Control Methods for Sclerotial Root Rot in Walnut Seedlings
Sclerotial root rot, also called southern blight, mostly affects one-year-old seedlings, causing the cortex of the main root and lateral roots to rot, the aboveground parts to wither and die, and sometimes the entire plant to die. 1. Disease symptoms: Under high temperature and high humidity, white silky mycelium is produced at the base of the seedling root collar and on the surrounding soil and fallen leaves, after which small sclerotia grow...
Sclerotial root rot, also called southern blight, mostly affects one-year-old seedlings, causing the cortex of the main root and lateral roots to rot, the aboveground parts to wither and die, and sometimes the entire plant to die.
1. Disease symptoms: Under high temperature and high humidity, white silky mycelium is produced at the base of the seedling root collar and on the surrounding soil and fallen leaves, after which small sclerotia grow, initially white and later turning tea-brown
2. Disease development pattern: The pathogen overwinters on diseased plant residues and in the soil, and mostly invades through the seedling collar. The disease is severe under high temperature and high humidity. It generally begins in late May, with the peak period from June to August. Seedlings raised on heavy clay soil, acidic soil, or land previously cropped with vegetables or grain are prone to the disease
3. Control methods:
1) Choose a good nursery site, avoid continuous cropping in diseased nurseries, and select a nursery site with good drainage and a low groundwater table; in rainy areas, use raised seedbeds for raising seedlings
2) Air-dry the soil or replace it with sand brought in from elsewhere; soil replacement can be done once a year, and generally takes effect after 1-2 times
3) Seed disinfection and soil treatment: before sowing, dress seeds with 0.3% carbendazim 50% powder; for acidic soil, appropriately add lime or plant ash to neutralize the acidity, which can reduce disease incidence. In addition, irrigating the roots of diseased trees with 1% copper sulfate or a 500-1000 times dilution of thiophanate-methyl, then spreading slaked lime on the seedling collar base, or irrigating the soil with a 1000 times dilution of amobam aqueous solution, all have a certain inhibitory effect on the disease.