Survival and infection of root-knot nematodes added to soil amended with rye at different stages of decomposition and cropped with cotton

The incorporation of a rye (Secale cereale L.) cover crop into the soil pri or to planting cotton (Gossypium hirsutum L.) has been shown to restrict da mage caused by root-knot nematodes (Meloidogyne incognita (Kofoid and White ) Chitwood). A greenhouse study was conducted to determine the duration of the effectiveness of rye decomposition in controlling root-knot nematode da mage in relation to the time between rye incorporation and cotton planting. Fresh, chopped-rye foliage was mixed into pots of soil and root-knot nemat ode eggs were added to the rye + soil mixture or a non-amended soil at 0, 1 , 3, 5, 7, 9, Il, 13, 15, 17, 19, and 21 days following rye incorporation. This resulted in a sequence of pots containing nematode eggs exposed to rye at different stages of decomposition. Cotton plants were transplanted into the pots after the addition of nematode eggs and assessed fur damage after 28 days of exposure. Although the effectiveness of the rye treatment decli ned over the 21 days of the incubation, the root-knot nematode populations were significantly reduced by the rye treatment for all planting dates. Thi s suggests that it is not necessary to plant cotton immediately after plowi ng in a rye cover crop, thereby providing some flexibility in the cotton pl anting date, minimizing any associated phytotoxicity to the young cotton pl ants. (C) 1999 Elsevier Science B.V. All rights reserved.