Vol. 16—1962 - NorthEastern Weed Science Society

101
WEEDCONTROLSTUDIESIN SEElED ONIONSV
J. C. Cialone, G. Bayer and R.D. Sweet.
Introduction
New York with about 15,000 acres ranks all one of the leading onion p:L'0­
ducing sta1ies, with the majority of the production centered in the muck soil
areas where 'Weeds are a serious problem. Growers have shown great interest in
herbicides as an aid in reducing weeding costs.
Most of the acreage in NewYork this year was treated with cbloro-N-Ndiallyl-acetamide,
CDAA,sold as Randox. This prosram consists of a 6 lb/acre
rate of the liquid formulation of CDAAin the crook stage of onion development
and subsequent applications of the granular formul~ion as they are needed
throughout the remainder of the season. CIPC (cbloro-isopropyl-phenyl carbamate)
is used in combination with the CDAA,primarily in situations were purslane
(Portulaca sp.) has not been controlled by the CDAA. In general, the above two
chemicals have given .very satisfactory results over a wide range of environmental
conditions on muck soils. CDAAdoes have the limitation that it will not control
purslane other·than in the seedling stage of development and does not have a
very long period of residual activity in the soil.
Since CDAAoften gives injury when applied immediately after planting, if this
application is followed by rain, and since liquid formulations may give Uljury
when the onion has reached the nag stage of development, the early period of
safe use is a short and crucial one. l't can readily be seen that with the great
variations in spring weather conditions this period of safe use may not alw.ys
coincide with the stage of weed growth at which CDAAwill be most effective. Any
chemical which could eliminate this crucial timing with respect to the crOp and
still be an effective herbicide would be very valuable. Tests conducted on muck
soil in 1960 by Althaus, Langlois and Gleason (1) indicate that a combination ef
CDAAand TCBC(Tricblorobenzylcbloride) sold as R8l'1doxT, was effective e.ge.1nSt
purslane, gave generally good weed control and g8velittle stand reduction wbOn
used at 6 and 9 qt/acre rates. Romanowski in 1960 (4) indicated that this e