A field of chickpea plants affected by Ascochyta blight

Quick links to topics below:

• Ascochyta blight
• Chickpea variety ratings
• Phytophthora root rot
• Botrytis grey mould
• Viral diseases
• Environmental disorders
• Fungicide registrations

Ascochyta blight (causal fungus: Ascochyta rabiei)

Industry note: Ascochyta blight is a serious disease of chickpeas. Complacency about Ascochyta is a significant threat to the northern region chickpea industry. It is vitally important for the industry to follow protocols for managing Ascochyta blight.

For southern Queensland consult the Chickpea Disease Management Strategy - Northern Region 2008

For central Queensland consult Central and Coastal Queensland - Ascochyta Blight Management.

Symptoms of early Ascochyta blight infection are often very difficult to detect, because they tend to be in the lower plant canopy. Images of Ascochyta blight symptoms can be sourced from the above documents and Symptoms and Identification of Ascochyta Blight in Chickpea.

There can be a strong temptation to back off in both seed treatment and program spraying, and adopt a wait-and-see approach. This approach should be avoided, because:

• several successive winter growing seasons of dry weather usually results in low levels of Ascochyta blight in chickpea crops, which can lead to complacency in years of good rainfall, when the risk from the disease is much greater
• the consequences of adopting a wait-and-see approach could result in a need to resort to more expensive fungicides (chlorothalonil), higher final levels of the disease, and even the possibility of crop failure under wet conditions.
• it is critical that we stay on top of the Ascochyta problem in this region and that we continue preventative disease strategies developed in consultation with industry.

Key points preventing ascochyta

• Implement the Ascochyta management strategy appropriate to your region and the paddock´s risk situation (high, medium or low). Further details are outlined in the Chickpea Disease Management Strategy - Northern Region 2008 and Central and Coastal Queensland - Ascochyta Blight Management.
• If high levels of Ascochyta infection have been observed on volunteer chickpea plants over the summer fallow period, avoid planting adjacent to, or near last year´s chickpea ground. Use a registered herbicide to kill chickpea volunteers.
• Sow within the optimum planting window for your district. Consider deep planting (moisture seeking) provided you have high-germination, high-vigour seed. Sowing rates will need to be increased when moisture seeking.
• Always sow seed treated with a thiram-based fungicide. Growers in coastal and central Queensland are urged to use seed sourced from crops grown in central Queensland.
• Assess whether row-cropping configurations and band-spraying of fungicide/insecticides is practical.
• Assess your capability to implement early harvest management. Understand the correct growth stage for application of desiccants.

The information above is based on current knowledge and understanding. However, because of advances in knowledge, growers are reminded to ensure that information they rely on is up-to-date and to consult with their local Queensland Primary Industries and Fisheries or private agronomist.

Three levels of Ascochyta risk in the northern region

Low-risk areas (Central Queensland)

Ascochyta has now been detected in Central Queensland in several Dawson-Callide and Central Highland crops, but has not been found in coastal Queensland crops. The seasonal weather conditions in Central Queensland are considered to be not as conducive to Ascochyta blight as conditions in southern Queensland. Please check protocols for managing an outbreak and check on media reports and this webpage for updates.

Medium-risk areas

Most chickpea crops grown in southern Queensland and northern New South Wales are considered to be in the medium-risk category. Chickpea crops in this zone are expected to contain some level of Ascochyta, which could result in serious economic losses if not effectively managed.

High-risk situations

The crop is considered to be at high risk of Ascochyta infection if:

• susceptible and very susceptible varieties (see table in step 4 below) are being grown
• planting in close proximity, or adjacent to last year's chickpea paddocks
• where the preventative management strategies have not been followed i.e. using untreated seed of unknown disease status.

In these situations the control measures should be strictly followed. The major change in the fungicide recommendations is that chlorothalonil will often be required much earlier in the spray schedule, particularly during showery, wet conditions.

