May 16, 2014
I would like to remind people that our seed treater is up and running. We can run custom blends for any type of seed treatment available. We will also treat anyone’s seed. Give us call if you need something done. I think the conditions are right for seed treatment to really show some value.
I might be a little late but here is some information on sudden death.
Management options for SDS are limited. Although soybean cultivars that are less susceptible to SDS have been developed, no highly resistant cultivars are available (Njiti et al., 2002). Fungicides applied in furrow during planting or as seed treatments have only limited effects on disease reduction. Fungicides applied to foliage have no effect on SDS suppression, presumably because the fungal infection is restricted to root systems and fungicides typically do not move downward in the plant to reach this site of infection. Several management practices may reduce the risk of SDS damage, although they will not prevent the disease:
Early planting predisposes soybean to infection. In cool, wet soils, young soybean plants are vulnerable to infection by the SDS pathogen. If early spring conditions are favorable for rapid soybean growth, and if saturating rains do not occur during early reproductive stages of growth, the risk for SDS may be less even though the fungus is present in the soil. Fields with no history of SDS should be planted first; fields where SDS has been a problem should be planted last.
Compacted soils impede water percolation and restrict root growth. A heavy rain when soybean has reached the reproductive stages will saturate compacted areas, which promotes SDS development. Correcting soil compaction and water permeability problems may reduce the risk for SDS. Soils respond differently to tillage system intensity changes; plowing, chiseling, or similar drastic soil disturbances strongly affect drainage, crop residue position, and the microbial composition of soil (Aon, 2001; Kladivko, 2001). Not surprisingly, reports on effects of tillage on SDS are contradictory. In some soils, no-tillage can be beneficial in reducing the severity of SDS compared to plow or chisel plow tillage (Seyb et al., 2007; Abney, unpublished). In other soils, intensive tillage reduces SDS presumably by maintaining sufficient vertical water movement compared to no-till (Vick et al., 2006). The best drainage and the most root growth-enhancing soil management may be facilitated in various ways — in some instances, this may require intensive tilling in some soil types, but no-till may be more appropriate in other soil types.
Crop rotation may reduce the risk for SDS (Rupe et al., 1997), but corn-soybean in yearly rotation, common in the Corn Belt, does not reduce the incidence and severity of SDS (Westphal, unpublished). Severe outbreaks of the disease have occurred even after several years of continuous corn. Crop rotation reduces the inoculum potential of other soybean pathogens, but shifting to annual rotations of corn and soybean (compared to longer rotations that involved small grains and perhaps forages) fails to reduce the risk for SDS. Studies at Purdue University have found that soybean roots are not visually healthier after a rotation with corn compared to continuous soybean (Xing and Westphal, unpublished). When corn is grown in the field, soilborne pathogens may decline to some extent, but not enough to substantially reduce the disease pressure when soybean is grown in the field the following year. Although a two-year rotation may hold SCN population densities below threshold levels when the initial population density is low, such a rotation appears to be too short to reduce risk for SDS.
Resistant Soybean Cultivars
Soybean breeders are striving to develop SDS-resistant cultivars, but progress has been slow. Greenhouse and field methods, employing high rates of artificially produced fungal inoculum on grain sorghum and carefully selected watering regimes were developed (Hartman et al., 1997; De Farrias et al., 2006). While most seed companies have removed highly susceptible cultivars from their inventories, no highly resistant cultivars are available. Because seed companies continually introduce new cultivars and retire older ones, accurate information about the reaction of new cultivars to SDS is essential.
Under these challenging management conditions, planting highly susceptible soybean cultivars into fields with high risk for SDS must be avoided. Field records of when and where SDS and other soilborne diseases occur are essential for management of SDS and other soilborne diseases. Handheld GPS receivers may assist in this strategy, but even simple sketched maps will help record problem areas. Fields severely affected by SDS should be earmarked for later planting and operations to improve water permeability should be considered, including compaction-correcting tillage or tile drainage. Finally, cultivars with some degree of resistance should be planted.