When aphids and weeds start showing up in area wheat and corn fields, farmers need to consider the cost of herbicides before application, according to Jill Scheidt, agronomy specialist with University of Missouri Extension.
“I scouted fields … around Golden City and see any aphids yet but temperatures were still cool,” said Scheidt. “If temperatures are below 60 degrees, aphids are not active. If aphids are not present in wheat fields and if temperatures are below 60 degrees, an insecticide is not economical to apply.”
Kevin Bradley, a state weed specialist with University of Missouri Extension, recommends a two-pass herbicide program when spraying corn.
“Over the past 11 years, in 67% of corn trials, the highest yield was obtained by using a pre-emergent, followed by a post-emergent herbicide application; regardless of whether you plant conventional or not,” said Bradley.
The economic threshold level of weeds depends on species and growth stage of the weed.
To estimate weed density in wheat, count the number of plants in a square foot in 5 to 10 random places in the field. If weeds make up more than 30% of the plant population in that square foot, treatment is justified.
“If weeds make up 5% to 29% of the plant population, wheat prices and herbicide costs should be considered first,” said Scheidt.
Source: Missouri Ag Connection