor is among the greatest biological threats to western honey bee (Apis mellifera L.) health worldwide. Beekeepers routinely use chemical treatments to control this parasite, though overuse and mismanagement of these treatments have led to widespread resistance in Varroa populations. Integrated Pest Management (IPM) is an ecologically based, sustainable approach to pest management that relies on a combination of control tactics that minimize environmental impacts. Herein, we provide an in-depth review of the components of IPM in a Varroa control context. These include determining economic thresholds for the mite, identification of and monitoring for Varroa, prevention strategies, and risk conscious treatments. Furthermore, we provide a detailed review of cultural, mechanical, biological, and chemical control strategies, both longstanding and emerging, used against Varroa globally. For each control type, we describe all available treatments, their efficacies against Varroa as described in the primary scientific literature, and the obstacles to their adoption. Unfortunately, reliable IPM protocols do not exist for Varroa due to the complex biology of the mite and strong reliance on chemical control by beekeepers. To encourage beekeeper adoption, a successful IPM approach to Varroa control in managed colonies must be an improvement over conventional control methods and include cost-effective treatments that can be employed readily by beekeepers. It is our intention to provide the most thorough review of Varroa control options available, ultimately framing our discussion within the context of IPM. We hope this article is a call-to-arms against the most damaging pest managed honey bee colonies face worldwide.     

Differential Expression of Three Dopamine Receptors in Varroa-Resistant Honey Bees

Various stocks of honey bees (Apis mellifera L. (Hymenoptera: Apidae)) employ multiple mechanisms to control varroa mite (Varroa destructor Anderson & Trueman (Mesostigmata: Varroidae)) infestations. Identification of trait-associated genes and markers can improve efficiency of selective breeding. Dopamine receptors show promise in this regard in their association with numerous traits in honey bees, high plasticity, and indicated association with varroa resistance through QTL analysis. We assessed the relationship between exposure to mite-infested brood and gene expression of the honey bee dopamine receptors, Amdop1, Amdop2, and Amdop3, in bees and stocks with known levels of varroa resistance, in Spring 2016 (VSH vs Italian) and Summer 2019 (Pol-line vs Italian). Relative mRNA expression levels varied both by honey bee stock and before/after exposure to varroa-infested brood, in 7-, 10-, and 14-day-old bees. However, the trials revealed contrasting patterns in expression of the three dopamine receptors. In 2016, downregulation was evident in VSH bees, but varied by days post-emergence and by gene. The 2019 trial showed upregulation post-exposure in both stocks, and at all ages, for Amdop1, Amdop2, and Amdop3, with the exception of 14 d Italian bees for Amdop2 and Amdop3. Stock comparison in 2019 showed upregulation of all three dopamine-like receptors in post-exposure bees of all ages. Season and associated differences in mite loads may have contributed to the differences observed across trials. Differential expression of all three dopamine receptors suggests a role for the dopaminergic system in varroa resistance and suggests that further characterization of these receptors for breeding potential is warranted.     

The Life Span and Levels of Oxidative Stress in Foragers Between Feral and Managed Honey Bee Colonies

Molecular damage caused by oxidative stress may lead to organismal aging and result in acute mortality to organisms. Thus, oxidative stress resistance and longevity are closely linked. Honey bees (Apis mellifera) are the most important managed pollinator in agriculture, but the long-term survival of honey bees is seriously threatened. Feral honey bee colonies can be used as natural resources to improve honey bee health. One question we ask here is whether feral honey bees are stress resistant or survive longer than managed bee populations. More work is needed to determine the impact of oxidative stress on honey bee health and survival. In this study, we used paired colony designs to compare the life span of worker bees (foragers) between feral and managed colonies and their levels of oxidative stress. Each pair of colonies shared similar foraging resources. The results indicated that foragers in feral colonies had longer survival times and life spans than those in managed colonies. The levels of oxidative stress from lipid damage content in feral colonies were higher than those in managed colonies, indicating that they used a tolerance mechanism rather than a repair mechanism to survive. Our study provides new insights into a colony difference in the physiology and oxidative stress resistance of feral honey bees compared with managed colony stocks.     

