Anthracnose

Colletotrichum gleosporioides (Avocado), Colletotrichum gleosporiodes and Colletotrichum acutatum (Mango), Colletotrichum orbiculare (Rockmelon, watermelon, honeydew and cucumber), Colletotrichum musae (Banana), Colletotrichum lindemuthianum (Bean), Colletotrichum lupini (Lupin), Sphaceloma rosarum (Rose), Microdochium panattonianum (Lettuce), Elsinoe ampelina (Grape)

Anthracnose is one of the most prevalent and serious fungal diseases of many horticultural crops in Australia. It is also a problem in broadacre cropping programs, affecting pulse crops including lupins and lentils, although it hasn’t yet been discovered in lentil crops in Australia. Anthracnose is also known as pepper spot disease on avocado twigs, de-greening burn in citrus, blossom blight in mango, and black spot in grapes. Yield losses from anthracnose are generally associated with prolonged periods of wet weather.

Refer to the links below for more detailed information on anthracnose in other crops.

Description

In avocadoes, anthracnose presents as a fruit rot that remains latent until the fruit ripens and is often only discovered when being prepared by the consumer.

In cucurbits, the symptoms vary between hosts. On the leaves of cucumbers and melons, small brown spots with halos appear which can later develop into round, reddish spots before the centres fall out, resulting in a ‘shot hole’ appearance. On watermelon leaves, the spots are angular, irregular and turn dark brown or black. Spots also appear on the stems and fruit.

In mangos, young leaves are the most susceptible to infection. Small, black and irregular spots form before expanding to larger areas that eventually dry and fall out. The disease can also cause blight of flowers and young shoots and in mature fruit, upon ripening dark brown to black spots form with orange-pink spore masses.

In lettuces, symptoms appear as tiny black spots on the leaves before turning yellow and then brown with a reddish margin as they grow (up to 4 mm). Like cucurbits and mangos, the centres of the lesions can also fall out.

Anthracnose can be seed-borne (although not in lettuce) and carryover via crop residue on the soil before the spores are spread to infect new plants via wind and rain splash.

Control

Management of anthracnose across a range of crops requires an integrated approach using cultural methods and registered fungicides. In some crops, it can be difficult to obtain good control with fungicides as it is hard to get fungicide coverage where it is required. i.e. leaf bases of lettuces. Registered fungicides are also generally best applied before an infection event (i.e. rain) rather than afterwards.

Cultural practices to manage anthracnose include;

Minimising periods of leaf wetness

Rotating crops to allow spores on the soil or crop residues to lose viability

Remove or bury contaminated trash residue

Allow a buffer zone in horticultural crops to minimise disease spread from wind or water splash

Control alternative hosts

Plant more tolerant varieties

Prune trees to aid airflow and reduce humidity

Inspect regularly to identify disease symptoms early.

Serenade® Opti is registered for the control of anthracnose in avocados, mangos and other tropical fruit, excluding bananas, and should be applied preventatively before disease symptoms are visible. Antracol® is registered for the control of anthracnose in watermelons and rockmelons (Qld, WA only) and Blue Shield® is registered for the control of anthracnose in avocados, lettuces, mangos and macadamias. Check the label for additional information, including State restrictions.

Related Pests

Blossom Blight

Monilinia laxa

Blossom blight is a rot disease of stone fruit and hosts include apricots, cherries, nectarines, peaches, plums and almonds. Blossom blight is also a symptom of brown rot, which causes the death of flowers, fruit and occasionally shoots Blossom blight can result in significant losses as it can reduce fruit set and potential yield. Apples and pears can also be affected by blossom blight, although economic damage is rarely seen.

Black spot

Elsinoe ampelina (grapes - anthracnose), Alternari solani (tomatoes, capsicums and potatoes - target spot or early blight), Venturia inaequalis (apple and pears - apple and pear scab), Guignardia citricarpa (citrus), Xanthomonas campestris (mangoes - bacterial black spot), Phoma medicaginis var. pinodella, Ascochyta pisi (field peas - black spot complex)

A number of horticultural crops are challenged by black spot, which is also referred to by a number of names. It affects grapes where it is also known as anthracnose. Black spot affects apples and pears and is also known as apple scab and pear scab. In mangoes, black spot is caused by a bacteria rather than a fungus and is referred to as bacterial black spot. In broadacre, field peas are also affected by black spot.

Black spot Grapes

Elsinoe ampelina

Black spot, also known as anthracnose in grapes, is a serious disease, particularly in areas which experience cool wet springs which favour disease outbreak. Currently it is successfully managed with fungicides, however prior to their introduction, blackspot was a major problem. Table grape varieties including sultana and red globe are more prone to black spot than wine grapes. Once established black spot is unrelenting and regular treatments are required to manage it.

Refer to links below for more information on black spot in other crops.

References

Applied Horticultural Research (Viewed December 2019), ‘Fact Sheet: Management of Lettuce Anthracnose’, (http://ahr.com.au/wp-content/uploads/2015/03/Management-of-lettuce-anthracnose.pdf

Department of Agriculture and Fisheries (2018), ‘Anthracnose’, Queensland Government,
https://www.daf.qld.gov.au/business-priorities/agriculture/plants/fruit-vegetable/diseases-disorders/anthracnose

Department of Agriculture and Fisheries (2018), ‘Pests and diseases of avocado crops’, Queensland Government, https://www.daf.qld.gov.au/business-priorities/agriculture/plants/fruit-vegetable/fruit-vegetable-crops/avocado/pests-and-diseases-of-avocado-crops

Jackson, G (2017), ‘Cucurbit anthracnose (200), Pacific Pests and Pathogens – Fact Sheets, PestNet, http://www.pestnet.org/fact_sheets/cucurbit_anthracnose_200.pdf

Minchinton, E (1999), ‘Anthracnose of beans’, Agriculture Victoria, http://agriculture.vic.gov.au/agriculture/pests-diseases-and-weeds/plant-diseases/vegetable/anthractnose-of-beans

Tsatsia, H and Jackson, G and (2017), ‘Masngo Anthracnose (009), Pacific Pests and Pathogens – Fact Sheets, PestNet, http://www.pestnet.org/fact_sheets/mango_anthracnose_009.htm