Slump In Supply and Brown Rot

June 26, 2008

For the past 10 - 14 days or so we have had a slump in supply of fresh out of the orchard peaches. Primary factor atributing to this seems to be the late March freeze. Many varieties, especially those in the 650 to 750 chill hour range when the freeze hit ended up with a light crop. I believe the volume will be picking up as we move along from here out.

Brown rot has been more prevalent in some orchards this year with more rainfall occuring in mid-June. We have been about 10-14 days now without a thunder shower here at our Research and Extension facility but, where brown rot has started it seems to be a little harder for us to slow down. This brings several important things to mind.
1) Open up centers of trees if possible. This will increase spray penetration and reduce drying time.

2) Use sufficient spray water volume. Full canopy mature trees will need from 100 to 130 gallons per acre.

3) Spray every row. Alternate row sprays while sufficient for insect control will not provide sufficient coverage for brown rot control.

4) Be sure to use the proper rate of a recommended fungicide and rotate chemical classes (see Peach IPM Guides).

5) If possible remove damaged or diseased fruit from the tree while picking. Take care not to damage marketable fruit since brown rot spores are waiting for a nick or cut to sporulate on.

6) Control (to extent possible) piercing sucking insects such as leaffooted bugs and stink bugs. Since many of our insecticides that would be effective for these pests have a 14 day pre-harvest interval control approaching harvest and during harvest is more difficult. Cyfluthrin (7d phi), beta cyfluthrin (7d phi), malathion (7d phi) and carbaryl (3d phi) can be used closer than 14 days.

Dr. Guido Schnabel and others from Clemson have developed a rapid test for brown rot resistence. We are using this method to check brown rot samples in Alabama. So far we have not found any resistence in the infected fruit we have sampled. We will be continuing to sample fruit over the next couple of weeks.