Evaluating and Comparing the Natural Cell Structure and Dimensions of Honey Bee Comb Cells of Chinese Bee,Apis cerana cerana (Hymenoptera: Apidae) and Italian Bee,Apis mellifera ligustica (Hymenoptera: Apidae)

The hexagonal structure of the honey bee comb cell has been the source of many studies attempting to understand its structure and function. In the storage area of the comb, only honey is stored and no brood is reared. We predicted that honey bees may construct different hexagonal cells for brood rearing and honey storage. We used quantitative analyses to evaluate the structure and function of the natural comb cell in the Chinese bee, Apis cerana cerana and the Italian bee, A. mellifera ligustica. We made cell molds using a crystal glue solution and measured the structure and inclination of cells. We found that the comb cells of A. c. cerana had both upward-sloping and downward-sloping cells; while the A. m. ligustica cells all tilted upwards. Interestingly, the cells did not conform to the regular hexagonal prism structure and showed irregular diameter sizes. In both species, comb cells also were differentiated into worker, drone and honey cells, differing in their diameter and depth. This study revealed unique differences in the structure and function of comb cells and showed that honey bees design their cells with precise engineering to increase storage capacity, and to create adequate growing room for their brood.     

An acaricide-treated net to control phytophagous mites

A new technique to control phytophagous mites was tested in West Africa on the African eggplant Solanum macrocarpon. This technique consisted of covering plants with a net impregnated with the acaricide dicofol. The net was applied during the night to protect the net fabric and the active ingredient from UV degradation and to avoid interference of the net with overhead watering. The technique was evaluated in three trials at the INRAB research station and in a grower's field in 2006 and 2007. Results showed that the broad mite Polyphagotarsonemus latus (Banks), the major pest of S. macrocarpon which causes severe damage to leaves, and spider mites (Tetranychus spp.), were completely controlled by the dicofol-treated net. Very few mites and practically no mite injury were observed on plants covered with the dicofol-treated net compared to 12–94% damaged leaves in the unprotected control plots. The acaricide-treated net was as efficient when used temporarily (once every three nights) as when used every night. No difference in the percentages of leaves damaged by mites was apparent at harvest between plots covered with a non-acaricide deltamethrin-treated net (40%) and unprotected control (32%). This new concept of mite control using an acaricide-treated net temporarily covering vegetable crop appears to be an efficient tool which is easy to use. It can be used repeatedly reducing costs and poses a very low risk of environmental pollution when used in the dry season or in greenhouses.     

A new tray-type arena to mass rear Neoseiulus baraki, a predatory mite of coconut mite, Aceria guerreronis in the laboratory

Neoseiulus baraki Athias-Henriot (Acari: Phytoseiidae) is an important predatory mite of the coconut mite, Aceria guerreronis Keifer (Acari: Eriophyidae) and attempts are now being made to evaluate the effectiveness of augmenting N. baraki to control coconut mite in the field. These studies require a steady supply of N. baraki in large numbers. One major constraint of the existing method to mass rear N. baraki on Tyrophagus putrescentiae Shrank (Acari: Acaridae) in a closed arena without a water barrier was frequent contamination of cultures by other mites. This paper describes the development of an efficient method to mass rear N. baraki in the laboratory with less monitoring and relatively minimal contaminants. Three box-type arenas and a tray-type arena were tested to mass rear T. putrescentiae. Mites were successfully developed on two box-type arenas and the tray-type arena, but the production (2197 mites per tray in 4 weeks) of T. putrescentiae was significantly higher on the tray-type arena. A 110-fold increase of T. putrescentiae was achieved in tray-type arenas in 4 weeks. None of the box-type arenas could be maintained more than 5 weeks without acarine and fungal contaminations. N. baraki could be successfully reared on the tray-type arena at least for 6 weeks. More than 4800 mites per tray, a 240-fold increase was achieved in 5 weeks when T. putrescentiae was added at 3-week intervals. Advantages and disadvantages of the new method are described.     

North American Prairie Is a Source of Pollen for Managed Honey Bees (Hymenoptera: Apidae)

Prairie was a dominant habitat within large portions of North America before European settlement. Conversion of prairies to farmland resulted in the loss of a large proportion of native floral resources, contributing to the decline of native pollinator populations. Efforts to reconstruct prairie could provide honey bees (Apis mellifera) a source of much-needed forage, especially in regions dominated by crop production. To what extent honey bees, which were introduced to North America by European settlers, use plants native to prairies is unclear. We placed colonies with pollen traps within reconstructed prairies in central Iowa to determine which and how much pollen is collected from prairie plants. Honey bee colonies collected more pollen from nonnative than native plants during June and July. During August and September, honey bee colonies collected more pollen from plants native to prairies. Our results suggest that honey bees’ use of native prairie plants may depend upon the seasonality of both native and nonnative plants present in the landscape. This finding may be useful for addressing the nutritional health of honey bees, as colonies in this region frequently suffer from a dearth of forage contributing to colony declines during August and September when crops and weedy plants cease blooming. These results suggest that prairie can be a significant source of forage for honey bees in the later part of the growing season in the Midwestern United States; we discuss this insight in the context of honey bee health and biodiversity conservation.     

