Cucurbit Downy Mildew Found in SC

Prepared by Rob Last, Justin Ballew, and Tony Keinath.

Cucurbit downy mildew was identified in South Carolina on 5/12/23. The identification came from butternut squash grown in a sentinel plot at the Coastal REC in Charleston.

The same strain that affects butternut squash also affects watermelon and summer squash. Now that downy mildew has been found in the state, making fungicide applications seven days apart is important. A stretch longer than this is likely to increase the potential for disease spread.

For squash and watermelons, use the following products in rotation:

• Ranman (Cyazofamid)
• Orondis Opti (Oxathiapiprolin and clorothalonil)
• Orondis Ultra (Oxathiapiprolin and mandipropamid)
• Gavel (Zoxamide and Mancozeb)
• Manzate (Mancozeb)

For cucumbers:

• Omega ( Fluazinam 7 day PHI in Cucumbers)
• Bravo (clorothalonil)
• Ranman (Cyazofamid)
• Presidio (fluopicolide)
• Orondis Opti (Oxathiapiprolin and clorothalonil never use Orondis ultra in cucumbers)
• Elumen (Ethaboxam)
• Gavel (Zoxamide and Mancozeb)

For cantaloupes:

• Ranman (Cyazofamid)
• Presidio (fluopicolide)
• Orondis Opti (Oxathiapiprolin and clorothalonil never use Orondis ultra in cantaloupes)
• Elumen (Ethaboxam)
• Gavel (Zoxamide and Mancozeb)
• Manzate (Mancozeb)

Remember to limit the number of Orondis applications to 1/3 of the spray program. So if making 1 to 5 applications, just one should be Orondis. If making 6 to 8 applications, then two may be Orondis. For cucumbers, we suggest just one application of Orondis per crop. For more information, see Cucurbit Downy Mildew Management on Clemson’s Land Grant Press.