Mango bacterial black spot

Xanthomonas campestris pv. mangiferaeindicae

Bacterial black spot (BBS) was first found in Australia in the early 1980’s and it now appears in most northern mango growing areas of Australia. It has the potential to be a serious disease of mangos, in some cases up to 90 per cent of fruit is discarded due to spots on fruit deeming them unacceptable for market.

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

Description

Bacteria is concealed in stem lesions (cankers) on seedlings and bud wood from which it can spread to leaves and fruit. BBS can be present without symptoms, not being detected until the plant has grown. Spread is driven by wind and rain and favoured by warm humid conditions, initial infection occurs through natural openings in stems and leaves, while fruit injuries from wind damage can provide additional entry points.

Leaf lesions are black, raised, angular areas often surrounded by a yellow halo. Large areas of infected leaf turn grey and crack. Elongated lesions (cankers) on the stem form on bark and can result in terminal dieback. Affected fruit form black, oval to irregular raised spots, which when merged, crack and ooze sap full of bacteria, resulting in quality downgrades or rejection.

Control

To minimise the risk and spread of BBS, source disease free plants and plant in sites which are protected from wind. Trees should be pruned to prevent limbs rubbing together and pruning tools should be sterilised with bleach. During harvest remove fruit by clipping stems rather than tearing fruit off which reduces penetration points for the disease. Remove infected material after harvest and destroy it to reduce disease risk for the following year.

Monitor leaves for spots and fruit for raised black spots. If BBS is present, an application with a copper fungicide every two weeks may be required from panicle emergence to fruit set. Blue Shield® is registered for the control of BBS in mangos.

Related Pests

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.

Blackspot of field peas

Mycosphaerella pinodes, Phoma mediccaginis var. pinodella, Phoma koolunga, Ascochyta pisi

Commonly referred to as ascochyta blight, blackspot is one of the most serious diseases of field peas and is widespread in Victoria and South Australia. In field peas, blackspot is produced by four different pathogens, producing symptoms that are indistinguishable from each other. Yield losses of up to 60 per cent have been reported, particularly in wet seasons.

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

Black Spot Tomatoes and Potatoes

Alternaria solani

Black spot, also commonly known as early blight or target spot, is a serious fungal disease affecting vegetables belonging to the Solanaceae family. Disease hosts include tomatoes, potatoes, capsicums and eggplants. Outbreaks are favoured by warm, wet growing conditions and yield losses can be significant.

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

Black Spot Apples and Pears

Venturia inaequalis (Apple scab), Venturia pirina (Pear scab)

Black spot, also known as apple scab or pear scab, is a serious disease found in pear and apple growing regions across Australia. Whilst symptoms in apples and pears are similar, the disease is caused by different fungi and cross infection from one host to the other isn’t possible. Leaves and fruit at early development are highly susceptible and serious yield and quality reductions are likely if not managed properly, especially in wet seasons.

Symptoms in pears and apples are very similar and therefore have been described as such unless otherwise indicated.

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

References

Pestnet (2017), ‘Mango bacterial black spot’, Pacific Pests and Pathogens – Fact Sheets, http://www.pestnet.org/fact_sheets/mango_bacterial_black_spot_213.htm

Pitkethley, R (2006), ‘Bacterial Black Spot of Mangoes’, Agnote No: I24, Northern Territory Government, https://dpir.nt.gov.au/__data/assets/pdf_file/0016/233611/605.pdf

Stovold, G and Dirou, J (2004), ‘Blight Diseases in mangoes’, NSW Department of Primary Industries (DPI), https://www.dpi.nsw.gov.au/__data/assets/pdf_file/0009/120114/blight-disease-mango.pdf