Selective control of mite and collembolan pests of pastures and grain crops in Australia

Control of invertebrate pests in broad-acre agriculture largely relies on the application of broad-spectrum pesticides, however resistance problems and environmental concerns are driving a search for alternatives including more selective products. Here we explore the feasibility of using novel chemical groupings in the control of problematic pests that attack germinating pastures and grain crops in Australia. A modified laboratory bioassay is described for testing the response of several invertebrate pests to pesticides that have contact and systemic/translaminar properties. Two contact pesticides (fenitrothion and gamma-cyhalothrin) and three pesticides with strong systemic/translaminar properties (lambda-cyhalothrin, abamectin and diafenthiuron) showed promise for control of the collembolan Sminthurus viridis and four mite pests (Halotydeus destructor, Balaustium medicagoense, Penthaleus falcatus and Bryobia sp.). No single pesticide emerged as the most efficacious against all these pests, highlighting the need for correct pest identification before making control recommendations. Incorporating these new chemical options into pest control programs may help to control emerging pests and counter pesticide resistance issues. Selective pesticides in particular are likely to be compatible with integrated control programs that promote the establishment and maintenance of beneficial natural enemies.     

Spiromesifen resistance in Tetranychus urticae (Acari: Tetranychidae): Selection,stability, and monitoring

The two-spotted spider mite, Tetranychus urticae Koch, is an important pest of many agricultural crops. Studies on artificial selections, stability of resistance and monitoring of spiromesifen resistance were carried out to provide basic information for a spiromesifen resistance management program in T. urticae. Artificial laboratory selections for resistance to spiromesifen were performed in a population originating from a mixture of four field populations collected in commercial chrysanthemum fields in the State of São Paulo, Brazil. After 20 cycles of selection for spiromesifen resistance, the resistance ratio (RR₅₀) reached 121. Spiromesifen resistance was shown to be unstable in the absence of selection pressure under laboratory conditions. The frequency of spiromesifen resistance decreased from 75 to 0.15% in six months. The evaluation of 23 T. urticae populations from several crops in the States of Goiás, Mato Grosso and São Paulo in Brazil indicated that the susceptibility of the spider mites to spiromesifen was variable, with percentages of resistant mites ranging from 0.0 to 81.5%. The highest resistance frequencies were observed in ornamental plants (roses and chrysanthemum) in the State of São Paulo. Populations of T. urticae with up to 29.8% resistant mites were also detected in strawberry fields, in the same State. This is the first report on spiromesifen resistance in T. urticae on several crops in Brazil. Strategies for the management of acaricide resistance are discussed.     

Single versus multiple releases of predatory mites combined with spinosad for the management of western flower thrips in strawberry

Western flower thrips, Frankliniella occidentalis (Pergande), is a major pest of strawberry and other horticultural and ornamental crops. Biological control of F. occidentalis with predatory mites is recommended as an additional management strategy to chemical control in glasshouse and protected crops. However, it is not known whether multiple (two or three) species releases of predatory mites are more effective than single species releases. The effect of an application of spinosad followed by mite releases could further increase suppression of F. occidentalis. In a series of trials in the glasshouse, we evaluated three commercially available predatory mite species, Typhlodromips montdorensis (Schicha), Neoseiulus cucumeris (Oudemans) and Hypoaspis miles (Berlese). Strawberry plants were sprayed once with either spinosad at the recommended rate or with water. F. occidentalis adults were released onto plants 24 h after spraying, and mites were released six days later. Spinosad significantly reduced F. occidentalis compared to the control (water). T. montdorensis, N. cucumeris and H. miles significantly reduced F. occidentalis compared to the ‘no mite’ treatment. Spinosad had no effect on T. montdorensis and N. cucumeris, as their numbers did not differ between the spinosad and control treatments; H. miles was not recovered. When mites were released after an application of spinosad, greater suppression of F. occidentalis was achieved than with releases of predatory mites alone. When released as a double species combination, ‘T. montdorensis and H. miles’ was the most effective combination. There was no difference in efficacy between releases of ‘T. montdorensis and H. miles’ or ‘T. montdorensis, N. cucumeris and H. miles’. We conclude that multiple species releases are more effective than single species releases, and that biological control of F. occidentalis with predatory mites can be used together with spinosad.     

