DISEASE
 
   NAME
     Leaf Blight (General)
     Various Leaf Blight Species

Description
A fungal problem that attacks the leaves and may spread to other parts.

Symptoms
Generally light to dark brown patches or spots appear on the leaves. These join together causing the leaf to become dried and withered. Infected leaves fall prematurely and dieback occurs in the stems. The overall effect is a sparsely foliaged tree.
On Carrots the fungus (Alternaria dauci) forms small spots that turn the affected area yellow. This can spread over the entire plant resulting in the death of the plant.

Leptosphaerulina Leaf Blight (Leptosphaerulina species) infects Turf Grass. Generally the leaves turn light brown and wilt and from a distance, appear as irregular yellow brown patches. The leaves initially die back from the tip forming water soaked lesions that extend to the sheath and give them a bleached appearance. The fruiting bodies develop on the dead material and the spores are distributed by wind. This fungus appears on many grasses but is only a significant problem for Agrostis palustris (Bent) particularly during hot humid conditions.

Palm Leaf Blight (Pestalotia palmarum) forms grey brown spots on the leaf blades and penetrates into the leaflet axil turning the leaflets brown and killing the frond. Spores appear in black masses on the upper leaf surface.  Another Palm Blight (Pestalotia palmicola) infects leaflet tips and progresses down throughout the frond turning it brown.

Strawberry leaf blight (Phomopsis obscurans) infects the leaves primarily with a triangular shaped patch that is reddish turning to brown. It is also found on the petioles and stolons and the tiny black fruiting bodies occur on damaged areas.

The fungal Leaf Blight (Didymascella thujina) forms brownish raised spots on small leaves tuning them brown during late spring and giving them a scorched, dead appearance, eventually falling from the plant during autumn. Commonly found on large Thuja species, but may also attack smaller varieties. 

Umbrella leaf blight (Alternaria panax) forms dark brown to black patches that enlarge and distort immature leaves.

Source and Dispersal
The spores originate from other infected trees and are dispersed by wind or infected nursery stock. Once a plant is infected it can moves rapidly throughout. Certain species of tree can tolerate infection.

Favoured Conditions
It prefers humid still conditions with warm temperatures and is particularly a problem in tropical areas.	

Affected Plants
A wide range of plants including vegetables, shrubs and trees may be affected.

Hibiscus species leaves are infected by Pellicularia koleroga a soil born fungus.

Leaf Blight (Pestalotia palmarum) infects several palms including Syagrus romanzoffianum and leaf blight (Pestalotia palmicola) attacks Phoenix, Syagrus and Washingtonia species.

Primula species are infected by the Leaf Blight (Phyllosticta prinulicola).

Syringa species are infected with the leaf blights (Cladosporium herbarum) and (Heterosporium syringae) which form large brown spots on the leaves that become dry and fall out.

Tilia species particularly young trees are in infected by the casual fungus (Cercospora microsora), which forms brown spots with darker borders, resulting in the death of the leaf. 

Tsuga species are infected by the leaf blight (didymascella tsugae), which turns the leaves brown causing them to fall prematurely. 

Non-chemical Control
On small trees remove and destroy the infected parts or in a nursery remove and destroy infected stock. Perennials and annuals should be removed and destroyed.  Remove any fallen leaves from around the base of the plant as they contain fruiting bodies. 

Chemical Control
Plants may be sprayed at five day intervals with copper oxychloride if possible. Turf infected with Leptosphaerulina Leaf Blight may be sprayed with a broad spectrum fungicide.
Note
Always read the label for registration details and direction of use prior to application of any chemicals.