September 3, 2013 11:39
Can you identify this plant? Do horses eat it?
Plant sample cut in hayfield
Plant samples in garden, yard and hayfield
Photo credit: HorseOwnerToday.com
August 23, 2013 16:21
Alfalfa field March 21, 2014
Photo credit: Bonnie Newton
Alfalfa field, one month after first cut.
If not properly managed, alfalfa can suffer winter injury or winterkill. Several factors play into good winter survival of your alfalfa stand.
Taking a Second Cut
For alfalfa, early fall is a critical time as plants are storing nutrients needed to survive the upcoming winter. Cutting plants during this period adds double the stress to the plants as they have to expend energy for regrowth as well as nutrient storage. During a minimum of six weeks after cutting, alfalfa plants need good growing conditions to ensure sufficient regrowth and energy storage to support winter survival. Plants harvested after August 15th may not have six weeks before a killing frost and may be susceptible to winter kill. A killing frost is considered minus five degrees Celsius or lower. Harvesting after a killing frost does
not affect food reserves but reduces the amount of stubble which helps trap snow. The trapped snow provides an important insulating blanked for alfalfa crowns.
If alfalfa makes up 50% or more of the production in the stand and was properly inoculated at seeding, nitrogen is generally not a concern in the forage stand as the alfalfa will fix the nitrogen required by the stand. Phosphorus, potassium and sulphur are the three nutrients which should be considered in stands with large proportions of legumes. Phosphorus and potassium are particularly important as they support root and nodule health and over-wintering capability. Both of these nutrients can be fall applied as they are relatively immobile in the soil and will not leach or volatilize to the atmosphere like nitrogen. The most cost-effective way to maintain adequate soil fertility is to do a fall soil test.
An otherwise healthy stand can be impaired by insects and disease such as alfalfa weevils and downy mildew. Scouting for insects during June is important in noticing and minimizing insect feeding damage while disease resistant alfalfa varieties are your best defense against various root and leaf diseases.
Not all factors in alfalfa fall management are under your control. For example, wet soil conditions in the fall can reduce the plants ability to harden prior to winter. Lack of snow cover is also a concern as alfalfa crowns can be exposed to extreme cold. Snow cover can be improved by leaving sufficient stubble height.
Planting cold tolerant and disease resistant varieties along with a good fertility program and careful cutting management will help winterize your alfalfa stand for better longevity and productivity.
For more information on this or other topics please call me at the Watrous Ministry of Agriculture office (306) 946-3219, the Agriculture Knowledge Centre at 1-866-457-2377 or visit our website http://www.agriculture.gov.sk.ca/
July 23, 2012 17:51
BY MICHEL TREMBLAY, PAG.
PROVINCIAL SPECIALIST, FORAGE CROPS
The 2012 growing season has been characterized by significant rainfall across the agricultural zone of Saskatchewan, following a dry, warm winter. In Saskatchewan, spring precipitation is the largest single determinant of yield of cool season forage species. With favorable soil moisture present in nearly all areas of the province, a good forage crop should be expected. Some producers have noticed that their alfalfa fields are not yielding, considering the soil moisture present. The following factors may be contributing to decreased alfalfa vigor and yield.
The alfalfa weevil (Hypera postica) is a pest of alfalfa crops, and is increasing in occurrence in Saskatchewan. Alfalfa weevils have been observed predominately in the southeastern and east-central parts of the province in alfalfa hay and seed fields. Adult weevils are approximately 5 mm in length, brown in colour, with a darker brown stripe from the head running down the back. The alfalfa weevil is a snout beetle, with a pronounced hook shaped proboscis at its anterior end. The larvae, when newly hatched, are yellowish green. At maturity, larvae are approximately 8 mm in length, and have a black head and a white stripe down the centre of its back. Adult weevils overwinter under plant debris and soil in and around alfalfa fields. Weevils emerge in spring and begin feeding on alfalfa leaves, creating round holes in the leaves. Females, when ready to lay eggs, chew a hole in the stem of the alfalfa plant and deposit from one to 40 eggs per stem. The bright yellow eggs can be seen with the naked eye if the stem is cut open. Eggs hatch one to two weeks after being laid, and the emerging larvae initially feed within the stem before moving to the developing buds, then newest leaves.
Alfalfa weevil larvae leaf damage.
Source: Saskatchewan Agriculture
Damage begins as pinholes and progresses to extensive feeding damage to leaf surfaces between veins, resulting in a ragged, skeletonised leaf. Heavily infested fields may not have flowers present, as the larvae will remove developing inflorescences. Often the first sign of weevil damage is the discoloration of the crop as the larvae feed. Evident from the field edge, the crop will develop a whitish sheen, or frosted appearance, due to foliar damage.
Alfalfa weevil larvae.
Source: Saskatchewan Agriculture
Larvae feeding occurs predominantly early in the season, in mid-June to mid-July. Mature larvae move down to the base of the plant or onto the soil and spin a lace-like cocoon. The adults emerge from the cocoon in one to two weeks. The larvae represent the most destructive stage of the alfalfa weevil life cycle, and most weevil damage occurs on the first cut. Usually a single generation of the weevil occurs per season in northern climates.
The most cost effective control can be cultural. Cutting when the potential for significant weevil damage becomes apparent will stop yield losses. If the infestation is severe and early cutting is not feasible, alfalfa weevils can be controlled by using insecticides as per economic thresholds indicated below.
Economic thresholds for alfalfa weevil pesticide application
Foliage: 35-50 per cent of foliage tips show feeding damage.
Larvae: 20-30 3rd/4th instar larvae per 90o sweep of insect sweep net.
30 cm crop height and one larva per stem.
40 cm crop height and two larvae per stem.
Three larvae per stem requires immediate action regardless of height of crop.
Two or more active larvae per crown (four to eight larvae per sq. ft) on regrowth after the first cut.