The Protective Effect of Whole Honey and Phenolic Extract on Oxidative DNA Damage in Mice Lymphocytes Using Comet Assay

In this study, the antioxidant activity and the protective effect against hydrogen peroxide-induced DNA damage were assessed for five honeys of different botanical origin. Seven phenolic acids were detected in the honey samples. Ferulic acid was the most abundant phenolic acid detected in longan honey, jujube honey and buckwheat honey. Ellagic acid, p-hydroxybenzoic acid and protocatechuic acid were the main phenolic acids detected in vitex honey. Of all honey samples tested, the highest total phenolic content and antioxidant activity were found in buckwheat honey, whereas the lowest total phenolic content and antioxidant activity were found in locust honey. Treatment with hydrogen peroxide induced a 62% increase in tail DNA in mice lymphocytes, and all studied honeys significantly inhibited this effect (P < 0.05). The buckwheat honey with higher antioxidant capability also exhibited super protective effect than others. Phenolic extracts of honey displayed greater protective effects than whole honey in comet assay. The hydrogen peroxide-generated increase in 8-hydroxy-2-deoxyguanosine (8-OHdG) was effectively inhibited by the honeys studied (P < 0.05). Moreover, a dose-effect relationship between honey concentration and its protective effect was clearly observed in this study. It can be deduced that phenolic acids of honey can penetrate into lymphocytes and protect DNA from oxidative damage by scavenging hydrogen peroxide and/or chelating ferrous ions.     

Pollen Treated with a Combination of Agrochemicals Commonly Applied During Almond Bloom Reduces the Emergence Rate and Longevity of Honey Bee (Hymenoptera: Apidae) Queens

Honey bee (Apis mellifera L.) colonies that pollinate California’s almond orchards are often exposed to mixtures of agrochemicals. Although agrochemicals applied during almond bloom are typically considered bee-safe when applied alone, their combined effects to honey bees are largely untested. In recent years, beekeepers providing pollination services to California’s almond orchards have reported reductions in queen quality during and immediately after bloom, raising concerns that pesticide exposure may be involved. Previous research identified a synergistic effect between the insecticide active ingredient chlorantraniliprole and the fungicide active ingredient propiconazole to lab-reared worker brood, but their effects to developing queens are unknown. To test the individual and combined effects of these pesticides on the survival and emergence of developing queens, we fed worker honey bees in closed queen rearing boxes with pollen artificially contaminated with formulated pesticides containing these active ingredients as well as the spray adjuvant Dyne-Amic, which contains both organosilicone and alkyphenol ethoxylate. The translocation of pesticides from pesticide-treated pollen into the royal jelly secretions of nurse bees was also measured. Despite consistently low levels of all pesticide active ingredients in royal jelly, the survival of queens from pupation to 7 d post-emergence were reduced in queens reared by worker bees fed pollen containing a combination of formulated chlorantraniliprole (Altacor), propiconazole (Tilt), and Dyne-Amic, as well as the toxic standard, diflubenzuron (Dimilin 2L), applied in isolation. These results support recommendations to protect honey bee health by avoiding application of pesticide tank-mixes containing insecticides and adjuvants during almond bloom.     

Surfing the Sweet Wave: Migrating Giant Honey Bees (Hymenoptera: Apidae: Apis dorsata) Display Spatial and Temporal Fidelity to Annual Stopover Site in Thailand

Apis dorsata F. (Hymenoptera: Apidae), the giant honey bee of southern Asia, is an important pollinator of crops and non-cultivated angiosperms, and a producer of honey and beeswax. Its populations are in decline in many areas. Colonies migrate seasonally between highland and lowland nesting sites, taking advantage of available food sources. In 2009, a stopover site was discovered in Thailand where numerous migrating colonies bivouacked near one another. Bivouacs used the site again in 2010. I went to the site in 2016 to test the hypothesis that bees use the site regularly as part of an annual migration. I witnessed many bivouacs, spanning almost precisely the same time period and occupying the same area as in 2010. Here I describe their migratory dances in preparation for departure and their subsequent flights as well as periodic mass flight and defensive behavior. Analysis of photographs indicated that the bivouacking bees aged slowly and may thus live long enough to be capable of intergenerational transmission of migratory route knowledge. I describe attributes of the stopover site, e.g., abundant food and water availability, its location along a major river, and other possible navigational cues. Although the site is the only one of its kind so far known to researchers, such stopover sites probably exist wherever giant honey bees undertake long seasonal migrations. I recommend searching for bivouacking sites, particularly along rivers, wherever giant honey bees migrate. Stopover sites are undoubtedly essential to the life history and health of migratory bee populations, and thus warrant conservation policies.     

