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CORESTA Congress, Quebec, 2014, Agronomy/Phytopathology Groups, AP 08

Root-knot nematode control on tobacco: alternatives to fumigant nematicides

MAKUNDE P.T.; MAHERE T.S.; DIMBI S.
Tobacco Research Board, Harare, Zimbabwe

The root-knot nematode is an economically important pest of tobacco in Zimbabwe and research on management methods dates back to the 1940s when compost and rotations using sunnhemp (Crotalaria juncea) were investigated. In the 1950s, the Tobacco Research Board’s attention shifted to evaluation of nematicides with ethyl dibromide (E.D.B) being reported as both effective and economic. In the 1960s, the relationship between rotations and fumigations was studied and it was reported that a combination of soil fumigation and grass rotations was the most effective method for controlling nematodes. While fumigant nematicides provided a reliable return on investment, awareness of potential and actual environmental damage prompted research on alternative control strategies. Here, an overview of research carried out with an objective to validate and secure economically viable alternatives for nematode control in tobacco production systems post the fumigant nematicide era is presented. Seedbed and field trials designed as randomised complete block designs and replicated three times were carried out from 2011 to 2013. Among the test products were the methyl-isothiocynate generators (metham sodium and metham potassium) and green label alternatives namely sesamin (extracted from sesame) and Velum (fluopyram). In all tests a resistant (KRK64) and a susceptible (KM10) tobacco cultivar were included. Results showed that methyl-isothiocynate generators were effective in conventional seedbeds. However, metham sodium displayed inconsistent performance in the field pointing to the need to perfect application methods. Sesamin and Velum performed significantly better than the standard fenamiphos in controlling root-knot nematodes in the field. While none of the tested products were as effective as the fumigants, effective root-knot nematode management can be achieved through a combination of these alternative nematicides, resistant tobacco varieties and proper rotations.