Squash (Cucurbita spp.)-Pythium Root Rot


Cause Several Pythium spp. have been described. P. aphanidermatum causes a sudden wilt. Cool, wet soils favor these fungus-like microorganisms.

Symptoms Mature plants wilt and collapse. Roots have light-brown, depressed, water-soaked lesions. Lesions may coalesce and cause extensive root portions to rot. Both primary and secondary roots are affected. Sudden wilt is characterized by secondary roots that appear healthy but have necrotic feeder roots.

Cultural control

  • Provide good soil drainage.
  • Rotate at least 2 years to nonsusceptible crops.
  • Do not over-irrigate so that water puddles in the field.

Chemical control

  • Regalia (Group P5) at 1 to 2 quarts/A as an in-furrow treatment. Does not benefit from the addition of an adjuvant. 4-hr reentry. O
  • Ridomil Gold SL at 0.25 to 0.4 pints/A as a soil spray directed to the base of the plants, and lightly incorporate or irrigate in. Not for greenhouse crops. Do not apply within 5 days of harvest. 48-hr reentry.

Biological Control

  • Rootshield Home and Garden at 1 to 3 Tbsp/gal water as a soil drench at planting. H O
  • Rootshield WP at 3 to 5 oz/100 gal water for greenhouse soil drench and field chemigation or at 16 to 32 oz/A as an in-furrow spray. 0-hr reentry. O
  • Serenade ASO (Group BM02) at 2 to 4 quarts/A. Applications can be made up to and the day of harvest. 4-hr reentry. O
  • Stargus at 3 to 4 quarts/A as a soil drench on 10- to 21-day intervals. Preharvest interval is 0 days. 4-hr reentry. O