Efficacious and cost-effective

Ask the Experts - Herbicides

Aaron Palmateer, Ph.D, a technical service support professional within Bayer’s Environmental Science – Turf & Ornamentals department, presents on yet another herbicide tool in the toolbox available to greenhouse growers.

April 21, 2021

Greenhouse Management: What are some of the key benefits provided by Marengo herbicide for greenhouse ornamental growers?

Aaron Palmateer, Ph.D.: Greenhouses that do a good job of managing weeds are laser focused on controlling them at their source, and Marengo offers a cost-effective option to accomplish this. Marengo is a selective, preemergence herbicide that will control 98 different weed species including broadleaves, grasses, and annual sedges, providing up to eight months of control from a single application. The active ingredient in Marengo — indaziflam — has a unique mode of action making it ideal for rotation and weed resistance management. Marengo is labeled and can be safely used inside the greenhouse to provide bare ground weed control beneath benches and potted plants where weeds may germinate.

GM: What recommendations do you have for applying Marengo in greenhouses?

AP: For optimum results, apply Marengo before weed seed germinates. When weeds are already present, add a postemergence herbicide specified by the label. If fans are present, turn them off during an application. Applicators can treat cracks or crevices in concrete floors or other impervious surfaces where weeds are likely to grow. Do not allow Marengo to puddle or pool, especially where potted plants will be placed. When treating greenhouse floors and areas around potted plants (i.e. under benches), try to minimize direct contact with the foliage of desirable plants. If the spray does contact the plant canopy be sure to rinse it off the plants before it dries. A light irrigation event after application will help to activate Marengo prior to weed germination.

“A single application of Marengo allows for greenhouse growers to focus their time and effort on other factors besides weeds for up to eight months.” — Aaron Palmateer

GM: What is Marengo’s re-entry interval and how does it allow crews to get back into the growing bays and working again?

AP: Marengo has no signal word on the label and offers a 12-hour restricted entry interval. However, workers can enter treated areas of the greenhouse at any time if wearing coveralls, waterproof gloves and shoes plus socks.

GM: What are some other key characteristics of Marengo that growers seek?

AP: When it comes to weed control inside of greenhouses or other enclosed structures, preemergence herbicide options are limited. Greenhouse growers look to Marengo for convenience, because they can apply it inside the greenhouse when plants are present. This characteristic separates Marengo from other preemergence herbicides where applications can be made only in the absence of plants. A single application of Marengo allows for greenhouse growers to focus their time and effort on other factors besides weeds for up to eight months. This long-lasting residual control reduces the frequency of reapplication and clean-up applications, reducing labor and product costs and ultimately making Marengo a cost-effective solution for controlling weeds in the greenhouse.