Chemical and cultural control of <i>Tropilaelaps mercedesae</i> mites in honeybee (<i>Apis mellifera</i>) colonies in Northern Thailand - Fig 3

<p><b>Average (mean ± SEM) number of frames covered in adult bees (A) and number of <i>Tropilaelaps</i>-infested cells observed by uncapping 100 sealed brood cells (B) from parent honey bee colonies that were used to make a single nucleus colony or unmanipulated control colonies.</b> Letters indicate significant differences between treatment means (ANOVA, P < 0.05).</p

Chemical and cultural control of <i>Tropilaelaps mercedesae</i> mites in honeybee (<i>Apis mellifera</i>) colonies in Northern Thailand

<div><p>At least two parasitic mites have moved from Asian species of honeybees to infest <i>Apis mellifera</i>. Of these two, <i>Varroa destructor</i> is more widespread globally while <i>Tropilaelaps mercedesae</i> has remained largely in Asia. <i>Tropilaelaps</i> mites are most problematic when <i>A</i>. <i>mellifera</i> is managed outside its native range in contact with Asian species of <i>Apis</i>. In areas where this occurs, beekeepers of <i>A</i>. <i>mellifera</i> treat aggressively for <i>Tropilaelaps</i> and <i>Varroa</i> is either outcompeted or is controlled as a result of the aggressive treatment regime used against <i>Tropilaelaps</i>. Many mite control products used worldwide may in fact control both mites but environmental conditions differ globally and thus a control product that works well in one area may be less or ineffective in other areas. This is especially true of volatile compounds. In the current research we tested several commercial products known to control <i>Varroa</i> and powdered sulfur for efficacy against <i>Tropilaelaps</i>. Additionally, we tested the cultural control method of making a hive division to reduce <i>Tropilaelaps</i> growth in both the parent and offspring colony. Making a split or nucleus colony significantly reduced mite population in both the parent and nucleus colony when compared to un-manipulated control colonies. The formic acid product, Mite-Away Quick Strips®, was the only commercial product that significantly reduced mite population 8 weeks after initiation of treatment without side effects. Sulfur also reduced mite populations but both sulfur and Hopguard® significantly impacted colony growth by reducing adult bee populations. Apivar® (amitraz) strips had no effect on mite or adult bee populations under the conditions tested.</p></div

Crop Pollination Exposes Honey Bees to Pesticides Which Alters Their Susceptibility to the Gut Pathogen <i>Nosema ceranae</i>

<div><p>Recent declines in honey bee populations and increasing demand for insect-pollinated crops raise concerns about pollinator shortages. Pesticide exposure and pathogens may interact to have strong negative effects on managed honey bee colonies. Such findings are of great concern given the large numbers and high levels of pesticides found in honey bee colonies. Thus it is crucial to determine how field-relevant combinations and loads of pesticides affect bee health. We collected pollen from bee hives in seven major crops to determine 1) what types of pesticides bees are exposed to when rented for pollination of various crops and 2) how field-relevant pesticide blends affect bees’ susceptibility to the gut parasite <i>Nosema ceranae</i>. Our samples represent pollen collected by foragers for use by the colony, and do not necessarily indicate foragers’ roles as pollinators. In blueberry, cranberry, cucumber, pumpkin and watermelon bees collected pollen almost exclusively from weeds and wildflowers during our sampling. Thus more attention must be paid to how honey bees are exposed to pesticides outside of the field in which they are placed. We detected 35 different pesticides in the sampled pollen, and found high fungicide loads. The insecticides esfenvalerate and phosmet were at a concentration higher than their median lethal dose in at least one pollen sample. While fungicides are typically seen as fairly safe for honey bees, we found an increased probability of <i>Nosema</i> infection in bees that consumed pollen with a higher fungicide load. Our results highlight a need for research on sub-lethal effects of fungicides and other chemicals that bees placed in an agricultural setting are exposed to.</p></div

Quantity and diversity of pollen collected in pollen traps on individual honey bee hives.

<p>Letters indicate statistically different groups.</p

Load varied by pesticide category.

<p>Letters indicate statistically significant differences. The total load for each category is weighted by the number of chemicals in that category, to facilitate comparison across categories.</p

Pollen collection from the crop where a hive was located was low for most crops.

<p>Bars show mean ± se. Letters indicate statistically significant differences (<i>p</i><0.05).</p

Pesticide diversity found in pollen samples, but not pesticide load, varied by crop.

<p>White bars show pesticide diversity, gray bars show pesticide load (mean ± se). Post-hoc testing found the following groups, where letters indicate statistically significant differences: apple a, b; blueberry c; cranberry_early d; cranberry_late b, d, e, f; cucumber e; pumpkin c, d, f; and watermelon d.</p

Fungicide and neonicotinoid diversities varied by crop.

<p>Bars show the total number of pesticides in each category found in each crop. Kruskal-Wallis test statistics comparing pesticide diversity between crops are: fungicides, H₆ = 16.1, <i>p</i> = 0.01; cyclodienes, H₆ = 6.9, <i>p</i> = 0.33; neonicotinoids, H₆ = 17.9, <i>p</i> = 0.007; organophosphates, H₆ = 14.3, <i>p</i> = 0.03; pyrethroids, H₆ = 7.8, <i>p</i> = 0.26. We only compared pesticide diversities for categories containing at least three chemicals. Sequential Bonferroni adjusted critical values are: 0.01, 0.0125, 0.0167, 0.025, 0.05. A * indicates that the total number of pesticides varied between crops within that pesticide category.</p

Pesticides found in pollen trapped off honey bees returning to the nest.

a<p>We divided LD₅₀ values given as µg/bee (g) by 0.128 (equivalent to multiplying by 7.8) to obtain ppm when necessary <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0070182#pone.0070182-Johansen1" target="_blank">[85]</a>. If multiple values have been published, we include only the smallest.</p>b<p>Heptachlor has been banned for use on cranberries since 1978 <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0070182#pone.0070182-US12" target="_blank">[87]</a>, but can persist in the soil for extended periods of time.</p>c<p>Ap = apple, Bl = blueberry, Cr = cranberry, Cu = cucumber, Pu = pumpkin, Wa = watermelon.</p>*<p>Used by beekeepers within the hive for parasitic mite control.</p>†<p>Relative risk different from 1 at the 95% confidence level.</p><p>NA indicates information that is not relevant to control diets.</p

A national survey of managed honey bee 2015–2016 annual colony losses in the USA

<p>Managed honey bee colony losses are of concern in the USA and globally. This survey, which documents the rate of colony loss in the USA during the 2015–2016 season, is the tenth report of winter losses, and the fifth of summer and annual losses. Our results summarize the responses of 5725 valid survey respondents, who collectively managed 427,652 colonies on 1 October 2015, an estimated 16.1% of all managed colonies in the USA. Responding beekeepers reported a total annual colony loss of 40.5% [95% CI 39.8–41.1%] between 1 April 2015 and 1 April 2016. Total winter colony loss was 26.9% [95% CI 26.4–27.4%] while total summer colony loss was 23.6% [95% CI 23.0–24.1%], making this the third consecutive year when summer losses have approximated to winter losses. Across all operation types, 32.3% of responding beekeepers reported no winter losses. Whilst the loss rate in the winter of 2015–2016 was amongst the lowest winter losses recorded over the ten years this survey has been conducted, 59.0% (<i>n</i> = 3378) of responding beekeepers had higher losses than they deemed acceptable.</p