Nematode issues in cover cropping systems Dr. Charles Overstreet Dr. Josielle Rezende Deborah M. Xavier-Mis

What is the impact of cover crops on nematode problems in Louisiana? Forage radish

Reniform nematode Southern root-knot nematode

Reniform nematode Southern root-knot nematode

Cover Crops and Nematodes Host status to the nematode Range from very susceptible to immune S MS MR R I Populations may reflect the host status to the nematode Increase or decrease nematode levels at planting time to main crop Cover crop may increase, decrease, or not influence yield for the following crop

Cover crops that are specific for reducing certain nematodes Sugarbeet cyst nematode- oilseed radish (Defender) and white mustard (Master) Northern root-knot – oilseed radish (Defender) Columbia root-knot- oilseed radish (Control) Stubby root and lesion nematodes- black oats (Pratex) Southern root-knot and reniform nematodes- sunn hemp (Tropic Sun) Southern root-knot nematode- sorghum sudangrass (Green Grazer)

Host status of some cover crops to nematodes in Louisiana Crop Southern root-knot Reniform Grass Oats Poor Poor Rye Poor Poor Wheat Good Poor Legume Austrian winter peas Good Good Crimson clover Good Good Red clover Good Good Subterranean clover Good Poor Vetch Poor*-Good Good White clover Good Good *Cahaba white vetch

Host status of some cover crops to nematodes in Louisiana Crop Southern root-knot Reniform Crucifers Canola Good Poor Oilseed Radish Good Poor Turnip Good Poor White Mustard Good Poor

Southern root-knot nematode reproduction on some cover crops Mi race 3 on cover crops. The cover crops are ‘Bigbee’ berseem clover (Trifolium alexandrinum), ‘Dixie’ crimson clover, ‘AU Sunrise’ crimson clover (T. incarnatum), common hairy vetch, AU Early Cover hairy vetch (Vicia villosa), ‘Paradana balansa’ clover (T. balansae), ‘Cherokee’ red clover (T. pratense), Cahaba’ White vetch (V. sativa), and ‘Wrens Abruzzi’ rye (Secale cereale). Pots were inoculated with 8,000 nematode eggs. Eggs were extracted from roots 60 d later. Bars are the mean of eight replicates and two trials (n = 16). Bars with the same letter are not different (P > 0.05). Timper et al., 2006. J Nematology 38: 83–89.

Galling on cotton after the cover crop Timper et al., 2006. J Nematology 38: 83–89.

Cotton yield after the cover crop Yield in pounds/acre Timper et al., 2006. J Nematology 38: 83–89.

Planting date impact on southern root-knot nematode in Wren Abruzzi rye and Coker 797 wheat Date Root-knot Adult Crop Planted Sampled Juveniles egg masses Rye 1 Oct. 3 Nov. 53 5 3 Dec. 115 20 3 Jan. 123 21 Rye 1 Nov. 3 Dec. 12 0 3 Jan. 22 0 Wheat 1 Nov. 3 Dec. 19 0 3 Jan. 42 0.6 Wheat 1 Dec. 3 Jan. 10 0 Johnson and Motsinger, 1990. J Nematology 22:348-355

Quesenberry et al. , 2014. Crop and Pasture Science DOI: 10 Quesenberry et al., 2014. Crop and Pasture Science DOI: 10.1071/CP13437

Southern Root-knot galling Osceola white clover Ocoee white clover O koi Quesenberry et al., 2014. Crop and Pasture Science DOI: 10.1071/CP13437

Barrel medic (Medicago truncatula) Southern root-knot nematode damage Resistant breeding line Susceptible breeding line Dhandaydham et al., 2008. J Nematology 40:46-54

Management plans using cover crops in fields with nematode problems Know which type of nematode is present in the field Avoid cover crops that are good hosts for that nematode if possible Planting date can be very important 65° F important temperature to remember Termination in spring can be important

Cover crops and plant-parasitic nematodes Winter cover crops may not suppress nematodes effectively Considerable variation in Southern root-knot nematode from one location to another Weeds can serve as suitable hosts for nematodes and can reduce effectiveness Unknown what happens when mixtures of two or more cover crops are used together