White Grub Infestations

January - March 2003

Virgil Schmitt , crops field specialist

Situation
In early May 2002, a dealer discovered several cornfields within a few miles of each other with heavy infestations of white grubs. He was preparing to tell the producers to destroy the corn crop and re-plant using Counter® for the white grubs, but he contacted the extension crops specialist for a second opinion.

Response
The extension crops specialist examined insects from each field and in each case the insects were identified as annual white grubs, which do not cause economic losses in corn, as opposed to true white grubs, which do cause economic losses in corn. Therefore, it was recommended to leave the existing corn stands.

Impact
1. Cost of destroying the existing corn crop. Assuming spraying it with Roundup® would have destroyed the existing corn crop, the cost of the Roundup® would have been approximately $4.00 per acre. With an application cost of $4.70 per acre, according to FM-1698 "2002 Iowa Farm Custom Rate Survey," the total cost to destroy the existing crop would have been $8.70 per acre.
2. Cost of Re-planting. According to FM-1698 "2002 Iowa Farm Custom Rate Survey," the cost of planting was $9.80 per acre.
3. Cost of Seed. According to FM-1712 "Estimated Costs of Crop Production in Iowa 2002" the cost of seed would have been $30.00 per acre.
4. Cost of Insecticide. According to FM-1712 "Estimated Costs of Crop Production in Iowa 2002" the cost of the insecticide would have been $14.00 per acre.
The total cost to replant would have been approximately $53.80 per acre.

As there were approximately 500 acres involved in the various sites, total savings over all of the sites was approximately $26,900. This assumes no loss of yield due to later planting or additional compaction from the extra trips that would have been made across the field.

 

Page last updated: July 10, 2006
Page maintained by Linda Schultz, lschultz@iastate.edu