Planting soybean into cool and wet soils is a recipe for more seedling disease problems. Sometimes, you may never notice that there is a problem and, other times, certain areas of the field may be almost wiped out. More commonly, the field in general is just not growing the way it should.
Some of our most noteworthy seeding diseases include: fusarium root rot, phytophthora rot, pythium damping-off and root rot, and rhizoctonia damping off and root rot. Of these, fusarium and rhizoctonia are the most common in Virginia. Some of these diseases can be managed with fungicide seed treatments, but some cannot.
Certain insect pests can also cause problems to seedling soybeans. Thrips or leafhoppers can stunt growth when in high numbers on drought-stressed plants. Bean leaf beetle seem to feed on young plants every year. Both insects can transmit certain viruses. Some companies are promoting insecticide seed treatments to help manage soybean aphid, but this is not relevant in Virginia. Other soil insect problems include seed-corn maggot, wireworm, grub, and slugs.
Seed treatments are becoming more and more popular in all crops. Benefits over soil treatments include lower use rates, less direct contact with toxic chemicals, and ease of use. Fungicide seed treatments are sold under various brand names, but usually include one or more of the following active ingredients (with their most common trade names): captan (Captan), thiram (Thiram), fludioxonil (Maxim), thiabendazole(TBZ), carboxin (Vitavax), PCNB (Rival), metalaxyl (Allegiance, Acceleron DX-309), mefenoxam (Apron XL), ipconazole (Racona), azoxystrobin (Dynasty), pyraclostrobin (Acceleron DX-109), or trifloxystrobin (Trilex). Insecticide seed include the active ingredients: thiamethoxam (Cruiser) and imidacloprid (Gaucho, Acceleron IX-409), and clothianidin (Poncho).
Finally, there is a new seed treatment (VOTiVO) that employs a biological mode of action with bacteria. The product is being marketed in combination with clothianidin as Poncho/VOTiVO. The bacteria lives and grows with young roots and supposedly creates a barrier against nematodes. The verdict is still out with this product. We have seen it increase yields in some nematode infested fields but not in others. We will continue to evaluate this product.
In the near future, I’ll be exploring some of the disease and insect pests that could be causing early-season problems in soybeans. We’ll start with an overview of individual pests and describe their potential damage. Then later, we’ll talk about the potential benefits, if there are any, to applying one of the seed treatments currently available.