Plenty of evidence shows that pesticide-treated seed helps corn and grain sorghum yields by curbing damage when there's a hefty insect infestation, but Kansas State University research indicates that using treated seed also boosts yields when few pests are present.

"A likely explanation for this is that the seed treatment allows plants to stay healthier by minimizing damage caused by minor pests that ‘nibble' away at yields," said Mark Claassen, professor and agronomist-in-charge of the Harvey County Experiment Field near Hesston. "While we encountered mainly flea beetles or chinch bugs, it is possible for growers to encounter low levels of these or other insects, such as wireworms, that can affect stands; seedling vigor; and, ultimately, yield."

The research was conducted over a three-year period by Claassen and Gerald Wilde, professor and field crop entomologist with K-State Research and Extension. Soil at the Hesston site is a Ladysmith silty clay loam. The crops were planted in different rotational sequences each year. Corn followed wheat, sorghum, and soybean, while sorghum followed wheat, corn, and sorghum in successive years.

The study involved two corn hybrids, two sorghum hybrids and several seed treatments, including no treatment, Gaucho, Cruiser and Prescribe. The corn was planted in mid-April at 20,000 to 23,000 seeds per acre, and the grain sorghum was planted in late April or early May at 46,000 to 47,000 seeds per acre. There were only light to moderate infestations of flea beetles and/or chinch bugs over the study period.

In two of the years, corn yields were depressed by hot, dry conditions. Over the three-year study period, yields ranged from 30 to 93 bushels per acre. The three-year average corn yield for the no- treatment (check) site was 51 bushels per acre, while the average for crops grown from treated seed was 61 bushels per acre – a 10-bushel difference.

In 2000, there was a 24-bushels-per-acre difference between the corn check treatment (77 bushels per acre) and the average of the treated- seed crops (101 bushels). In 2001, however, there was no difference between the check treatment (29 bushels per acre) and the average of the crops grown from treated seed (29.7 bushels per acre). In 2002, there was a 3.5-bushels-per-acre advantage for the treated-seed corn (51.5 bushels per acre) over the check treatment (48 bushels per acre).

The average grain sorghum yields over the three years ranged from 48 to 107 bushels per acre, the researchers said. The three-year average grain sorghum yield for the no-treatment (check) area was 63 bushels per acre, while the average for the treated seed area was 71.5 bushels per acre – an 8.5-bushel difference.

In 2000, there was an 11-bushel difference between the check (100 bushels per acre) and the average of the crop grown from treated seed (111 bushels an acre). In 2001, there was a 4-bushels-per-acre difference between the check treatment (48 bushels per acre) and the average of the seed treatments (52 bushels an acre). In 2002, there was a 9-bushels- per-acre advantage for the crop grown from treated seed (51 bushels per acre) over the check treatment (42 bushels).

For more information about this study, interested persons can check with their local K-State Research and Extension office and ask for the publication "Agronomy Field Research-2003," SRP 913. The results are on pages 37-40.

K-State Research and Extension is a short name for the Kansas State University Agricultural Experiment Station and Cooperative Extension Service, a program designed to generate and distribute useful knowledge for the well-being of Kansans. Supported by county, state, federal and private funds, the program has county Extension offices, experiment fields, area Extension offices and regional research centers statewide. Its headquarters is on the K-State campus in Manhattan.