A comparison of the effectiveness of the aqueous extracts of garlic, castor beans and marigold in the biocontrol of root-knot nematode in tomato

Abstract

A glasshouse experiment to control RKN (Meloidogyne javanica) on tomato with aqueous extracts of marigold (Tagetes erecta) leaves and flowers, castor beans (Ricinus communis) and garlic (Allium sativum) was conducted from March to May 2011 in Harare. The plant material was dried and pulverized and diluted with water at a rate of 25g/100ml. Four-week old seedlings were planted in twenty micro plots arranged in a randomized complete block design with five treatments and four replicates. Approximately 5000 J2 nematodes were pipetted onto each plant. The botanicals were drenched around each plant. Nemacur® and non-amended plots served as control. Data collection was done fortnightly. Results showed that tomato is susceptible to RKN infestation and the application of botanicals significantly (P < 0.001) controls RKN by reducing galling and reproduction. While the botanicals were also effective in reducing galls, further tests will establish optimum concentrations.