Tough Year for Early Peas | Weekly Crop Update

Gordon Johnson, Extension Ag Agent, Kent Co.; gcjohn@udel.edu

Pea harvest has begun on early plantings on Delmarva. Many early planted pea fields have reduced yield potential due to stand issues, drowned out areas, root rot in wet and compacted areas, and general poor rooting due to compacted soils. March and early April was a tough period for planting peas. It started with as much as a foot of snow the first week – delaying early plantings. While rainfall totals the rest of March were moderate, the first three weeks of April were wetter, with heavy rain during the middle of the month. May has seen significant periods of rainfall with a week of wet weather to begin the month and heavy rainfall on the 25^th and 26^th (some areas received as much as 4 inches). Over this period, temperatures were cool most of the time.

As growers well know, peas do not perform well in soils that are worked when they are too wet or when they receive heavy rainfall after planting. Compaction and crusting over will lead to poor emergence and reduced growth. Root rot is can be a major issue. According to the Crop Profile for Peas in Delaware:

“Aphanomyces root rot, or common root rot, is one of the most destructive diseases of peas. It occurs in most pea producing regions of the U.S., including the Mid-Atlantic. In the Northeast, average annual yield loss to this disease is about 10%, though losses in individual fields may be up to 100%. Wet soil conditions and poor drainage are associated with higher rates of infection. The disease is most damaging in years when a cool, wet spring is followed by an early, warm summer with low rainfall.”

Aphanomyces root rot is caused by the fungal pathogen Aphanomyces euteiches, although other soil-borne organisms contribute to the disease complex. Oospores can remain dormant in the soil for years. When conditions are favorable, the spores germinate and pass through several life stages before developing into hyphae that can grow through host plant tissue. Infection can occur at all temperatures favorable for pea development. Once pea roots are infected, the mycelium of the fungus begins to decay the root tissue. As roots decay, the oospores return to the soil to serve as inoculum in years to come. Characteristic symptoms of Aphanomyces root rot include water-soaking, softening, and slight discoloration of the taproot and lower stems of infected plants. The outer root tissue of infected plants can be easily sloughed off. Symptoms develop faster at warmer temperatures.

“Attempts to control this disease through the development of resistant host plant strains have not been successful. Crop rotation is an extremely important practice, but because oospores can survive in the soil for years, even the recommended rotations of 4 to 5 years may not be sufficient in all cases. Other host plants such as beans, alfalfa, and spinach must be avoided in the rotation. Many leguminous weeds can also serve as host plants and should be controlled. The best management strategy includes using long rotations, planting in fields with well-drained soils, avoiding soil compaction with heavy farm machinery, and avoiding planting in moderately to highly infested fields.”