Assessing Hail Damaged Crops Continued...

• Evaluate potential maximum yield from original final stand and planting date. Again, this isn't the 150,000 seeds planted per acre, it is the final stand in the field.
• Soybean yield loss can come from stand loss, defoliation on plants, and loss of nodes or breaking of stems on individual plants
  • Vegetative stage soybeans are considered to have 0% loss in yield potential from even total defoliation; many soybeans were still in vegetative stages or were just this week reaching R1
  • We are most concerned about stands thinned to very low numbers and nodes lost from plants
  • Like corn, damage to stems is difficult to quantify, but may result in lodging later this season
• To evaluate stand: count plants in a known length of row in several areas (at least 5) across the field or hail damaged area. You could do a small area like 3 feet of row or evaluate the full length of 1/1000th of an acre. More counts = more accurate assessment. Separate plants into "will survive", "won't survive", and "questionable" categories. These categories can help in estimating a % stand loss from the original final stand in the field.
  • Plants should begin producing new leaves at axillary buds that will be visible within the next week.
  • Soybean stands generally need to be below 50,000-60,000 evenly-spaced plants at this late in the season to receive a yield potential increase from replant. Soybeans have an incredible ability to make up for stand loss, as long as some plants are still there!
    • If many of the surviving plants fall into the "questionable" category, replant or filling in may pay from a yield perspective
  • Again, resources below are helpful for estimating potential yield loss from stand loss and node loss on soybean plants, but cannot easily assess potential lodging issues from stem damage
• The value of canopy to help suppress late season weed pressure is also not easily quantified. Soybean fields should be monitored for weed emergence that requires control.
• If replanting, don't bother tearing up the current stand, but do try to plant across rows (at an angle or perpendicular to rows) and try to increase the stand closer to 140,000 plants per acre (i.e. don't plant a full rate).
  • Find a shorter maturity variety well-adapted for the area (0.5 to 1.0 shorter).

• IPM 0079: Hail on Soybeans in Iowa
• Soybean replant decisions
• Soybean Loss Adjustment Standards Handbook (Crop Insurance Adjusters Handbook) - see pages 62-67 and 71-73

• Small grains (oats, wheat, rye, etc.): For those with small grains, Joe Lauer at the University of Wisconsin put together a good resource for evaluating hail damage, which can be found here.
   
• Forages: For those with hail damage to forage crops like alfalfa or red clover, Dan Undersander and Dan Wiersma at the University of Wisconsin explain how to evaluate the damage in this resource here.

Fungicide Use on Hail Damaged Crops

Insects incoming - what should we be scouting for?

Insect issues haven't been too problematic to this point in the season, but they're showing up now. Keep an eye out for the ones I've highlighted below and let me know if you're seeing other issues!

Corn rootworm - Larvae have hatched in central Iowa and can be found feeding on corn roots in fields. Scout fields, especially long-term continuous corn or fields with known Bt trait performance issues, for larvae and feeding on the roots. Now is a great time to look as feeding is fresh and easily identifiable. Erin Hodgson wrote a nice blog last summer on how to scout for corn rootworm larvae using either black plastic or a 5 gallon bucket.

Soybean aphid - It seems a bit early for soybean aphid, but the first ones were spotted in central Iowa soybeans late last week. Check out Ashley Dean's blog on the find for more information and read this article for information on speed scouting for aphids. Here's a speed scouting resource sheet for you as well.

Soybean gall midge - this is a relatively new pest to central Iowa, only known to be in Boone, Dallas, and Madison Counties, along with counties to the west. We have no known effective management option in soybean once they are discovered but trust many researchers are working to find effective management options for us! Let me know if you see any suspicious death of soybeans near field edges or find reddish larvae feeding on soybean stems. See this article for more information and images of what to look for.

Japanese beetle - The first Japanese beetles have been spotted out in central Iowa, so we'll soon see them in corn and soybean fields. This pest very rarely would reach infestation levels to warrant treatment in soybean or in corn (aside from maybe field edges in corn). Read more in this article about thresholds for treatment and identification.

Potato leafhoppers (alfalfa, soybean) - I spotted my first "hopperburn" (image below) in a central Iowa alfalfa field, which means leafhoppers are probably present and need to be scouted for in other alfalfa fields. First should be monitored weekly following the first cutting of alfalfa until the end of the growing season. This pest was abundant in alfalfa last summer due to the dry conditions and I wonder if we're in for another similar case this year. This 2019 ICM News article from Erin Hodgson and Ashley Dean contains information on scouting and treatment thresholds for potato leafhoppers.

Herbicide Field Days coming up!

 
June 29 - Join us for a Herbicide Resistance Management Field Day at the south farm of the Northern Research Farm from 1-3 p.m.! This field day is the sister event to the June 15 field day looking at herbicide resistance management in corn.  We will tour soybean herbicide plots to talk about using effective modes of actions, effective rates and appropriate timing strategies. We will also look at impacts of cover crops on weed pressure.


July 8 - Hold this date for the ISU Weed Science Program Field Day! This will be a public field day with plot tours focused on corn and soybean herbicide programs, herbicide resistance screening updates, harvest weed seed control, cereal rye termination timing, and other research updates from the ISU Weed Science Program. Please call or email me at 319-331-0058 or mjanders@iastate.edu to register for the free lunch!