Investigation on the biology of Heterodera schacthii in Italy

Abstract

The sugarbeet cyst nematode, Heterodera schachtii Schmidt, is widespread in Italy. It greatly affects sugarbeet yield because this crop often is cultivated in a short term rotation. In some instances sugarbeet is rotated with Cruciferous hosts such as cauliflower (Erassica oleracea L. var. botrytis D.C.) and broccoli (E. oleracea L. var. italica Plenk). Moreover, the nematode has a very wide host range and can reproduce on a number of wild plants. Weed control on non cultivated land is often disregarded. The nematode has been extensively investigated in order to provide information on its biology and for better control. The number of generations per year has been shown to be variable, the variation probably reflecting different environments and management practices. Triffit (1930) stated that only one generation per growing season is possible, but Jones (1950) in England and Duggan (1959) in Ireland found 2-3 generations. In warm climates, such as in the Imperial Valley, Southern California, 5 generations per year have been demonstrated experimentally (Thomason and Fife, 1962). The number of generations per year could also be affected by the hatching behaviour of eggs in H. schachtii cysts. Raski (1950) found that juveniles emerge from eggs of mature females, but Jones (1956) stated that hatching of beet cyst nematode is affected by the previous crops. Poor hatching often occurs in in vitro tests using cysts collected in the winter and spring following a host crop. It is suggested that a maturation period is required for the cysts to became fully sensitive to the hatching stimuli. Hough and Thomason (1975) report that there was no substantial hatching during the first 10 days using newly formed cysts. Evidence of a hatching periodicity has also been shown for other cyst-forming nematodes (Oostenbrink, 1967). There was little knowledge of the biology of H. schachtii under Italian conditions. Therefore investigations were undertaken in 1976-1978 to provide information on: i) the dynamics of populations in the soil and in the root of sugar beet; ii) the number of generations per growing season; iii) the emergence of juveniles from cysts.