July 27, 2012 15:14
BY MURRAY FEIST, RUMINANT NUTRITION SPECIALIST
Weather conditions this summer have been conducive to the formation of blue-green algae blooms on dugouts and ponds. Nutrient rich runoff flowing into a body of fresh water combined with warm daytime temperatures in the summer accelerates algal growth, including that of blue-green algae.
Blue - green algae is not an algae, but a bacteria called "cyanobacteria." This bacteria produces toxins that can cause skin and eye irritations, gastroenteritis, liver and nervous system damage, sickness and, at times, death.
A surface bloom of blue-green algae may look quite differently depending on which species is dominant. Some will have a shimmering blue-green colour. The bloom may also have a foamy sheen-like appearance that looks like spilled paint floating on top of the water. Heavy blooms may appear like a solid shimmering blue-green sheen across the water’s surface, may have an appearance and consistency similar to pea soup, or may have a mixture of the colors tan, purple, grey, green or blue-green.
If blue-green algae is identified in a water source, all livestock, pets, and human contact should be prevented. The water will require treatment.
The most common treatment of blue-green algae in an open dugout or pond is with a registered product containing copper sulphate. A treatment rate of one pound (0.45 kilogram) of copper sulphate (by weight) will treat 100,000 gallons (1 kg/1,000,000 litres). There are two common application methods: the copper sulphate can be dissolved in warm water, which is then sprayed over the water’s surface; or, the copper sulphate can be weighted into a cloth bag with a rope spread from side to side, and with the assistance of another individual, the bag can then be dragged back and forth across the water’s surface. When treating dugouts, the objective of the treatment is to target the top meter (1.0 m) to kill the algae.
Copper sulphate works by killing the blue-green algae. Doing so releases the blue-green algae toxins into the water. Therefore, it is recommended that 12 to 14 days should pass prior to any livestock, pet and/or human contact with the contaminated water. If treating a dugout containing fish, it is recommended that only one-third of the dugout should be treated, using one-third of the recommended copper sulphate weight applied in treatments over a three day period.
The treatment process described above applies to non-draining waterbodies, such as dugouts, which are wholly contained on private land. In the case of waterbodies that drain to adjacent properties or waterways, a permit for the chemical control of aquatic nuisances is required from Saskatchewan Environment.
For more information, call the Agriculture Knowledge Centre at 1-866-457-2377.
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.