Weed management practices and herbicide resistance in weeds in Florida citrus.
Herbicide-resistant weeds have been confirmed in some crop production systems in Florida but not in citrus groves. A grower survey was conducted in 2012 to determine the current weed management practices in Florida citrus and to determine awareness of citrus growers about herbicide-resistant weeds. A questionnaire was sent to 60 randomly selected growers, of which 33 turned in their responses representing 20% of the citrus growing area in Florida. Most of the respondents (47%) indicated that weed problem and species in Florida citrus did not change over the years with the top 3 problematic weeds: Spanishneedle (Bidens spp.), balsam apple (Momordica charantia L.), and panicums (Panicum spp.). Weed control in citrus groves is primarily with the use of herbicides applied alone, in tank-mixes, or applied sequentially in a year. Diuron, simazine, and indaziflam are the top 3 PRE herbicides while glyphosate, paraquat, and saflufenacil are the top 3 POST herbicides applied in Florida citrus. Glyphosate is the most commonly applied herbicide in the vast majority of citrus groves and as frequently as 3-5 times in a year. Citrus growers in Florida are aware of herbicide resistant weeds and their negative impact on citrus production. Although, there are no confirmed herbicide resistant weeds in Florida citrus, few weeds including Spanishneedle, ragweed parthenium (Parthenium hysterophorus L.), and nightshade (Solanum spp.) are inadequately controlled with the recommended rate of glyphosate, thus, should be tested for possible resistance.