Take home message  

Planting your 2016 chickpea crop into paddocks that had chickpeas in 2015, or earlier, is risky and you could lose money.

Further, it puts current disease management practices under pressure and could lead to reduced life of chickpea varieties, development of fungicide resistance and problems with weeds and insects.

Growers are urged to follow recommendations for current best practice especially with regard to crop rotation.

Background

Tempting as they are, current chickpea prices should not lure growers into thinking back to back chickpea is a viable option.  Why not?  For growers, the biggest risk is you stand to lose money – a lot of money.  For the chickpea industry, the concern is that current best practices will become redundant prematurely or will fail completely.

What are the risks of back to back chickpea?

The main risks are seed borne, stubble borne and soil borne diseases.  Successful disease management in chickpeas relies heavily on an integrated management package involving paddock selection (crop sequencing), variety choice, seed treatment, strategic fungicide use and hygiene.

Back to back chickpea - which diseases are of concern?  There are four major chickpea diseases that will be favoured by planting chickpea on chickpea, ie:

• Ascochyta blight (AB, Phoma rabiei – previously called Ascochyta rabiei)
• Phytophthora root rot (PRR; Phytophthora medicaginis)
• Sclerotinia rot (“Sclero” Sclerotinia sclerotiorum and S. minor)
• Root lesion nematode (RLN, Pratylenchus spp)

Of these, Ascochyta, Phytophthora and Sclerotinia have the potential to cause 100% loss if conditions are conducive. 

The risks of Botrytis grey mould (BGM, Botrytis cinerea), Botrytis seedling disease (BSD, B. cinerea) and viruses (several species) are unlikely to increase with chickpea on chickpea UNLESS some consequence of back to back chickpea favours these diseases eg patchy, uneven stands caused by Ascochyta, Sclerotinia or Phytophthora will increase the risk of virus.

If I did not find any disease in my 2015 crop, is it safe to plant chickpea on chickpea in 2016? 

The short answer is NO.  Severe disease can occur even if disease was not detected in the 2015 crop or even in earlier chickpea crops.  This was demonstrated clearly in 2015 in north western NSW/southern QLD. 

Case 1: The bulk of one paddock had been planted in 2013 to PBA HatTrick but a narrow strip was sown with the new variety PBA Boundary.  The soil was a clay grey vertosol conducive to Phytophthora root rot when wet.  PBA HatTrick has some resistance to Phytophthora (rated MR) but PBA Boundary is susceptible.  In 2013, no Phytophthora was observed in either variety.  The entire paddock grew wheat in 2014 and in 2015 was sown to PBA HatTrick.  On 2 September 2015, Phytophthora (confirmed by lab test) was obvious in the area sown to PBA Boundary in 2013 but was not detected in the bulk of the paddock sown to PBA HatTrick in 2013.  The 2015 Phytophthora was so severe in the 2013 PBA Boundary strip that it was not harvested whereas the 2013 PBA HatTrick area went over 2t/ha.

Case 2:  In 2014 several paddocks on one farm were planted to Kyabra (susceptible to Ascochyta blight).  Ascochyta was not detected in 2014 either on the farm or in the district.  This, together with the prediction of an El Nino kicking in towards the end of July 2015, led to a decision to plant Kyabra in the paddocks that had Kyabra in 2014.  It was reasoned that if Ascochyta did occur in 2015, it could be controlled with fungicides.  What was not considered would be how to manage Ascochyta if it was too wet to spray – which unfortunately is what happened in early winter.  Even though no Ascochyta was detected in 2014, the pathogen was clearly on farm and infected plants in late autumn/early winter.  The first fungicide was not applied until 14 July by which time the disease was well established.  When inspected on 29 July 2015, Ascochyta was rampant in all paddocks and was especially severe in those that had chickpeas in 2014, with many areas of dead and stunted plants.  Although no rain fell after end July, these “bad” areas only went 0.6 – 0.8 t/ha compared with Kyabra planted into wheat stubble that went 1.0 – 1.5 t/ha.

What are the impacts of back to back chickpea on a grower?

The main short term one is losing money both from lost yield and quality and, for those diseases that can be controlled in-crop eg Ascochyta, increased production costs.  Longer term consequences include increasing inoculum loads in paddocks, rendering them less productive and less flexible.  For example with Sclerotinia spp, which have wide host ranges (including cotton), the survival structures (sclerotia) remain viable in soil for many years.  Thus any practice that increases the sclerotial load reduces the potential of the paddock for host crops such as faba bean, canola, lupin, field pea, cotton (and future chickpea crops).

What are the impacts of back to back chickpea on the industry?

There are three:

1. Increased risk of changes in the pathogen ie it becomes more virulent and aggressive.
2. Reduced commercial life of varieties i.e. back to back chickpea increases the risk of the pathogen establishing in the crop early which increases the potential for more disease cycles throughout the growing season which means resistance genes are subjected to more challenges by the pathogen. Resistance genes are limited; the loss of any gene will severely hinder the development of new chickpea varieties. 
3. Increased risk of pathogens developing resistance to fungicides i.e. reduced life of fungicide.  For diseases that can be managed with in-crop fungicides e.g. Ascochyta, the earlier the disease establishes, the more likely is the need for repeated applications of fungicides.  If you wanted to find resistance to chlorothalonil in the Ascochyta pathogen, a good place to look would be in early sown back to back Kyabra.  The problem here is that any isolate that is resistant to chlorothalonil is unlikely to be confined to the paddock (or farm) in which that resistance developed.  Thus an Ascochyta isolate with resistance to chlorothalonil on a single farm in say Moree could become established in the Darling Downs and elsewhere in northern and north central NSW within a few seasons.  This would be the end of chlorothalonil as a disease management tool for chickpeas.

Planting 2016 chickpeas into 2015 chickpea paddocks – is it worth it? 

Definitely NOT.  Besides it is doesn’t make sense.  As well as increased risk of disease, weed and insect management will also be more challenging.  At $800/t, surely growers should be doing everything to reduce risk and maximise yield and quality.

Further information on chickpea disease management can be found at the following:

GRDC chickpea disease management factsheet

Pulse Australia website

Chickpea: Aschochyta blight management (Pulse Australia)

Chickpea production: Northern region (Pulse Australia)

Chickpea: integrated disease management (Pulse Australia)

Chickpea: Managing botrytis grey mould (Pulse Australia)

Chickpea: Managing phytophthora root rot (Pulse Australia)

Chickpea: Identifying Sclerotinia (Pulse Australia)

Chickpea: Managing viruses in pulses (Pulse Australia)

and in the NSW DPI 2016 Winter Crop Variety Sowing Guide

Acknowledgements

This research is made possible by the significant contributions of growers through both trial cooperation, field access and the support of the GRDC; the authors most gratefully thank them and the GRDC.  We also thank agronomists for help with the crop inspections and submitting specimens, Gordon Cumming, Pulse Australia for industry liaison and chemical companies who provide products for research purposes and trial management.

Contact details

Kevin Moore
Ph: 02 6763 1133
Mb: 0488 251 866
Fx: 02 6763 1100
Email: kevin.moore@dpi.nsw.gov.au

Kristy Hobson
Ph: 02 6763 1174
Mb: 0400 955 476
Fx: 02 6763 1100
Email: kristy.hobson@dpi.nsw.gov.au

Sean Bithell
Ph: 02 6763 1117
Mb: 0429 201 863
Fx: 02 6763 1100
Email: sean.bithell@dpi.nsw.gov.au