Infertile flowers often form during the transition from vegetative to reproductive growth and these flowers will not form pods. Cold nights and frost will cause chickpea plants to abort fertile flowers and immature pods but the plants will attempt to compensate for these losses. (Photo: G. Cumming)
Setting early chickpea pods
by Gordon Cumming, Senior Industry Development Manager (Northern)
Warmer day temperatures and earlier plantings in some districts have initiated early flowering in many chickpea crops this season. A number of growers have been wondering why many of these flowers have dropped without setting pods and how to encourage pod set early in the season.
Chickpeas are known to be sensitive to low temperatures (below 5°C) and frost (0°C) during the flowering period. The critical average daily temperature (i.e. average of the daily maximum and minimum temperatures) for chickpea is 15°C. Below this critical mean value, flowers may be initiated (in fact, pseudo-flowers are often produced in the transition between vegetative and reproductive phases), but these flowers will be aborted because the pollen is infertile. Flowers will continue to be produced and then aborted until average daily temperatures increase to above 15°C.
Even after pods and seeds have formed, cold weather can cause pod and seed abortion, particularly in smaller pods and seeds developed in the few days prior to the cold event.
Conditions of extreme moisture stress (as in 2009) or extreme waterlogging (as in 2010) can exacerbate the effects of low temperatures and/or frost. Under adequate moisture conditions, chickpea plants can produce new terminal growth or branches to compensate for aborted flowers and/or pods, but this will delay crop maturity.
Conversely, and of particular value in the northern grains region, chickpea plants are more tolerant of heat during flowering than all other winter pulse crops. Days that reach maximum temperature of 35°C or more will also cause chickpea flowers to abort, and grain fill ceases if the crop becomes moisture stressed.
Whilst there have been reports of aschochyta blight in chickpea crops in northern NSW and near Goondiwindi, these crops are being very effectively managed with appropriate fungicide applications, helped by early disease identification. To date there have been no confirmed cases in central or southern Queensland.
Correct identification remains the key to effective disease management so closely inspect your crops 7 to 10 days after a rain event when spores may have been moved higher in the canopy or to surrounding plants by rain splash. Look for the typical concentric rings of black fruiting bodies within any leaf lessons.
As we move into the podding period of production the name of the game is protection of the pod as pod infection can result in poor quality, discoloured seed or seed abortion and yield loss in severe situations. If ascochyta has been confirmed in the crop, apply a registered fungicide at early podding, prior to the next likely rain event to ensure pods are protected, and high quality, disease-free seed is produced.
Remember that chickpea fungicides are protectants only—unlike wheat stripe rust fungicides—they have no systemic or kickback action and they will not eradicate an existing infection. To be effective they must be applied before infection i.e. before the next likely rain event. The key to a successful ascochyta spray program is regular monitoring combined with timely application of registered fungicides after disease has been positively identified within your crop.
So far, this season is not favouring botrytis grey mould (BGM) in chickpea, unlike the wet conditions experienced in 2010 that is still vivid in our memory. At this stage I do not believe that there is any need for BGM fungicide applications. The key drivers of a BGM epidemic are:
- The combination of early canopy closure, prolonged plant wetness and overcast weather results in high relative humidity and rapid leaf death in the canopy.
- Dense crop canopies—such as crops where it is very difficult to walk down the row.
- Average daily temperature (ADT) is 15°C or higher with the optimal conditions for BGM being moderate maximum daily temperatures (20–25°C).
- Frequent rainfall events promote spread of BGM. Free moisture is necessary for germination and infection.
It is currently too cold, and in most districts too dry, for BGM to be developing at the moment, but keep an eye on your crops, especially those that have high biomass and complete canopy closure. BGM lesions and the grey ‘fuzz’ are evident 5–7 days after infection under ideal conditions.
Both mancozeb and carbendazim are registered for BGM control in chickpea, although carbendazim is considered to be the superior product.
Supply of both chlorothalonil and mancozeb remains tight, however some resellers and suppliers do have additional supplies slowly becoming available. If you are looking to source additional fungicide please contact your local supplier to discuss your needs as significant lead times are still needed.
Pulse Australia has successfully applied for and been granted permits for the use of the following fungicides for the remainder of this season: Captan, Amistar Xtra and Prosaro 420 SC. Be sure to refer to the complete permit, which can be found on the Pulse Australia or APVMA websites. Familiarise yourself with all of the permit conditions including the withholding periods to harvest, spray drift restraints and critical use comments.
For more detailed information refer to the Pulse Australia website www.pulseaus.com or feel free to call me on 0408 923 474.