DISEASE

NAME
Anthracnose (General)
Various Anthracnose Species

Description
This fungus is a casual organism that attacks leaves, flower, fruit, seed and twigs of the host.

Symptoms
Circular black spots appear primarily on the leaves or fruit but may also occur on the stems and flowers. The spots have a definite margin that may turn purple or black with age. As the spot enlarges the centre dries and may fall out giving the leaf a shot hole appearance or become sunken in some fruit while others form soft blackened areas. Infected leaves turn yellow then fall prematurely and fruit that is infected generally becomes black and rotten as it matures.

There are many variations in the symptoms depending on the type of plant and the species of fungus but generally as the fungal spots merge they form brownish to black dead areas.

PlaneAnthracnose(Gnomonia platani) first appears on young leaves and as the leaves mature light brown spots appear along the veins and eventually engulf the entire leaf causing death. The twigs are also infected and often fall to the ground when dead and branches die after cankers appear lower down. This is a serious problem for Platanus occidentalisin North America.

Anthracnose in turf

The Anthracnose(Colletotrichumspecies) and (Microdochium bolleyi) infects winter Turf Grasses. At first yellow patches appears which turn red brown then the leaf blades turn whitish and die. This forms bare areas and (Colletotrichum species) forms spine-like fruiting bodies that are tiny and can only be seen using a hand lens.

Wither Tip(Colletotrichum gloeosporioides) forms spots on the leaves and flowers and the stems form cankers that cause wilting at the top of the branches. Commonly found on Aucuba species.

Source and Dispersal
The fungal spores are dispersed by wind from infected plants or parts of plants. It is also dispersed by splashing water or contaminated stock.

Favoured Conditions
The fungus prefers cool humid climates and is not commonly seen in warm coastal regions and may continue living in dead wood, leaf litter or harvested fruit.

Affected Plants
The Anthracnosespecies is found shrubs, vegetables, trees particularly fruit trees such as mango or macadamia and large trees such as Platanusspecies.

     Acer negundo

Acerspecies are infected by the Anthracnose (Gloeosporium aporcryptum). Irregular shaped light brown spots appear on the leaf, joining to form large dead brown areas and giving the leaf a scorched appearance. Leaves may be fully or partially damaged, often causing the leaf to die prematurely. During constant wet weather this can become a serious problem. Acer saccharinum(Silver Maple) and Acer negundo(Box Elder) are particular susceptible and small plants may be sprayed with a fungicide as the new foliage appears to help control infection

      Agave species

Agave species are susceptible to Glomerella Leaf Blight(Glomerella cingulate). This causes dark coloured depressed spots to appear on the leaves. The leaf apex dies and the spreading rot in Orchid species can infect the pseudobulbs causing the death of the plant.
Orchidssuch as Cattleya, Cymbidium, Cypripedium, Dendrobium, Epidendrum, Oncidium, Paphiopedilum, Phalaenopsis and Zygopetalumspecies are infected by Glomerella Leaf Blight(Glomerella cingulate).

Agrostis palustris(Bent Grass) is particularly susceptible to Anthracnose (Colletotrichumspecies) and (Microdochium bolleyi), but this fungal problem is also found on Cynodon dactylon(Couch), Lolium perenne(Ryegrass) and Festuca arundinacea(Tall Fescue). These grasses are infected in areas of poor drainage or where leaf wetness is prolonged. Low soil fertility may also contribute to infection and it is commonly found in coastal regions.

Anthuriumspecies are susceptible to the Anthracnose (Gloeosporium minutum) which causes circular spots on the leaves, along the margins. These meld together forming dead brown areas that dry and fall out. It is commonly found in a glasshouse situation. The spadix is also infected by Spadix Blight(Colletotrichum gloeosporioides) which forms dark spots that enlarge, spoiling the flower.

Antirrhinumspecies are susceptible to the Anthracnose (Colletotrichum antirrhina) which attacks stems and leaves forming sunken oblong spots that are yellowish with a brown margin.

Cactusspecies are susceptible to anthracnose causing shot hole disease, which attacks the pads of Opuntiaspecies (prickly pear). It appears and during the hot humid months of the year and is distinguished by the appearance of small brownish spots that turn grey with black spores under the drying skin. Control methods include removal of infected pads and treating wounds with disinfectant.

Digitalisspecies are infected by the Anthracnose (Colletotrichum fuscum). This fungus forms rounded spots that are purplish-brown and may have a purplish border. Fruiting bodies appear in the centre as the spots enlarge.

Leucadendronand Leucospermumspecies are susceptible to Anthracnose(Colletotrichum gloeosporioides). This causes the new growth to die back, leaf spots appear and cankers to form on the stems. It also causes damping-off of seedlings, which can be a major problem forProteaspecies as the fungus can be carried in the seeds.

Limoniumspecies are infected by Wither Tip(Colletotrichum gloeosporioides). This is a serious disease causing spots on the leaf, flower and stems or rotting the crown.

Ribesspecies are attacked by (Pseudopeziza ribis). This infection causes circular brown-black spots on the leaves and premature defoliation of the plant. The spots may also appear on the petioles or stems. Infected areas may be sprayed with wettable sulphur weekly.

Schizanthusspecies are infected by Anthracnose (Colletotrichum schizanthi) which forms eater soaked areas on the stems and petioles, preferring new growth and maturing with canker-like lesions that girdle the stems.

Symphoricarpos albusis infected by the anthracnose (Gnomonia cingulata) which infects the fruit causing cinnamon coloured spots and produces flesh coloured fruiting bodies. The affected fruit becomes black with rough texture, then is mummified before falling prematurely.
This species is also infected by the anthracnose (Sphaceloma symphoricarpi) which appears on the leaves as tiny dark purplish blackish spots with a grey centre. This infection also causes distortion of the stems and the fruit becomes pinkish with the dried up appearance. Controlmethods include removal of the infected wood or cutting back the shrub to ground level. Remove diseased material off site.

Tiliaspecies are infected by the anthracnose (Gnomonia tiliae), which forms light brown spots on the leaf venation, towards the tip and can defoliate an entire tree.

Spot Anthracnose (Elsinoe ilicis) infectsIlex cornutaforming black spots that may lead to leaf disorder. Opuntia species are infected by (Gleosporium cactorum) in warmer regions.

Vaccinium ovatum is infected by (Gloeosporium minus) and commonly known as Fleckand appearing on the leaf and stems.

Violaspecies are infected by (Colletotrichum violae-tricoloris) which produces brown blotches with black margins on the leaves.

Non-chemical Control
Avoid watering plants from above or wetting the foliage especially in the late afternoon. When planting allow space between each plant for good air circulation. Remove affected foliage or wood by pruning and dispose off site.
Turf grassesshould have well drained soils, high fertility and avoid excessive watering to reduce possible infection.

Chemical Control
Regular spraying where possible during the periods that are favourable for fungus development. Fungicides include;
Systemic types, Biteranol, carbendazim, triforine
Protectants; chlorothalonil, copper oxychloride, mancozeb, thiram, zineb

Note
Always read the label for registration details and direction of use prior to application of any chemicals.