Suppression of Pratylenchus penetrans populations in potato and tomato using african marigolds

Current strategies for management of Pratylenchus penetrans in both white potato and tomato consist of the use of fumigant or non-fumigant nematicides or crop rotation. The objective of this study was to determine if double-cropping African marigolds (Tagetes erecta) with potatoes or tomatoes could reduce P. penetrans populations. Plots were 10 m x 3 m arranged in a randomized complete block design with four replications. Treatments included marigolds, potatoes or tomatoes, and natural weedy fallow followed by either potatoes or tomatoes. Nematode populations were sampled before spring planting, between crops in August and after harvest in November. During the 3 years of the study, P. penetrans soil population density declined by an average of 93% from the pre-plant level when marigold was grown in rotation with potato and by 98% when marigold was grown.in rotation with tomato. Weedy fallow preceding potato resulted in an average decline in P. penetrans soil population density of 38%, and a similar decrease (37%) was seen when fallow preceded tomato. There was a significant reduction in the number of P. penetrans found in both potato and tomato roots when the crops followed marigolds. These results suggest that P. penetrans population density may be significantly reduced when marigolds are double-cropped with potatoes or tomatoes.