Dr Desmond Layne, associate professor of pomology, tree fruit specialist, and state program team leader for horticulture at Clemson University

Stone Fruit

The Easter Freeze:  A Follow Up

Desmond R. Layne
dlayne@clemson.edu

In my last column (July 2007), I spoke about the Easter freeze that occurred during the weekend of April 7-8, 2007.  This freeze occurred in much of the eastern half of the U.S. and it was particularly devastating in the southeastern states.  Although many farms had a total or near com- plete loss in a number of fruit crops, some were spared completely or had partial crops that were managed or abandoned.  This latter case will be the focus of my column this issue.

Easter freeze damaged fruit; Unusually cold weather, such as that which occurred this Easter, can result in freeze-damaged fruit and the development of brown rot disease.

Unusually cold weather, such as that which occurred this Easter, can result in freeze-damaged fruit and the development of brown rot disease.  Photo courtesy of Desmond Layne

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In non- or light-crop years, grower choices to eliminate or reduce cover sprays result in an increased pressure of tree-attacking diseases and insects.  Orchard sanitation and preventative control measures taken now and in the dormant season can dramatically reduce potentially epidemic problems next year.

In peaches, the primary fungal disease of concern is brown rot.  Diseased fruit may mummify and remain on the tree providing a potent source of inoculum for next spring. Removal of mummies from the orchard is necessary as soon as possible.  If labor is not available now, these mummies and any cankerous wood should be removed during the winter dormant pruning process.  Inoculum density may be very high next spring, so growers should pay particular attention to their spring fungicide program.  Depending on weather conditions, one or two bloom sprays for blossom prior to next spring.

Not Just Disease

Pressure from mites, scale, and borer insects will increase if these pests are not suppressed by cover sprays. For borers (i.e., peach tree borer and lesser peach tree borer), postharvest applications of chloropyrifos (Lorsban, Dow AgroSciences) or esfenvalerate (Asana, DuPont Crop Protection) will be necessary.  Handgun applications of a coarse, directed spray to the tree trunk should result in a visible puddling of material at the ground line.

Mite and scale populations can be reduced dramatically by applications of superior oil during the dormant season.  Two high-gallon applications are better than one.  The second application should be made during the delayed dormant period but oil concentrations may need to be reduced as bud break approaches.  European red mites that overwinter on the tree are controlled even better when chloropyrifos is added to the delayed dormant oil application.  This may also result in some suppression of the lesser peach tree borer early in the spring.  Limbs that have been compromised by scale or lesser peach tree borer should be removed.  This sanitary practice will help improve spray and light penetration into the canopy.

Finally, all growers are advised to check their local state pesticide regulations to ensure compliance with state law and follow all label requirements.  Drs. Guido Schnabel, Clemson University, and Dan Horton, University of Georgia, are gratefully acknowledged for their input to this column.

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This column by Dr. Desmond R. Layne, “The Easter Freeze:  A Follow Up” appeared in the September/October 2007 issue of The American Fruit Grower magazine on page 34.

Desmond R. Layne, Ph.D., is an associate professor of pomology, tree fruit specialist, and state program team leader for horticulture at Clemson University. He is also president of the American Pomological Society.

For more information, go to www.clemson.edu/peach.