Long-term pre-exposure of the pest mite Tyrophagus putrescentiae to sub-lethal residues of bifenthrin on rapeseed did not affect its susceptibility to bifenthrin

Tyrophagus putrescentiae on rapeseed was exposed to a sub-lethal residue of 0.15 μg of bifenthrin per 100 g of rapeseed over 147 days, i.e. 14 generations. Every 21 days, samples of mites were collected and mortality was evaluated using a bifenthrin-treated filter paper bioassay. The sampled mites were also introduced onto newly-treated seeds. The susceptibility of the mites to bifenthrin remained similar after pre-exposure for all intervals from 21 to 147 days. The, LD₅₀ ranged from 0.16 to 1.14 μg of bifenthrin per cm² of filter paper. After 147 days, the rates of population increase and respiration of mites pre-exposed to the sub-lethal dose of bifenthrin were evaluated on bifenthrin treated (sub-lethal dose) and untreated rapeseed. Pre-exposure to bifenthrin had no significant effect on respiration, but influenced the rate of increase of mites on rapeseed: The mites pre-exposed to the sub-lethal dose of exhibited a higher rate of increase on the bifenthrin-treated rapeseed than on untreated rapeseed. Thus a decrease in the susceptibility of T. putrescentiae to bifenthrin with selection on a sub-lethal bifenthrin dose on rapeseed during up to 147 days of exposure during which the mite completed approximately 14 generations was not observed. However, the sub-lethal doses of bifenthrin stimulated the population growth and metabolic activity of the mites. Under such conditions, the production of hazardous proteins will probably be higher than on untreated rapeseed.     

The use of bees for the purpose of inter-mating in potato

The pollination behavior of bumblebees and honey bees was studied on potato flowers in screened enclosures and in the field. In enclosures, the domestic honey bee (Apis mellifera L.) and the bumblebee species,Bombus fervidus Fabricius, seemed to lack any “cue” to initiate visitation of the flowers. When honey was placed on a few flowers, visitation was stimulated. The honey bee tore and chewed at the anther cone to collect pollen, whileB. fervidus probed for nectar which was not present. Shortly afterward, both species ceased visitation and could not be induced to visit further, regardless of the honey stimulus. Neither species was effective as a pollinator. It is concluded that neither species will be useful for large-scale crossing of potato populations. However, another bumblebee species,Bombus impatiens Cresson, is very effective in pollinating potatoes in the field. Manipulating the behavior of such indigenous populations of bumblebees is likely to be the most effective method of exploiting insect pollination in the potato.     

Quality Evaluation of Honey Harvested From Selected Areas in Tanzania With Special Emphasis on Hydroxymethyl Furfural (HMF) Levels

The physicochemical properties of honey harvested from popular honey-producing areas in Tanzania were investigated. Honey from Shibe-Dodoma had the highest values of specific gravity, total acidity, free fatty acid content, diastatic number, overall acceptability, and lowest hydroxymethyl-furfural (HMF) level as compared to honey samples from other areas. There was no significant difference (p>0.05) in terms of HMF in the other honey samples from Tanga, Morogoro, Same, Arusha, and Tabora. HMF levels in all honey samples were far below the maximum acceptable level of 40 mg/kg as recommended by the Codex Alimentarius Commission Standards before storage for 6 months. No traces of streptomycin and phenol were detected in all honey samples. It was concluded that according to the values of the studied quality parameters, the types of Tanzanian honey obtained from the popular honey producing areas may be judged to be of high quality.     

玉米自交系对朱砂叶螨的抗性评价

采用田间罩网接螨和室内盆栽接螨,以叶片危害指数、螨情指数、田间种群密度和种群增长倍数为指标,评价8份自交系玉米对朱砂叶螨(Tetranychuscinnabarinus)的抗性。田间鉴定表明,在苗期和花粒期用叶片危害指数、螨情指数和田间种群密度3种抗性评价指标评价时,自交系HL6044均表现为高抗;用叶片危害指数和螨情指数评价时,自交系ES40在苗期和花粒期均表现为高感;用田间种群密度评价时,ES40在苗期表现为高感,花粒期则表现为中感。室内接螨后20 d,朱砂叶螨种群增长倍数在HL8039和ES40上分别为23.36和24.13倍,在HL6044上仅为2.44倍。8份自交系玉米中,HL6044对朱砂叶螨表现为高抗,叶片危害指数适用于田间玉米抗螨性评价。