Treating Seeds To Prevent Diseases

make sure that the soil is not infested before planting and that the transplants are free of nematodes. The type of cover crop used in peach orchards can have a considerable effect on the degree of attack by root knot nematodes and consequently on the growth and yield of the trees. In experimental plots in Georgia, trees on plots where root knot resistant cover crops were planted produced about six times as many peaches in four seasons as trees on control plots where cover crops highly susceptible to root knot were planted. Where no cover crops at all were used and the plots were kept free of weeds, about five times as many peaches were produced as on the control plots. Some species of the nematode Aphelenchoides, which parasitize the aboveground parts of such plants as strawberries and chrysanthemums, can be controlled by repeated spraying of the plants with parathion. Undoubtedly the simplest method of preventing nematode damage is the use of plant varieties or rootstocks which are not susceptible to attack. Examples are the Shalii, Yunnan, and S-37 peach rootstocks, which are highly resistant to attack by some of the most common species of root knot nematodes in this country, though not to all of the root knot nematode species. Some advances have been made in the development of varieties of other crops resistant to root knot and other nematodes, but progress is necessarily slow and it will be many years before satisfactory nematode-resistant varieties of all crops will be available.