Effect of Late Bloom Fungicide Treatment On Nine Roundup Ready Cotton Varieties to Manage Corynespora Leafspot

Corynespora leaf spot has been identified as yield limiting disease in cotton. Fungicides have shown that they can help manage corynespora leaf spot and protect yield. Exact timing of a fungicide spray is thought to be the 3^rd or 4^th week of bloom based on limited research. Concerns and questions from growers and cotton industry professionals about late season fungicide treatment efficacy and yield effect were present. A replicated trial with nine round-up ready cotton varieties were treated with the fungicide containing pyraclostrobin and metconazole (Twinline) at 8oz per acre during the beginning of the six week of bloom.  Field counts were done pre-treatment on each variety and again two weeks after treatment to evaluate treatments. Final yield and gin data was collected to evaluate effect of treatment.