Depending on planting date and maturity, you could have soybeans that are already in reproduction or are quickly approaching this critical growth stage. Reproduction is when the plant starts reallocating most of its resources towards making seed. Soybean plants, and more importantly yield, are more drastically affected by insect and disease pressure now than during earlier vegetative growth stages. It’s extremely important to keep plants healthy and protect against insect damage and disease during this time to maximize yield.
Common soybean diseases in our Hutson territory are Frogeye Leaf Spot (FLS), Septoria Brown Spot, and Cercospora Leaf Blight. Most years FLS is the largest yield robber as far as disease is concerned. It’s usually not hard to find FLS lesions in bean fields during reproductive stages. There are a few management practices that can be implemented to help control FLS:
- Crop rotation – the disease overwinters on soybean residue, so rotating to a non-host crop will help decrease disease inoculum
- Resistant varieties – plant varieties with a high FLS resistance rating
- Fungicide – there are several fungicide options on the market that provide very good control. Keep in mind when selecting a fungicide that there are strobilurin-resistant strains of FLS, so using a product with multiple modes of action will increase control. All these practices used in combination will provide the best control.
Frogeye leaf spot lesions
We’ve had success with our Ag Data Works customers targeting a fungicide application at R3 (beginning pod) growth stage. University data has shown the most effective and economical timing for fungicide to be R3.
This is also a great opportunity to get out and scout fields for insect damage. Some common soybean leaf defoliators are green cloverworms, soybean loopers, and armyworms. Since soybean yields are more easily affected during the reproductive growth stages, treatment thresholds for defoliation are reduced from 30% to 20% for R1-R6. The defoliation chart demonstrations levels of defoliation.
Soybean defoliation chart
If you have any questions or need assistance with any agronomic issues feel free to contact a Hutson, Inc agronomist.