Recorded Pest Message – May 2, 2007

The wet weather today did not cause an apple scab infection period. The average temperature during the wet weather was 49 degrees. At 49 degrees, 11 hours of leaf wetness are needed to cause an apple scab infection period. And since the rain started in the night time, we do not start counting hours of leaf wetness until the sun is up. So from 7am till noon is only 5 hours of leaf wetness. The way I see it, we have had only one apple scab infection period so far this year. That infection period was last Friday, April 27th into Saturday the 28th.

At this time, it is estimated that 15% of the ascospores from primary scab season have been discharged. We are moving into the most important time for apple scab control – pink through bloom. Primary apple scab season is over shortly after petal fall. The goal is to keep your trees scab-free through primary scab season. Remember, it takes about 2 weeks after an infection period for scab lesions to appear.

I’ve been looking for winter moth larvae the last two days. What I have decided is winter moth caterpillars are easy to find in Newport County, but not in Providence or Washington County. I do find them in Kent County, but only along the coast. Also, in Newport County, I do not see them in apple orchards. I find them primarily in maples on the edges of woods. I think that if the population of winter moths gets very large some year, winter moth will be more of a problem blowing in from outside the orchard. Right now I do not see them in sprayed trees. Perhaps later in May, if winter moth larvae are defoliating nearby trees, an orchard spray may be needed to keep the winter moth out of the orchard. For now, the winter moths do not appear to be in the orchards.

There is still time to apply dormant oil against European red mite eggs. Reduce the rate to 1 gallon of oil/100 gal since the trees are beyond tight cluster. According to Orchard Radar, European red mite eggs should begin hatching May 7 in the Greenville area and May 8 in Newport County. Little Compton will be later than this. You can see Orchard Radar yourself from Click on Greenville or Newport County, which ever is closer to your orchard.

Next message will be recorded 5/8/07 949-1456.