230-Management Strategies for Reduced Inputs

Fact Sheet No. 230

Prepared by David E. Yarborough, Extension Blueberry Specialist, Frank Drummond, Professor of Insect Ecology and Seanna Annis, Associate Professor of Mycology, The University of Maine, Orono, ME 04469.  March 2019.

The decision to rest land, cut back on inputs, or manage for optimal production has to be made on a farm-by-farm and field-by-field basis considering both production costs and productivity of the field. Use the following considerations in determining what management strategy is best for you. It is very important to know your production costs in detail.

Do not manage fields or portions of fields with low cover and low yields.  Do not manage land that must be burned and hand-harvested unless you have markets established or available that provide higher prices.

Consider resting land until prices are above your production costs. If you do rest your land, you should continue to mow (or bush-hog to 2-3 inches) in the fall or in spring pre-bloom, to cut or wipe any woody weeds, and scout and pull any new weeds to prevent new infestations.  These maintenance costs should go into your calculations of the benefits of resting land.

Manage fields that you keep in production for good yields; this will keep your cost/pound low. Evaluate all inputs to reduce input costs to the minimum needed:

For Fertilizer: Take leaf samples at tip dieback and do not fertilize if your leaf samples indicate you do not have a deficiency. Not fertilizing also will reduce your weed pressure. This input should be the first one you cut back in.

For Weeds: Scout to determine weed pressure and use lower herbicide rates and less expensive herbicides (for example, Velpar 1 lb/a, plus Matrix 3 oz/a, plus Diuron 2 lb/a), and then evaluate control and determine if any post-emergence weed applications are needed. Having a few weeds will not reduce your yields but be sure you do not allow any new weeds to invade, such as milkweed.

For Pest Insects: Scout your fields and use action thresholds for deciding if control is necessary. You should be much more liberal and base decisions on pest levels that are 1.5 to 2 times the recommended threshold. This use of higher thresholds means more risk of damage, but because the value of the crop is lower, more damage risk at a lower value balances out the cost of insecticides for control. For example, the blueberry spanworm threshold in a crop field is 10 spanworm caterpillars per set of ten sweeps. Using a more liberal threshold of 15 or 20 caterpillars per set of ten sweeps is warranted. We have provided a range of thresholds for Spotted Wing Drosophila. Use the higher end of 7-16 males as a more liberal threshold:

REMEMBER that wild blueberry fields have considerable natural enemy insects that prey on your pest insects. These enemies will tend to buffer the risk due to pests. The other tactic is to use less expensive, but still effective, insecticides. Check our recommendations for effective insecticides for each pest insect using:

For Pollination: If you have not measured native bee foraging densities and fruit set in your fields in previous years using the Schedule for Monitoring Pollinators then do so, see:

Use this information to decide if you can cut back on honey bee rentals or bumble bee purchases. Strong native bee populations measured at 0.5 bees/square yard of bloom/minute will provide 20-35% fruit set. Generally, this level of native bee abundance with an additional two hives of honey bees per acre will provide about 65% fruit set (the result being about 4,000 lbs/acre [range 1,800-9,000 lbs/acre]). Reducing honey bee stocking density to 1 hive per acre under this scenario (0.5 native bees/square yard) will provide about 45% fruit set, which in a year that has good blueberry fruit production conditions will result in a pretty good crop (about 3,000 lbs/acre [range 1,000-5,000 lbs/acre]). Just relying on native bees without honey bees at all will result in about 1,800 lbs per acre (range about 1,000-2,800 lbs/acre). The estimates of BOTH fruit set and yields are only averages, and they vary considerably with weather and inputs such as fertilizer, irrigation, pesticides, and pest and pathogen crop losses. BUT, no matter what the stocking density of honey bee hives you choose, it is paramount that you rent strong colonies. Do not rent less expensive, but weak colonies in order to save money. Weak colonies only send out a fraction of the foragers to the bloom and so it is never worth saving $10-20/hive. Always monitor the field strength of the colonies that you rent, see:

For Diseases: Control mummy berry if you have had losses from this disease in your field in the past. Minimize your applications of fungicide by waiting to apply your first application until your plants show at least 40% of their flower buds are open to the crown stage (F3), since your plants are protected by their budscales before this stage. You also should wait until Monilinia cups and weather conditions for infection, over 6 to 8 hours of rain or fog, are reported in your area. Use the disease reports for information on the above factors to determine your timing of fungicide applications for control of mummy berry. The disease reports are available from the Wild Blueberry Blog page, by email, or by telephone (call 1.800.897.0757 and select option 3 for the disease forecast).  To sign up for the disease report emails, send an email to sannis@maine.edu. You can also sign up to receive the wild blueberry newsletter by email and receive the disease report on the:

Do not control for Botrytis blossom blight unless you find early symptoms in your field.  The presence of this disease is highly variable and dependent upon early infection and rain around bloom. Most fields do not require control of this disease.

If you have not seen high levels of leaf loss in late July and August in the past, consider skipping fungicide applications for control of Septoria leaf spot and leaf rust. Fungicide applications in the crop year for control of leaf spots may not be worth their cost.  Leaf spot severity levels are variable each year, and significant leaf loss usually does not occur until after harvest.

Continue to scout for Valdensia leaf spot which is much less costly to control if it can be caught as a small patch and burned out. Scout for other disease problems to catch them early before they can spread.

Consider alternatives to selling your fruit to the freezer, which includes:

Fresh pack which requires investment in cleaning equipment, purchase of boxes and clamshells, trained labor to hand-harvest into half boxes, and labor to pack your fruit. You will also need to find a market for your fruit, such as farm stands, farmers markets, or selling to local stores.

Organic production requires certification by MOFGA, with fee and records certifying that no non-OMRI approved pesticides or fertilizers have been used in your fields for the last three years.  If your fruit is sold fresh then you would also have to consider all of the requirements for a fresh pack. If you are considering selling your organic crop processed, Merrill Blueberry Farms in Hancock is the only organically certified freezer in Maine.

To evaluate your inputs use the updated Wild Blueberry Fact Sheet No. 260 Blueberry Enterprise Budget which gives examples of organic, low, medium and high input costs and returns. There are interactive Excel budget sheets that illustrate where your major costs occur and allow substitution of your own values to evaluate how adjustments will affect your predicted returns.

These new budgets on the wild blueberry website may be found on the:

Wild Blueberry Management Tool – V1.1 Maine, is a cost-benefit analysis Excel file that growers can use to help estimate field costs and returns.  It was developed in Nova Scotia by Dr. Travis Esau from Dalhousie University and has been modified to have average costs for Maine growers, but allows you to input your own costs to evaluate your fields.

You can download it as an Excel file from the Maine Wild Blueberries website on the page:

Information in this publication is provided purely for educational purposes. No responsibility is assumed for any problems associated with the use of products or services mentioned. No endorsement of products or companies is intended, nor is criticism of unnamed products or companies implied.

© 2018, 2019

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