Evaluation of botanical and chemical products for the control of foliar nematodes Aphelenchoides fragariae

• Twenty-four chemicals and botanicals were tested for foliar nematode control.
• Eight out of the tested products were effective against nematodes with direct contact.
• Nemakill and Pylon showed the highest efficiency for management of foliar nematodes.

Foliar nematodes Aphelenchoides spp. Pose a serious threat to floriculture by causing significant economic losses in home gardens, production nurseries and arboretums, and threatening precious germplasm collections of many ornamental plants. Control of foliar nematodes has become difficult due to the loss of nematicides following the implementation of the U.S. Food Quality Protection Act. Herein, we used a three-stage approach to evaluate 24 products for their potential to control foliar nematodes Aphelenchoides fragariae in hosta. We first performed a direct contact assay in well-plates where A. fragariae nematodes were exposed to the aqueous suspension of high (2-fold dilution) or low (20-fold dilution) concentration of the test products. The products causing 100% nematode mortality at the low concentration were then tested through a drench application for their effectiveness against foliar nematodes in soil, followed by a leaf-disc test to determine their efficacy against nematodes in leaves as a spray application. Of the 24 products, Ammonia, Clorox, grapefruit seed extract, KMnO4, NaDCC, Nemakill, Pylon and ZeroTol caused 100% nematode mortality in aqueous suspension at 20-fold dilution. Drench application of Ammonia, Clorox, KMnO4, NaDCC and ZeroTol reduced over 85% and over 75% A. fragariae population in soil 7 and 42 days after treatment, respectively. Spray application of ZeroTol could reduce over 70% A. fragariae population in leaf discs, whereas Ammonia, Clorox, KMnO4 and NaDCC caused about 50% reduction. Pylon (24% chlorfenapyr) and Nemakill (32% cinnamon oil, 8% clove oil, 15% thyme oil mixture) showed 100% mortality of A. fragariae in all three types of tests, and thus have great potential to serve as effective alternatives to manage foliar nematodes in floriculture.