An organic celery field in Santa Maria was severely infested with an unknown aphid feeding on plant roots. Aphid feeding reduced plant growth and resulted in 80% yield loss. The aphid was later identified by the California Department of Food and Agriculture (CDFA) as the rice root aphid and honeysuckle aphid. In California, there was only one earlier record of honeysuckle aphid infestation on celery. Rice root aphid has never been reported on celery.
Strawberry and Vegetable Crops Advisor and Affiliated IPM Advisor Surendra Dara responded by working with CDFA to identify the aphid. He also tested several organic microbial and botanical insecticides. Microbial insecticides are bacteria or fungi and botanical insecticides are compounds from plants that kill insects. The insecticides tested were rosemary oil plus peppermint oil, azadirachtin (compound from the neem plant), Beauveria bassiana (fungus), Burkholderia spp. (bacterium), and Chromobacterium subtsugae (bacterium).
Dara counted the number of aphids before applying the test insecticides and after two applications. Two of the insecticides alone, Beauveria bassiana and azadiractin, did not reduce aphid numbers, but when combined together did reduce aphid numbers. Burkholderia spp. and Chromobacterium subtsugae also somewhat reduced aphid numbers, providing moderate control.
Growers and pest control advisers now know of two new aphids that they need to be aware of and the damage they can cause to celery stands. Dara tested organic insecticides and combinations of insecticides, providing an option for growers to manage these new pests. He has been checking with the growers since the initial outbreaks. They have been using Beauveria bassiana and azadiractin and no longer have outbreaks of aphids.