Post-Hurricane Weed Management

By Ramdas Kanissery

Hurricanes and the associated flooding will impact weed management in the affected season and the following years. Weeds should be effectively managed after these severe weather events as weeds may take advantage of the reduced competitiveness of recovering trees.

INTENSIFY SCOUTING
A critical step in weed management after hurricanes is to scout groves and note the emergence of new weed species. Storms and floods can potentially wash in weed seeds not found previously in the groves and will cause new weed management problems in the upcoming seasons. Check groves regularly to monitor new weed development, make a field map of these weed locations and use the information toward planning future weed control programs.

CHEMICAL WEED CONTROL
Weed pressure in citrus groves may increase after a hurricane due to the reduction in tree canopy and the consequent decrease in shade in tree rows. Consider applying post-emergent herbicide products as early as possible to prevent the existing weeds from maturing and seeding. Seed production will worsen the weed pressure.

If there are continual flushes of weed seed emergence from the soil, pre-emergent herbicides are an option for suppressing germination. If the groves were treated before the storm with pre-emergent herbicide product(s), excessive rain and flooding could impact their effectiveness. In the event of re-application, pay attention to herbicide product labels for maximum annual application rates.

Additionally, some herbicide labels caution against using the product if the trees are stressed. Trees recovering from hurricane damage should be considered under stress. The labels for most herbicide products used in citrus can be accessed at www.cdms.net.

HERBICIDE MOVEMENT
Wind and flooding associated with a hurricane can move residues from herbicides sprayed before the storm, resulting in an elevated concentration or “hot spots” of herbicides in some areas in the grove. If any herbicide-related injury symptoms in the trees are found, consider doing soil analysis for herbicide contents in this area. This will help determine if the affected regions have herbicides at concentrations high enough to impact tree health, particularly if resetting of trees or new plantings are being planned in the grove.

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