April 24, don’t think yesterday was an infection period

Hi Fruit Growers,

I was hoping Orchard Radar would be up and running by now, but it’s not. We do have another tool for checking different apple models to predict what is happening in the orchard. That tool is NEWA from Cornell. There are two NEWA weather sites in RI – one at TF Green Airport and one at Newport Vineyards in Middletown. It takes a little while to become comfortable with NEWA, but it’s worth the effort. NEWA can be found at http://newa.cornell.edu/
Here’s the link directly to the apple scab model: http://newa.cornell.edu/index.php?page=apple-diseases

So according to NEWA, we did have an apple scab infection period that started Tuesday evening and ended yesterday afternoon at 2:00. This apple scab model is not considering that nearly all apple scab spores are not released at night and wait until the morning to be released. We really don’t need to start counting hours of leaf wetness until dawn. Counting hours from 7am to 2pm, we get only 7 hours of leaf wetness at an average temperature of 50 degrees. At 50 degrees we need 14 hours of leaf wetness to cause an apple scab infection period. So I don’t think we had an infection period April 23rd. Next chance for rain looks like Saturday.
All the winter moth eggs I’ve been watching have hatched by now. Before you spray¬† again, look inside flower buds and see if you see little caterpillars or caterpillar frass. I’ve attached a picture of winter moth caterpillars in apple during pink. This is from a couple of years ago – trees aren’t at pink yet and the caterpillars aren’t this large yet.

If you find many caterpillars, it’s probably a good idea to spray insecticide again. Be sure to check apple trees closest to woods. Caterpillars can blow in from surrounding trees.

winter moth in apple at pink