Possible pollination, ergot risks in grain sorghum

The later sowing of grain sorghum
crops this summer raises the risk of impaired pollination and infection from ergot,
but producers should not be alarmed.

“Over recent weeks most regions
have seen temperatures at or below average for this time of year. Although the weather data suggests the risk
of any problem occurring is possible, any drop in temperature such as this does
always pose some risk,” said Pacific Seeds sorghum manager Andrew Short.

Mr Short said as many
Queensland and northern New South Wales crops were planted late, they were
flowering in the months more conducive to these weather related issues.

“Like with hot temperatures,
sorghum pollination can be negatively impacted through exposure to low

“If any growers had a flowering
sorghum crop during a period of cool weather, it would be worth checking seed
set to see if it was affected.”

He said his team had been monitoring
Bureau of Meteorology weather stations to track both maximum and minimum
temperatures, noticing that in a number of areas the minimum temperature
recorded dipped in the period covering the last few days of January and the
beginning of February.

“In some of these cases,
overnight temperatures dropped as low as 10°C or 12°C. Thankfully these drops were short-lived, as once
minimum temperatures drop to levels of 13°C or lower, pollen viability
decreases which in turn could reduce seed set.”

Mr Short said the recent cool
and wet conditions meant it was also timely to revisit ergot and the factors
affecting its development.

According to the Queensland Department
of Agriculture, Fisheries and Forestry, ergot can occur at any time during the
growing season if suitable weather conditions occur.

“In experiments, a constant
temperature of 20°C and relative humidity close to 100 per cent favours maximum
infection,” its latest report says.

“Outbreaks in main heads during
summer are associated with at least two days of rainy weather, with daily
maximum temperatures below 28¬∞C.”

QDAFF states there is a trend
for increasing ergot severity as the temperatures drop towards the end of the
growing season.

“The requirement for rainfall
seems to be less critical, perhaps because dew periods are common during this

“For late tillers, forage
sorghums and male sterile lines, infection can occur under a much broader range
of conditions due to the naturally lower pollen production in these situations
during flowering.”

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