CORN.  Of course it is too late to really be thinking about what seed treatment you will order in corn, but knowing the strengths and weaknesses of what you have is still important.  Seed treatments are good not perfect for controlling all the soil and early-season insects that could be found in corn.  In a previous article, I discussed the potential value of supplementing seed treatments with liquid or granular in-furrow insecticides, but I have to throw in the disclaimer that yield responses will be hit or miss depending upon the circumstances. 

The rates of insecticide seed treatments that come standard on corn seed are Poncho 250 or Cruiser 250.  However, you may have ordered rates of Poncho 500, Poncho 1250 or Cruiser 500.  The seed treatment and rate options are dependent upon the seed company but are essentially unchanged from last year.  Clearly the higher use rates offer more potential residual control and better initial control of some pests, but they are not stand alone treatments against others.  Cutworms and sugarcane beetles are two examples where the seed treatments are just not adequate in many cases.  The articles below address some management considerations for these two pests.

In-furrow insecticides in corn and soybean (article written April 2, 2013).

Refresher on cutworms (article written April 1, 2013)

Corn seed treatment option (article written December 31, 2012)

COTTON.  There is really nothing new here.  Unless you somehow found some Temik, you will and should be using an insecticide seed treatment, either imidacloprid (e.g., Gaucho, Aeris, Acceleron I) or thiamethoxam (e.g., Cruiser, Avicta Duo).  These treatments typically provide 3-4 weeks of control of thrips infestations, but they may require a supplemental foliar application in cases of poor emergence, slow growth and high thrips numbers.  Also, conventional tillage increases the risk of thrips damage.

The insecticide rate will be 0.375 mg ai/seed.  However, Bayer varieties such as Stoneville and FiberMax come from the factory with a 0.135 mg ai/seed rate of imidacloprid (in part to help protect against stored grain insect pests).  This is NOT an adequate rate for thrips control, but when the standard insecticide treatments are also applied at the factory or downstream, you get an extra dose.  It has been pretty obvious the last two years that this extra shot of imidacloprid has improved thrips control.  Phytogen is also using thiamethoxam for stored grain protection, but the rate used (0.01 mg ai/seed) is too low to add significant thrips control.  These storage rates are causing some confusion because they are listed on the treatment codes found on the bag even though they are not stand alone for thrips control.

There have been some issues with the performance of insecticide seed treatments the last few years, with Cruiser seeming to be more affected.  I am convinced that the increased use of pre-emergent and residual herbicides is to blame in most cases.  We have some research planned to verify this, but it appears these herbicides are causing some injury and delaying growth.  This is likely increasing the window to which seedlings are susceptible to thrips injury.

There have been a few questions about adding acephate as a downstream seed treatment on top of imidacloprid or thiamethoxam.  In the old days, it was not uncommon to use a rate of 8 oz of Acephate 90S per 100 pounds of seed.  I’ve not looked at this combination in a long time.  This low rate would only supplement thrips control for a short while, and in my experience, should not be expected to improve what you are getting with imidacloprid or thiamethoxam (unless they are completely failing or applied at the wrong rate).  I am adding this into my testing program in 2013 but am not recommending this as a standard practice.

My suggestion:  Growers should plan on making one (and usually only one) foliar insecticide application to seedling cotton.  A few points to consider are below. 

• This is not an automatic application.  If the cotton blows out of the ground and looks great, with little evidence of thrips or injury by the second true leaf, then don’t make the application.  Consider the risk factors mentioned above.
• This application should be made before the second true leaf is fully expanded.  There is a lot of research showing that this is typically the best timing.  There is even more data showing that two applications is RARELY needed on top of at-planting treatments. Multiple applications increase the risk of flaring early season spider mites or aphids.
• There are several foliar insecticides listed for control of thrips in cotton in the UT Insect Control Recommendations.  These include Acephate (0.18 – 0.25 lb ai/acre), Bidrin (2.0 – 3.2 oz/acre), Dimethoate (4-8 oz/acre) and Radiant SC (1.5 – 3.0 oz/acre).  All do pretty well. 
• Radiant is the product of choice if facing western flower thrips, but despite the problems in other states last year, they are usually not a big part of the thrips complex in Tennessee.  It is one of a few insecticides that consistently benefits from using a surfactant, so I suggest using the 1.5 oz rate with a recommended surfactant.  My counterpart, Gus Lorenz at the University of Arkansas, found last year that some herbicides that already contain surfactant such as RoundUp and Liberty sufficed as a surfactant for Radiant when applied in a tank mixed.  But we need more experience.
• Acephate is still my standard recommendation for foliar thrips control in cotton unless fighting western flower thrips.  We’ve not shown any significant issues or injury when tank mixing acephate with herbicides including RoundUp or Liberty.
• Pyrethroid insecticides are NOT recommended for thrips control.

SOYBEAN.  With good commodity prices, and especially with early planting, growers should still consider using an insecticide seed treatment on at least some of their soybean acres.  The options are unchanged from last year and include imidacloprid (e.g., Acceleron FI or Gaucho), thiamethoxam (Cruiser), or clothianidin (NipsIt).  You can have treatments made at the factory or downstream in many cases, but the options vary by the seed company.  You can refer to the list of seed treatment options I listed in an article last year.

Soybean is less likely than either corn or cotton to consistently benefit from an insecticide seed treatment, but a lot of data shows an average yield response of about 2 bushels per acre in Tennessee, with a more consistent response on early planted soybean.