Weather requires close monitoring and is a primary driver for crop disease and pest issues. Kansas has a unique tool called the Kansas Mesonet (weather station network) which can provide weather information assisting with agriculture management decisions. Using Mesonet data, we can evaluate the presence and stage of a primary pest of alfalfa -- the alfalfa weevil.
The Kansas Mesonet has launched a new tool just in time for 2017 spring weevil concerns. Our “Degree Day Calculator” (mesonet.ksu.edu/agriculture/degreeday) can help with alfalfa weevil detection and scouting. This tool utilizes weather data from 56 stations across the state. The data can be used to estimate the stage of alfalfa weevils in alfalfa fields. This article briefly summarizes the Degree Day Calculator and will describe how to use it with weevil scouting.
When to scout…
Figure 1. Graph displaying normal vs. actual accumulated degree days for the Mesonet Lake City station.
Comparing to normal…
Using “Normal” values (climatology of 1981-2010), we can estimate when the initial period may begin for weevil scouting in a “normal” or “average” year. The second data column in the table is the calculated normal for the period you entered. The “Departure” column to the right of Normal is the difference between the Actual versus the Normal. Positive values indicate that weevil progression is occurring sooner than normal and scouting will be required ahead of what “normal” climatology would indicate. Negative values indicate the opposite. This comparison to normal can also be viewed on the graph and is represented by a blue line.
2017 Conditions (as of 3/27/17)
Currently, after a very warm late winter/early spring the entire state of Kansas is averaging 400+ Degree Days. The average climatology for March 27th is 100 Degree Days over the whole state. To be more than 300 Degree Days ahead of normal at this point in the year is an incredible feat. Typically in Kansas, the climatological normal for alfalfa weevil scouting recommendations would be early April. However, with a 300 Degree Day surplus, most locations are already likely seeing leaf pinholing as a result of weevil feeding. Some consistency and variability needs to be considered in these values. Although, with such high values, it is recommended that a scouting program should be ongoing statewide at this time.
For more information, see:
Alfalfa Weevils, K-State Research and Extension publication MF2999.
Kansas Mesonet (March 2017). Degree Day Calculator, Department of Agronomy Weather Data Library. http://mesonet.k-state.edu/agriculture/degreedays
Christopher Redmond, Assistant Scientist/Mesonet Manager
Mary Knapp, Weather Data Library
Dan Regier, Weather Data Library Web and Database Developer
Jeff Whitworth, Extension Entomology