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 prior to planting cotton (Gossypium hirsutum L.) has been shown to restrict damage 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 damage in relation to the time between rye incorporation and cotton planting. Fresh, chopped-rye foliage was mixed into pots of soil and root-knot nematode eggs were added to the rye + soil mixture or a non-amended soil at 0, 1, 3, 5, 7, 9, 11, 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 for damage after 28 days of exposure. Although the effectiveness of the rye treatment declined over the 21 days of the incubation, the root-knot nematode populations were signi®cantly reduced by the rye treatment for all planting dates. This suggests that it is not necessary to plant cotton immediately after plowing in a rye cover crop, thereby providing some ̄exibility in the cotton planting date, minimizing any associated phytotoxicity to the young cotton plants. # 1999 Elsevier Science B.V. All rights reserved.