August 29, 2006
University of Georgia research has consistently shown 10-percent-plus yield increases with an application of Dimilin and boron in soybeans at the R2-R3 stage. The R2-R3 stage usually occurs in Coffee County from Aug. 1 until as late as Sept. 5, depending on the maturity and planting date.
The R2 stage is at full bloom with an open flower at one of the two uppermost nodes on the main stem with a fully developed leaf.
The R3 stage is the beginning of pod growth, with pods (3/16 inch) long at one of the four uppermost nodes on the main stem with a fully developed leaf. Soybean pod elongation (R3) usually does not begin for 10 to 14 days after full bloom.
The “window of opportunity” for making the Dimilin-Boron spray is typically 15 to 20 days.
Several soybean fields in Coffee County look amazingly well with good yield potential considering the severe heat and drought we have had. Growers need to survey their fields and determine if a 10-percent yield increase would justify the cost of 2 ounces of Dimilin and .25 pounds of actual boron.
Studies show that 2 ounces of Dimilin 2L is sufficient to suppress velvetbean caterpillars (a severe last season pest) and green cloverworms. Dimilin also helps to prevent soybean loopers and other foliage feeding caterpillars.
Boron should only be applied at the .25-pound per acre rate as higher rates can sometimes burn foliage and reduce yields. Below are the rates of common boron products needed to give a grower .25 pound of actual boron:
• Solubor — 1.2 pounds per acre.
• Ten-percent boron (liquid) — 1 quart per acre.
• Five-percent boron (liquid) — 2 quarts per acre.
Growers need to compare prices of these products to give them the .25 pound of actual boron and look at the convenience of the products (many growers prefer paying a little more for liquid boron because it is easier to use than solubor).
Also, solubor, a wettable powder, will raise the pH of tank mixtures where most of the liquid formulations don't But as long as a grower is not starting with a high water pH (above 8.0) or lets the mixture stand in the tank for a long period of time (three to four hours), this should not negatively affect the effectiveness of pesticides in a tank mix.
Soybean growers should also start scouting for stink bugs. Dimilin will not control stink bugs. After full bloom and up to mid-pod fill stage, stink bugs should be controlled when an average of one per 3 feet of row is found. After mid-pod fill and through maturity, they should be controlled when an average of one per foot of row is found. If beans are being grown for seed, one stink bug per 6 feet of row will justify control measures.
The pyrethroids (Baythroid, Prolex, Karate and Mustang Max) are labeled in soybeans for stink bug control.
They will give excellent control of green stink bugs but only 60 to 70 percent control of brown stink bugs.
Methyl parathion and Penncap-M will give excellent control of both the green and brown stinks.
Orthene also is labeled but is most used in combination with a pyrethroid for additional control of brown stink bugs.
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