What is wrong with my kowhai tree?

Are the older leaves turning yellow and wilting, an overall decline in plant vigor is apparent?

Does the plant wilts, leaves turning brown or pale yellow?

Are there any rust-colored spots on foliage?

Are there any oozing cankers on the branches and buds?

Are the leaves mottled with yellow, young growth may be narrow and twisted?

These symptoms indicate fungal disease Verticillium wilt. Verticillium infects a wide range of plant species. Destroy all infected plants, as there is no cure. Prevent problems by presoaking seed in a 10 percent bleach solution.

These symptoms are most likely caused by Fusarium wilt. There is no cure for Fusarium wilt, so the infected plants should be destroyed. Do not plant any susceptible plants to Fusarium wilt in the same spot for several years.

Rust-colored spots on foliage indicate a fungal disease - Rust. Provide good air circulation around plants by thining them. Avoid making leaves wet when watering. All infected leaves should be removed. Spray leaves with sulfur early in the season to prevent rust or to treat mild infections.

Oozing cankers on the branches and buds are caused by bacterial blight. The spread of the disease is greatest during humid, wet weather conditions. Practice good garden hygiene at the end of the season and discard, do not compost, possibly diseased plants and plant parts. Space plants to allow for adequate air circulation. Prune all infected branches below cankers.

Leaves mottled with yellow usually indicate a Tobacco mosaic virus. There is no cure for viral diseases, remove and destroy infected plants. Presoak seed in 10 percent bleach solution before planting to prevent problems. Control aphids as they are the most likely carriers of the tobacco mosaic virus.

Mineral deficiencies can cause tip chlorosis or necrosis or cause foliage to discolor, fade, distort, or become spotted, sometimes in a characteristic pattern that can be recognized to identify the cause. When nutrient deficiencies occur, nitrogen and iron are the most commonly seen deficiencies. Apply only the mineral found to be deficient. Excess nutrients, on the other hand, cause symptoms like leaf tip dieback, marginal leaf chlorosis, necrosis (or burn), branch dieback, and pest problems. In this case, you should provide good drainage, and use good practices during fertilization and irrigation.