Step guide to avoiding Ascochyta

1. On-farm hygiene (fallow management)

The Ascochyta fungus can only carry over from one season to the next on infected chickpea seed, chickpea stubble, and volunteer chickpea plants. The fungus can build up rapidly on volunteer plants or chickpea stubble, especially if wet conditions are experienced during the spring-summer period. Monitor chickpea stubble paddocks and volunteer plants for any evidence of Ascochyta over the summer-autumn period (especially after heavy rain, flooding or strong winds).

To reduce the potential impact of diseased stubble as a source of infection either:

• avoid planting adjacent to, or in proximity to last year's chickpea paddocks
• maintain a cultivated fallow for 2-4 months, in which all stubble is buried (the Ascochyta fungus only survives 2-4 months when buried), and volunteer chickpea plants are controlled.

2. Paddock selection

Growers should aim to separate this year´s chickpea crop from last year´s chickpea stubble by as great a distance as practical. The Ascochyta blight pathogen can survive in infected chickpea stubble, which can be spread from an infected paddock by wind or overland water movement. While a minimum distance of 500 m is recommended, a kilometre or more is preferable when situated downhill, or on a floodplain. Growers need to re-assess their rotational farming program, and grow chickpeas in a large single block or blocks, rather than scattered in smaller blocks or strips around the farm.

3. Seed quality

Plant high-quality seed that has a low risk of Ascochyta infection. Aim for a plant population of 25-30 m². All seed should be treated with a registered thiram-based seed treatment, and sourced from a crop where Ascochyta was not detected (low-risk seed). Do not mix inoculant directly with fungicide seed dressings. Guidelines for treatment are outlined in the publication, 'Treating chickpea seed with P-Pickel T^®'. Seed retained on-farm should be from the cleanest paddocks, preferably those where the disease was not detected during the previous season. Seed for central and coastal Queensland plantings must be sourced from crops grown in Central Queensland.

The use of Pulse Australia industry recommended seed is preferred if buying-in seed. This seed has undergone a pre-harvest inspection, seed testing, and treatment with P-Pickel-T ^® at a registered plant. A list of growers supplying recommended seed is available on the Pulse Australia website. Avoid using severely weather damaged seed as it often results in patchy, uneven plant stands, reduced plant vigour, lower yields and uneven and delayed maturity.

4. Avoid varieties highly susceptible to Ascochyta

Avoid planting susceptible and very susceptible varieties in high-risk Ascochyta situations. Flipper and Yorker have the best level of resistance currently available in commercial desi lines suited to southern areas of Queensland, and are the preferred variety in high-risk Ascochyta situations. All varieties agronomically suitable for central and coastal Queensland are very susceptible or susceptible to Ascochyta blight.

Agronomic and marketing issues are other factors to consider when selecting a variety.

Chickpea variety ratings

Description	Ascochyta blight	Phytophthora root rot	Virus diseases	Botrytis grey mould
Resistant (R)	Genesis 090, 508, 509 & 425
Moderately Resistant (MR)	Flipper	Yorker	Gully
Moderately Resistant - Moderately Susceptible (MR-MS)	Yorker, Almaz, Nafice	Flipper, Jimbour, Kyabra, Moti*	Flipper
Moderately Susceptible (MS)		Genesis 425, Howzat,		Genesis 509, Howzat, Moti*
Susceptible (S)	Amethyst, Howzat, Jimbour, Kaniva, Kyabra	Almaz, Amethyst, Genesis 090, Genesis 508, Genesis 509, Gully, Nafice	Almaz, Amethyst, Bumper, Genesis 090, Genesis 508, Genesis 509, Genesis 425, Howzat, Jimbour, Kaniva, Kyabra, Nafice, Yorker	Almaz, Amethyst, Genesis 090, Genesis 508, Genesis 509, Genesis 425, Howzat, Jimbour, Kaniva, Kyabra, Nafice, Yorker
Very susceptible (VS)	Bumper, Gully, Macarena Moti*	Bumper, Kaniva, Macarena		Gully

NB. Reactions to diseases vary with seasonal weather conditions and/or inoculum loads. For example, a variety rated moderately susceptible to Ascochyta may sustain severe yield losses or even plant death if planted next to last year´s chickpea paddock. These ratings are for average disease pressure at the start of the season and average conditions for the disease during the season. * Moti is not to be grown south of Theodore, Queensland.

