Green Fruit Rot (Jacket Rot)

Green fruit rot begins during the latter part of the bloom period when the fungus infects senescing petals and anthers. Infected petals develop water-soaked brown spots. Some infected petals may fall onto leaves causing secondary infections. Anther infections can spread to floral tubes or flower jackets causing them to wither and stick to developing fruit. As fruit sets and starts to grow, a brown spot develops where the jacket sticks to it. This is particularly a problem where nut clusters trap senescing flower parts. Frequently this leads to rot of entire nut clusters.

This disease is of little importance in many years, but when conditions are cool and wet during bloom, it can cause severe losses. One or more of several pathogens may be involved.

When bloom is extended and moisture is abundant, apply a fungicide at full bloom to prevent green fruit rot. Continue treatment until rain stops. Be sure the fungicide you choose is effective against all three potential pathogens; demethylation (sterol) inhibitor fungicides such as myclobutanil (Laredo) and propiconazole (Orbit) are not effective against Botrytis cinerea.