After 25 years, the Tri-State Fertilizer Recommendations for Corn, Soybeans, Wheat, and Alfalfa has been comprehensively updated and is now available. The full version can be downloaded as a free pdf, or a printed copy can be purchased: https://extensionpubs.osu.edu/search.php?search_query=974§ion=product
A summarized version of findings can be found here: go.osu.edu/fert-recs
The recommendations are based on more than a decade of field trials evaluating N, P, K, S and micronutrients, including over 300 on-farm trials across 41 Ohio counties. This work confirms that the original Tri-State recommendations provided sound guidelines for nutrient management. However, some changes in the recommendations have been made to keep pace with contemporary practices in Ohio’s field crops. This new guide provides an objective framework for farmers to manage nutrients as judiciously and profitably as possible.
Red counties reflect the Ohio counties where fertilizer trials were conducted (2014 – 2018).
Source: Kelley Tilmon, Andy Michel, OSU
As the summer progresses we are receiving reports of insect problems often encouraged by hot, dry weather. Last week we reported on spider mites and especially if you are in an area of continued dry weather we recommend scouting your soybeans and corn https://agcrops.osu.edu/newsletter/corn-newsletter/2020-22/watch-spider-mites-dry-areas .
Some areas are also reporting increases in young grasshoppers in soybeans, another insect favored by dry weather. Grasshoppers of often start on field edges so early scouting may allow for an edge treatment. Japanese beetles are another common defoliator of soybean that are starting to appear. Both of these pests fall into a general defoliation measurement, and we recommend treatment if defoliation is approaching 20% on the majority of plants in post-flowering beans. Download our guide to estimating defoliation in soybean at https://aginsects.osu.edu/sites/aginsects/files/imce/Leaf%20Defoliators%20PDF_0.pdf
A weird problem being reported not just in Ohio but in parts of the Midwest as far-flung as Minnesota is the red headed flea beetle, which is being found in corn and soybean. This is a small, narrow, shiny black beetle with a red head which springs like a flea when disturbed. Feeding in soybean creates small round holes and in corn longer narrow strips of damage. This feeding is seldom economic. In soybean follow the general defoliation threshold of 20%. Leaf feeding in corn is almost never economic, but be on the watch for silk-clipping, which is rare but possible. There are no thresholds in corn, but our Minnesota colleague Bruce Potter suggest this guideline: “flea beetles are very numerous (it is likely more than 5-10/plant), pollination is less than 50% complete, and numerous plants have silks clipped to within 1/2 inch, you might consider an insecticide.”
Finally, earlier in the season we reported higher than usual numbers of potato leafhopper in alfalfa and encouraged stepping up scouting. In some fields third-cut alfalfa is being heavily impacted by this insect. You can review our scouting advice for this insect at https://agcrops.osu.edu/newsletter/corn-newsletter/2020-17/time-start-scouting-potato-leafhoppers-alfalfa
Green alfalfa weevil larvae (the main feeding stage) at various growth stages, and brown adults. Photo by Julie Peterson, University of Nebraska.
Though it seems like spring has been slow to come this year, we have actually accumulated enough degree days to see potential outbreaks of alfalfa weevil in some locations. Ohio experienced its 5th warmest winter on record (1895-2020) and March temperatures averaged 2-8°F above average. Overwintered adults begin laying eggs when temperatures exceed 48°F. Peak larval activity and feeding damage occurs between 325 and 575 heat units (based on accumulation of heat units from January 1 with a base of 48°F). Current (Jan. 1 – Apr. 11, 2020) heating units range from near 100 in far northeastern Ohio, 100-200 across much of northern Ohio, and 200-300 units across much of central, southwest, and southeast Ohio. South central Ohio has currently eclipsed 300 units as evident at OSU South Centers in Piketon.
In short, now is the time to start scouting. Alfalfa fields should be scouted weekly for weevils until at least the first harvest. Don’t let your guard down with the recent turn to cooler weather! We’ve seen significant weevil infestations in past years when early warm weather pushed weevil development earlier than normal, followed by cooler weather later that slowed alfalfa growth. Continue reading