The Biology of Heterodera Carotae

Publisher： Brill

ISSN： 1875-2926

Source： Nematologica, Vol.32, Iss.4, 1986-01, pp. : 447-460

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Abstract

The biology of Heterodera carotae was investigated under laboratory and field conditions in Italy. Juveniles emerged from cysts all the year round and in greatest numbers (37.6-40.6%) at 15-20°C. Egg hatch was also substantial at 5-10°C, but negligible at 25°C. The age of carrot plants affected hatch and most juveniles (67-80.4%) emerged in root leachate from 5-7 week old carrots. Forty six per cent of the eggs from the egg masses were still viable at the end of the summer, but in November only 7 % of the eggs in soil were eggs from egg masses. Invasion of carrot roots by juveniles occurred over a range of temperatures from 8 to 20°C, but no nematode development was observed at 8°C. Heterodera carotae required 26 and 36 days to develop females and cysts at 20°C, when 260 and 360 day degrees above 10°C, respectively, had accumulated. Second stage juveniles appeared within egg masses and cysts after an accumulation of 510 and 570 day degrees above 10°C, respectively. Two generations can be completed by the nematode during a carrot growing season and no nematodes invade carrot roots in summer.