The Effect of Cover Crops on Suppression of Nematodes on Peanuts and Cotton in Alabama

Abstract

Cover crops were evaluated in the greenhouse and in field locations to determine their host status and nematode suppressive effect on root-knot nematodes, Meloidogyne incognita and M. arenaria and the reniform nematode, Rotylenchulus reniformis. The winter grain cover crop cultivars included commercially available cultivars of wheat ‘Triticum aestivum’ ‘Pioneer 26R12’, ‘AGS 2000’, ‘Coker 9152’, ‘Panola’; oats ‘Avena sativa’ ‘Georgia Mitchell’ and ‘Bob’; rye ‘Secale cereale’ ‘Elbon’ and ‘Abruzzi’. This research also evaluated the host status and nematode suppressive effect of Crotolaria juncea populations. The treatments included the C. juncea populations; PI 207657, PI 314239, PI 322377, PI 391567 and PI 426626 collected in different countries and the commercially available cultivar ‘Tropic Sun’.

Field evaluations of winter grain cover crop cultivars described previously were conducted at WREC in Headland, AL and in a grower’s field in Huxford, AL. There were no significant differences (P = 0.05) between cover crop cultivars on nematodes. This was most probably due to severe drought and uneven rainfall during both the cropping years. However, the greenhouse studies indicated that ‘Elbon’ rye; oats ‘Bob’ and ‘Georgia Mitchell’ supported low populations of M. incognita. While ‘Bob’ oats and the rye ‘Elbon’ and ‘Abruzzi’ supported significantly (P = 0.05) lower R. reniformis populations. C. juncea populations were able to significantly suppress (P = 0.05) M. incognita and R. reniformis in the greenhouse tests. C. juncea roots stained with McCormick Schilling® red food color were found to contain all juvenile stages, low numbers of mature females of M. incognita with egg masses and 1-2 female reniform nematodes per 10 gm of roots, indicating that these nematodes were able to infest and reproduce on C. juncea populations. Freeze-dried root exudates tested against both M. incognita and R. reniformis demonstrated that concentrated exudates could kill both nematodes whereas the water control had no effect. Field trial at EVSRC in Shorter, AL indicated that there were no significant differences observed on Meloidogyne spp. suppression among the C. juncea populations, might be due to severe drought and extreme high temperatures. The knowledge obtained from this study suggests that some winter cover crop cultivars and C. juncea populations may be poor hosts and suitable for crop rotation in a region with specific nematode histories, thus minimizing usage of synthetic nematicides and yield losses. However, further research studies should focus on extensive long-term field studies under controlled irrigation conditions.