5. Plant on 50-100 cm row spacings

Planting on a row crop configuration (up and back on 50-100 cm rows) is recommended to assist with tram-lining and ground application of protectant fungicides.

Other benefits of wider rows include:

• improved aeration can slow the spread of disease
• use of precision planters provide more uniform stands
• provide an option for inter-row cultivation or directed (shielded) sprays
• band spraying can cut fungicide/insecticide costs
• more efficient harvesting, especially in lighter crops.

Crops on 1 m spacings can be more predisposed to lodging. This can be partially offset by reducing the target plant population to match the row spacing.

6. Planting time

Plantings made prior to the recommended planting window tend to be more vegetative, and are more predisposed to frost, Ascochyta and Botrytis grey mould. Weigh the risks against problems encountered with delayed planting.

See recommended planting timetable for suggested sowing times.

7. Early program spraying with fungicides

Early application of fungicides is critical in restricting the early development and spread of Ascochyta. Comprehensive details of the spray strategies for particular varieties are provided in Chickpea Disease Management Strategy - Northern Region 2008 and Central and Coastal Queensland - Ascochyta Blight Management. The fungicides currently registered to control Ascochyta blight in chickpea are preventative, not curative.

Southern Queensland

Prophylactic sprays (programmed sprays applied before symptoms are found) are necessary for most varieties. The 2-1-0 rule needs to be applied. Two prophylactic sprays are required for Ascochyta S and VS varieties, including Jimbour, Kyabra, Amethyst and Macarena. One prophylactic spray is required for the MR-MS variety Yorker, while for more resistant (R) varieties eg., Flipper, no prophylactic sprays are necessary. A mancozeb product at a low rate (eg., 1 kg/ha of a product with an active ingredient of mancozeb at 750 g/kg) is the preferred option for these early sprays. The recommended timing of these prophylactic sprays is:

• First prophylactic spray (for MR-MS, S and VS varieties) - prior to the first rain event, three weeks after emergence, or at the three leaf stage, whichever comes first
• Second prophylactic spray (for S and VS varieties) - three weeks after the first spray, but if two weeks have elapsed since the first spray and rain is forecast, apply the second spray before the rain event

When Ascochyta blight is found in any variety (including Yorker and Flipper), a mancozeb or chlorothalonil product (eg., 2 kg/ha of a product containing 750g/kg of mancozeb or 1 L/ha of a product containing 720 g/L of chlorothalonil) should be applied before the next rain event. Further sprays may be required if wet weather persists.

Central and coastal Queensland

The risk from Ascochyta blight in these regions is considered to be lower than in southern Queensland, due to generally less favourable weather conditions, so a different strategy is recommended for the regions in 2009. However, extreme care needs to taken, and careful monitoring for Ascochyta blight must be conducted, because under the right weather conditions the disease is capable of causing significant yield losses even in these regions. Chickpea crops irrigated from overhead sprinklers or centre pivot are at greater risk than other crops. The following two risk secenarios, with their respective spray strategies, have been identified:

• Low Risk - fungicide-treated seed purchased from a seed supplier, planted into or beside a paddock in which chickpeas have not been grown for the past three seasons. Such crops should be carefully monitored, particularly 7-10 days after rain events, and if Ascochyta blight is found, apply a mancozeb product (eg., 2 kg/ha of a product containing 750 g/kg mancozeb) before the next rain event. Closely monitor the crop and repeat as necessary.
• Medium Risk - all other situations, including planting seed from any source into or adjacent to a paddock in which chickpeas were grown within the last three seasons, and planting grower-kept seed into any situation. The seed must be treated with a thiram-based dressing prior to planting. A foliar spray of a mancozeb product (eg., 1 kg/ha of a product containing 750 g/kg) should be applied before the first rain event. The crop then needs to be carefully monitored, and if Ascochyta blight is found, apply a mancozeb product (eg., 2 kg/ha of a product containing 750 g/kg mancozeb) before the next rain event. Repeat as necessary.

