Is Target Spot Management Getting Tougher?

Best practices in the field help achieve target spot management.

Growers are reporting more difficulty managing target spot effects on tomatoes. A perennial threat to quality and marketability, target spot (caused by Corynespora cassiicola) now appears to be responding differently to some fungicides.

Perhaps because strobilurin fungicides have been such dependable workhorses for so many years, overuse has contributed to strobilurin resistance in some target spot strains, making management difficult. University of Florida research dating back to 2011 has demonstrated resistance to azoxystrobin.

With any disease-control program, one of the best ways to avoid resistance development is to alternate modes of action during the season. For maximum flexibility in disease-control programs, DuPont Crop Protection has focused on developing single-active-ingredient products. DuPont Fontelis® fungicide (penthiopyrad, FRAC Group 7 fungicide) is an excellent example of that strategy. Fontelis® helps handle the unexpected while guarding against target spot damage. Apply no more than 72 fluid ounces of Fontelis® per acre per crop and alternate with a non-Group 7 fungicide.

Continue to use cultural practices to reduce disease pressure throughout the season. University of Florida IFAS Extension specialists offer these reminders:

  • Use plastic mulch to help control fruit rot development due to Rhizoctonia and Phytophthora infections. Staking plants helps minimize losses from fruit rot damage.
  • Use disease-free transplants to avoid early blight, late blight, bacterial spot and key viruses. Planting certified pathogen-free seed can help prevent tomato mosaic and bacterial spot losses.
  • Eliminate volunteer plants and rotate crops to reduce pathogen carryover between seasons.
  • Increase soil pH with lime application, especially on sandy soils. Soil pH in the 6.5 to 7.0 range helps suppress Fusarium wilt.
  • Choose planting date to avoid recurrence of specific disease or to help plan scouting around particular concerns. Cool-weather diseases in the Southeast include late blight, Sclerotinia stem rot and leaf mold. Warm weather is more likely to bring bacterial spot, southern blight, and bacterial wilt.
  • Avoid excessive plant handling, especially when plants are wet.
  • Sanitize stakes and decontaminate equipment before moving to another field.
  • Destroy crop material immediately after harvest to help manage tomato yellow leaf curl virus (TYLCV) by eliminating shelter for whitefly populations.
  • Keep weeds under control during production and the off-season to minimize disease inoculum and insect populations that carry pathogens.

DuPont Fontelis® is not available in all states. See your local DuPont sales representative or retailer for details on availability.
The information provided on this website is for reference only. Always refer to the product labels for complete details and directions for use.