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
VegetablesSakata Seed Highlights Specialty Golden Beet
January 29, 2015
The company highlights specialty golden beet, Touchstone Gold. Read More
FruitsUse The Off-Season To Focus On Farm Safety
January 29, 2015
Prevention, planning, and preparedness are essential for all agritainment operations. Read More
Protected AgricultureHow To Successfully Produce Vegetables In Controlled Environments
January 28, 2015
Greenhouse expert Merle Jensen offers pointers on growing systems, pest control, plant nutrition, harvesting, and more. Read More
IPMWhat You Need To Know To Maintain An Effective IPM Program In The Greenhouse
January 28, 2015
Greenhouse expert Karin Tifft discusses the importance of scouting, pest identification, control options, and the importance of sanitation. Read More
Apples & PearsPears Get A Hefty Shout-Out From Rapper
January 28, 2015
The pome fruit is on mainstream media's radar thanks to a rapper's quote and ensuing social media blitz. Read More
FruitsHighlights From The Mid-Atlantic Fruit And Vegetable Convention
January 28, 2015
Bio-control use, media literacy, and disease control were just a few of the topics discussed at the convention held in Hershey, PA. Read More
GrapesCalifornia Table Grape Growers Offer Agricultural Scholarships
January 28, 2015
The application deadline for the agricultural scholarships is 5 p.m., Feb. 13. Read More
GrapesNew Wine Hybrid Establishment Cost Resource Available
January 28, 2015
Research from Cornell University breaks down the cost of producing hybrid winegrapes. Read More
FertilizerEasy Access To Fertilization Guidelines
January 28, 2015
New, easy-to-follow brochures take the guesswork out of almond and walnut fertilization. Read More
BerriesDormant Pruning Tips For Your Berries
January 28, 2015
Proper dormant pruning increases berry size and improves overall health of blackberry and raspberry plants. Read More
The Latest
VegetablesSakata Seed Highlights Specialty Golden Beet
January 29, 2015
The company highlights specialty golden beet, Touchstone Gold. Read More
FruitsUse The Off-Season To Focus On Farm Safety
January 29, 2015
Prevention, planning, and preparedness are essential for all agritainment operations. Read More
Protected AgricultureHow To Successfully Produce Vegetables In Controlled En…
January 28, 2015
Greenhouse expert Merle Jensen offers pointers on growing systems, pest control, plant nutrition, harvesting, and more. Read More
IPMWhat You Need To Know To Maintain An Effective IPM Prog…
January 28, 2015
Greenhouse expert Karin Tifft discusses the importance of scouting, pest identification, control options, and the importance of sanitation. Read More
Apples & PearsPears Get A Hefty Shout-Out From Rapper
January 28, 2015
The pome fruit is on mainstream media's radar thanks to a rapper's quote and ensuing social media blitz. Read More
FruitsHighlights From The Mid-Atlantic Fruit And Vegetable Co…
January 28, 2015
Bio-control use, media literacy, and disease control were just a few of the topics discussed at the convention held in Hershey, PA. Read More
GrapesCalifornia Table Grape Growers Offer Agricultural Schol…
January 28, 2015
The application deadline for the agricultural scholarships is 5 p.m., Feb. 13. Read More
GrapesNew Wine Hybrid Establishment Cost Resource Available
January 28, 2015
Research from Cornell University breaks down the cost of producing hybrid winegrapes. Read More
FertilizerEasy Access To Fertilization Guidelines
January 28, 2015
New, easy-to-follow brochures take the guesswork out of almond and walnut fertilization. Read More
BerriesDormant Pruning Tips For Your Berries
January 28, 2015
Proper dormant pruning increases berry size and improves overall health of blackberry and raspberry plants. Read More
NutsHow Freezing Temperature Affect Bearing and New Trees
January 28, 2015
Key points before and after the critical bloom period make exposure to freezing temperatures relevant. Read More
CitrusFlorida Citrus Is Still A Big Deal [Opinion]
January 28, 2015
Even while in the grips of greening, citrus continues to be a big contributor to the Sunshine State's economy. Read More
FruitsUSDA Forecast Predicts Normal Water Supply For Parts Of…
January 27, 2015
The Southwest, Sierra Nevada region, and Pacific Northwest are starting the year drier than normal. Read More
Apples & PearsThe Story Of Honeycrisp Is One Of Challenges And Succes…
January 27, 2015
‘Everything’s different’ in this world of 150 million 40-pound box world of apple growing. Read More
BerriesWhy You Should Be Growing Black Raspberries
January 27, 2015
Amazing health benefits for consumers and production and marketing benefits for the grower make this berry a must-consider option for your operation. Read More
Apples & PearsThe Dark side Of Honeycrisp
January 27, 2015
Growers say there’s a love-hate relationship with America’s darling apple. Read More
Apples & PearsExpanded Market Access For U.S. Grown Apples To China
January 26, 2015
Agreement expected to boost apple exports by $100 million per year. Read More
CitrusNominees Sought For Florida Agricultural Environmental …
January 26, 2015
Honor recognizes those developing and adopting environmentally innovative farming practices. Read More