Disease Note

Pathogenicity of the Spiral Nematode Helicotylenchus dihystera to Guava. P. Willers, Citrus and Subtropical Fruit Research Institute, Nelspruit, South Africa. N. M. Grech, Citrus and Subtropical Fruit Research Institute, Nelspruit, South Africa. Plant Dis. 70:352. Accepted for publication 9 December 1985. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/PD-70-352b.

A countrywide survey of guava (Psidium guajava L.) orchards disclosed the presence of the spiral nematode Helicotylenchus dihystera (Cobb) Sher, 1961, in 96% of Transvaal plantings and in all plantings investigated in the Cape Province of South Africa. The average nematode infestation was 2,200/250 ml of soil, although levels as high as 13,000/250 ml were recorded. Pathogenicity of H. dihystera to the guava cultivar Fan Retief was tested on 1-mo-old container-grown seedlings. Individual plants were inoculated with 1,200 surface-sterilized spiral nematodes per 2.5-L container to simulate the field populations encountered during the survey. Uninoculated seedlings served as controls. After 4 mo, the height of nematode-infested plants was suppressed by 53.3%, compared with that of controls. Leaf size was also considerably inhibited by H. dihystera.