Blue-green algae, or cyanobacteria, is a photosynthetic organism that can proliferate, or “bloom”, in waters that are warm and stagnant. It is a concern for human and animal health because it can produce toxins that cause nerve and liver damage. Blue-green algae has been in the news recently. In mid-July, residents of Discovery Bay reported seeing it in the waters of that community. More recently, it has been observed in other Delta waters. While the presence of blue-green algae does not guarantee the presence of toxins, the water around Discovery Bay was tested and confirmed to have the toxin microcystin, and the public has been advised not to enter waters where blue-green algae blooms are observed. Blue-green algae affected waters appear as olive-colored, have surface scums or the appearance of oil slicks, or have green flecks of material. The waters may also have a musty odor.

I was recently asked by a grower if irrigating with water having blue-green algae can damage crops. I have not been able to find much local or statewide knowledge on this, but I have found some pamphlets out of Australia that address this question.  I have attached those documents below. Both documents indicate that there is more to learn about whether irrigation water having blue-green algae will affect plants. If there are detrimental effects, they would mostly likely reduce germination or seedling growth, which could ultimately reduce productivity. Another concern for growers is that the blue-green algae could clog irrigation equipment and reduce its efficiency. Because blue-green algae toxins are heat-stabile, it is advised not to use overhead irrigation on crops that are eaten directly, and it is advised that animals not be put on grazed crops (where irrigation water may have touched foliage) for at least seven days after irrigating. The toxins are water soluble, so advice for consumers is to thoroughly wash produce with clean water before consuming, whether eating it raw or cooked.

Luckily, the blue-green algae population should decrease as winter approaches and the weather (and waters) cool down. In the meantime, the State Water Resources Control Board has developed a website (http://www.mywaterquality.ca.gov/habs/index.html ) where the public can see where blue-green algae blooms have been verified and report a bloom that has been encountered. In addition to the website, bloom reporting and information is available by phone (916-341-5357 or toll free at 844-729-6466) or email (CyanoHAB.Reports@waterboards.ca.gov).