Grease Spot

This is caused by the bacterium Pseudomonas passiflorae and is one of the most serious diseases of passionfruit in New Zealand. It infects leaves, stems and fruit, leading to severe crop losses and even death of vines.

Symptoms
On leaves, it causes irregular olive-green to brown lesions, often surrounded by a light-yellow halo. If unchecked severe defoliation can result. On the stems of young growth the first signs of infection are small slightly sunken, dark-green, water-soaked spots. These develop into light-brown, markedly depressed areas.

On older wood, symptoms range from small, slightly sunken, smooth, dark-green circular spots, to large, dark-brown, cracked lesions, which may completely girdle shoots and kill vines. Early signs of infection on the fruit are small, dark-green, oily spots. These develop into roughly circular, greasy, or water-soaked patches. Premature fruit drop and fruit decay result. Grease spot is said to be most active in autumn and winter, between March and August. However, a condition known as hard grease spot, also caused by Pseudomonas passiflorae, has become prevalent on passionfruit and is active in summer. The symptoms are similar to ordinary grease spot except that the fruit infections dry out and cause a hard brown patch on the skin, instead of leading to decay. This results in a downgrading of fruit and loss of income.