Timing Key on Soybean Fungicide Applications

Apply too late and throw money away.

Published on: Jun 29, 2011

Corn isn't the only crop getting attention as possible needing fungicide applications. Interest is picking up amongst those going for top soybean yields to consider fungicide applicants for soybeans.

One of the questions in an upcoming Crops Corner question in the August issue of Indiana Prairie Farmer will deal with this issue. The column is based on answers from members of the Indiana Certified Crop Advisors Association. Members complete certain requirements to become certified, and then must continue their education by attending meetings and workshop for credit to retain the title.

Willis Smith, Senesac's Inc., Fowler , Ind, will tell you in the upcoming issue that if soybeans are in the R3 to R4 stage, a fungicide application will likely make you money. This is relatively deep into the reproductive stage. The article series 'Soybean Basics' with Purdue University's Shaun Casteel talks about growth stages. They're also depicted in pictures in the July and August issuers.

However, if soybeans are already past that stage, Smith sees no economic benefit. In fact, you could incur a net economic loss. He's also one that believe in adding an insecticide when you apply a fungicide only if there is an insect threat at work in the field at economic threshold numbers. Otherwise, he feels you will be wasting your money and time making the application. If you're combining fungicides and insecticides in one pass, read labels of both products carefully to make sure that the products are compatible.

Gene Flaningam, a crops consultant operating independently in southwest Indiana, near Vincennes, agrees with Smiths' assessment. He also believes that R3 and R4 are the critical sages when soybeans need protection. It's also the stages at which soybeans can stand the least amount of total leaf loss before yield could possible be affected.

He adds that as the season turns dry and you want to control spider mites, you'll need a different chemistry than if you're after other insects. Make sure there is a pest problem, and know which pest you're going after, before you elect to spend money on spraying insecticides, he notes.

Steve Dlugosz, an agronomic consultant with Harvestland Co-op in eastern Indiana, and the true trained entomologist in this particular panel, says you need to determine if a response of two to five bushels per acre will pay for the fungicide application. Given today's soybean prices, it likely would.

He also says late-season insecticides can help if you have experiences or expect to experience problems with certain soybean insects, including stink bug and late-season bean leaf beetles.

Look for complete details in the August issue.