Sayonara, spurge

OHP’s Biathlon is a pre-emergent herbicide with two active ingredients: oxyfluorfen and prodiamine, formulated on the Verge granule. One active ingredient controls broadleaf weeds, one controls grassy-type weeds, which gives growers a one-two punch.

Bob Black, vice president of horticulture, at Bennett’s Creek Nursery, uses Biathlon as part of a rotation with two other herbicides. After a round of hand weeding to remove existing weeds, it’s time for the pre-emergent herbicide.

“We use it over the top,” he says. “We apply the granular herbicide at many locations with a boom sprayer that also has an air delivery system so the granular herbicide can be distributed extremely evenly over the top of the plant. And then watered in, of course, following label directions with an irrigation cycle after it’s put on.”

Black says the top target for Bennett Creek’s herbicide rotation differs depending on the time of year.

“In the winter months, the main weeds are bittercress and groundsel,” he says. “But in the summer the main weed we’re going after, the biggest threat to us, is spotted spurge.”

Spotted spurge is known for its prolific seed production, which makes it dangerous. A single plant can produce several thousand seeds, which are small and can remain dormant in the soil until conditions are suitable for germination. Seeds produced in summer germinate immediately while those produced in late fall mostly will lie dormant and won’t germinate until spring.

Biathlon has become a valuable weapon against spurge, but Black stresses the importance of rotation.

“Rotate through different chemistries that have different modes of action,” he says. “With fungicides, insecticides, miticides, herbicides, all chemistries are rotated so we don’t build up resistance to the problem, whether it be a weed, insect, mite, fungal or bacterial disease.”

Bennett’s Creek uses other herbicides with different active ingredients in rotation with Biathlon. The other actives are indaziflam and dimethenamid-P - combined with pendimethalin.

Black uses 150 pounds of Biathlon per acre, a lower rate than the 200 pounds per acre of the other product.

Resistance management is a major concern, but Black says the most important factor in nursery weed control is the ability to stay on schedule.

“Timing is very essential with any pest control, and especially with weeds,” he says. “Stay on your schedule, catch a problem early before it becomes a big problem and you’ll get your best result in controlling your weeds.”

Bennett’s Creek applies these herbicides five or six times per year, Black says.

Black also suggests that any grower using a product for the first time conduct a trial on the crop you grow under the condition in which you grow it. Some plants are more sensitive than others, and this ensures you won’t have any phytotoxicity issues with your crops when applying a new product. Apply it on a small scale first, then once you’ve seen positive results with no damage, apply it on a nursery-wide scale.