Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu
Cherries, blueberries and some grape varieties are susceptible to bird damage. Cherry season is over for this year; however, blueberry harvest is under way and grapes will be harvested later this summer. Netting is effective, particularly in grapes where it can be mechanically applied. However it can be expensive in dwarf cherries and blueberries where structures will be needed to support the nets.
The following are some other methods to consider in managing birds in fruit crops:
Methyl Anthranilate
Methyl anthranilate is chemically similar to the major flavor component of Concord grapes and is manufactured in large quantities by food processors. Birds are repelled by its taste, and it is regarded as safe for human consumption. There are many bird repellent products available containing this chemical. It needs to be applied multiple times during the season.
Sugar
Applications of sucrose sugar syrup have been shown to repel birds from blueberry plantings. Many bird species cannot digest disaccharides. The sugar is applied when the fruits begin to turn blue, and reapplied after episodes of rain.
Audio Scare Devices
Devices such as “Bird-Gard” with digitized, species specific bird distress calls can be effective. There are several types available with different species recorded such as crows, robins and starlings that sound every minute during daylight hours. Other types use calls of birds of prey such as hawks or owls.
Visual Scare Devices
Reflective tapes, balloons, waving air man devices, predatory bird models, and other visual devices can help to scare birds but may not work as stand-alone methods for long periods.
Netting
Vineyard managers should take care to control birds in mid-late summer when sugar contents are peaking in grapes, making them a highly desirable food source. Netting is probably the most effective control method, followed by scaring devices.
It is possible to completely exclude birds from the grapes by netting the vines. The initial expense of the netting is quite high, but when amortized over the life of the netting (5-10 years) it becomes much more affordable. Applying and removing the netting are labor-intensive tasks. However, a number of bird netting implements have been designed that dramatically reduce the time and labor required to making bird netting more feasible. If the netting is just draped over the grapevines, birds have a knack for finding ways to get under the netting to feed. Therefore, it may be necessary to pin the ends of the netting together under the vines
Multiple layers of hay bale net wrap has been used as an alternative to the expensive bird netting. It is inexpensive and can be replaced each season.
Bird netting in grapes.
Applying multiple layers of hay bale wrap as bird netting in grapes.