Spider mites are a ubiquitous problem for greenhouse growers; in fact, if you ask Steve Bogash, Territory Business Manager, Northeast and Mid-Atlantic, at Pro Farm Group (formerly Marrone Bio Innovations) about when you’re most likely to see spider mites, he’ll give you a simple answer: “When you have a crop in the greenhouse.”
Scouting is the most important tool when it comes to spider mite control.
“Scout any plant you bring in to make sure you’re not inviting a problem,” Bogash says. “The most likely place for early-season spider mites to turn up is on existing plants. But you might also find them in your fertilizer injection system, behind a bench, or in any errant weeds.”
Scouting should start with looking at the bottom of plant leaves, ideally with a hand lens so your eyes don’t get tired.
“It will also make it easier to spot tiny eggs, which normally show up on leaf veins,” Bogash says.
Damage comes in the form of stippling, or a light color left behind at the leaf feeding source. Ideally, you will find stippling marks before you find webbing, because if you see webbing, “you’ve already lost the battle,” Bogash says.
Best Control Comes With Rotation
As with most other pests, Bogash says the best way to protect your plants from spider mites is to follow the normal process of producing a healthy crop. When a management program does become necessary, he recommends a proactive approach based on rotations of conventional and biological materials, with the goal of building long-term resistance management.
“At Pro Farm Group, we recommend a rotation between Grandevo CG and Venerate CG to help with suppression,” Bogash says. “The key is tank mix them with a potassium salt-based insecticidal soap at 1.5%. Azadiractin products in a tank mix will also give you some level of control.”
Bogash also recommends looking at your spray interval timing. Because you’re likely battling multiple generations at once, adjusting your timing from weekly to four to five days apart can make a huge difference.
“By the time you get to your third application over a ten-day period, all the eggs have hatched and there’s no more adults to lay eggs,” Bogash says.
Learn more in the video below.
Bogash can be reached at sbogash@profarmgroup.com. Pro Farm Group Inc. was created on July 12, 2022, when Marrone Bio Innovations merged with Bioceres Crop Solutions. Learn more at ProFarmGroup.com.