Be aware of the withholding periods for these fungicides and follow label directions closely. No more than four sprays of either a mancozeb or chlorothalonil product can be applied to a crop. Crops sprayed with a chlorothalonil-based fungicide cannot be grazed or fed to livestock. Chlorothalonil fungicides for use on chickpeas to control Ascochyta blight are under APVMA permit only until November 2009.

8. Monitor the crop closely

While a rain event is the major means of spread within a crop, dews alone can allow spread on a plant, or between plants that are touching. Irrespective of the water source, the plant only needs to be wet for six hours for infection to occur.

Spring is a critical time as it is the most rapid period of crop growth. Also, during pod fill all varieties can be considered to be susceptible, so extra care needs to be taken during this period. Monitoring should continue through to 10-14 days prior to harvest as the disease can spread rapidly on senescing crops.

Crop inspections need to be conducted in different parts of a paddock, with emphasis placed on inspection of the lower parts of the canopy.

9. Use correct fungicide application techniques

Fungicides used for the control of Ascochyta blight are only protectants and need thorough coverage over the entire plant to prevent further infection and spread. Growers need to ensure that their application equipment is set up to maximise spray coverage on the plant, i.e.:

• a flat fan nozzle at a pressure that will produce a small droplet size
• minimum water volume for ground application (preferred method) is 80 L/ha, for aerial application the minimum is 30 L/ha.

Refer to Chickpea Disease Management Strategy - Northern Region 2008 for further information.

10. Harvest as early as possible

Harvest as early as practical to minimise ascochyta infection on pods, and maximise profitability of the crop. Ascochyta can spread rapidly on senescing or mature chickpea plants, and can create marketing problems if the grain receival standard for Ascochyta infection is exceeded. (See Pulse Australia for current minimum receival standards) Harvesting chickpeas at 14-15% and either drying or aerating will normally result in higher yields, better quality, fewer harvest difficulties, and less problems with late Ascochyta infection. While PH wheat harvest normally receives the priority at harvest time, in order to maximise returns, harvest delays can be just as costly to the chickpea crop that is commonly worth $350-$450/t.

The strategies outlined above are designed to assist growers produce a profitable chickpea crop this coming season. While adoption of the management package does not guarantee complete freedom from Ascochyta blight, adhering to the appropriate strategy should minimise the risk of incurring serious economic losses.

Phytophthora root rot (causal organism: Phytophthora medicaginis)

This root-rot disease has the potential to cause serious losses and is widespread in southern Queensland. It is most prevalent under cool, wet conditions and waterlogged soils. The fungus survives in the soil for up to 3-4 years, and on other legume hosts, mainly lucerne and pasture medics. Phytophthora-infested soil can be spread by water and on machinery.

Infected plants usually occur in patches in low-lying areas of a paddock. Occasionally, individual plants over an entire paddock may be affected if the weather conditions are conducive, and there has been a previous history of the disease in the paddock. The lower leaves turn yellow, wilt, and begin to die off. Below-ground the lateral roots will be rotted off, and later the taproot will decay and turn dark brown-black. Diseased plants can be easily pulled from the ground.

Assess the risk of phytophthora root rot prior to planting, based on previous paddock history, and select a variety with some resistance (Yorker, Flipper, Jimbour, Kyabra and Moti have useful resistance) if there is any likelihood of this disease. Unlike Ascochyta blight there are no in-crop management options.

While the disease is usually observed late in the season, infection can occur from seed germination onwards if wet conditions are experienced after sowing. A fungicide seed dressing containing metalaxyl (i.e. Apron XL® and other products) can provide up to 5-8 weeks protection in the seedling crop.

Maintain a rotation of at least three years (and preferably four) between chickpea and lucerne crops, and medic pastures, to minimise the risk of phytophthora root rot.

Botrytis grey mould (causal fungus: Botrytis cinerea)

Grey mould can cause total crop failure. Crop losses are worst in wet seasons, particularly when crops develop very dense canopies. Early symptoms of the disease include flower abortion and failure to set pods. This can often go undetected unless the crop is closely monitored. Affected areas on the stem and leaf develop a soft rot and become covered in a fluffy grey mould. As the disease progresses, infected plants wither and die.

