Wilt and near-wilt of pea is caused by the soiborne fungus Fusarium oxysporum f. sp. pisi. Certain races of the pathogen (races 1, 5, and 6) produce wilt symptoms; race 2 produces near-wilt symptoms. Races 5 and 6 are known to be economically important only in western Washington and southwest British Columbia. Races 1 and 2 occur throughout most pea growing regions of the US. The pathogen is an efficient soil saprophyte, and can colonize the roots of many plants, including nonhosts and resistant pea varieties. Disease is initiated when soilborne resting structures (chlamydospores) germinate and infect fibrous roots, growing into the water-conducting tissues of the plant. The pathogen reproduces in and on roots of susceptible and resistant pea. Wilt and near-wilt are most severe when soil temperature are near 68ºF. The pathogen can be disseminated among fields by the movement of contaminated soil and plant parts by equipment, wind, water, and infested seed. F. oxysporum survives between pea crops in the soil as chlamydospores, on the roots of weeds and alternate hosts, and as a saprophyte on decaying organic matter.
Wilt symptoms appear as yellow and stunted plants. Leaves tend to curl and wilt, usually in definite areas within the planting. Often, the vascular system is reddish to yellow-brown, especially at the nodal area of the stem. Near-wilt caused by race 2 usually occurs in scattered plants in the field (1 to 3% incidence) and is evident when the plant approaches green or canning maturity. Near-wilt can be severe when susceptible cultivars are grown in short rotations.
No biological control strategies have been developed for wilt and near-wilt of pea.
Resistant varieties are available and effectively control wilt and near-wilt, but must be used along with a five-year or longer crop rotation to be most effective. Race-specific and race-nonspecific resistance is available, but race-nonspecific resistance often breaks down when disease pressure is high. If susceptible varieties are grown, they should be planted early to avoid soil temperatures favorable for the pathogen.
No chemical controls are necessary for wilt and near-wilt management.
Categories: Pulse Crops, Disease, Wilt, Near-Wilt, Pea
Date: 04/02/2007