-5- 



Treflan is one o£ the least-soluble herbicides (less than 1 p.p.m.). But with 

 excessive moisture degradation, certain chemical or biological processes in the 

 soil may be increased. As soil moisture moves up to the surface and evaporates, 

 some herbicide may move upward with the moisture and might be relocated in the 

 effective zone. Or some may move with the water vapor into the air. 



Your best indication of how much herbicide you have left is to check on how good 

 your weed kill is. If you used a preemergence herbicide and it's working, count 

 your blessings. But if weeds are growing, don't hesitate to cultivate as soon as 

 you can- -even though you used a herbicide. Weeds may sometimes emerge and then 

 die, but don't wait too long if you could be cultivating. 



With the sun coming out, crusting may be a problem on some fields. The rotary 

 hoe is still one of the best implements for breaking crusts and killing early 

 weeds. For weeds that are too far along for the rotary hoe, the row cultivator 

 is one of your next lines of defense. 



Postemergence herbicides may help, especially on large acreages or where it's too 

 wet to cultivate. If you haven't used any atrazine on the field yet and you don't 

 think cultivation or 2,4-D is the answer, consider atrazine and oil . 



If you used a half rate of atrazine with Ramrod preemergence on dark soil and if 

 Ramrod isn't holding the grass, consider another half rate of atrazine with oil. 

 Weigh the cost against possible loss due to weeds. 



For most broadleaved weeds, 2,4-D is still your best bet for postemergence applica- 

 tion. Atrazine plus oil can help on both broadleaved and grass weeds that are less 

 than 1-1/2 inches tall. Lorox or Dowpon are possibilities a little later for 

 directed postemergence application in corn, but you will need special equipment 

 and a lot of care in application. 



We haven't been overly optimistic about aerial applications of atrazine and oil. 

 But they may help out in emergency situations, where fields are wet and it looks 

 as if the weeds will get too large for cultivation. If you decide on aerial appli- 

 cation, insist on as uniform an application as possible. Avoid overlapping that 

 can cause residue problems. It will be difficult to eliminate overlap completely. 

 If you use an aerial application of atrazine, plan on corn in treated fields again 

 next year. Don't use more than 2-1/2 pounds per acre of Atrazine 80W, and be sure 

 to keep atrazine off crops other than corn. 



Make your decisions and control weeds as early as possible. We don't have any 

 good answers for knee-high grass in corn and soybeans. 



Atrazine and Oil 



Atrazine and oil can help control weeds when it's too wet to cultivate, but users 

 should realize that corn can sometimes be injured. This may be a good year for 

 killing weeds with atrazine and oil. But adding oil to atrazine can increase the 

 possibility of injury to corn. Last year, some corn showed early stunting but 

 usually recovered well. There were a few cases of fairly severe injury. With 

 the cool and wet weather, corn is growing slowly and is already under stress. 

 Applying oil may further reduce respiration, resulting in some injury. However, 

 when it warms up and plants are growing rapidly, entry into the plant may be 

 greater, also creating some possibility of injury. 



