Weed And Disease Control In Organic Apple Orchards

Weed Control
Plans for weed control should be in place prior to planting the orchard. Many options have been investigated, and the perfect option remains elusive. Hay mulches and synthetic mulches harbor vole populations, and controlling weeds along edges of synthetic mulches is difficult because mowers snag the mulches. Some burn-down herbicides are approved for use in organic plantings, but these are expensive and must be reapplied frequently. Propane flamers sound like fun for pyromaniacs but are expensive and have proven only marginally effective over the long haul.

Wood chip mulch has provided acceptable weed control without harboring voles, but the transport and installation costs for a wood chip mulch can be substantial. Wood chip mulches must be renewed every several years, and perennial weeds such as Canada thistle can become a problem in wood chip mulches. Wood chip mulches provide some benefits for fertility and moisture retention, but long-term management is more complex than for weed control by tilling. Wood chips should never be tilled into the soil because they will tie up all of the available nitrogen for several years after incorporation. Thus, one cannot mix wood chips and tillage.

An option worth exploring would be a removable and re-usable synthetic mulch. Several companies manufacture durable plastic and/or fiberglass-based ground covers that have worked well to suppress weeds. When left in place during winter, these mulches harbor damaging populations of voles. However, it should be feasible to design a machine that would mechanically install the mulch in spring (perhaps in early May) and then recover that mulch onto a roll in mid-August so that it could be stored until it is reinstalled the next spring. A plastic mulch installer like those used for vegetables might be modified and off-set so that a ground cover could be installed on one side of a tree with the outside edge buried in soil to hold it in place. After installation was completed on both sides of a tree row (with separate 3-foot-wide strips of mulch on each side), the center overlap along the tree row would need to be manually stabilized to resist wind by inserting long wire “staples” into the ground or by weighting the center edge with rocks, wood chip mulch, or a long water-filled hose. Wood chip mulch installed over removable synthetic mulch could presumably be shaken to the ground when the synthetic mulch is removed in fall and then covered over with the synthetic mulch the next year. However, removable synthetic mulches need to be tested experimentally and will become practical only if their installation and removal can be mechanized.

Disease Control
Various plant pathologists working with organic apple production have all agreed that the two most problematic groups of diseases in organic apple production are rust diseases and summer fruit rots. Sulfur and liquid lime-sulfur (LLS) can be used to control most other diseases, although, as noted before, using these fungicides at the rates and intervals needed to control apple scab will cause yield reductions. To date, all of the organic fungicides promoted as alternatives to sulfur are more expensive and less effective than sulfur.

Fire blight is another potential problem with many cultivars, but streptomycin is currently acceptable within organic programs so long at is used only on an as-needed basis. Strategies for fire blight control are therefore similar in organic and conventional orchards.

Cedar apple rust and quince rust are very difficult to control with sulfur. Therefore, organic plantings that include rust-susceptible cultivars should be located at least 300 feet away from the nearest cedar trees. Powdery mildew can become a problem on some cultivars, but three or four applications of sulfur beginning at petal fall may suffice to keep mildew in check. Where mildew becomes established, however, the sulfur program should be initiated no later than pink.

Sooty blotch and flyspeck can be controlled by using low rates of LLS during summer. In trials in New York’s Hudson Valley, LLS applied at 1 quart per 100 gallons of dilute spray was very effective when applied on a 10-day schedule during July and August, whereas 2 quarts per 100 gallons were required for good control on a 20-day schedule. In regions where conditions favor development of flyspeck and sooty blotch, sprays with LLS must be continued into late September to prevent disease on late-maturing cultivars.

Unfortunately, LLS does not control summer fruit rots such as black rot, white rot, and bitter rot. Low rates of copper fungicide can be tank-mixed with LLS during late July and August LLS to increase activity of these sprays against summer fruit rots. However, organic apple growers may need to resort to sanitation measures to control summer fruit decays as plantings mature. In the northeast, much of the inoculum for summer fruit decays comes from fruitlet mummies that are retained after fruit set and that remain on the trees over winter. Manually removing all of these fruitlet mummies during winter pruning should significantly reduce problems with summer fruit rots. However, as is the case with many other aspects of organic production, that hypothesis has not yet been tested.

