ANTHRACNOSE
The main symptom of these anthracnose diseases appear as either; dead (dark coloured) spots, or sunken spots with a slightly raised rim.
Spots can be small or large.
Dark brown, purplish, red or black sunken spots appear on stems, fruits or seeds.
This disease may cause fruit drop and fruit rot.
Plants Affected:
Common diseases on beans, grape vine and willows.
Also deciduous trees including walnut, oak, sycamore, linden, elm and hickory.
Various ornamentals including azalea, cyclamen, sweet pea, poinsettia and violet.
Some fruits including apple, cranberry and raspberry.
Control:
Spray with copper-based sprays such as Bordeaux.
Zineb and Maneb are being recommended more often than copper sprays today.
Anthracnose of Beans (Colletotrichum lindemuthianum)
Symptoms: On small plants: dark brown marks around 12mm long on stems.
On mature plants: spots appear on stems, leaves and pods; veins become blackened; black sunken spots to 12mm across on pods; long black sunken marks may occur on stems.
Control: Plant only disease-free seed. Do not collect seed from diseased plants.
Spray with mancozeb or zineb, ensuring undersides of leaves are sprayed.
Do not plant beans in an area previously affected by this disease for a minimum of two years. On a commercial scale this disease is considered relatively rare now due to widespread use of approved disease free seed.
Anthracnose of Grapes (Glomerella spp.)
Also called ripe rot because it appears when the fruit is almost ripe.
It is most likely to occur in warm, humid conditions.
Symptoms: On white grapes: small red brown spots appear first, spreading and becoming darker; dark purplish in the centre and light brown on the edge.
On red grapes: the berry rots the same as for white grapes, but there is no real change in skin colour. This disease can also affect other fruits.
Control: The fungus spreads from affected stems, leaves & fruit left from the previous autumn. This makes it important to collect and burn prunings, fallen leaves, fruit, etc. which might spread the infection. It can also be spread by wind or insects.
Pay attention to plants growing between or under vines. Rotate under vine plantings.
Spray with Bordeaux, mancozeb, or benomyl.
Anthracnose of Cucurbits (Colletotrichum orbiculare)
This is a very destructive disease on many cucurbits, but particularly watermelon and cantaloupe. All parts except roots can be affected.
Symptoms: Often at first small, water soaked, yellow patches or spots on leaves appear; which grow up to 2 cm diameter. They turn black on watermelons, brown on other cucurbits. Fruit stalks sometimes develop dead patches, which cause fruit to become darkened, then shrivelled, then to die. Fruits may become infected close to ripening (round sunken watery patches develop on the skin, then expand and develop dark centres.
Stems can also sometimes become infected, leading to death of the entire plant.
Infected parts become dry and break up. The disease can overwinter in fruit or even in seed.
Control: Spray Mancozeb or Zineb every 7 to 14 days once plants start to run.
Want to Learn More?
Check out publications in the ACS Bookshop: www.acsbookshop.com/
For more information on Courses on Pests & Diseases:
In Australia: http://www.acs.edu.au/Courses/General-Horticulture-courses.aspx
In the UK: http://www.acsedu.co.uk/Courses/General-Horticulture-Courses.aspx
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