Phoma of chickpea
Phoma can be a serious disease of chickpea when soils remain wet for extended periods following sowing. Relatively few serious outbreaks have occurred in Victoria, however the disease is common in southern Australia.
Seed-borne infection often results in black-brown discolouration of the root near where the seed is attached (Figure 1).
Blackening may spread up the root and cause lesions at the base of the stem. Black lesions may completely girdle the base of the stem and root where infection is severe (Figure 2).
Initial above ground symptoms are small, dark tan coloured, irregular flecks on leaves, stems, and pods. The flecks on leaves enlarge to lesions and the surrounding tissue yellows. Within the lesions numerous pinhead-sized black fruiting bodies of the fungus develop. On the stem, similar but more elongated lesions form (Figure 3).
Pod lesions are sunken, with pale centres and dark margins, and may be covered by small black spots. The fungus may penetrate the pod and infect developing seeds. Badly affected plants may be totally defoliated when infected leaflets deteriorate and fall.
Phoma disease cycle
Phoma, caused by the fungus Phoma medicaginis var. pinodella can survive on infected seed, in soil and on crop residue from one season to the next.
Infection can occur at any stage of plant growth provided conditions are favourable. Moisture is essential for infection to occur.
Seed to seedling transmission of the disease only occurs when the soil moisture content is high enough. Spores produced on the diseased plants are carried by wind and rain splash onto neighbouring plants causing secondary infection.
Pod infection can occur when the fungus penetrates the pod wall and infects developing seeds late in the season.
Economic impact of phoma
The most serious outbreaks of this disease on chickpea in Australia have occurred in very wet years and are often associated with water logging. Phoma affected plants usually fail to set seed. When the disease is spread throughout a paddock it can significantly reduce grain yield.
The fungus can attack most pulses and pasture legumes and the disease is best controlled by crop rotation. The inclusion of non-legume crops in crop rotations prevents the carry-over of the disease from year to year.
Fungicide seed dressings can be used to control seed-borne infection.
Selecting chickpea varieties
All current commercial chickpea varieties are susceptible to the disease. Select the chickpea varieties best suited to your growing region.
Selecting chickpea seeds
The use of disease-free seed will help prevent seed to seedling transmission of this disease.
Treating chickpea seeds
Seed-borne infection can be controlled with fungicide seed dressings.
For more information see the Pulse Australia Bulletin Pulse Seed Treatments and Foliar Fungicides.
Selecting paddocks for chickpea crops
In paddocks where chickpeas have been affected by phoma, a three-year break from non-legume crops will minimise the disease risk. Crops that host phoma include:
- field pea
- faba bean
- vetch and legume pasture species
Cereal and oilseed crops will provide an effective disease break.
Follow the recommended sowing rates for your district and remember that sowing rates can vary between varieties.
Time of sowing
Plan to sow at the optimum sowing time for your district.
For the optimal sowing time for your district refer to the Victorian crop sowing guide.
No foliar fungicides are effective for the control of the disease.
If you need more information or help contact:
Field Crops Pathology
Grains Innovation Park
110 Natimuk Rd
Telephone: (03) 5362 2111
Or call the Customer Service Centre, 136 186