Orchard Disease Prevention During Warm Spells

By Blake Jackson

Although Punxsutawney Phil predicted six more weeks of winter in 2026, forecasts suggest a sharp warm-up beginning the week of March 8, with daytime highs in the 70s and nighttime lows in the 50s.

Such unseasonably warm conditions could rapidly advance bud development, particularly in early peach varieties. Growers who did not complete late-fall fungicide sprays and sanitation still have time to reduce disease pressure before the season progresses further.

Stone Fruit

Peaches and other stone fruits are especially vulnerable during warm late-winter periods. If peach leaf curl sprays were not applied in the fall, growers should treat trees immediately. The disease can only be effectively managed while trees remain dormant, before buds swell.

Once buds begin to open, they shield the fungal spores, reducing fungicide effectiveness. With warm temperatures expected, early varieties may advance quickly, leaving a narrow application window. Recommended products include copper, ziram, lime sulfur, or chlorothalonil.

Winter pruning also presents an opportunity to remove mummified fruit and dead wood. These remnants can harbor brown rot spores, acting as significant infection sources during bloom and fruit development. High spore loads may overwhelm fungicide programs, making sanitation a critical defense strategy.

Apples and Pears

For apples and pears, late dormant copper sprays can help suppress fire blight, apple scab, Marssonina blotch, and bitter rot. Growers should target 2 pounds per acre of metallic copper, carefully reviewing product labels to determine metallic copper equivalents.

Horticultural oil applications during dormancy can also manage certain overwintering insects. Copper and oil may be combined safely when little green tissue is present, but close monitoring is essential as bud break approaches.

To further limit disease risk, growers can accelerate decomposition of fallen leaves and fruit by applying a 5% urea solution 40 pounds dissolved in 100 gallons of water per acre before bud break or at green tip. Reducing overwintering inoculum on the orchard floor significantly lowers the risk of early-season infections and helps set the stage for a healthier crop year.

Photo Credit: gettyimages-richard-7