by Joel Bagg, Forage Development Specialist & District Sales Manager, Quality Seeds Ltd
June and July weather has been hot and very dry. Rainfall has mostly been received in storm fronts with some areas receiving very little moisture. First- and second-cut forage quality has been excellent, but growth and yields have typically been below average. The weather has been very good for making dry hay and some excellent quality hay has been made. However, with low carryover forage inventories and lower than normal growth and yields so far, there is growing concern about producing enough forage to meet livestock needs this winter. Annual forage crops following winter wheat harvest is an option. Some new seedings are very drought stressed, but should improve with adequate rain. Be careful not to overgraze drought-stressed pastures because it will significantly reduce regrowth and total seasonal pasture yields. Although it may seem counter-intuitive, supplementing hay now rather than overgrazing pastures actually saves hay in the long run.
There was some alfalfa weevil larvae feeding damage in June, but most affected fields were cut rather than sprayed. Potato leafhopper pressure is building and some fields have been sprayed with insecticide. It is especially important to check new alfalfa seedings and spray if needed to prevent permanent damage to the stands. With the dry weather, boron deficiency symptoms are appearing in many alfalfa fields.
To Cut Or Not Too Cut?
A question often asked during extended periods of severe dry weather with poor growth is “should I cut or not?” Cutting decisions should be made on a case-by-case basis, depending on the condition of the stand and whether rain is in the forecast. Moisture stress during the 2 weeks following cutting results in a reduced number of stems per crown and reduced regrowth. Significant alfalfa growth will not occur until some drought-ending rains occur. Short, drought-stressed alfalfa yields are significantly reduced, but forage quality is usually higher than normal, even when plants are flowering. The stem internode length is reduced and the leaf-to-stem ratio is high. Harvesting at later maturity will allow alfalfa plants to build root reserves for better regrowth when rain returns. As a general suggestion, stands greater than 10 inches tall and in full flower should be harvested. In stands less than 10 inches tall, delaying cutting until rain is forecasted is suggested because yields are low and mowing will not increase growth until significant rainfall occurs. To enable faster grass regrowth, grassier stands should not be cut less than 4 inches high. Harvesting drought-stressed new alfalfa seedings should sometimes be delayed depending on the weather forecast, but mowing may be needed to control weeds.
Potato Leafhopper Damage
Potato leafhoppers (PLH) are being reported at damaging levels in alfalfa in some parts of the province and some spraying is being done. Damage is often confused with moisture and heat stress, and dismissed as “drought damage”. Control of PLH can significantly reduce drought stress and provide additional yield. New seedings are very susceptible and if untreated can be permanently damaged for the life of the stand, so be sure to check these fields. Once the V-shaped yellow “hopperburn” on leaf tips is observed the damage is already done, so fields should be scouted for the presence of leafhopper before this occurs. Do not confuse the presence of aphids, which can be quite numerous, with the wedge-shaped leafhopper. (Potato Leafhopper In Alfalfa www.qualityseeds.ca/blog/19-quality-time-with-joel)
Figure 1 - Potato leafhopper damage to new seeding. Injury is most severe in new seedings and in young regrowth.
Figure 2 – The same field 15 days after spraying with insecticide.
Figure 3 – Second-cut regrowth - untreated (left), sprayed with insecticide (right).
(Photo credit – Paul Sullivan)
Figures 4 - “Hopperburn” symptoms start as a “V” yellowish pattern on the leaf tips.
Figure 5 - Potato leafhopper adults are pale green, wedge-shaped, winged insects. Immature nymphs are smaller and wingless. Do not confuse aphids with leafhoppers. (Photo credits – OMAFRA)
Boron Deficiency In Alfalfa
Boron deficiency symptons can be seen in many alfalfa stands. It is characterized by a yellowing or reddening of the upper leaves of the plant, and is sometimes referred to as “yellow top”. Lower leaves will stay green. The field, or patches in the field, assume a bronze color. Stem growth between leaves becomes shortened, giving plants a stunted appearance. It is sometime confused with potato leafhopper damage, but with boron deficiency the discolouration appears on leaves at the top of the plant, while with potato leafhopper the discoloration appears on both the upper and lower leaves.
Boron deficiency shows up mainly on high-pH, sandy soils and is seen most frequently on droughty soils under dry conditions. In Ontario, it is more common east of the Niagara escarpment.
Growth can be severely stunted and winter hardiness reduced. Confirming a boron deficiency can be done by tissue testing with a properly taken sample and laboratory analysis. Boron deficiency can usually be prevented by a broadcast application of 1 - 2 lbs/acre of boron blended with the P and K. (http://www.omafra.gov.on.ca/english/crops/pub811/3fertility.htm#micronutrients)
Figures 6 & 7 - Boron deficiency appears on the upper leaves of alfalfa, becoming yellow to red with stunted growth. It is sometimes referred to as “yellow top”.
Summer Options For Providing Extra Forage
Many farmers are considering their options to increase forage inventories. An early winter wheat harvest enables more time for better volunteer wheat control, followed by timely planting of alternate annual forage crops, or alfalfa summer seedings. (Refer to “Summer Seeding Alfalfa” www.qualityseeds.ca/blog/2-summer-seeding-alfalfa)
Seeding oats or oat-pea mixtures in late-July or early-August following wheat for an early-October harvest as haylage or baleage can be a useful low-cost option for extending forage supplies. Forage quality can be improved by earlier harvest (flag-leaf to early-boot stage). The challenges can sometimes be lack of adequate moisture in August for germination and growth, and having dry enough weather in October for adequate wilting.
Refer to “Summer Seeding Oats & Oat-Pea Mixtures For Extra Forage”. www.qualityseeds.ca/blog/23-quality-time-with-joel)
Figure 8 – Oat or oat-pea mixtures following winter wheat can provide a low cost forage option.
QS “Evolution” Italian ryegrass can produce very high quality, leafy, palatable forage suitable for high producing dairy cows. It can be seeded in August following wheat for harvest in late-fall and then again the following May, making it an excellent double-crop option if managed properly. Evolution is noted for its high fibre digestibility (NDFD), high relative forage quality (RFQ), palatability, ease of establishment, and its yield response to nitrogen. (“Evolution” Italian Ryegrass Forage Options www.qualityseeds.ca/blog/3-evolution-italian-ryegrass-forage-options)