Evaluating foliar fungicides, insecticides

decrease font size  Resize text   increase font size       Printer-friendly version of this article Printer-friendly version of this article

There are many fungicides and insecticides labeled for use in Iowa soybean. In this study, we evaluated common foliar fungicides and insecticides at six locations across Iowa in 2011 to determine yield responses to an R3 (beginning pod set) application timing (Fig. 1). Figure 1. Iowa field locations for the 2011 soybean fungicide and insecticide study.

Materials and Methods
The experimental design was a randomized complete block with at least four replications at each location. Details on variety and planting, application and harvest dates are listed in Table 1. Treatments (Table 2) consisted of an untreated control, fungicides alone, insecticides alone, fungicides and insecticides in combination and pesticide application based on aphid scouting (IPM). In applicable treatments, fungicides and insecticides were applied at growth stage R3 (beginning pod) at all six locations. Disease was assessed when soybeans were at the R6 growth stage (full seed set). Soybean aphid populations were observed between R3 and R6 but an IPM spray was only necessary at Sutherland. Total seed weight and moisture was measured, seed weight was adjusted to 13 percent and yield was calculated. click image to zoom

Yield varied across locations ranging from 39.4 to 75.9 bu/ac in the untreated control (Table 2). Differences were observed between pesticide treatments and the untreated control at the Sutherland and Ames locations (Table 2).

Foliar disease did not differ between fungicide and insecticide treatments and the untreated control at the Armstrong, Crawfordsville, Kanawha and Nashua locations. There were foliar disease differences between the fungicide treatments and the untreated control at the Ames location and insecticide treatments and the untreated control at the Sutherland location (Table 2). The two most predominant diseases found were Septoria brown spot and frogeye leaf spot. click image to zoom

Septoria brown spot did not move into the upper canopy before R6 at any of the six locations, thus it likely had minimal impact on yield. The average severity in the untreated control in the lower canopy was less than 3.5 percent at all locations except Nashua (7.5 percent) and Ames (6.6 percent). At both of these locations, fungicides reduced brown spot severity in the lower canopy, but again, disease probably had minimal impact on yield.

Frogeye leaf spot was found in a few locations, but was greater than 1 percent severity in the untreated control at only the Ames location (4.9 percent). All fungicides significantly reduced frogeye severity (averaged 1.1 percent). As expected, insecticides alone did not have any affect on frogeye leaf spot severity (averaged 5.2 percent severity). There were no significant differences in disease control between fungicide products.

Soybean aphids averaged 320 aphids per plant at the Sutherland location, which exceeded the economic threshold of 250 per plant. Aphids did not reach the threshold at any other location. At Sutherland, the IPM insecticide and insecticide+fungicide treatments were applied at the R4 growth stage on Aug. 3, which was 13 days after the R3 application. IPM treatments were not applied at the other five locations.

Seed moisture ranged from 8 to 11 percent depending on the location, but did not differ more than a few tenths of a percentage amongst treatments within any location.

The results of this experiment illustrate the benefits of foliar fungicide and insecticide applications for the management of foliar diseases and insects. There were very small amounts of foliar disease across the state of Iowa in 2011 due to high heat and low rainfall amounts in July and August. Also, this was a moderate soybean aphid year across much of the state. At the four locations with very low insect populations and disease severity, there were no significant yield responses to either insecticides or fungicides. However, at the Ames location, fungicides reduced frogeye leaf spot in the upper canopy and the largest yield responses to fungicides were at this location.

Also, only one of the six locations (Sutherland) reached the threshold level to spray aphids and this was the only location where all insecticides had significant responses to insecticides. Using foliar fungicides and insecticides is an effective way to prevent yield losses to foliar diseases and insect pests. Also, only applying pesticides when needed can reduce overall production costs and preserve product efficacy for when severe outbreaks do occur.

Buyers Guide

Doyle Equipment Manufacturing Co.
Doyle Equipment Manufacturing prides themselves as being “The King of the Rotary’s” with their Direct Drive Rotary Blend Systems. With numerous setup possibilities and sizes, ranging from a  more...
A.J. Sackett Sons & Company
Sackett Blend Towers feature the H.I.M, High Intensity Mixer, the next generation of blending and coating technology which supports Precision Fertilizer Blending®. Its unique design allows  more...
R&R Manufacturing Inc.
The R&R Minuteman Blend System is the original proven performer. Fast, precise blending with a compact foot print. Significantly lower horsepower requirement. Low inload height with large  more...
Junge Control Inc.
Junge Control Inc. creates state-of-the-art product blending and measuring solutions that allow you to totally maximize operating efficiency with amazing accuracy and repeatability, superior  more...
Yargus Manufacturing
The flagship blending system for the Layco product line is the fully automated Layco DW System™. The advanced technology of the Layco DW (Declining Weight) system results in a blending  more...
Yargus Manufacturing
The LAYCOTE™ Automated Coating System provides a new level of coating accuracy for a stand-alone coating system or for coating (impregnating) in an automated blending system. The unique  more...
John Deere
The DN345 Drawn Dry Spreader can carry more than 12 tons of fertilizer and 17.5 tons of lime. Designed to operate at field speeds up to 20 MPH with full loads and the G4 spreader uniformly  more...
Force Unlimited
The Pro-Force is a multi-purpose spreader with a wider apron and steeper sides. Our Pro-Force has the most aggressive 30” spinner on the market, and is capable of spreading higher rates of  more...
BBI Spreaders
MagnaSpread 2 & MagnaSpread 3 — With BBI’s patented multi-bin technology, these spreaders operate multiple hoppers guided by independent, variable-rate technology. These models are built on  more...

Comments (1) Leave a comment 

e-Mail (required)


characters left

Larry Alne    
Forest City Iowa  |  January, 16, 2012 at 10:33 AM

It was extremely interesting to see the response in a low aphid year and a year with little rain.

LPV Seed Treater

The LPV Seed Treater has set a new standard boasting three configurable weighing methods for any-sized operation, a standard 42” ... Read More

View all Products in this segment

View All Buyers Guides

Feedback Form
Feedback Form