A late June field status update

Many growers planted a bit late this year due to very wet spring conditions, but finally got the weather needed to get started in late May. Most areas finished planting soybeans by mid-June, except for few “pockets where wet conditions prevailed”. Late planting and replanting conditions were good in mid-June. At that point in time, most corn crops ranged from the V3-V5 stages, and general, plant stands and crops were looking good. The exception was some localized, heavier textured soil regions where planting conditions of earlier planted corn may have been damaged, and replanting was needed. Now, at the end of June, it looks like most corn and soybeans are emerging nicely.

Throughout the mid-western US, agronomists are reporting variable or delayed growth due to the wet spring conditions and standing water, especially for corn. Soybeans that were planted late seem less affected. Several states have since seen crops bounce back somewhat due to hotter, drier conditions, but others are still behind where they would typically be in late June.

PROSeeds field of Legend Corn w Genuity Traits

With planting and replanting finished, the time has come for scouting and diagnosis of early diseases. According to OMAFRA’s June 29 Crop Report, “soybean seedling diseases and root rots are the second most important yield limiting diseases” in Ontario soybeans, and this year shows no exception. With this year’s cool temperatures and abundance of early rain, many fields needed to be replanted, and recent significant rainfall “has had a negative impact on soybeans in many areas”. Many of the seedling blights and root rots exhibit similar symptoms, making diagnosis tricky. Four common early soybean diseases include:

  • Phytophthora root rot – prevalent in clay and clay loam soils; occurs across many environments, but is most common in warm soils (more than 15 degrees C / 60 degrees F) and wet conditions.
  • Rhizoctonia root rot– characterized by reddish-brown lesion which appears at the base of the seedling stem and on roots just below the soil line.
  • Fusarium root rot – affected plants may be stunted, and have poorly developed root systems with black or brown discolouration.
  • Pythium seedling blight – occurs in very wet soils, but does not require standing water to develop; symptoms include rotten, mushy seeds or seedlings with poorly developed roots.

Resistant and tolerant varieties are available for Phytophthora root rot but no commercial varieties are resistant/tolerant to Pythium, Fusarium or Rhizoctonia. OMAFRA notes that: “Seedling diseases may be more prevalent in no-till or reduced tillage systems since these soils typically warm up slower in the spring and retain more moisture”, and recommends making improvements to field drainage. Fungicide seed treatment may also be needed. Typically, fungicides that are effective for controlling Pythium and Phytophthora diseases don’t affect Fusarium or Rhizoctonia, and vice versa. Furthermore, fungicides that work on most Fusarium are not effective against Fusarium virguiliforme which causes sudden death syndrome (SDS). This requires a different seed treatment. As a result, correct diagnosis is important in choosing the correct treatment.

Rainy weather, delayed planting, and slow emergence also give early season pests a chance to thrive, and there are a few pests causing problems in corn now as a result:

  • Seedcorn maggots – fields with manure or green vegetation incorporated are at higher risk, but other fields are seeing these pests this year too.
  • Grubs and wireworms – very active at soil surface, and even fields with a high rate of insecticide seed treatment may have some injury.
  • Slugs – thrive in a wet spring; moving crop residue away from seed row and ensuring seed slots are closed help keep slugs from having direct access to the seed.

 

For more information on seed treatments, see OMAFRA publication 812, Field Crop Protection Guide (http://www.omafra.gov.on.ca/english/crops/pub812/p812toc.html) or visit The Crop Protection Network (CPN) for their series of Soybean and Corn Disease Management publications to help growers in Canada and the US fight against disease in their fields (www.cropprotectionnetwork.org). More information on early season field crop pests can be found at: Guide to Early Season Field Crop Pests.

You can also contact your PROSeeds Regional Sales Manager (RSM) or agronomist for advice on disease or pest management and on nurturing your soybeans and corn hybrids as the growing season progresses.

 

 

Resources:

OMAFRA Crop Reports:
http://fieldcropnews.com/2017/06/crop-report-june-15-2017/

http://fieldcropnews.com/2017/06/crop-report-june-22-2017/

http://fieldcropnews.com/2017/06/crop-report-june-29-2017/

http://fieldcropnews.com/2017/06/good-year-for-seedcorn-maggot-and-other-early-season-pests/

 

Midwest US Crop Reports:
Midwest agronomists talk late June crop progress: http://www.cornandsoybeandigest.com/crop-report/midwest-agronomists-talk-late-june-crop-progress