Corn rootworms are usually managed by rotating corn with another crop or by using a granular soil insecticide at planting. If an insecticide is used, performance, safety, environmental impact, control of other pests, and cost should be considered.

Liquid soil insecticides, such as Dyfonate 4EC, Furadan 4F, and Lorsban 4E are labeled for use against corn rootworms, but have not been used often in recent years. Since Furadan 4F is now being marketed as an alternative to at-planting applications of granular insecticides, I will attempt to answer some of your questions about its performance.

What data did I evaluate?

University data were gathered from entomologists at land-grant universities in Illinois, Indiana, Iowa, Kansas, Kentucky, Minnesota, Missouri, Nebraska, South Dakota, and Wisconsin. Data were collected from 64 tests during the last four years. To be included in this evaluation, the Furadan 4F applications had to be applied:

1. between May 15 and June 15;
   
2. at the rate of one quart per acre; and
   
3. root injury on untreated plots had to be greater than 3.0.

How did I evaluate the university data ?

I evaluated the insecticides based on their consistent provision of a good level of root protection. Consistency was determined from the percentage of tests in which the untreated roots averaged moderate to heavy root injury (greater than 3.0 and considered as economically damaging) and the treated roots had moderate to minimal root injury (3.0 or less and not economically damaging). The consistency percentage is similar to a batting average; the higher the number, the better the performance. If the insecticide-treated roots from a test had a rating higher than 3.0, the insecticide was categorized as not providing good root protection and its consistency percentage decreased. I used Counter 15G at planting (or Counter CR in some tests) as a standard to compare with the Furadan 4F performance.

How well did Furadan 4F protect corn roots from rootworm injury?

A summary is presented in Table 1 (refer to printed newsletter). Broadcast application did not consistently provide root protection during the past four years. When the quart rate was banded instead of broadcast, performance improved. However, neither was as consistent as an at-planting application of Counter. When the 1994 data are examined alone, the broadcast application showed improved performance. What we are seeing is the influence of weather on the performance of the insecticide. Furadan 4F is highly-water soluble, and when sprayed on the soil, rainfall can move the insecticide down around the roots for better protection. A wet spring will improve performance, and a dry spring hinders performance. The realistic approach is to look at all the data together, from both the dry and wet years, and critically review the performance.

Are there any special directions for using Furadan 4F?

Several notes appear on the Furadan 4F label (the 2ee label) that arent on granular insecticide labels. First, the application period is narrowly defined and should be timed to closely coincide with corn rootworm hatch, usually May 15 through June 15. The label also recommends cultivating the insecticide into the soil unless rainfall is imminent. Cultivation into the soil should improve root protection, especially if the insecticide was applied before June 5 and no rainfall has occurred. If the insecticide is tank mixed with a herbicide, consult the herbicide label for cultivation restrictions.

Are there any environmental concerns?

The label states that Furadan 4F can seep or leach through the soil and can contaminate groundwater. Do not apply it where the water table is close to the surface and where soils are very permeable.