Every year at the same time in January, we are increasingly faced with bird populations migrating from breeding grounds into our precious wine grape crops.
The vineyard managers’ nightmare has become reality and the dilemma of how to deal with the problem sets in.
Many methods of scaring and eradication have caused some social problems in recent years with some groups in our society, whilst the disadvantaged grower tries to protect his crop at all costs.
Methods such as gas guns, screechers, flashing mirrors, balloons, and the oldest of all, the drive around on a quad with a double barrel shot gun, have been the preferred management strategy.
The problem with these methods is that continual sound of noise from these methods seem to welcome birds, and makes them feel at home whilst taking up the focus within our vineyard management.
This article is designed to bring to light a newer form of bird management without the headaches of the above-mentioned methods insuring peace of mind for the grower.
At Llangibby Estate in the Adelaide Hills, John Williamson, Chris and David Addams Williams have developed 34 acres planted to Shiraz, Cabernet Sauvignon, Tempranillo, Pinot Noir and Sauvignon Blanc.
Disillusioned by methods described above, they investigated the full lock-out netting (33gsm, white in colour) promoted and sold by Grigson Trading in Adelaide.
Measurements for each row were taken for four row roll-on application. Supply costings amounted to $2200/acre for the full 34 acres.
After final fungicide and herbicide applications were applied in early February, to ease machinery operations under the netting after application, the process began to roll on the netting.
Using contractors working at a slow pace of 3-4km/hr, progress of 1 acre/hr was achieved. At a rate of $75/hr for applicator/operator and four personnel on the ground to coordinate tie downs, the cost per hour for the team totaled $135/hr/acre. Total application cost being $4590.00.
A crucial task in the application was to ensure adequate rope to ensure crossovers were tied down adequately.
The roll-off procedure proved to be slower than roll-on, due to canopy growth and to ensure sections were packed away efficiently for the roll-on procedure next season.
Overall cost difference was some $1000 in labour than the roll on amount.
Total purchase of netting was $2200/ac and the roll-on, roll-off procedure amounted to $299/ac.
In the first year of operations, Llangibby Estate owners analysed what percentage of fruit was being eaten by birds and what percentage was being destroyed or damaged.
This assessment is vital before a decision to purchase full cover netting is made.
Analysis proved that some 2-3 % was being eaten and 2-3 % was damaged, causing valuable juice to overrun on to viable berries in the bunch. This caused an acetic nature to occur within the bunches, then after an onset of bee’s and other vectors a decrease in the quality of fruit was occurring due to lack of flavour and colour development. Overall 4-6 % of the crop was destroyed/damaged, representing 8.5 tonnes per year. With the average grape price being $2000 per tonne, this equated to a$17,000 loss every year, not to mention the effect on morale, winemaker’s concerns with quality and general frustration to all concerned.
Overall when assessing the
purchase/application costs vs production losses, the owners at Llangibby Estate
would be ahead of their investment in five to six years and all involved in the
investment would rest easy at night.
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Be sure to tie ends down tightly as rabbits, hares and some larger birds such as magpies tend to break into it. |
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Easy to spray under with correct equipment. A Rovral fungicide application was applied in April after 25mm of rain. Personnel were utilised in lifting ends to allow easy access in and out. |
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Monitor cross over points to ensure ropes are keeping tension. |
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Ripeness occurred at optimum times throughout the season and the netting’s white colour didn’t seem to impede ripening process. |
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Gets dusty and tends to hold on to canes when rolling off. |
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Be positive about the investment of netting to ensure crop safety. |
Overall a successful 2001 was experienced at Llangibby Estate, using full cover netting to assist in realising investments and maintaining grape/wine quality. An important factor about this application is that in bird prone districts/areas, it must be said that the purchase of netting should be treated the same as the purchase of posts in a new development. It is an investment that should be considered at the time of site selection and design. At $2200/ac purchase cost and $299/ac roll-on, roll-off operational cost, consider its inclusion in the development and operational budgets.
It’s a simple way to win the war against a pest that invariably could contribute to fruit rejection at your winery and investment dollars lost.
Finally, with the crop fully protected against birds, the owners at Llangibby were able to concentrate their resources on other areas such as fruit sampling, crop estimation, disease monitoring and harvest coordination in the lead up to vintage. Not to mention the golf after lunch.
