Almond Facts, May-June 2021

IN YOUR ORCHARD Varroa Loads Varroa destructor is a pernicious pest of honey bee colonies, not only do they feed on the bees fat body, they also transmit a variety of viruses. Varroa populations usually increase during the beekeeping season. Most beekeepers treat their colonies to keep Varroa loads below the standard industry threshold of 3%. To determine Varroa levels, our field specialists perform an alcohol wash on a sample of approximately 300 bees. During almonds this year, Varroa loads were low overall. Varroa were found between 3% and 75% of colonies depending on the region of origin and the week sampled. 33 beekeepers were sampled during this period across the five regions. They had Varroa mites in anywhere between 0% and 90% of their colonies, but only four of those beekeepers had colonies over the 3% threshold. Some of the higher Varroa loads came from a few outliers from the North Central region, but that region was also the most heavily sampled. The average Varroa load for all samples (all teams) was 0.32 mites per 100 bees. Fig. 1: Proportion of colonies with fewer than four frames (red), between four & six frames (yellow) and over six frames (blue) of bees for each of the 31 beekeepers sampled (with a minimum of 15 colonies sampled) during 2021 almond pollination. Fig. 2: Number of frames of bees recorded for all colonies sampled during almond pollination 2021. The dashed line represents the six frame of bees requirement, showing the vast majority of colonies sampled above threshold. Beekeepers sampled ranged between 38% and 100% of their colonies ranking above the six frames of bees requirement (Fig. 1). However, overall, our BIP Tech Transfer Team participating members had an average of 9.8 frames of bees across all operations, regions of origin and time period sampled (Fig. 2). Varroa levels were low overall but nosema spore counts spiked near the end of bloom. — Ben Sallmann, Northwest Region Field Specialist 3 6 A L M O N D F A C T S