Invasive weeds are of great concern to any rancher or farmer. They can reduce crop yields and many are unpalatable or toxic to livestock. In pastures, invasive weeds can produce virtual monocultures, which limits the variety of plants in the diets of livestock. Livestock will often not eat invasive plant species, instead they selectively feed on native plants. This reduces competition for the invasive plants allowing them to grow and spread. Farmers are concerned about invasive plants in fields also. Invasive plants crowd out crop plants, as well as consuming fertilizer and water intended for crops. Controlling invasive weeds in fencerows and ditches adjacent to fields and rangelands reduces the chances of these areas becoming re-infested.
Spotted knapweed, Centaurea stoebe ssp. micranthos
Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
Spotted knapweed was introduced into North America in the 1890's. Since then, it has spread to almost every state in the nation and has been disastrous to the rangelands of Idaho, Montana, Washington and Minnesota. Spotted knapweed is unpalatable to livestock and is only eaten when other plants are not available. Spotted knapweed also releases a chemical from its roots that inhibits germination and slows the growth of many native plants. Plants can produce thousands of seeds each year and once a seed bank is established, eradication can take several years.
Asian soybean rust was first detected in the United States in the winter of 2004. It is now present in Florida, Georgia, Alabama, Arkansas, Louisiana, Texas and Mississippi. Almost all commercially grown soybean cultivars are susceptible to this disease. Asian soybean rust is caused by Phakospora pachyrizi, an invasive fungus. The fungus causes tan to reddish brown lesions on the surface of leaves, petioles, cotyledons, stems and pods. The disease progresses rapidly and leads to smaller seed and reduced yields. The spores of this fungus can only survive in the presence of its host; hosts include soybean, vetch, lespedeza, kudzu, and many legumes.
Feral pigs, Sus scrofa
Vladimir Dinets, University of Miami, Bugwood.org
Feral hogs can cause a wide variety of problems for farmers and ranchers. They are omnivores and will eat almost anything including crops and feed. Feral hogs have also been known to prey upon young livestock and other small animals. Hogs are wallowers and rooters. These activities can destroy livestock and game fences, as well as banks of agricultural ditches and streams. Feral hogs have also been shown to spread brucellosis to humans and livestock. While symptoms of a mild case of brucellosis can resemble the flu, severe infections can affect the central nervous system and the lining of the heart.
Africanized honey bees were first reported in the United States in south Texas in 1990. Since then they have spread to Florida, Oklahoma, Arkansas, Louisiana, New Mexico, Arizona, Nevada and California. Africanized honey bees are a hybrid between African bees and European honey bees. The hybrid bees can only be distinguished from European honey bees by microscopic measurements. However, Africanized honey bees are much more defensive than European honey bees. Since introduction into the U.S. the bees have caused 16 human deaths. Deaths to livestock and animals are much more frequent, but are not currently being reported. Many human deaths are because of inability to get away from the swarming bees. Animal deaths are usually due to being tied or penned. Bees nest in any enclosed area, such as barbeque grills, mailboxes or other containers. A person walking within 50 feet of a nest can trigger an attack, while things that produce vibrations, such as a tractor, lawn mower or power tools, can trigger an attack from 100 feet.