Leave a Reply

Featured Stories
Marco Rubio tours a Central Florida citrus grove with industry dignitaries
Insect & Disease Update
July 22, 2016
Marco Rubio Backs Bill To Save Florida Citrus
Senator co-sponsors measure that would provide growers with incentives to plant more trees. Read More
Holly Rippon-Butler
GenNext Growers
July 22, 2016
Farming’s Next Generation Seeking Room To Grow
Several innovative resources are available to help first-time growers acquire the property they need. Read More
Live music woman playing guitar free image FEATURE
Farm Marketing
July 22, 2016
How To Book A Great Band For Your Festivals
Want to add live music to your fall festivals? Here's a step-by-step guide on how to find the right band for the right price. Read More
Valery Cordrey on a radio show
Farm Marketing
July 22, 2016
How To Entice The Local Press To Cover Your Farm Market
Sometimes getting publicity for your business is easier than you think. All you need to do is figure out how Read More
cantaloupe
Cucurbits
July 22, 2016
California Cantaloupe Growers To Celebrate First-Ever “Cantaloupe Week”
The Golden State’s cantaloupes are now in peak production from major areas in the San Joaquin Valley. Read More
Closeup of buckwheat blooms
Cucurbits
July 21, 2016
Study Shows Buckwheat Can Help Stifle Squash Pests
Unique cover crop choice attracts beneficial bugs, increasing pollination prospects and reducing insect threats. Read More
farm labor pic for web
Citrus
July 21, 2016
Farm Labor Delays Taking Toll On Crops [Opinion]
When it comes down to it, we have a choice to make. We either have to import our labor, or we'll have to import our food. Read More
Urban vegetable farm in rural Cuba
Citrus
July 20, 2016
My First Trip To Cuba Proves Fruitful
The five-day journey was enlightening, providing participants with a better perspective of the state of agriculture in this country 90 miles off Florida’s coast. Read More
Shinsuke Agehara of UF/IFAS holding an artichoke in the middle of a Central Florida farm plot
More Vegetables
July 19, 2016
So You Think You Can Grow Artichokes In Florida?
Field trials are in progress to determine if this highly sought-after superfood can survive the swelter of the Sunshine State. Read More
The Latest
Insect & Disease Update
July 22, 2016
Marco Rubio Backs Bill To Save Florida C…
Senator co-sponsors measure that would provide growers with incentives to plant more trees. Read More
GenNext Growers
July 22, 2016
Farming’s Next Generation Seeking …
Several innovative resources are available to help first-time growers acquire the property they need. Read More
Farm Marketing
July 22, 2016
How To Book A Great Band For Your Festiv…
Want to add live music to your fall festivals? Here's a step-by-step guide on how to find the right band for the right price. Read More
Farm Marketing
July 22, 2016
How To Entice The Local Press To Cover Y…
Sometimes getting publicity for your business is easier than you think. All you need to do is figure out how Read More
Cucurbits
July 22, 2016
California Cantaloupe Growers To Celebra…
The Golden State’s cantaloupes are now in peak production from major areas in the San Joaquin Valley. Read More
Farm Marketing
July 22, 2016
Find Out Where Growers Want To Sell Thei…
Earlier this year, we asked farm marketers which of their current business channels they would like to increase. Not surprisingly, Read More
Cucurbits
July 21, 2016
Study Shows Buckwheat Can Help Stifle Sq…
Unique cover crop choice attracts beneficial bugs, increasing pollination prospects and reducing insect threats. Read More
Citrus
July 21, 2016
Farm Labor Delays Taking Toll On Crops […
When it comes down to it, we have a choice to make. We either have to import our labor, or we'll have to import our food. Read More
Citrus
July 20, 2016
My First Trip To Cuba Proves Fruitful
The five-day journey was enlightening, providing participants with a better perspective of the state of agriculture in this country 90 miles off Florida’s coast. Read More
More Vegetables
July 19, 2016
So You Think You Can Grow Artichokes In …
Field trials are in progress to determine if this highly sought-after superfood can survive the swelter of the Sunshine State. Read More
Citrus
July 19, 2016
Funds Allocated To Address Impact Of Cli…
NIFA announces $8.4 for study and development of new approaches to mitigate effects of climate change. Read More
Disease Control
July 19, 2016
Open Your Eyes To Common Smut In Sweet C…
Learn how to identify, the survival and spread, as well as management methods for this formidable fungus. Read More
Crop Protection
July 18, 2016
Early Infection Of Downy Mildew Confirme…
The pathogen has been confirmed in Michigan cucumbers in Bay County for the 2016 season. Read More
Citrus
July 18, 2016
USDA Awards More Than $26 Million For Af…
The funding is to support more than 400 rental units in four states. Read More
Crop Protection
July 18, 2016
Potato Growers: Be On The Lookout For Ne…
Standard measures have been typically less effective against new strains. Read More
Business Planning
July 18, 2016
Financial Fortitude Key For Small Farm S…
Local threats like citrus greening create additional challenges for many of Florida's more modest enterprises. Read More
Citrus
July 18, 2016
Bayer Ups Bid To Buy Monsanto
Reports indicate new offer at nearly $65 billion. Read More
Cucurbits
July 18, 2016
21 Pumpkin Varieties You Need To Know
Leading seed breeders and distributors highlight some of the latest pumpkin varieties available. Read More
[gravityform id="62" title="false" description="false"]