Pacific Pests, Pathogens and Weeds

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Summary

• Worldwide distribution. On peanuts, and other plants belonging to the genus Arachis. An important disease.
• Rust infects all parts of peanuts above ground: the red-brown spots produce masses of spores. Losses in pod yields of 40%.
• Spores spread in wind; infection needs water on plant surfaces, and high humidity.
• Cultural control: avoid planting next to old crops; leave at least 4 weeks between crops – rusts do not survive in plant debris or the soil; remove “volunteers”; inspect twice weekly; tolerant varieties.
• Chemical control: begin to spray as soon as spots are seen and no later than 30-35 days; use chlorothalonil (also effective against leaf spots) at 10-14 days until 14 days before harvest.