July 2019 will see the start of an investigation to correlate pathogen densities of charcoal rot and fusarium stalk rot with disease expression, lodging and yield loss, using PreDicta®B tests.
Sorghum growers and agronomists are invited to participate in this investigation, so a clearer picture can be established of the effect these diseases can have on sorghum production.
Please contact Dr. Dante L. Adorada, for soil sampling and disease assessment of your sorghum paddocks.
The 2018-2019 summer cropping season demonstrates the effect environmental factors such as rainfall and temperature, can have on stalk rot diseases in sorghum. Different rainfall and temperature patterns were observed in northern New South Wales (NNSW) to Southern Queensland (SQ) and Central Queensland (CQ) in the northern grains region (Figure 1), resulting in different levels of the disease.
Acute moisture stress coinciding with grain filling (during a terminal drought) predisposes the plants to root and stalk rots, leading to severe lodging and loss of grain yield and the quality and quantity of the stover.
Sorghum crops planted at Inverell and Gunnedah in NNSW in September had average post-flowering temperatures of 26 and 29 °C and rainfall of 68 and 21 mm, respectively, from January to February, resulting in low or no stalk rot disease at all (Figure 2).
The same was true for sorghum crops at Capella and Clermont in CQ (Figure 3). However, compared to NNSW, they received higher rainfall (236 mm) with an average temperature of 25 °C during the post-flowering months from mid-February to end of April 2019. Although disease was not a problem in CQ, sorghum sprouting due to intermittent rain kept those CQ growers who decided to spray to desiccate and salvage their crops, on their toes.
It was a different situation for the sorghum crops in SQ as they were not spared from stalk rot diseases, particularly charcoal rot. Dalby in SQ received only 5.66 mm rainfall with an average temperature of 26 °C during January to February 2019. The sorghum planted in September receiving December rainfall during flowering to maturity did well, whereas November to December-planted sorghum that matured from February to March suffered due to high levels of charcoal rot and fusarium stalk rot that eventually contributed to high incidence of lodging (Figure 4).
However, there were paddocks in some parts of the region that were moisture stressed and yet did not get the disease. This was due to several factors, other than temperature and rainfall, contributing to charcoal rot disease development. There are three main factors which must interact to cause plant disease: susceptible host, disease causing organism (the pathogen) and favourable environment for pathogen to cause disease. If any of these factors are missing disease will not develop.
What can be done?
As growers are preparing for the next summer cropping season, the best disease management option is to practice preventive measures to minimise the incidence of the disease.
Disease management options are described in the following resources:
GRDC GrowNotes(TM) – Sorghum diseases.
GRDC Communities – Re-visiting management options for charcoal rot in sorghum.
Please contact Dr. Dante L. Adorada, if you have sorghum paddocks available for soil sampling and disease assessment.
Dr. Dante L. Adorada Centre for Crop Health University of Southern Queensland | Toowoomba, Queensland Ph: +61 7 4631 1262 | Mob: 0477 718 593 Email: firstname.lastname@example.org
Dr. Precila Gonzales, USQ Centre for Health
Agronomists from NNSW, SQ and CQ