Cultures of pathogenic Phomopsis fungus. Phomopsis sp. is a normally benign fungus that under certain conditions becomes a destructive pathogen affecting plants. Infection causes spots on the leaves, weakening of stems and stunted fruit development. It is an agricultural pest as it can ruin entire crops of soybeans, citrus fruit, blueberries, apples and cucumbers. It is hoped that by better understanding of the reasons the fungus becomes pathogenic, it can be controlled.