Pulse diseases 2016

Take home messages

• Ascochyta lentis isolates from Mallala and Maitland have caused a susceptible reaction on PBA Hurricane XT lentils in controlled environment tests, as well as on PBA Ace and PBA Bolt. Growers in these regions should manage these cultivars as a potentially higher risk for ascochyta blight.
• Faba bean cultivars have not changed reactions to ascochyta blight since 2015. Screening of isolates of Ascochyta fabae identified three reaction groups — Farah is susceptible to ascochyta blight, PBA Rana and PBA Zahra are partially compromised, while PBA Samira and Nura remain resistant.
• Faba bean growers are encouraged to proactively move toward adoption of newer PBA varieties which show superior seed quality and greater tolerance to agronomic practices than Fiesta, Farah and Nura. This trend continued in 2016 trials as elite NVT lines exhibited less disease to chocolate spot and ascochyta blight, demonstrating the progression of accumulative dual-resistance being developed within the Australian breeding program.
• Chickpea cultivars in the southern region are now all moderately susceptible or susceptible to ascochyta blight, requiring multiple fungicides and a thiram-based seed dressing.
• Bacterial blight (BB) affected some field pea crops following severe frost. Consider avoiding field peas in frost prone paddocks, or, in these paddocks, sow to PBA Oura or PBA Percy which are less susceptible to BB, and remove stubble before sowing to reduce the frost risk.
• Cucumber mosaic virus (CMV) and bean yellow mosaic virus (BYMV) infected pulse crops in the upper Yorke Peninsula, Mid and Upper North. These are seed borne viruses, so growers with affected crops should source new seed, or have seed tested for virus infection.
• The presence of sclerotinia in canola and pulse crops during 2016 will mean an increased risk of infection for pulse and oilseed crops from soil borne sclerotes for up to five years, particularly in wet seasons. Cereal rotations in infected paddocks will reduce the risk. Sclerotes in grain samples are not harmful to stock or humans.

Ascochyta blight in pulse crops

Lentils 

Ascochyta lentis isolates collected in 2016

Leaf lesions of ascochyta blight (AB) were observed on PBA Hurricane XT lentils in the Maitland and Mallala regions in 2016. Lesions were collected and eight isolates were tested against a number of cultivars in controlled environment conditions at SARDI (Table 1). A susceptible reaction was observed on PBA Hurricane XT lentils in these tests and disease reactions were also observed on PBA Ace and PBA Bolt, although field reactions have not been confirmed on the latter two cultivars. In 2017, growers in these regions should manage these cultivars as a potentially higher risk for AB, in particular thiram-based seed dressing should be used and growers should be prepared for a fungicide spray during podding. Crops should also be monitored closely in case an additional spray is required during the season to control AB, especially in a wet season. PBA Jumbo2 and Boomer exhibited a resistant reaction to these eight isolates.

 

Table 1. Reaction of lentil cultivars when inoculated with Ascochyta lentis isolates collected from PBA Hurricane XT in 2016.

Isolate collection site	Host Varieties
	Cumra (susceptible check)	PBA Hurricane XT	PBA Ace	PBA Bolt	PBA Giant	PBA Herald XT	PBA Blitz	Boomer	PBA Jumbo2
Maitland	2.5	10.0	4.5	0.8	1.7	3.8	2.7	1.9	1.0
Sunnyvale	6.3	5.2	4.8	2.9	1.0	2.3	1.7	1.5	1.0
Mallala	6.3	13.1	4.8	2.7	1.9	4.0	4.0	3.1	1.3
Maitland	7.9	13.3	7.9	3.3	1.7	6.9	5.0	2.9	0.8
Maitland	14.0	5.6	4.8	4.4	10.0	2.3	2.7	1.7	0.2
Maitland	15.8	10.2	6.5	6.7	8.5	4.4	5.0	3.1	2.1
Arthurton	16.0	5.6	10.8	7.1	5.8	5.8	2.7	1.9	0.2
Mallala	18.3	10.0	6.7	12.9	5.4	1.9	2.1	4.0	0.6

Average %disease of whole plants when inoculated in controlled screening with A. lentis isolates collected from PBA Hurricane XT in 2016.

lsd=4.2
0-4.2 Resistant (R)
4.3-8.4 Moderately Resistant (MR)
8.5-12.6 Moderately Susceptible (MS)
>12.7 Susceptible (S) 

Ascochyta lentis isolates collected in 2015

In addition to the above testing, 40 isolates of A. lentis collected in 2015 from lentil field trials and commercial paddocks were tested on a differential host set that included PBA Hurricane XT and Nipper (Table 2). On Nipper, the majority of the isolates caused a moderately susceptible or susceptible reaction, and only two caused a moderately resistant reaction, confirming the widespread loss of foliar AB resistance in Nipper. Nipper requires a fungicide spray during podding to prevent pod and seed infection and crops should also be monitored closely in case an additional spray is required during the season. In contrast to the findings in Table 1 above, none of the 2015 isolates caused a susceptible or moderately susceptible reaction on PBA Hurricane XT, indicating that the susceptible reactions noted above on PBA Hurricane XT are a very recent change in the population.

