Grapevines are in various stages of early growth throughout Indiana, ranging from bud swell to 2-4 in shoot growth. A cold weather event came across the state from 4/20-4/22 bringing temperatures as low as 27 F. Damage is still being assessed, but if significant primary bud damage occurs we will expect to see emergence of secondary shoots.
With rising temperatures and a high chance of rain expected over the next 2 weeks, it will be important to monitor pest populations and take preventative measures for disease control. Climbing cutworms can cause damage all the way from bud swell to when shoots are 10-15 cm long. Scout your vineyard to identify regions with high cutworm pressure. Grape flea beetle can cause damage during this time as well, but usually only until the buds are ½ inch long.
Insecticide application is recommended if more than 10% of the buds are showing damage. IRAC 3A products (Baythroid, Danitol) and Carbaryl/Sevin are effective on climbing cutworm & flea beetle.
Bud swell is also the most important time to control for Phomposis. Many varieties grown in Indiana are especially susceptible to phomopsis, inlcluding Traminette, Seyval, Chardonel, La Crescent and Marquette. A lime-sulfur application is recommended at bud swell to get rid of inoculum that has overwintered and prevent spread to cluster stems & developing berries. A lime-sulfur application can also help reduce incidence of powdery mildew. Phomposis can also be controlled with captan or mancozeb. Mancozeb is a broad-spectrum that also control black rot and downy mildew. Captan and mancozeb are protectant fungicides that must be applied before the next rain event and reapplied after a major rain event. Fungicide applications are recommended at a 7-day interval through bloom.
Please see the Midwest Fruit Pest Management Guide for more information. — By Miranda Purcell, Purdue University