By Ramdas Kanissery
Even a small amount of leftover herbicide in the spray tank can harm citrus trees. Contamination often occurs when the same sprayer is used on trees of different ages without being cleaned properly between applications. It can also happen when the sprayer is used for other pesticide products without a thorough rinse.
Herbicide residues from certain herbicide products — such as oil-based formulations, dry flowables, systemic herbicides and auxin types — can easily stick to the inside surfaces of tanks, hoses, pumps, filters and nozzles. Examples include products that contain diuron, pendimethalin, glyphosate and 2,4-D. These residues can remain in the sprayer and later mix with other sprays. When the same equipment is used in young or newly planted citrus areas, even a small amount of leftover herbicide can cause leaf burn, shoot injury or tree decline (see Figure 1).
To avoid problems, follow these best practices for herbicide tank cleaning:
RINSE RIGHT AFTER SPRAYING
Never leave herbicide solution sitting in the sprayer overnight. As soon as you finish spraying, flush the tank, boom and hoses with clean water. This prevents residues from drying and sticking to the equipment.
TRIPLE RINSE AND CIRCULATE
- Fill the tank about one-quarter full with clean water and run the sprayer for a few minutes to circulate.
- Drain completely and repeat this process three times.
- Be sure to open all nozzles, including off-center ones, and strainers so every line is cleared.
USE A TANK CLEANER OR DETERGENT
During one of the rinses, add a commercial tank cleaner or an ammonia-based detergent. These cleaning agents help loosen and remove residues that plain water may not wash away. Always follow product label directions for best results.
CLEAN FILTERS AND NOZZLES SEPARATELY
Take out all filters and nozzle tips and wash them separately in the cleaning solution. Residue buildup in these parts is one of the most common causes of contamination.
RINSE IN A SAFE AREA
Always rinse the sprayer in a designated area away from wells, canals or tree rows to avoid contamination or creating “hot spots” of herbicide in the grove.
MORE REMINDERS
Spraying until the herbicide tank is empty does not mean the sprayer is clean. Taking a few extra minutes to rinse and clean every part of the sprayer can help prevent damage to citrus trees. Always check the herbicide label for specific cleaning directions, as some products may need stronger solutions or extra rinse time to remove residues completely.
Ramdas Kanissery is an associate professor at the University of Florida Institute of Food and Agricultural Sciences Southwest Florida Research and Education Center in Immokalee.
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