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.

Description

Blackspot causes lesions on the stems, leaves, pods and seeds. Lower stem lesions appear as purplish black streaks, which can cause rot at the plant base and sometimes death. Leaf spots are small, dark brown, and irregular shaped and dispersed over the leaf. Spots on pods are purplish black and can merge to develop sunken areas. Infected seeds can be discoloured and look purplish brown.

Blackspot is seed-borne or soil-borne and can survive on infected stubbles. Ascospores are the main source of primary infection, produced in perithecia on old stubbles and are released and spread via wind and rain. Infection can occur at any growth stage and in wet weather the disease proliferates. Infection can also arise when infected seed is planted and typically in wet years the effect from seed-borne infection is worse.

Control

Although a serious disease, blackspot can be successfully managed. Removal of infected field pea trash and volunteers is vital. Disease-free seed should be treated with a seed dressing before sowing, and when planting, aim to have a separation of at least 500 m from the previous year’s pea stubble.

The fungi can remain in the soil and on trash for several years and therefore as a minimum, field peas should not be grown in the same paddock more than once every three years.

Avoid sowing early with high seeding rates as this increases the exposure of seedlings to the disease and can produce a large crop canopy, creating conditions conducive for the disease to develop.

Control of blackspot with fungicides is not considered economical unless yields are likely to be over 2 t/ha. Aviator^® Xpro^®is a protective and curative fungicide which should be applied before infection develops. Crops should be monitored after each rainfall event for further blackspot infections.

Aviator Xpro is registered for the control of blackspot (Mycosphaerella pinodes, Phoma medicaginis var. pinodella, Ascochyta pisi) in field peas.

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.

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.

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.

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

CropPro (2014), ‘Ascochyta Blight (Blackspot) of Field Peas’, http://www.croppro.com.au/crop_disease_manual/ch07s02.php

Agriculture Victoria (2016), ‘Black spot of field peas’, Department of Economic Development, Jobs, Transport and Resources, Victoria, AG0150, http://agriculture.vic.gov.au/agriculture/pests-diseases-and-weeds/plant-diseases/grains-pulses-and-cereals/ascochyta-blight-of-field-peas

Herbiguide (Viewed Oct 2019), ‘ Ascochyta Black Spot of Peas’ http://www.herbiguide.com.au/Descriptions/hg_Ascochyta_Black_Spot_of_Peas.htm