Blueberry insect management overview for 2010

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.  

As blueberry growers prepare for pollination and for keeping their berries free of insect pests during the 2010 growing season, it is a good time to review the available insect management options, consider integrating some new tools into your integrated pest management (IPM) program, and make plans for the coming season.

If you missed the various MSU Extension talks this winter at the Great Lakes Expo or Southwest Michigan Horticulture Days, or even if you attended these programs, you should make plans to attend one of the four in-season blueberry meetings organized by MSU Extension this year. These meetings are a chance to update growers on the new developments in blueberry culture, report on our research trials, and provide timely updates on recent crop scouting. The meetings are free and open to all who want to attend.

This article is a chance to provide some food for thought about your 2010 insect management program based on our research projects, demonstration trials at farms, and discussions with growers and extension colleagues.

Scouting

This is an essential component of blueberry production, so you know what is in your field during the period from now until harvest. Investing in a knowledgeable pair of eyes who can visit your fields each week to look for various potential problem issues (insect, diseases, and weeds) makes good business sense to protect your investment. Whether you do it yourself, or have a scout from a cooperative visit your farm, hire an independent scout, or work with a consultant, this is time or money well spent. To help with scouting, MSU has developed a Pocket Blueberry Scouting Guide that is available in both English (E2928) and Spanish (E2928SP), and we have the same information posted online at www.blueberries.msu.edu. We will be scouting blueberry fields this summer in a few locations in southwest Michigan and will report the findings in this newsletter each week. But, there’s no substitute for your own information from your own fields.

Spotted wing drosophila

If you haven’t heard about spotted wing drosophila yet, you’ll be hearing about it this summer because we want to be vigilant against this invasive pest. This small fly infests many fruit crops (including blueberries), and it is now in west coast fruit production regions from California to British Columbia. It has also recently been detected in Florida. The fly is different from our typical vinegar flies because it can lay eggs in intact fruit. We have not seen it in Michigan yet, but there has not been focused monitoring. That will change this month with the establishment of a multi-agency group focused on early detection. If this fly is detected, an industry-wide effort will be needed to ensure its impact is minimized.

Guthion update

The EPA’s phaseout plan for Guthion continues to reduce the availability of this highly effective pest management tool. Aerial application of Guthion is now banned in blueberry. Growers can apply up to a seasonal maximum of 1.5 pounds of product/acre for the next three seasons, but Guthion will be banned completely by the end of September 2012. This rate restriction effectively means that growers have one application of Guthion remaining in their toolbox, because rates lower than 1 pound/acre do not provide the longevity of residual activity growers expect in their fruitworm program. The REI remains at seven days, with the PHI of seven days in commercial farms and up to 30 days re-entry interval for U-pick fields.

If Guthion is still a cornerstone of your insect IPM program, there are effective alternatives available that should be considered for 2010. The next Fruit CAT Alert will contain a fruitworm management article to cover this topic in detail.

Insecticides – many options to fit into your IPM program

The blueberry industry has a number of established and effective broad-spectrum insecticides for use against key pests including Guthion, Imidan, Lannate, Sevin, etc. Grower’s IPM programs should also include rotating to new chemical classes, using selective insecticides to reduce impacts on natural enemies, and minimizing impacts on pollinators. With the blueberry industry receiving many new insecticides in recent years, including Intrepid, Delegate, Assail, Asana, Danitol, Mustang Max, Provado, and Actara, growers now have a range of insecticides with different pest spectrums and properties that can provide effective insect control. Each of these has a fit for components of the pest spectrum in Michigan blueberries, and a grower’s decision of which of these to use will be guided by efficacy, spectrum of activity, price, and resistance management considerations.

Addressing the recently-registered insecticides in turn…

Intrepid is an insect growth regulator that has proved to be a highly-effective insecticide for fruitworm control. Growers who applied Intrepid in 2009 using the MSU degree day model for fruitworms (available through www.enviroweather.msu.edu) reported very low levels of fruitworm infestation. Intrepid is safe to bees allowing application during bloom when fruitworm egglaying starts, plus it is soft on beneficials. We have been testing programs with commercial growers who apply Intrepid during bloom then switch to Delegate after bloom for the next fruitworm spray (also controls maggot), or switch to Assail for control of fruitworms, maggot, and aphids. These programs are providing equivalent control to an Intrepid-Guthion program, or an Intrepid-Asana program. Asana has provided excellent control of fruitworms and Japanese beetle, and gives good control of blueberry maggot. The 14-day PHI for this product can make it challenging to fit in the postbloom timing for fruitworm control, especially in early harvested cultivars. Growers now have two other pyrethroids available: Danitol and Mustang Max. These both provide high levels of control of key insect pests similar to Asana, but with much shorter PHIs. Pyrethroids are toxic to natural enemies and will not provide long-term control because aphid populations can rebound in the absence of biological control. Aphid control, if needed, is best achieved using members of the neonicotinoid chemical class such as Assail, Provado, and Actara. Each of these products is highly effective on aphids, with a broader spectrum of control that can help control other pests at the same time. Assail also provides fruitworm and maggot control, and Provado also controls maggot and Japanese beetle. The Actara label has aphids and Japanese beetle listed.

A new registration for 2010 is Avaunt 30WDG insecticide now labeled for fruitworm and plum curculio control in blueberry. This provides a new chemical class, the oxadiazines, with activity at the sodium channel that leads to insect paralysis and death. It is considered “reduced-risk” by the EPA, with a 12-hour REI and seven-day PHI. Rates are up to 6 oz/acre. Do not apply during bloom.

Blueberry gall wasp

In the past few years, grower reports of problems with blueberry gall wasp have increased. Some Jersey fields were hit hard by gall wasp in 2009, and this was even in fields where growers applied Assail immediately pre-bloom to try and stop the wasps infecting the shoots. Clearly, we need a new approach and my lab will be working this summer on some examination of the biology and control of gall wasp. We hope to have some clearer answers for you later this year.

Preparing for pollination

Make sure you are getting strong hives for your pollination rental fee by checking colonies with the beekeeper. This is an important part of the pollination puzzle because bees from weak hives do not work hard and this may reduce the level of yield you can achieve if you are stocking fields based only on the number of hives. Bumble bees are another option or can be used in combination with honey bees, but large orders for those need to be placed in January and February to guarantee bloom-time delivery. Still, you may consider calling Koppert Biologicals near Detroit to enquire about availability.

If you are interested in learning more about beekeeping and about inspecting bee hives for their strength, the Kalamazoo Bee Club will host a meeting this week on Thursday (April 15) titled “How to Inspect Your Hives.” This will be held from 7:00 to 9:00 PM at the Comstock Community Center. The program will be taught by Dr. Larry Conner, a highly knowledgeable “bee-guy”. The meeting is free and you can learn more about it at www.michiganbeekeepers.com/

Best wishes for a productive, profitable, and pest-free season!

Dr. Isaacs’s work is funded in part by MSU‘s AgBioResearch.

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