Control At 5 



One of the most important is for control of ectoparasites or endopara- 

 sites in or around the root.s of living plants, particularly perennials, 

 such as orchard trees and ornamentals. Two of the presently available 

 nematocidps may be generally recommended for this purpose (1,2-dibromo- 

 3-chloropropane and V-C13 Nemacide). Most of the nenatocides currently 

 available are more or less toxic to plants and might do more harm than 

 good. There are some recent experiments which point out that even with 

 a phytoxic material (D-D) a dosage applied to one side of a tree one 

 year end the other side the following year can be an overall beneficial 

 treatment. However, a degree of balance between plant injury and nema- 

 tode control must be obtained. This kind of application is rather an 

 exception, not the general rule. An intensive search is being made for 

 nematocides which are less toxic to plants. 



Tliere is also a specialized but important need for nematocides which 

 will kill nematodes on bare-rooted plants to be transplanted, but at 

 this time no material is being generally recommended for this purpose. 

 Search is also being made for suitable chemicals for this purpose, 

 because of the hazard of nematode transport in infected plant stocks. 



It has been shown that foliar nematodes in chrysanthemums and certain 

 other plants can be killed by nematocides which apparently have a 

 systemic action. One of these is sodium selenate, which is applied to 

 the soil. However, it should be remembered that selenivim taken up by 

 edible plants can be very poisonous to man and to domestic animals, 

 IfJhere selenium occurs naturally in soils, serious trouble with live- 

 stock has been encountered. Selenium, once added to the soil, might 

 remain for a long time, so its use is discouraged. It has also been 

 shown that repeated spraying with Parathion will control foliar nema- 

 todes on chrysanthemums and other plants. Amounts used are 0.2^ to 

 0.50 lbs. active ingredient (as wettable powder) to 100 gallons of 

 water, and control is obtained by h or more applications by spraying 

 at weekly intervals, 



V.Tiite tip of rice is caused by Aphelenchoides oryzae carried on the 

 seed. Control can be obtained by seed treatment with several compounds, 

 the most satisfactory of which seems to be 3-p-chlorophenyl-5-inethyl 

 rhodanine (N-2iiij., made by Stauffer Chemical Company) . 



Space fumigation is also mentioned because it has been used for many 

 years generally for disinfecting non-living materials. The generally 

 used chemical is methyl bromide which, although highly phytoxic, can 

 be safely used for a few special problems involving nematodes on living 

 plant materials. Examples are fumigation of onion and clover seed 

 infested with the stem or bulb nematode. 



Materials and Methods 



Selection of a nematocide for any particular purpose involves considera- 

 tion of the area to be fumigated, the crop to be grown, and other factors, 

 including economic ones. 



