A new study from the Federal University of Vicosa in Brazil has found that copper sulfate, when used as a leaf fertilizer, is lethal to the native Brazilian bee known as Friesella schrottkyi. In addition, the study, which was published in the Journal of Economic Entomology, found that sublethal exposure also affected the bee’s behavior.
The use of copper sulfate in agriculture dates back to the 1800s and is widely used as a fungicide on organic and conventional crops. It is also found in some fertilizer products.
“This could have implications for growers who use copper sulfate as a leaf fertilizer, and as a fungicide,” said Dr. Raul Narciso Guedes, one of the co-authors.
The researchers were surprised to find that, under oral exposure, the copper sulfate fertilizer killed all of the test bees within 72 hours, and was more lethal than the spinosad control.
Stingless bees are the prevailing wild pollinators in this region and are more efficient than honey bees, which is partially why the researchers chose to study the effects of copper sulfate on Friesella schrottkyi.
“When considering agricultural production as a potential threat to Neotropical stingless bees, the problems likely go beyond pesticide use,” the authors wrote. “Leaf fertilizers seem to deserve attention and concern regarding their potential impact on native pollinators, notably Neotropical stingless bees such as F. schrottkyi.”
Does This Mean Organic is Contributing to Colony Collapse?
Opponents of organics may take this study as an opportunity to say that organic agriculture is contributing to colony collapse disorder due to the use of copper sulfate. To fully understand the issue we have to look at how copper sulfate is actually used and allowed in organic agriculture.
Copper sulfate is highly regulated in organic agriculture, and can only be use under certain conditions:
- Organic rice growers may use copper sulfate to kill off algae or tadpole shrimp in their aquatic systems, once every two years, and only if used in a concentration that doesn’t affect the levels of copper in the soil.
- Can be used as a fungicide to treat blight on leaves, only if other measures have proven not to be working, and it has to be applied sparingly so it doesn’t accumulate in the soil.
Copper sulfate is not approved or used as a fertilizer in organic agriculture. As opposed to conventional agriculture, copper sulfate cannot be sprayed without restriction in organic agriculture. While copper sulfate is toxic to bees, it is used in organic agriculture very sparingly and only as a last-ditch effort to save a crop.
It is unknown if copper sulfate is toxic to honeybees and native pollinators in other parts of the world.
Sources:
http://articles.extension.org/pages/18351/organic-management-of-late-blight-of-potato-and-tomato-with-copper-products
http://www.ecfr.gov/cgi-bin/retrieveECFR?gp=1&SID=e7b9a24ce90876c43c98f49af1c99fe7&ty=HTML&h=L&mc=true&r=SUBJGRP&n=sg7.3.205.g.sg0
http://www.eurekalert.org/pub_releases/2016-04/esoa-csf041116.php