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.