In This Issue:
Potato Leafhopper
With most alfalfa having had their first cutting, it is time to begin sampling for potato leafhoppers as the crop reaches a sufficient height for sweep-net sampling. A single sample is 10 sweeps of a sweep net. When the average number of adults and nymphs in a sample is equal to or greater than the average height of the alfalfa stand, insecticide treatment is warranted. For example, if the alfalfa is 6 inches tall and the average number of leafhoppers is 6 or higher, insecticide treatment is warranted. If the average is lower, the grower should re-sample in a few days. In glandular-haired, leafhopper-resistant alfalfa, the economic threshold is 3X the normal threshold, or three leafhoppers per inch of growth (18 leafhoppers for 6 inch tall alfalfa, for example). However, if the resistant alfalfa is a new planting this spring, growers might want to use thresholds meant for regular alfalfa during the very first growth from seeding. After the first cutting, growers can then use 3X times the normal level threshold. More information on potato leafhopper, including how alfalfa growing conditions might affect the threshold, is available at http://ohioline.osu.edu/ent-fact/pdf/0033.pdf .
Uneven Soybean Emergence
In many areas of Ohio, soybeans are emerging unevenly. This is something that I observed last week in western Ohio. Most of the soybeans were at the VC stage (unifoliate), but there were areas that had not yet emerged. The soil was very dry and crusted over which contributed to some of the uneven emergence. Where we didn’t see any soybeans emerged, we dug up the seed and saw the soybean crooks (hypocotyls) emerged from the seed. I have not been back to western Ohio to check the field, but with this weekend’s rainfall, more soybeans are likely to have begun breaking through.
Uneven soybean emerged related dry soil has led to questions about replanting. Before replanting due to an uneven stand, do two things. First, dig around in areas where there are no plants. If you find seed that is healthy and germinated, but just not broken through – you can wait. The soil temperatures have finally reached optimum germination conditions, with a little bit of moisture they will continue to emerge. We saw this last year, when soybeans sat in the ground for a full 6 weeks before they received enough moisture to germinate. If you find, dead seedlings (disease) or no seed or seedlings (insects), then follow the next step very closely.
Second, take a stand count to determine the number of plants remaining. To quickly estimate stand, count the number of plants in 70 foot of row for 7.5 inch row spacing, 35 foot of row for 15 inch row spacing, or 17.5 foot of row for 30 inch row spacing. These counts represent 1/1000th of an acre (i.e., 120 plants in 35 foot of row grown at 15 inch row spacing represents a stand of approximately 120,000 plants per acre). Previous research conducted by the Ag Crops Team at Ohio State, indicates that soybean populations of 50,000 plants per acre yield approximately 15% lower than soybean populations of 175,000 plants per acre. Also, keep in mind soybean yield is decreased by approximately half a bushel per acre every day when planting later than mid-May. When considering replanting soybean, make sure to take into account existing stand, yield loss due to late planting, and the cost of additional seed (we recommend higher seeding rates when planting in June).
- Glen Arnold (Nutrient Management Field Specialist),
- Debbie Brown (Shelby),
- Bruce Clevenger (Defiance),
- Sam Custer (Darke),
- Nathan Douridas (FSR Farm Manager),
- David Dugan (Adams, Brown, Highland),
- Mike Gastier (Huron),
- Jason Hartschuh (Crawford),
- Mark Koenig (Sandusky),
- Greg LaBarge (Agronomy Field Specialist),
- Rory Lewandowski (Wayne),
- Mark Loux (Weed Science),
- Tony Nye (Clinton),
- Les Ober (Geauga),
- Pierce Paul (Plant Pathology),
- Steve Prochaska (Agronomy Field Specialist),
- Eric Richer (Fulton),
- Adam Shepard (Fayette),
- Alan Sundermeier (Wood)