Table 2. Forty Ascochyta lentis isolates collected in 2015 were inoculated onto a lentil host differential set in controlled conditions. Entries in the Table are the number of isolates per category.

Test reaction	Cumra (susceptible check)	Nipper	PBA Hurricane XT	ILL7537 (resistant line)	Indianhead (resistant line)
R	0	0	29	36	38
MR	0	2	11	4	2
MRMS	2	19	0	0	0
MS	10	14	0	0	0
S	28	4	0	0	0

Faba beans

Ascochyta fabae isolates collected in 2015
Forty isolates of A. fabae collected in 2015 from faba bean field trials and commercial paddocks were tested on a differential host set that included the Australian commercial cultivars. Faba bean cultivars have not changed reactions to AB since 2015 (Table 3) and screening of the isolates identified three reaction groups— Farah is moderately susceptible to AB in the Lower to Upper North of SA, PBA Rana and PBA Zahra are partially compromised, while PBA Samira and Nura remain resistant. Testing of a smaller set of isolates collected in 2016 has confirmed that these new pathotypes are also starting to become established in the Yorke Peninsula and South East growing regions. A three spray fungicide strategy is now required to control AB in Farah, while podding sprays should be planned for PBA Rana and PBA Zahra to prevent pod and seed infection. 

Table 3. Forty Ascochyta fabae isolates collected in 2015 were inoculated onto a faba bean host differential set in shadehouse conditions. Entries in the Table are the number of isolates per category.

Test reaction	Icarus	Farah AR	PBA Zahra	PBA Rana	PBA Simira	Nura AR
R	0	3	3	4	17	38
MR	0	1	7	7	17	3
MRMS	0	5	26	16	5	0
MS	1	25	4	14	2	0
S	40	7	1	0	0	0

Chickpeas

A virulence change in the AB pathogen of chickpeas in southern Australia now means that all current varieties are rated as either susceptible or moderately susceptible to AB infection (Table 4). This follows observations of severe AB on previously resistant chickpea varieties in 2015 and 2016 across South Australia (SA) and Victoria (VIC). Chickpea growers now need to carefully consider their risk to AB infection along with the ability to effectively control the disease prior to choosing to grow this crop in southern Australia. This will be the case in both high and low rainfall regions as severe disease outbreaks can still occur in the latter in all current variety options during wet seasons such as 2016. All chickpea crops will need to be regularly monitored for AB infection. 

Table 4. Ascochyta blight categories of chickpea cultivars and disease scores from trials in SA and VIC in 2016 show all cultivars are now either moderately susceptible or susceptible to this disease.

Variety	Ascochyta blight foliage disease scores 2016
	Rating for 2017	Curyo Vic 1-9 disease score	Kingsford SA 1-9 disease score
Desi type
Ambar	MS	5.8	6.3
Genesis™ 509	MS	6.0
Howzat	S	8.0	9.0
Neelam	MS	6.3	5.7
PBA HatTrick	S	7.7
PBA Maiden	S	7.0	7.0
PBA Slasher	MS	7.3	5.3
PBA Striker	S	7.5	7.3
Sonali	S	8.8
Kabuli type
Almaz	MS	6.3	6.3
Genesis™ 079	S	7.0	5.0
Genesis™ 090	MS	6.7	3.7
Genesis™ 114	S
Genesis™ Kalkee	MS	5.5	4.7
PBA Monarch	S	7.5	8.0
LSD (P=0.05)		1.7	1.5

• Moderately susceptible varieties will generally require three to four strategic fungicide sprays ahead of rain events offering 2-3 weeks protection, starting at 6-8 weeks post sowing.
• Susceptible varieties will require regular fungicide sprays every 2-3 weeks throughout the growing season in front of rainfall events. 
• As the pods of all commercial varieties are susceptible to AB, they will also require fungicide sprays during pod setting ahead of rain fronts to protect the pods from seed staining and seed abortion.
• It is imperative that all chickpea seed is treated with a thiram based fungicide to prevent seed transmission of AB onto the emerging seedlings in 2017. 
• The disease will also survive on stubble and organic matter for a number of years, so growers must observe a minimum of a three year rotation between chickpeas in the same paddock, and avoid planting adjacent to last year’s chickpea stubble.

Botrytis diseases in pulse crops

Botrytis grey mould (BGM) was reported in early sown lentils sown into narrow row which produced heavy canopies thereby promoting this disease. All lentil crops, irrespective of BGM status, in SA should be treated with a canopy closure fungicide spray and follow up sprays are determined by seasonal conditions. The majority of crops had minimal damage from BGM in 2016. Chocolate spot was reported in many faba bean crops, especially those sown early which produced heavy canopies, thereby promoting this disease. All commercial varieties of faba bean, irrespective of differences in chocolate spot susceptibility, should be treated with a pre-canopy closure fungicide spray and follow up sprays are determined by seasonal conditions. The majority of crops had multiple applications of fungicide, but older varieties (Fiesta and Farah) were reported to have higher disease levels than newer releases (PBA Samira).