Intensity and buildup of potato cyst nematodes in varying ecological situations at Nilgiri hills

The potato cyst nematodes were encountered at varying levels from all the potato growing localities of the Nilgiris situated at 920 meters to 2470 meters above sea level. The nematode intensity was ‘Low’ below 1550 meters and nearer to tea plantation areas. ‘High’ to ‘Very High’ intensities were observed from localities where two or more crops were taken and at altitudes above 2000 meters. The nematode cyst build up was minimum (1.1 to 1.6) in low intensity areas and maximum (2.9 to 3.7) at localities where two or more crops are grown. The warmer localities where tea cultivation was predominant the cyst build up averaged only 1.7 to 2.0 while the cyst propagules increased 2 to 3 times only. Although the root infection was not observed in the foot hills (920 to 980 meters), the increase of total propagules in soil (2.1 to 2.5) at the completion of crop indicated a very slow build up of potato cyst nematodes even in warmer climates.