Intersexes of Leptonchus obtusus Thorne.

develop, the intrinsic microflora are either absent or, more likely, present at a very low titer. If they are present at a low level, they will not cause carrots to rot before the nematodes have increased, and they can be eliminated from the nematodes by surface-sterilization. Pratylenchus vulnus was originally obtained from around Juglans hindsii Jepson rootstock in a walnut orchard, and has been cultured 7 years in the laboratory. The first 4 years, the culture medium was a mixture of callus and differentiated alfalfa tissue (3). The last 3 years the medium was carrot disks. In 1971, nematodes with this history increased readily on J. hindsii and other fruit and nut tree rootstocks. There is no evidence that the 7 years of culture away from usual hosts has altered this nematode's ability to reproduce on those hosts. Previously, HcJgger (2) had reported no difference in infectivity on potato of P. penetrans from potato in the field, from 1973