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Insects and Diseases

Seedling rot,  or damping off, caused by Pythium spp.

 


Fungicide Seed Treatments

Damping-off diseases are a major concern for early-planted soybean. Because more and more growers are planting early, there is more interest in using seed treatments to promote good stand establishment.

Treating seeds with fungicides may be beneficial under the following conditions:
1. Early planting in cold, wet soils
2. Reduced till and no-till fields
3. Seed with low germination rate (<80%) or low seed vigor

Several kinds of fungi cause seed rot, seedling rot (damping off) and seedling disease. The most common ones in Iowa are Rhizoctonia and Fusarium, the water mold fungi Pythium and Phytophthora, and seed-borne Phomopsis.

The active ingredients mefenoxam and metalaxyl are effective in controlling the water molds Pythium and Phytophthora . When either one of these two chemicals is mixed with other active ingredients, the formulation can be used to control the other soil-borne fungi in addition to Pythium and Phytophthora (Table 1). We initiated an evaluation of fungicide seed treatments in 2004 and will continue in 2006.

For a good description of soybean seedling diseases, read Soybean Seedling Diseases in the Integrated Crop Management newsletter.

Table 1. Specific activity of fungicide seed treatments

Active Ingredient Trade 
names
Pythium Phytoph- thora Rhizoctonia Phomopsis Fusarium
metalaxyl
Allegiance formulations
excellent
excellent
no activity
no activity
no activity
mefenoxam
Apron formulations
excellent
excellent
no activity
no activity
no activity
azoxystrobin + metalaxyl
SoyGaard
good
poor
good 
good
good
captan
many formulations
good
poor
good
fair
fair
captan + PCNB +thiabendazole
Rival
poor
poor
good
excellent
excellent
captan + PCNB + metalaxyl
Rival Pak
good
good
good
good
good
carboxin + thiram
Vitavax-200
poor
no activity
fair?
excellent
poor
carboxin + thiram + metalaxyl
Stiletto
good
good
good
excellent
poor
carboxin + captan
Vitavax-captan
fair
poor
good
good
fair
fludioxonil
Maxim 4FS
poor
poor
good
good
good
fludioxonil + mefenoxam
ApronMaxx formulations
good
good
good
good
good
PCNB + ethazole
Terraclor Super-X Terra-Coat L-205N
good
poor
good
no activity
poor
thiram
many
fair
poor
good
fair
fair

 

Insecticide Seed Treatments

High numbers of bean leaf beetles have created a concern about direct losses from beetle feeding injury plus losses related to bean pod mottle virus. Previously, we have been able to manage the beetles using foliar insecticides, but we do now also have an insecticide seed treatment that can be used to manage the beetles. In 2004 and 2005, Cruiser and Gaucho were registered to use as a seed treatment on soybean in United State, respectively. They are both systemic insecticides and belongs to a new subclass of neonicotinoids. They moves systemically throughout the plant and protects against target pests through contact and stomach activity. We are evaluating both Cruiser and Gaucho in different trials in combinations with different fungicides. The largeste study will be finalized after the 2007 growing season and data will then be available.

 

 

Last Update: 10/17/07

Copyright 2003-. Palle Pedersen, Iowa State University Extension.
Please contact us with questions and comments.