weed management

Brassinosteroid and Weed Management Research Updated

Daniel CooperHLB Management, weeds

weed management
Spanish needle is a year-round weed in Florida citrus groves.

Brassinosteroids for HLB-infected trees and the latest on year-round weed management were discussed at a Jan. 17 OJ Break at the Citrus Research and Education Center in Lake Alfred, Florida.

University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) multi-county citrus Extension agent Chris Oswalt hosted the event. UF/IFAS assistant professors Fernando Alferez and Ramdas Kanissery made the presentations on brassinosteroids and weeds, respectively. Both work at the Southwest Florida Research and Education Center in Immokalee. 


Alferez said his research has shown that brassinosteroids:

  • Induce immunity to HLB in young citrus trees
  • Increase tree vigor
  • Reduce HLB-spreading psyllids in new flushes
  • Reduce canker and greasy spot
  • Synchronize flushing
  • Increase fruit yield and quality in different varieties

Learn more about brassinosteroid benefits here.


“The focus of a citrus weed management program is the tree, not the weeds,” Kanissery declared.

Key points he made regarding weed management included:

  • Weed management helps improve citrus yield.
  • Weed control may help management of HLB-spreading psyllids.
  • Citrus growers typically spend about 12% to 15% of their production costs on weed control.
  • Apply herbicides when there is ample daylight.
  • Don’t apply post-emergent herbicides when temperatures are below 60 degrees. Do apply residual herbicides if the label allows it. Avoid spray contact with trees during cold weather, because herbicide injury potential is high then.
  • Allow at least 6 hours of dry period after applying herbicides during the rainy season. Generally, rainfall within 6 hours after application may reduce effectiveness.
  • If spraying herbicides during hot weather, apply during the cooler part of the day. Efficacy of post-emergent herbicides drops when temperatures are above 95 degrees. The injury potential to the tree is high then.
  • Common weeds seen year-round in Florida citrus include Spanish needle, ragweed parthenium, goatweed, Bermuda grass, Guinea grass, dayflower and nutsedge.
  • Spray when weeds are young. Never let weeds grow and adapt.
  • For tree safety, avoid herbicide spray contact with stems, foliage and fruits.
  • Rotate post-emergent herbicides.
  • Use the lower end of the herbicide labeled rates during the first year after planting.
  • Cover crops offer numerous benefits to growers, including suppressing weed growth.
About the Author

Ernie Neff

Senior Correspondent at Large

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