Australia
June 6, 2011
Controlling chickpea diseases in 2011 begins with three pre-planting practices: stubble management, controlling volunteers and weeds, and paddock selection.
Dr Kevin Moore, NSW Department of Primary Industries (NSW DPI) plant pathologist, Tamworth told growers and advisers at the recent round of Grains Research and Development Corporation (GRDC) Updates that the buildup of pathogens in 2010 threatens northern region crops this year.
Dr Moore said floods and surface water flows in 2010 have also distributed inoculum of Ascochyta blight, Botrytis grey mould (BGM), Sclerotinia, Phytophthora and root lesion nematodes across large areas of the northern region cropping belt.
In addition, some diseases like chickpea Ascochyta are “community diseases” so what happens in the paddock next door or even several kilometres away can impact on crops.
“As such, these diseases should be managed at the community level,” Dr Moore said.
“For example: you are following the Ascochyta management recommendations and have delayed or suppressed early season disease. However, someone nearby (especially upwind or upslope) has not followed the recommendations and has allowed Ascochyta to get a hold of their crop early in the season.
“This puts your crop under extra disease pressure and in a season that favours Ascochyta may render difficult or impossible its management on susceptible varieties.”
Dr Moore said 2010 showed that growing varieties with improved Ascochyta resistance close to susceptible varieties made disease management in those “resistant” varieties challenging.
“Communities that work together will have a far better chance of successfully managing diseases like Ascochyta,” he said.
Dr Moore said the Ascochyta and BGM pathogens were likely to remain viable for as long as infected stubble remains on the soil surface.
“Burying stubble removes the ability of these pathogens to release spores and increases the rate of stubble breakdown, however some isolates of Botrytis produce sclerotia that can survive in soil,” he said.
“Although burning chickpea stubble will significantly reduce the amount infected residues, it will not guarantee freedom from Ascochyta when chickpeas are next grown in that paddock.
“Stubble management is unlikely to have any major beneficial effect on Sclerotinia, nematodes or Phytophthora.”
Dr Moore urged growers to control volunteer chickpea plants as these can harbour all chickpea pathogens.
He said paddock selection was another major consideration and standard recommendations of maintaining a distance of at least 500 metres from 2010 chickpea paddocks and a break of at least three years between chickpeas in the same paddock may not be effective as disease management tools in 2011.
“These tools work by reducing the amount of inoculum available to initiate infection early in the season,” he said.
“This has been compromised by surface water flow and floods which can move soil, roots, nematodes, chickpea stubble and pathogen survival structures great distances.
“Nevertheless, there are some basic rules that still apply i.e. never plant a crop back into it own residue or that of a related species and do not attempt to keep a paddock of volunteer chickpeas as summer crop.”
Dr Moore says the plants will be severely infected by pathogens (and heliothis) and will provide early season inoculum for 2011 chickpeas.
“Apart from the risks of Phytophthora and water logging, avoid growing chickpeas in poorly drained paddocks.
“Observations in 2010 indicate that the natural resistance all plants have to pathogens and pests is compromised when plants are stressed (from saturated conditions).”
In one 2010 GRDC-supported trial at Tamworth, waterlogged Flipper unexpectedly had more Ascochyta than an adjoining plot of waterlogged Yorker .
In another Tamworth trial there was more Ascochyta in the wettest Kyabra plot compared with better drained plots of Kyabra , in spite of the fact that all had been sprayed eight times with 1.0 litres per hectare of chlorothalonil product.
“Stress from water logging reduced our ability to manage Ascochyta with a strategy that worked in less stressed plots,” Dr Moore said.
Chickpea varieties in the GRDC northern region are susceptible to both Sclerotinia species, and all are susceptible to BGM (Howzat is rated moderately susceptible).
However, there are varying levels of resistances to Ascochyta and Phytophthora so growers should consider planting a variety with the highest levels of resistance to either or both pathogens, Dr Moore said.
Detailed chickpea disease management guides and strategies are available from the Pulse Australia website on the ‘Latest News’ page, or by contacting Gordon Cumming, Pulse Australia northern manager on 0408 923 474.
For more information, visit www.grdc.com.au/diseaselinks.
Table 1. Resistance ratingsa of some northern region varieties to Ascochyta rabiei and Phytophthora medicaginis and Botrytis cinerea
|
Variety
|
Ascochyta
|
Phytophthora
|
Botrytis
|
|
PBA HatTrick
|
MR/R
|
MR
|
S
|
|
Flipper
|
MR
|
MS
|
S
|
|
Yorker
|
MS/MR
|
MR
|
S
|
|
Howzat
|
S
|
MS
|
MS
|
|
Jimbour
|
S
|
MS/MR
|
S
|
|
Kyabra
|
S
|
MS
|
S
|
|
Genesis090
|
R
|
VS
|
VS
|
|
Genesis425
|
R
|
MS
|
S
|
|
Almaz
|
MS/MR
|
VS
|
S
|
a Resistance ratings are for low-moderate disease pressure situations. In a season such as 2010 when repeated cycles of infection occur, even MR varieties can have yield-reducing levels of disease
Species
