The culprits of major damage to sunflowers across New South Wales and Queensland in 2011 – looper insects – have prompted research to determine their effect on yield and oil content.
Queensland Department of Agriculture, Fisheries and Forestry (DAFF) principal entomologist Dr Melina Miles says yield and oil losses are linked to the level and timing of defoliation during the crop’s development.
Dr Miles says 2012 trials showed that sunflower yields declined up to 10 per cent where loopers had defoliated more than 75 per cent of the crop (Figure 1). But in instances where entire plants had been defoliated, yields were reduced by up to 90 per cent.
Figure 1 Yield response to defoliation at different growth stages.
However, the oil content of the seeds was only affected in situations where 100 per cent of the plant had been defoliated (Figure 2
). She says total defoliation at growth stages 3, 5 and 7 resulted in oil content declining by 10 per cent, 20 per cent and 25 per cent, respectively.
Figure 2 Oil content in response to defoliation at different growth stages
Dr Melina Miles,
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