Buckeye rot

Buckeye rot or Fruit rot is caused by the water-moulds Phytophthora capsici, Phytophthora drechsleri and Phytophthora parasitica.

Symptoms
The first symptom on the fruit is a grayish green or brown watersoaked spot that develops where the fruit touches the soil. Lesions that enlarge on the surface of infected fruit have a characteristic pattern of alternating light and dark brown concentric rings that resemble the markings on a buckeye. Buckeye rot lesions have a smooth surface and lack a sharply defined margin. These features distinguish the disease from late blight (caused by Phytophthora infestans), which is characterized by lesions with a rough surface and a definite margin. In contrast with Pythium rot, which results in a soft, watery rot of the fruit, tomatoes with buckeye rot initially remain firm. Buckeye rot lesions may, however, be invaded by soft rot bacteria in the later stages of disease development.

Treatment
None. Remove and destroy affected fruit.

Cultural
Grow tomatoes on raised beds in well drained soil. Stake and/or mulch plants to prevent fruit from contacting the soil. Avoid frequent irrigations that keep the ground wet.

Chemical Control
In commercial fields, fungicides containing mefenoxam (e.g. Ridomil Gold/Bravo, Ridomil Gold, Ultra Flourish) can be applied as a soil surface application under the vines 4-8 weeks before harvest. Alternatively, mefenoxam fungicides (e.g. Ridomil Gold/Bravo, Ridomil Gold/Copper) can be applied as a foliar spray beginning when crown fruit are 1/3 their final size. In home gardens, maneb (e.g. Maneb) can be used to prevent various fruit rots, including buckeye rot. Follow label harvest restrictions. Tie lower trusses up out of splash distance. Apply a peat mulch and water carefully once fruit is forming.