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Grape Berry Moth Spray Timing-Friday June 1, 2012

Timing Grape Berry Moth sprays:

Grape berry moth is a key insect pest of grapes in New York – and the only serious pest that feeds internally on intact grapes throughout the growing season.  It overwinters as a pupa, and adults emerge, mate, and start laying eggs on grapevines around the time that wild grapevines (Vitis riparia) are in bloom.  The first generation typically causes little damage on cultivated grapes (which bloom a few weeks after wild grapes), but the second generation in mid season can move into vineyards, and each larva can feed inside several berries before completing development.  It can complete 3 to 4 generations before harvest.

Timing sprays is important!  The larvae feed internally, and are shielded from insecticides on the berry surface – so the only ‘window’ for controlling them is between when eggs are laid and when the larvae burrow into the berry.  Newer insecticides require feeding by the larva (not just contact), so the ‘window’ for effective control of each generation is short – about 7 days.

Tools for timing:  The NEWA weather site has a tool for determining proper timing of sprays. It uses 1) a baseline date called a ‘biofix’ to determine when to start tracking growing degree-days.  Biofix for grape berry moth occurs when wild grapes are at 50% bloom. 2) growing degree-day accumulations after the biofix to determine when the next generation of eggs will be laid.  Research has shown that about 810 growing degree-days are required after the biofix to reach the next generation’s peak egg laying  – the appropriate timing for an insecticide spray to have its maximum impact.

For a complete description of the model and its use, see: New Grape Berry Moth Forecasting Tool Available Online

50% Wild grape bloom in the Clayton area is forecast for June 1.  The next generation’s peak egg laying will occur 810 growing degree-days (base 50) later.

To use the Grape Berry Moth Forecast Model, go to this interactive page,  select ‘grape berry moth’ from the drop-down list of pests and diseases, and select the appropriate weather station (‘Watertown’ is the only one in the Thousand Islands area), press ‘calculate’, then enter the ‘wild grapevine bloom date’.

See also:

Grape Berry Moth – NYS IPM Fact Sheet.

Risk Assessment of Grape Berry Moth and Guidelines for Management of Eastern Grape Leafhopper.



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