by Joel Bagg, Forage Development Specialist & District Sales Manager, Quality Seeds Ltd
Forage growth is extremely variable across the province. With the cool spring weather, grass growth and maturity was about a week more advanced than the alfalfa, but with the current heat the alfalfa growth and development is rapid. Dairy first-cut haylage is underway and will be in full swing shortly. There is some concern about having adequate inventories of high quality forage. Older, thin, stressed alfalfa fields showing some winter injury and now are yellow with dandelions, indicating reduced yields. Some of these fields were overseeded with Italian ryegrass to provide additional yield and quality. Late fall harvests and late fall manure applications were risk factors for winter injury and less aggressive growth this spring. Some older, damaged alfalfa fields will be harvested early and planted into corn for silage. Spring application of sulphur on alfalfa is becoming an increasinly common management practise. Winter cereal forage and Italian ryegrass have been harvested with good yields. There were lots of new forage seedings this spring, generally under good soil conditions.
Alfalfa weevil larvae feeding is being reported in in the south-west, but not yet at threshold levels and haylage harvest is underway. If you are more than 10 days away from when you would like to harvest, scout your alfalfa to determine if alfalfa weevil is above economic threshold levels. Control options are to cut or spray. Typically, alfalfa weevil do not reach significant levels until we are ready to take first-cut. However, sometimes alfalfa weevil larvae development is advanced relative to the alfalfa crop, and can do significant damage before the crop is ready to cut. Insecticides are recommended only when cutting is impractical.
Occasionally, if weevil populations are high on a first-cut, surviving larvae will feed on the re-growth as quickly as it develops. In 2017, alfalfa weevil larvae feeding persisted into late-June. Such feeding can eliminate alfalfa re-growth which may lead to a loss of the stand. With severe infestations, monitor weevil activity on stubble regrowth for 5 to 7 days or more. The characteristic symptom is that the alfalfa plant does not “green up” due to larvae and newly hatched adults feeding on the developing crown buds. The presence of 2 or more active larvae per crown, or 4 to 8 larvae per square foot indicates a need to spray the stubble with insecticide. Registered insecticide products are listed on p. 55 in the OMAFRA Publication 812, “Field Crop Protection Guide”, (http://www.omafra.gov.on.ca/english/crops/pub812/pub812.pdf) as well as application rates and other information. Also refer to product labels. Keep in mind that there are “pre-harvest interval” and other restrictions with these products.
For more information refer to “Alfalfa Weevil” on the Quality Seeds blog at www.qualityseeds.ca/blog/32-alfalfa-weevil.
Figures 1 & 2 – Alfalfa weevil feeding May 23rd, Middlesex County
2,4-DB Weed Control
2,4-DB can suppress legume growth in new forage seeding for a period of 2 – 3 weeks and severe injury can occur under drought or high temperatures. Monitor the stage of development of the new seeding to determine the optimum time of spraying . The risk of injury to alfalfa seedlings is greatly increased when 2,4-DB application is made outside of the “labelled” first- to the fourth-trifoliate stage window. Uniform emergence as a result of good seedbed preparation and packing make it easier to stage. Target the first-trifoliate stage, where weeds are smaller and easier to control. Grower experience has been that injury to seedling alfalfa plants can be minimized when reducing the lowest labelled rate of 2,4-DB by 25%. A reduced rate may reduce the level of weed control. (OMAFRA Publication 75, Guide To Weed Control www.omafra.gov.on.ca/english/crops/pub75/pub75ch10.pdf)
Forage Establishment Challenges
There are a few high risk management practices that frequently cause establishment problems that should be avoided:
- Using a cereal companion crop and combining it as grain and straw rather than harvesting it as a forage. Not only does this excessively compete with the forage seedlings for moisture and nutrients, but straw laying for extended time in windrows or not picked up cleanly by the baler damages forage seedlings.
- Not seeding into a firm seedbed with adequate packing. This is especially important in a dry spring and with summer seedings. A loose, lumpy seedbed dries out quickly, and lumps make the uniform emergence of young seedlings difficult. A firm, level, clod-free seedbed is important for uniform seeding depth and good seed-to-soil contact. (Successful Forage Establishment )
- Not controlling weeds with herbicide in direct seedings. Broadleaf weeds competing with new forage seedings result in much thinner, weaker forage stands. (OMAFRA Publication 75, Guide To Weed Control )
- Not controlling volunteer wheat adequately before August forage seedings. Volunteer winter cereals easily out-compete new forage seedings. Volunteer cereals should be controlled with tillage and glyphosate. (Summer Seeding Forages )
Refer to “Successful Forage Establishment” www.qualityseeds.ca/blog/9-successful-forage-establishment.
Planting Corn Silage After 1st Cut?
Some alfalfa fields suffering from winter injury are being harvested early to be planted into corn for silage. Inadequate moisture during a dry summer is a risk factor. Be aware that planting as soon as possible and adequate moisture are essential to successful corn silage yields. (“Corn Planting Following Early Hay Harvests” www.omafra.gov.on.ca/english/crops/field/forages/corn_earlyhay.htm)