UGA Entomologist Dr. Mike Toews is getting questions about treating shelled corn as it goes into storage. Here is updated information on products and efficacy from my recent tests in Georgia.
Actellic 5E (labeled for corn) – This is the standard product for shelled corn, but it is also the most expensive product to purchase. A full rate (12.3 oz per 1000 bu) will provide protection from weevils for at least 9 months, but reducing the rate will decrease the longevity of the protection. Actellic is susceptible to heat breakdown.
Centynal (labeled for corn and wheat) – Centynal is fairly inexpensive and will provide 3 to 6 months protection from weevils. It is critical to apply a full rate (8.5 oz per 1000 bu) or weevil control will be compromised. This material may also be used for treatment of empty bins.
Diacon (labeled for corn and wheat) – Diacon is an insect growth regulator that is effective at killing immature grain moths and beetles, except weevils. The 4 oz per 1000 bu rate is sufficient for tank mixing.
Storcide II (labeled for wheat) – Storcide II is an excellent option for stored wheat, but is not labelled for use on corn.
Malathion (labeled for wheat and corn) – This product has been widely used in the past, but is not currently recommended due to well documented resistance in many stored grain insect populations.
Tempo SC (labeled for empty bin use only) – Tempo is an excellent material for treating empty bins and elevator boots, but is not labeled for application directly to grain.
Three-way tankmix – Tests from 2015 showed that a three way tank mix of Centynal (8.5 oz) plus Diacon IGR (4 oz) plus PBO-8 Synergist (13.5 oz) will provide 6-9 months of protection from weevils. This is a moderately priced option for growers in markets where other products are unavailable or cost is a limiting factor.
Regardless of the product used, please be mindful that grain protectants are not a silver bullet. Applications should only be made to cooled grain (do not apply before sending grain through the dryer) that will be stored for more than 3 months. Apply protectants at the bottom of the auger so the kernels have a good chance to contact the insecticide while moving up to the top of the bin. Long-term grain storage also requires grain at an appropriate moisture content, proper housekeeping, use of a spreader when filling bins, and managed aeration.
Additional information is available in the 2016 Georgia Pest Management Handbook or in a recent Extension Publication (http://www.aces.edu/pubs/docs/I/IPM-0330/IPM-0330.pdf) that Dr. Kathy Flanders at Auburn University and I authored earlier this year.