• Thanks to the pheromone trap cooperators!
• Plenty of intensive moth captures this season.
• Southern Indiana should be scouting emerged corn for leaf feeding and/or cutting!

Every spring, dozens of cooperators throughout the state put forth considerable effort in trapping for the arrival and intensity of black cutworm moths. I’m personally indebted to these faithful bug counters, hoping you also appreciate their efforts as reported in the “Black Cutworm Adult Pheromone Trap Report.” If you recognize a name or two on this list of reporters, by county, please thank them! This year’s trap total, compared to the previous four, looks mediocre. Within these averages are many intensive moth captures over the six weeks of monitoring, follow up this moth arrival with larval damage scouting. Using the larval development model (see the accompanying “Black Cutworm Development Map”) it allows us to alert pest managers to be scouting emerging corn.

 

An email from Traci Bultemeier, Pioneer Hybrids, this week alerted us to the fact that Asiatic garden beetle grubs are making their presence known in fields of northeastern counties. She noted some high infestations in heavier ground than normal (Noble County). This pest is generally found only in light-textured soils. Seed applied insecticides have little effect in preventing these grubs from feeding on corn roots, more importantly the mesocotyl. Unfortunately there is no rescue treatment available. Damaged plants, if growing points aren’t compromised, may recover somewhat once temperatures warm and ample moisture is available. Don’t let the size of the small grubs fool you, they are like grubs on steroids!

 

Wk 1 = 3/31/16 - 4/6/16; Wk 2 = 4/7/16 - 4/13/16; Wk 3 = 4/14/16 - 4/20/16; Wk 4 = 4/21/16 - 4/27/16; Wk 5 = 4/28/16 - 5/4/16; Wk 6 = 5/5/16 - 5/11/16

Fields that were planted prior to the cool, wet conditions that have persisted across the state may experience stand establishment problems. Poor stand establishment may be due to several factors, including seedling blight diseases. Several different organisms can cause seedling blight diseases under a range of environmental conditions. The North Central Soybean Research Program and the United Soybean Board have sponsored several publications that can help farmers and agribusiness personnel understand and manage soybean seedling diseases.

Soybean Seedling Diseases—This publication discusses the organisms that cause soybean seedling blights, the conditions that favor each disease, and general management practices for preventing seedling blights.
http://cropprotectionnetwork.org/soybean-diseases/soybean-seedling-diseases/.

Scouting for Soybean Seedling Diseases and Disorders—This two-page scouting card is an excellent reference to help distinguish seedling blight diseases from common seedling disorders, such as herbicide injury. http://cropprotectionnetwork.org/soybean-diseases/scouting-soybean-seedling-diseases-disorders/.

Fungicide Efficacy for Control of Soybean Seedling Diseases—This publication is an annually updated table that includes the efficacy of the most widely marketed fungicide seed treatments against seedling blight pathogens. Ratings are developed by a national group of soybean pathologists as part of the NCERA-137 Soybean Disease Multistate Research Project. https://mdc.itap.purdue.edu/item.asp?Item_Number=BP-163-W.

Remember that to accurately determine the specific organism responsible for a suspected seedling blight issue, it is necessary to submit samples to a diagnostic lab such as the Purdue Plant and Pest Diagnostic Lab. https://www.ppdl.purdue.edu/PPDL/index.html.

These videos demonstrate how to sample fields to diagnose seedling blight and stand establishment issues.

Soybean seedling blight sampling:

Wet soil conditions can put soybean seedlings at risk for seedling blight diseases. Symptoms of seedling blights include wilting or discolored seedlings, poor stand establishment, and seedlings with discolored or rotted roots. There are several different seedling blights that can occur in soybean, and unfortunately they are difficult to diagnose in a field. If seedling blight issues are suspected within a given field, it is important to submit samples to a diagnostic laboratory to confirm the diseases present. To identify where you can send a sample for diagnostic confirmation please go to the National Plant Diagnostic Network at http://npdn.org/home. This diagnosis can help with future disease management decisions. For more information please see the Crop Protection Network Publication, “Soybean Seedling Diseases”:  http://cropprotectionnetwork.org/soybean-diseases/soybean-seedling-diseases/ (CPN-1008), and “Fungicide Efficacy for Control of Soybean Seedling Diseases”:  https://www.extension.purdue.edu/extmedia/BP/BP-163-W.pdf (BP-163-W).

There are many no till fields across Indiana that have either not been burned down or have had failed burndowns.  The wet weather of the last two weeks has kept sprayers out of the field and allowed winter annuals to continue to grow and the majority to go into reproductive growth.  Those fields that did receive a burndown, may need to be scouted and readdressed as many of the burndowns were applied just prior to the latest cold snap thus the herbicides were not effective in killing all the vegetation.

Farmers will need to have a plan as we approach any possible dry spell in which sprayers will be able to get back into the fields to make late burndowns.   Winter annuals that are in reproductive stages and larger in growth are tougher to control and will require an increased rate of glyphosate for effective control.  Rates of 1.25 to 1.5 lb. ae glyphosate (35-42 fl. oz. Roundup Powermax) will be needed to effectively control winter annuals in fields that have yet to receive any burndown applications. 

It is also recommended that farmers include 2,4-D and/or a saflufenacil product (Sharpen, Optill, Optill PRO, or Verdict) into the tank to improve control of the larger broadleaf weeds.  Farmers may be inclined to remove these products from the tank due to plant back restrictions in a time when our planting season has become more compressed.  Purdue weed scientists encourage farmers to NOT remove these products and to wait the 7-14 days in order to not only to achieve an improved burndown, but to assure that the field is clean as we always discourage planting into dirty/weedy fields as herbicide options become much more limited once the crop emerges.

There will also be fields that need a second burndown application to clean up weeds that were not controlled by a previous burndown applied just prior to the early May cold spell.  In these fields, remember that plants need to be actively growing to achieve an effective cleanup burndown with a glyphosate based program.   Farmers need to make sure that partially controlled or injured weeds have begun to regrow to assure that the second burndown application is effective.  Similar to what was mentioned above we encourage the use of at least 1.25 lb ae glyphosate and the inclusion of 2,4-D and/or Sharpen in the tank mix to improve burndown control.

Paraquat based burndown programs will be less effective for late spring burndowns if weeds are large, because effective spray coverage can be very difficult to achieve. If the wet weather prevented planting of a field that had been sprayed effectively in April, a paraquat based program can be effective on small, summer annual weeds.  We would still encourage the use of metribuzin (soybean), atrazine (corn), saflufenacil (corn or beans) or 2,4-D with paraquat to broaden the spectrum of activity if you are going after small, summer annual weeds. Although if farmers do choose to use a paraquat based program, they need to make sure to have a spray volume of at least 15 to 20 gal/A and apply with fine to medium droplets to achieve proper herbicide coverage.