Fungicide use and Colletotrichum acutatum levels over the past two years - a grower survey

Current New Jersey recommendations for anthracnose Colletotrichum acutatum control in highbush blueberry call for several fungicide applications starting at the beginning of bloom and continuing afterwards on more susceptible varieties such as Bluecrop. Chemistries are rotated for a resistance management program. Numerous growers are having problems with anthracnose infection control in New Jersey blueberry production. The objective of this study was to survey grower fungicide programs and anthracnose levels over 2 years to see if there was a weakness in commercial fungicide programs. Commercial packed pints of ripe blueberries, cv. Bluecrop, were collected along with grower spray records. Fruit was stored at room temperature (24 o C) for 10 days and read for percent infection. The timing for bloom infection periods was identified and compared to fungicide application records. In 2016, berries ranged from 1 to 72% infected, and in 2017, ranged from 0 to 63% infected. Data analyses attempted to correlate grower fungicide use and timing of fungicide applications with resulting anthracnose infections. Observations show that there is a more complex picture to anthracnose control other than starting fungicide cover sprays during bloom, and rotating chemistries. Some growers who are following current recommendations for anthracnose control still produce fruit with high infection rates, while others obtain excellent control. Further work will include looking at sprayer type and spray coverage.