Effects of Crop Sanitation and Ridomil MZ Applications on Late Blight Severity and Tomato Yields in Cameroon

Tomato (Lycopersicon esculentum) production in Cameroon is usually handicapped by late blight caused by Phytophthora infestans. A field trial was conducted during 1997 in Dschang, Cameroon, to assess the effect of Ridomil MZ (8% metalaxyl + 64% mancozeb) sprays, and sanitation (a weekly picking of diseased leaves) on late blight development and yield of five tomato varieties. Plots received Ridomil MZ (2.5 kg/ha) and sanitation singly or combined. Control plots were neither sprayed nor cleaned from diseased leaves. All treatments were applied ten times in a weekly schedule. Late blight intensity was assessed every 7 days and marketable fruit yields were obtained at maturity. Differences in late blight intensity between sanitation and control plots were not significant (P= 0,05). Fungicide treatments were more effective than sanitation in reducing late blight severity. Percent fruit infection was 100% in control or sanitation plots of ARP I366-1, ARP D1, ARP D2, Roma, and no marketable fruits were harvested on these treatments. Late blight was less severe on Mecline compared to the other varieties. Consequently, Mecline out-yielded Roma, ARP I366-1, ARP D1 and ARP D2 varieties. Results suggest that the fungicide-alternative method of late blight control, using sanitation is not as effective in tomato late blight management as appropriate fungicide sprays.