Weed Management Options In Blueberries ctd.
Many growers are utilizing plastic mulches or woven ground covers to prevent weed populations from becoming established in their fields. This is growing in popularity with organic growers. Growers should know what soil temperatures are possible below plastic mulches and possibly plant only during the cooler months to avoid damaging temperatures in the root zone.
Irrigation method has an effect on weed populations. Low volume systems such as drip and microsprinklers direct water to the crop root zone and not to other portions of the field where weedy plant species may become established.
Managing Weeds With Herbicides
The majority of commercial blueberry growers utilize herbicides as one of their weed management tactics. When determining which herbicide to use in a program, the most important factor is to have an accurate identification of all weed species in the field. Once identification is complete, there are several factors about herbicides that growers need to know.
Contact vs. residual weed activity – A contact herbicide will cause phytotoxicity to susceptible plants when spray solutions come in contact with plant parts. Most contact herbicides approved for use in commercial blueberries can harm the crop, if applied to susceptible portions of blueberry plants. Instructions explaining the importance of applying these products in a method where no contact to susceptible portions of the crop plant are included in the product label.
Residual herbicide products (often called preemergence) act upon germinating weedy species and prevent them from establishing. Many residual herbicides will have little to no activity on weeds, if applied after the weed seeds have germinated and begun to grow.
Some residual herbicides will also have limited contact activity on certain weeds, which is generally detailed on the product labeling. Product labeling on certain residual herbicides will have statements indicating it is necessary to apply the product in a manner which avoids contact with susceptible parts of the crop to avoid potential injury.
Selective vs. non-selective herbicides – Generally a selective herbicide has activity on weed species present in the field, with little to no detrimental effects on the host crop. It should be noted that some herbicides considered selective may harm the crop, if applied inconsistent to instructions on the product label.
Sources of information about herbicides – The only source for complete information about herbicides labeled for use in commercial blueberry plantings is the product label. UF/IFAS Extension has a publication entitled Weed Management in Blueberry (HS 90) on the on-line EDIS System (http://edis.ifas.ufl.edu) which has general recommendations about herbicides approved for use in blueberry. This document is a good source for general information about recommended herbicides but the individual herbicide product labeling contains all of the information about using the product. All product label instructions must be followed to be in compliance with Federal Law covering pesticide applications.
Blueberry growers who realize the importance of taking steps to prevent weed infestations from establishing and spreading in their plantings and take action to prevent such, should have fewer weed problems than those that do not. Eliminating potential perennial weed problems before establishing a planting and utilizing various tactics that prevent annual weedy species either in or around their plantings from going to seed should lead to lower populations in the field.