Threats To Soybean Production Caused By Pathogens And Pests

Fig 1. Soybean aphid (Aphis glycines) colonizing soybean stems. Photo courtesy of Curt Hill.

The soybean crop is grown on an estimated 6% of the world's arable land, and there has been a general increase in world production for the last 50 years. In 1960 soybean production was 17 million metric tons (MMT) and in 2010 about 250 MMT. Recent increases in production coincide with increases in demand for meal and oil. Along with increased production comes increased importance of abiotic and biotic constraints that threaten soybean production by directly reducing seed yields and/or seed quality. Abiotic constraints include extremes in nutrients, temperatures, and moisture. These may reduce production directly but also indirectly, through increases in pathogens and pests. Biotic constraints tend to be geographically and environmentally restricted.

The expansion of soybean pathogens and pests is the result of intense production and increased acreage of soybean throughout the world.Where soybean is grown every year or even every other year, pathogens often have increased in density to cause economic losses in yield. Parasitic microorganisms, such as bacteria, fungi, nematodes, Oomycetes, and viruses all contribute to economic damage. A similar story occurs for pests; many, such as aphids, beetles, mites, and stinkbugs, cause considerable economic damage to the soybean crop.

Fig 2. Soybean rust (Phakopsora pachyrhizi) lesions on soybean leaves. Photo courtesy of Glen Hartman.

Pathogens and pests of soybean infect and/or attack all parts of the plants, from roots to seeds. The extent of economic plant damage depends on the type of pathogen or pest, the plant tissue being attacked, the number of plants affected, the severity of the attack, environmental conditions, host plant susceptibility, plant stress level, and stage of plant development. To successfully reduce losses due to pathogens and pests, a number of practices used alone or in combination may be needed; these include cultural and seed sanitation techniques, pesticide applications, and deployment of soybean cultivars with resistance.

Specific examples of pathogens and pests, like red leaf blotch, Sclerotinia stem rot, soybean aphid (Figure 1), soybean cyst, soybean rust (Figure 2), sudden death syndrome, and others, are provided to show how these pathogens and pests potentially threaten the soybean crop in Illinois. As shown, these pathogens and pests have different threat levels and scenarios in terms of their importance to soybean production in Illinois.

Future soybean production has enormous potential to increase, and genetic resources, used through both traditional breeding and bioengineering, may provide the solutions needed to combat problems caused by abiotic and biotic constraints that may affect soybean production now and in the future.

Glen L. Hartman

Glen L. Hartman
USDA-ARS Research Scientist
Professor of Crop Sciences