Tree nut growers in California have been blessed with a rapidly expanding arsenal of miticides over the past few years, according to David Haviland, Kern County University of California Cooperative Extension Farm Advisor.

“All of a sudden, we've added eight new products to our portfolio in only the past two years,” he told attendees at a Bayer CropScience sponsored Tree and Vine conference held this winter. “I sincerely hope the days of monitoring and treating if and when you hit a threshold are back.”

Envidor 2 SC Miticide from Bayer is one of those new miticides expected to hit the market shortly. Envidor is expected to receive California EPA registration soon, according to Matt Ehlhardt, Bayer CropScience technical service representative. Envidor is a non-systemic foliar acaricide with the active ingredient spirodiclofen, a member of a new chemical class of tetronic acids developed by Bayer. The product will give growers a new chemistry with an entirely new mode of action to what is currently available in the miticide pool.

Envidor is effective on a range of mite species including twospotted spider mite, Pacific Spier mite, brown mite, European red mite and pecan leach scorch mite. It also has activity on San Jose scale. Envidor has a PHI of 7 days and a REI of 12 hours. It will be registered for ground application only. Envidor is active against all developmental stages of mites, including eggs and adult females, and has good residual activity, according to Ehlhardt.

In a large-scale, 110-acre trial on second leaf almond trees at Paramount Farms last season, Haviland compared Envidor to eight other miticides and an untreated check. The trial resembled a “real world” situation with applications made by commercial sprayers on 2.1-acre plots replicated five times.

In the miticide window, Agri-Mek best fits the early preventive application from April through June at leaf hardening if that's the approach growers take, according to Haviland. Envidor should probably come in a little later.

Best use window

“I think it will fit best in terms of timing when mite populations are low and building — probably the May through July window,” Haviland says. “Onager and Zeal also fit that window. Envidor gave us a good solid five weeks of control. It was up there with the best of treatments. It is not a contact, knock-down material. It requires a little more time to work than some of the other products. It has good to excellent residual compared to the others, and the control is comparable to Agri-Mek. The verdict is still out regarding whether or not is more effective with oil.”

Approaching and transitioning into hull split, miticides such as Savey, Nexter and Vendex are appropriate choices, followed by Kanemite, Desperado and Ecotrol after hull split, according to Haviland.

With the diverse miticide arsenal now available to tree nut growers, Haviland stressed the value of adopting a treatment program more in tune with Integrated Pest Management (IPM) principles than what most growers have been doing in the past few years.

“I understand the concept of putting a material out there early as a preventative measure,” he says. “I just don't think it's necessarily the right approach considering all the options we have now. If mite pressure doesn't materialize, that early application is unnecessary.”

Cultural practices

The first line of defense in a true IPM program is to use cultural practices that deter spider mite buildup. Simple steps like reducing dust in the orchard, avoiding factors that stress trees, and promoting early biological control can potentially reduce the need for chemical control.

When chemicals become necessary to achieve control, Haviland cautions growers against letting down their guard just because there are ample options at the moment. “We're very fortunate that we've had so many recent registrations,” he says. “It's a great opportunity to enhance our IPM program, but it's still up to us to use these products responsibly.”

Impact on beneficials should enter into treatment decisions, particularly early in the season, according to Haviland. “Be careful not to use Desperado and Fugimite early because those compounds are very toxic to beneficials,” he says. “ Envidor has a moderate effect on beneficials. That's another reason I think it will fit in that mid-range application window.”

Rotating chemistries with different modes of action is a key component and one that cannot be over emphasized, according to Haviland. Resource tools such as guidelines from the Insect Resistance Action Committee (IRAC) can help growers and PCAs quickly determine suitable rotations among miticides with differing modes of action. IRAC's newly revamped, user-friendlier website can be accessed at www.irac-online.org.