Ragweed not only causes allergic reactions for hay fever sufferers, the plants also can severely interfere with crop production and greatly reduce yields."Ragweed plants can have a serious impact on grain and forage crop production," said J.D. Green, Extension agronomist with the University of Kentucky College of Agriculture. "Giant ragweed, often called 'horseweed,' can compete with corn and soybeans for moisture and nutrients which greatly reduces crop yields. If not controlled, giant ragweed is capable of growing five to seven feet tall and often grows above the corn or soybean canopy. Heavy giant ragweed infestations can cause an estimated 60 to 70 percent yield loss to soybeans."Other species in Kentucky such as common ragweed, and to a lesser extent lanceleaf ragweed, are more frequently found in pastures and hayfields."In addition to the potential to reduce crop yields, ragweed is an economic cost to crop producers because of the time and money spent on control efforts each year," Green said.Many plant species cause hay fever reactions. A ragweed plant can produce up to one billion pollen grains that are a major contributor to allergy attacks in late summer.The best ways to help control allergic reactions to ragweed and other plants are to avoid contact with pollen by tracking the pollen count in your area, get away from the pollen when possible and stay indoors with central air conditioning, according to the Asthma and Allergy Foundation of America."The term 'hay fever' can be misleading because cut hay does not cause allergic reactions in people," Green said. "Problems start in August and early September when ragweed plants begin to flower and pollen is released into the air. Allergies due to ragweed may continue until frost kills plants. The oil produced by ragweed plants can cause the effects of dermatitis in some people."Ragweed plants not only have the potential to cause a negative impact on human health, they also frequently interfere with our agricultural production system," he said.