Effect of Time of Application on the Action of Foliar Sprays of Oxamyl on Meloidogyne hapla in Tomato.

Foliar sprays containing 3,000 or 4,000 ppm oxamyl applied before inoculation with Meloidogyne hapla completely protected tomato plants from intection for up to 36 days but sprays containing 1,000 or 2,000 ppm provided only partial protection. Postinoculation sprays were less effective than preinoculation sprays but they decreased the numbers of females and their rate of development and increased the numbers of males. Similar amounts of oxamyl applied to the soil as a drench or as granules controlled M. hapla more effectively than foliar sprays but the longer treatment was delayed after infection the fewer the larvae that were killed and the more that became male.

Development of Four Populations of Meloidogyne hapla on Two Cultivars, of Cucumber at Different Temperatures.

The infectivity and development of four populations of Meloidogyne hapla were compared, at three temperatures, on tomato and two varieties of cucumber. A population from Canada produced few root-galls on cucumber and, except at 24 C, no larvae developed into adult females and produced egg masses. In contrast, a population with 45 chromosomes from America produced many galls on cucumber and small proportions of larvae became females and produced egg masses at 20 and 24 C. At 18 C this population produced no egg masses on cucumber, but a population from Britain and one from America with 17 chromosomes produced more egg masses at this temperature than at 20 or 24 C. Dissection of the galls showed that on cucumber many larvae died or their growth and development was slowed.