Fall herbicide treatments. What else remains to be said?
5. Can I use dicamba alone?
No, and do not use 2,4-D alone either. Dicamba has been ineffective on several key species in the fall when applied alone, and appears to be more affected by cold weather than other herbicides. When applied alone, 2,4-D misses chickweed, especially in corn stubble, and is weaker on deadnettle, henbit, and dandelion compared to mixtures of 2,4-D with glyphosate, Canopy, Basis, etc.
6. My rep is recommending about half of the residual herbicide premix be applied in fall and then the rest in spring. Does this make sense?
Not usually. Chlorimuron is really the only herbicide that had substantial residual activity into spring when applied in fall. Where residual into spring is desired, we suggest the use of a relatively low rate of a Canopy/Cloak DF or EX, which works well because it is low cost, controls emerged weeds when mixed with 2,4-D, and still allows the use of effective rates of residual premix products in spring. Cloransulam (FirstRate) provides some residual into spring, but substantially less than chlorimuron. Using a premix product in the fall (eg Valor XLT, Sonic, Authority First) is not cost-effective, since the second component of the premix (Valor or Authority) provides essentially no residual weed control in spring (and residual into later fall is usually not that important – see question 1). We would rather see the full rate of the premix product applied in spring, to try to maximize control of marestail that emerge into June. Metribuzin also provides no residual activity into spring, but has enough activity on emerged weeds in fall that a mix of metribuzin (about 6 oz) + 2,4-D can be cost effective.
7. Seems like the cost of fall treatments being recommended is going up. How much do I need to spend?
The cost of fall treatments can go certainly up considerably when the approach in question 4 is taken. We still believe that the cost of herbicides for fall treatment should be less than $15. We doubt that spending more than this improves control or makes the entire weed management program for the 2014 season work any better in the end.
8. I am going to run some type of ripper, vertical tillage, or similar tillage tool this fall. Should I apply herbicides before or after the tillage?
Before, when weeds are still intact. Also- these tillage tools do not adequately control emerged weeds in the absence of herbicides.
9. Corn plants are large this year and there will be a lot of fodder on the ground after harvest. Should I delay herbicide application until later in fall where this occurs?