A post on: www.botanicalgarden.ubc.ca/blog/bagging-little-green-apples
Earlier this summer we caught up with Richard Hallman, one of our workshop instructors to ask him about his work and why he was bagging apples. If you are interested in learning more about Tree Fruit Horticulture Richard is teaching Fall Fruit Tree Pest & Disease Control on September 26, 2015.
In Richard’s own words:
The most destructive and frustrating insect pest of apples and pears in the Vancouver area are Codling Moth and Apple Maggot, the worms in our fruit. The Codling Moth adult is a moth that was introduced to BC from Europe in the early 1900’s. Apple Maggot adult is a fly that moved across the border from Washington State in 2006. Organic management of these two insects is difficult and often unsuccessful.
Codling Moth adults started emerging in the Vancouver area during the last half of May this year and Apple Maggot adults are now emerging as well. One of the most successful ways to prevent damage from these insects in home gardens is the use of exclusion bags and the UBC Botanical Garden is using a few this year on trial. Usually a small mesh bag is pulled over the small fruit and firmly tied to the stem. The first image attached to this post is of a bag newly installed. These bags protect the fruit from the insects and they expand with the fruit providing season long protection (see the second image). Installing these bags is a lot of work, a manageable job if your trees are small.
An alternative to using these mesh bags is to use Japanese Apple Bags to protect the fruit. These are double bags, an inside bag of rice paper and a outside bag of heavy paper. These bags were developed in Japan to improve the appearance of the fruit. These bags are only used on apples that ripen in late September to early October and are red at harvest. Chlorophyll (the green color) usually develops in apple fruit exposed to sunlight, inside these bags the apples are white or pale yellow. About 10 days before harvest the bag is taken off the fruit and a dark colored graphic is attached, then the rice paper bag is put back over the fruit to prevent sunburn. This late in the year there is not enough time for chlorophyll to develop so when anthocyanins (the red color) start to develop stimulated by cooling temperatures the color that results is a bright red rather than the usual dark red. At harvest the rice paper bag and the graphic are removed and you have a insect free bright red apple with a custom graphic. The above images are of a project using these bags in the Creston Valley.
Richard Hallman is the UBC Botanical Garden Fruit Tree Expert in Residence