The USDA Agricultural Research Service reports bee populations are on the decline due to nutrition deficiencies and pesticide use on crops on which bees feed.
Bee populations have been declining with the total number of managed honey bee colonies down from 5 million in the 1940s to 2.5 million in November 2015 (USDA Agricultural Research Service, or ARS).
ARS reported annual losses for bee colonies were 42.1 percent for April 2014 to April 2015 (up from 34.2 percent in 2013-14), with summer losses exceeding winter losses for the first time.
Although Colony Collapse Disorder evidence is down, Nosema fungi, Varroa mites, nutrition deficiencies from a lack of diverse plant pollen and nectar sources, and pesticide use are influencing overall losses.
Researchers at Oregon State University have been studying bees and hives to examine protein levels and the impact of mites and fungi. They monitor bee health as bees are transported from one field to another and again when the bees are brought home. They also respond to beekeepers’ requests to find out why their bees are dying.
In one case, the scientists, led by Dr. Ramesh Sagili, discovered the bees were dying of starvation within one week of exposure to a pesticide commonly used on the crop on which they were feeding. By changing the timing of application, the farmers were able to avoid contaminating the bees.
With crops such as hybrid carrots, there is not enough pollen to provide the foraging bees with the protein they need. Dr. Sagili added supplemental protein patties to the hives and was able to reduce the drop in protein levels. In addition, a diet devoid of diverse food sources isn’t healthy for bees. Dr. Sagili advised almond growers to improve nutrition for the bees by adding a variety of forages, such as mustard, clover and wildflowers, to their orchards. However, nutrition is only one issue.
The Varroa mite, found in the USA in 1987, is a parasite that sucks the blood out of bees and spreads a deadly viral disease. Dr. Sagili’s team found these mites were attacking bees sooner than beekeepers thought. The team recommended application of miticides as soon as bees were done pollinating fields, rather than waiting to apply until the bees were back home.
To help honey bees we shouldn’t apply pesticides without adequate research into whether a pesticide is the needed management strategy for a specifically identified pest. Pesticides (and this includes herbicides, insecticides, etc.) shouldn’t be applied during midday hours when bees are out foraging. We can also plant bee-friendly plants.
On Feb. 23, learn about dealing with pests in the landscape and garden from 6 to 8 p.m. at Bartley Ranch Regional Park in Reno. The class is free.
JoAnne Skelly is Associate Professor & Extension Educator, Emerita at University of Nevada Cooperative Extension. She can be reached at skellyj@unce.unr.edu.
