Grapevine Bird Damage Control

Grapevine Bird Damage Control

Summary

GOAL
Evaluate various bird netting materials and sprays in conjunction with trellis types and canopy management to determine the best method of damage control.

PROJECT DESCRIPTION
During the latter stages of the growing cycle, birds become attracted to grapes and often cause damage to the fruit. In difficult cases the birds can damage the entire crop of a vineyard. There are many different nuisance devices that have been created and marketed to “scare” the birds away from the fruit. For vineyards with bird pressure of any magnitude, these devices work only for a short time and the birds eventually find no threat.

Bird netting (a covering over the grapes) has been the only method that has proven successful enough to deter birds and greatly reduce or eliminate damage. To eliminate damage, it is paramount to place the nets long before the fruit is ripe enough to attract birds. The difficulty is the fact that when the nets are placed, the vineyard become very hard to maintain around the nets. Additionally, the growth characteristic (upward or downward) and leaf size can allow for the vines to grow through traditional nets making net removal very difficult. Ultimately grape quality for some varieties is determined by keeping sun exposure and air flow to the grapes. Some netting requires the nets to be sealed on the bottom, making it very impractical (from a labor cost basis) to manage the canopy growth and provide the highest quality of grapes.

Traditional netting has large holes which make it easier for the vines to grow through. Newer technology netting has a tighter weave and thus a small opening size. This study will evaluate the smaller and larger types to determine if either provides the best solution. Additionally, application of the nets to the fruit zone on the side versus over the top will be studied for the best method.

There are certain sprays that can help to reduce the bird pressure. Interestingly the most successful is derived from the Concord grape. Concord is one of the few varieties that have no reported bird damage. The flaw with this spray is the duration of UV exposure that must occur for the pressed juice to not have carry-over aroma. With the rapid nature of final stage grape ripening, there is not enough opportunity to use only this spray. However, a combination of the spray and netting could prove to be the best solution.

WORK ACTIVITIES
1. The vineyard test blocks were divided into the control, sprayed, top netted and fruit-zone netted rows.
2. The fruit zone rows required changing the vines from a top wire to a low wire (vertical shoot position). The additional shoot support wires that were required were installed.
3. In order to test one of the benefits of the fruit zone nets, they were installed on half of the rows without wires post bud break. This gave the platform to evaluate if the vines would grow up with the support off the nets and thus eliminate the extra support wires.
4. Fruit zone nets were procured as well as the bird spray to be tested. Top applied nets are already in use, so nothing was required to purchase.
5. Instead of fabricating a new net application attachment, we bought a wire fence installation attachment from Tractor Supply and made slight modifications. This attachment was used on the 3-point and the fruit zone nets were applied to their respective rows.
6. The determination was made to use the encapsulated bird spray after researching both products with existing producers.
7. The bird spray was applied following label instruction and reapplied as directed.
8. The top applied nets were installed at the same time as they are each season.
9. Data and photographs were compiled showing the results of the comparison of each method.
10. Relative costs for each method (including labor) were recorded.
11. Top applied nets were removed as is done each season. The fruit zone nets were rolled and left on the rows to test this benefit (labor savings).

RESULTS
1. The bird spray was effective.
2. The fruit zone nets provided great labor savings as well as the savings of the additional support wires. An additional big benefit of the quality using the fruit zone nets was discovered.
3. Additionally, the spray was evaluated for potential “carry over” that could affect aroma and/or taste. There was none detected.

WORK PLAN FOR 2009
The entire study will be repeated to ensure that the data, effectiveness and labor savings was repeatable. We did not discover anything that needed to be done differently, so will not require any changes in the protocol.

OUTREACH
We conducted open field days during the year for other growers to see the study and materials. During the annual Kansas Grape Growers and Winemakers (KGGWA) workshop the preliminary results were shared and discussed among growers. A formal presentation and workshop will be held at the vineyard both in May and again in October.