Avoid early plantings, high plant densities and narrow row spacings. The disease is also seed borne and can result in a substantial reduction in seedling establishment. Thiram-based fungicides are registered for the treatment of grey mould infected seed. While seed treatment can improve establishment, it does not provide any protection from air-borne infection later in the crop.

The disease can be controlled during flowering and podding with carbendazim-based fungicides. Mancozeb sprays applied for the management of Ascochyta blight will also control stem and foliar grey mould.

Viral diseases

A number of insect-transmitted viruses can attack chickpeas, and can cause substantial crop losses. Symptoms include a reddening or yellowing of the foliage, a reduction in leaf size, and twisting of shoots and tips.

Viral diseases tend to be very sporadic in Queensland and are largely influenced by seasonal conditions and proximity to broadleaf weeds and other crops e.g., lucerne. Problems tend to be associated with high levels of insect, particularly aphid, activity.

Viral infections tend to be difficult to diagnose, and are often confused with nutrient deficiencies, herbicide damage, physiological disorders, and waterlogging. Consult with your agronomist for further information. Several of these viral diseases are transmitted by seed (cucumber mosaic virus and alfalfa mosaic virus).

Control of broadleaf weeds on-farm will reduce the reservoirs for the viruses and insects. Planting into winter cereal stubble has been shown to reduce aphid activity in chickpea crops which can lead to a reduction in virus incidence.

Environmental disorders

Physiological reddening

This condition is often prevalent in Amethyst crops. It occurs where the crop has been subjected to severe heat and moisture stress and then receives rain close to physiological maturity. Crops affected by this reddening often drop their leaves faster than normal.

Physiological leaf spot

This leaf symptom occurs regularly in most regions, and in most years. The spotting always appears on the upper leaf surface, and is brownish in colour. No disease pathogens have been linked to this condition, which appears to be associated more with stress conditions on the crop.

Root lesion nematodes: (Mainly Pratylenchus thornei)

Nematodes are minute, worm-like parasites that attack the root system of susceptible crops. They are usually less than 1 mm long. The most obvious symptom of nematode damage is patchy, uneven crop development. Approximately 70% of the wheat-based farming country in southern Queensland is infested to varying degrees with root-lesion nematodes (RLN). In paddocks with moderate nematode numbers, relatively susceptible varieties such as Amethyst or Sona can suffer up to a 15-30% yield loss, whereas more tolerant varieties like Jimbour might suffer a 5-10% yield loss. Soil test levels above 2000 nematodes/kg of soil are likely to impact on chickpea yields (based on 0-30 cm soil sampling).

Nematode numbers will also build up on the root system of chickpeas. The extent that RLN numbers build up on the crop root system (resistance), may impact on subsequent crops in the rotation. Nematode build-up on chickpeas is similar to that on other susceptible hosts (barley, maize, and triticale), but much less than on susceptible wheat varieties (less than 50%).

Fungicide registrations

Fungicides currently registered or under permit for chickpea (as of May 2009)

Active	Method of application	Rate	Diseases controlled or suppressed
Mancozeb	Foliar	1.0 - 2.2 kg/ha	Ascochyta blight, Botrytis grey mould
Chlorothalonil*	Foliar	1.0-2.0L/ha	Ascochyta blight, Botrytis grey mould
Carbendazim	Foliar	0.5L/ha	Botrytis grey mould
Thiram (600g/L)	Seed dressing	2L/t of seed	Ascochyta blight, Botrytis grey mould, seedling root rots
Thiabendazole(360g/L) Thiram(200g/L)	Seed dressing	2L/t of seed	Ascochyta blight, Botrytis grey mould, seedling root rots
Metalaxyl (350g/kg)	Seed dressing	1.5L/t of seed	Phytophthora root rot

* = under permit from 07/04/09 - 30/11/09

Prior to use of any crop protection product, ensure that it is currently registered or that a current permit exists for its use in chickpeas. Registered labels and current permits can be found on the APVMA website.