Management of Nematode Problems on Soybean in the United States of America

Abstract

Nematode management may be nematicidal, resistance, cultural, or biological. Before the 19705 the prices received for soybeans was too low to justify the use of nematicides. During the 1970s and 19805 1,2-dibromo-3-chloropropane and ethylene dibromide were effective and were used to some extent on soybean. Both are banned from use in the USA now. Resistance is an effective and economical method of nematode management. However, resistance is not available for many of the nematodes discussed here. In addition, growers tend to overuse resistance when it is available and often the resistance becomes ineffective because of shiftsin the nematode population. The life of a resistant cultivar can be extended by proper management such as use in rotations. Cultural practices that can be effective in managing nematode population levels include rotation, subsoiling, modification of planting date, proper fertilization, and irrigation. Care must be taken to use the proper tactic at the right time. The right time may be determined by the nematode involved or environmental conditions. For example a nematode such as Pratylenchus penetrans, with a broad host range may be difficult to manage with rotations because nonhosts may be difficult to find. If one is found it may not be profitable for growers. Biological management occurs naturally in manysoils. Research aimed at utilization of these natural enemies has been ongoing for many years. The types of nematodes discussed here are the more difficult ones to manage biologically. Because they constantly move from one place to another they must be trapped before a fungus can infect them. Fungi with trapping mechanisms occur in the soil but so far they cannot be applied in such a way as to be effective in reducing population levels of plant parasitic nematodes enough to prevent yield suppression.