Looking for better economic returns on your fruit investment? Try an integrated pest integrated pest management (IPM) approach to weed control. One weed approach seldom works in a long growing and marketing season. Too many weeds can steal light, nutrients and growth from young orange trees. They also can increase the cost for removal if the overgrowth affects those trees, not to mention they can impede harvest. Their robbing ability can reduce yield, quality and profits.
Typical IPM weed management involves preventive and cultural controls, and mechanical and chemical controls, according to Stephen Futch, Brent Sellers and Megh Singh at the University of Florida. They noted in the Florida Citrus Management Guide that growers are wise to practice all these methods for weed control in orange groves.
Preventive and cultural control
Growers must not shun preventive measures when looking to control weeds. Part of preventive and cultural control consists of sanitation, spot spraying or removing weeds or weed seeds by hand, they noted.
They advised to keep fields free of weeds as much as possible and sanitize equipment used.
When surveying a field to plant young orange trees, they stress that growers must scout for weeds, identify and record what species are present and determine how many are there. Growers will notice that species may change depending on the field surveyed and crop season. Just as importantly, they must review these records each year so they can operate more efficiently by developing a weed control strategy based on how best to control weeds each year. New species of weeds may sprout up, but if this preventive measure is done yearly, growers will be able to track and control them more effectively. The Florida weed specialists noted that if growers can slow down the spread of weeds they might save in herbicide costs later in the growing season.
Growers can try cultivating weeds out of orange groves with tractors and cultivators, or other tillage equipment. Although this can be effective, it may not do much at controlling perennial grasses, according to Futch, Sellers and Singh. They indicated that many orange groves today are planted on raised beds, thus reducing the need for excessive cultivation. Using raised beds also helps reduce soil erosion that is always present after cultivating. In addition, they indicate that cultivating can hurt fresh roots that are growing. If growers plant their trees closer together, effective cultivating is almost nonexistent.
Another mechanical method consists of mowing with a bush hog or other cutting equipment. However, the guide indicates this control method is more expensive because of equipment used and the impact on fuel. Additionally, and probably just as important, a mower or other cutting equipment may blow weed seed under the tree, which increases the risk of weed growth.
An additional option for weed control is to apply chemicals. How that is done depends on the field location and region where the groves are located in the state of Florida, weed specialists point out. It also may depend on a grower’s soil type and environmental condition. Herbicide application may even make a difference, as will weed species.
According to Florida Citrus Management Guide, growers generally can apply two types of herbicides – soil-applied preemergence that is applied before weed seeds germinate and when young seedlings are just growing, and foliar-applied postemergence that is typically used after weed seeds have germinated. Postemergence herbicides are either systemic or contact modes of action. Systemics “are translocated within the target plant, killing the foliage and root system of the contacted plant,” the guide indicated. Contacts “kill only the plant parts which are contacted by the spray application.”
Futch, Sellers and Singh point out that some growers are increasingly using chemical mowing rather than mechanical mowing to rid fields of weeds. That is mainly because of the increase in equipment, maintenance and fuel costs. Under a chemical mowing plan, they indicate that growers will use a “sublethal” rate of glyphosate so they can suppress grass and broadleaf weed growth or even possibly regrowth. Usually, this row-middle application will last 45 to 95 days. Before growers apply the chemical, they typically mow the row middles, then let them regrow a bit before applying the systemic herbicide.
Importantly, growers should select the correct herbicides and mixtures for the right job. Growers are reminded to follow chemical label directions and contact their Extension agent or specialist with questions. The label will indicate how to use the chemical effectively and what personal protective equipment to use, what rate to apply and what weeds or grasses it will control. The guide points out that the rate, stage of weed growth, climate and application method all will dictate how effective the control may be. They remind growers that extreme dry weather or wet weather and high temperatures may stress out the orange tree and cause herbicides to be less effective. Futch, Sellars and Singh explained, “Stressed plants take up and translocate less herbicide than non-stressed plants.”