Some farmers raise forages by letting the grass grow tall in the field, cut it a couple times through the season, bale it, and call it hay. But growing healthy forage should be just like growing any other crop with consideration for seed variety, proper fertilizer (nutrition), crop monitoring and good field management. Healthy forage is important for raising healthy livestock. Healthy livestock means healthy dairy and meat for people.
Some forage crops, like alfalfa, can be very lucrative crops to grow. The higher the quality, the better the price. The higher the yield, greater the return. Unfortuately, due to is the increase in pest and disease pressure that seems to plague just about every crop being grown today, growing healthy forage can be a challenge. Potato leaf hoppers and Verticillium Wilt are two major issues that farmers face when growing forages. Ontario, alone, grows about two million acres of forage, and has about 1.6 million acres in pasture feeding over 1.2 million head of dairy and beef cattle, horses, sheep, and goats.
Preventing insect and disease damage is the key to producing the best forage crops. Taking a biological approach to fertilizing your hay or alfalfa crop is the best way to discourage insects and disease from attacking your crop. But, what does fertilizer have to do with insects? Everything. We'll explain that later, but let's learn a little more about the potato leafhopper and the Verticillium fungus.
The potato leafhopper is a pale, yellowish green insect about 1/8 inch long with wings. The young, known as nymphs, are smaller, have no wings and are mostly yellow with tinges of green. Potato leafhoppers cannot survive the cold winters of Canada, but they do migrate in from warmer climates through storm clouds. The adult potato leafhopper is stimulated by low pressure systems to fly into updrafts that draw it into clouds to be transported by the direction of the storm and dropped by the down drafts in front of these storms. As soon as the adult female leafhoppers drop into the fields, they lay their eggs in alfalfa stems and leaf veins. The population of potato leafhoppers can grow very rapidly as they reach maturity in just three to four weeks after hatching. Potato leafhoppers feed by sucking plant sap from alfalfa tissue, doing most of their damage from mid-June to mid-August.
Damage done by potato leafhoppers, just like many other sources of plant stress, causes a significant decrease in yield. Although there have been great advances in the types of chemicals used to kill insects, these chemicals do not choose which insects they kill. In addition to killing the the bad insects, they also destroy the beneficial microbes that have the important role to releasing minerals from the soil that feed and strengthen the alfalfa plant.
Verticillium Wilt is a serious disease that plagues alfalfa and is responsible for major yield loss. Verticillium Wilt was first discovered in Europe in the early to mid-1900. Verticillium Wilt causes yellowing in alfalfa due to the presence of a toxin which is produced by the colonization of the fungus inside the water conducting tissue (the xylem), plugging it and limiting water movement in the plant. Bunchy tops, short internodes and upward curling of leaves on stems are symptoms of Verticillium Wilt. Diseased leaves look wilted and pinkish to yellow in colour compared to healthy leaves. Verticillium Wilt may infect alfalfa plants through the roots or through the stem during harvest. Verticillium Wilt fungus takes hold when a plant is stressed due to a deficiency of nutrients such as phosphorus, calcium, and boron (which aid in the transfer of other nutrients and carbohydrates in plants), or attack by pests such as the potato leafhopper.
When you fertilize your alfalfa and supply adequate nutrients, your plant can produce carbohydrates and proteins. Once a plant's level of carbohydrates and protein levels reach a certain level, insects such as the potato leafhopper move on because they know that the plant tissue is now longer digestible by their relatively simple digestive system. So, the answer to preventing initial infestation and in keeping your valuable alfalfa free from pests and growing strong is proper fertilization (nutrition). Not only does proper nutrition help build plant strength and immunity, but fungicides and insecticides break down your plant's ability to fight off disease and insects. Its ironic that the very thing that farmers do to get rid of the insects and fungus actually cause the conditions to worsen. When chemicals are used to eliminate insects and kill fungal and bacterial disease, the plants that are sprayed are left with a reduced ability to take in nutrients which hinders the production of carbohydrates, which actually makes the plant more susceptible to insects and disease.
Alfalfa is long known as the "queen of forage" due to its high nutritional value for livestock. Because of the great economic value of alfalfa, it is important to monitor its growth, health and performance by measuring brix and tissue nutrient content frequently using common tools such as the refractometer and tissue analysis. This will allow you to ensure that your plant has the right balance of minerals so that it can stay free of pests and disease.
Bottom photograph of Verticillium Wilt taken by William M. Brown Jr., Bugwood.org and courtesy of WeedImages.org
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