Efficacy of five nematicides against root-knot nematode when applied via single and double drip tapes in a Florida sandy soil.

BACKGROUND: The efficacy of drip-applied nematicides depends on adequate product distribution, which can be difficult in sandy soils. Three new non-fumigant nematicides (fluazaindolizine, fluensulfone, fluopyram), together with two old nematicides, oxamyl and metam potassium, were evaluated when applied via single and double drip tapes to control root-knot nematode in cucumber and squash in Florida between February 2020 and December 2022. RESULTS: Nematicide applications via double drip tapes resulted in lower root gall infection (and tend to have higher yield) as compared to a single tape for fluopyram, but no difference was noted between single and double tapes for oxamyl and fluazaindolizine. Fluensulfone response was somewhere in between and metam potassium had higher squash yield when applied with double tapes. Root-knot infection was higher in cucumber than in squash, and metam potassium had the highest yields and lowest nematode infection compared to other nematicide treatments. CONCLUSION: The benefit of double versus single drip tapes depended on the type of nematicide that was applied and was evident for nematicides that have poor water solubility like fluopyram. Some benefit was noted for metam potassium, but no or limited benefit was noted for oxamyl, fluazaindolizine and fluensulfone. © 2023 Society of Chemical Industry.

Root-knot nematode damage to a cucurbit double crop is increased by chloropicrin fumigation on the previous tomato crop.

BACKGROUND: Double-cropping is a common practice in vegetable plasticulture whereby a second crop is planted on the same plastic bed as the first crop. Root-knot nematodes (Meloidogyne spp.) are one of the major soilborne constraints in double-cropped vegetables due to nematode population build-up on the first crop. We evaluated the effect of fumigant and non-fumigant nematicides applied on the first crop, on nematode infection and yield of the second crop in 10 field trials between 2017 and 2020. Fumigants were chloropicrin (Pic100), chloropicrin +1,3-D (PicClor60), and non-fumigant nematicides were oxamyl (Vydate), fluensulfone (Nimitz), fluopyram (Velum) and fluazaindolizine (Salibro). The first crop was tomato and double crops were cucumber, squash, zucchini, and cantaloupe. RESULTS: Fumigation with chloropicrin on the first crop increased root-knot nematode damage on the double-crop at the end of the season in seven trials, while the opposite was noted in one trial, and no difference was noted in two trials. Fumigation with chloropicrin+1,3-D resulted in root-knot nematode damage less than chloropicrin but more than non-fumigated plots. Cucurbit yield was greater in non-fumigated beds in four trials, and in chloropicrin-treated beds in two trials. Fluensulfone reduced root-knot nematode damage on the second crop in five out of 10 trials. CONCLUSION: Our results indicate that chloropicrin applied on the tomato crop may lead to increased root-knot nematode damage on the double crop. More research is needed to understand the processes behind this, but it is possibly related to a reduction in natural nematode soil suppressiveness due to the broad-spectrum fungicidal activity of chloropicrin. © 2022 Society of Chemical Industry.

Efficacy of nonfumigant nematicides against Meloidogyne javanica as affected by soil temperature under pasteurized and natural soil conditions.

BACKGROUND: Biotic and abiotic factors such as microbes and soil temperature can affect nematicide efficacy. Two experiments were conducted to test the effect of three soil temperatures on the efficacy of nonfumigant nematicides (fluopyram, fluensulfone, oxamyl and fluazaindolizine) against Meloidogyne javanica in pasteurized and natural soil in planta. RESULTS: The results showed that all tested nematicides were more efficacious in pasteurized than in natural soil. Temperature affected the nematicides differently with no effect of soil temperature on oxamyl and fluazaindolizine, whereas fluopyram and fluensulfone had greater efficacy at higher soil temperatures. CONCLUSION: Temperature effects were noted for some but not all nonfumigant nematicides. Fluopyram and fluensulfone were less effective when applied in cold soil, whereas oxamyl and fluazaindolizine were not affected by soil temperature. Although all nematicides resulted in almost complete control of M. javanica in pasteurized soil, this was not the case in natural soil, and much more root damage and nematode reproduction was noted in the latter. © 2021 Society of Chemical Industry.