Effects of fluopyram and azadirachtin integration with sunn hemp on nematode communities in zucchini, tomato and sweet potato in Hawaii

Abstract

Fluopyram (Velum ® One) is a synthetic nematicide and azadirachtin (Molt-X ® ) is a biological nematicide. Both have shown promise against plant-parasitic nematodes on several agriculturally important crops.There is a lack of information on integration of pre-plant sunn hemp (Crotalaria juncea) cover crop with these post-plant nematicides, aiming to improve plant-parasitic nematodes management and mitigate any detrimental effects on free-living nematodes. Three field trials were conducted to investigate the effects of fluopyram alone or in combination with pre-plant sunn hemp cover crop, and azadirachtin combined with pre-plant sunn hemp on Rotylenchulus reniformis and Meloidogyne spp., and free-living nematodes. Zucchini (Cucurbita pepo) and tomato (Solanum lycopersicum) were grown in Trials I and II, and sweet potato (Ipomoea batatas) only was grown in Trial III. In all three trials, early applications of fluopyram at crop planting were effective in suppressing the abundance of Meloidogyne spp. (M. incognita and M. javanica) but it was not effective in reducing R. reniformis in the soil. Combining sunn hemp with fluopyram was suppressive to R. reniformis on short-term zucchini crop, but not on longer term tomato and sweet potato crops. In addition, application of fluopyram at transplanting was the key to successful suppression of Meloidogyne spp. as later fluopyram chemigation (at 2 weeks after planting in Trial II or 1 month after planting in Trial III) had no effect against Meloidogyne spp. On the other hand, planting of sunn hemp followed by monthly postplant azadirachtin application consistently suppressed R. reniformis, but this treatment did not suppress Meloidogyne spp. Integrating sunn hemp with fluopyram increased zucchini yield by >2.3 folds and that with azadirachtin increased the zucchini yield by >1.7 folds. Although no yield improvement was observed on tomato in Trial II, integrating sunn hemp with azadirachtin and fluopyram increased tomato yield by 0.23 and 1.12 folds, respectively, in Trial I. Marketable yield of sweet potato was increased by 4.5-6.4 folds in all the fluopyram treatments but was only increased 61.5% by sunn hemp plus azadirachtin treatment. While fluopyram alone often reduced the abundance of free-living nematodes, integrating with sunn hemp mitigated the negative impacts of fluopyram on soil health.

Efficacy of Azadirachtin in the Integrated Management of the Root Knot Nematode Meloidogyne incognita on Short- and Long-Cycle Crops

“…This study also confirmed the nematicidal effectiveness of fluopyram against M. incognita on tomato, in agreement with previous literature reports [ 51 , 52 ]. The combination of azadirachtin with fluopyram or other synthetic nematicides, could be an effective response to the limited-in-time activity of azadirachtin treatments in long-cycle crops.…”

Meloidogyne incognita Management Using Fumigant and Non-fumigant Nematicides on Sweet Potato

“… Grabau et al . (2020) reported no effect of fluopyram on free-living nematodes in peanut production, while Waisen et al . (2021) and Waldo et al .…”

“…(2021) reported that fluensulfone can effectively decrease RKN density in the soil and increase marketable sweet potato yield. Waisen et al . (2021) reported early that fluopyram chemigation can reduce RKN population in sweet potato production.…”

Plant-Parasitic Nematodes and Their Management: A Focus on New Nematicides

“…At concentrations greater than 50 mg/L hatching inhibition is achieved without recovery [115]. In greenhouse and field trials on tomatoes, carrots, cotton (Gossypium hirsutum), potato, and soybean, fluopyram has been effective at managing PPNs [116][117][118].…”