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What to look out for

Canola aphid populations have continued to increase over the past few weeks in many regions, particularly in the Northern Country and Western districts of Victoria. The most common species presently found infesting canola crops is the cabbage aphid (Brevicoryne brassicae). This species forms dense colonies on the flowering spikes, which appear bluish-grey and are covered with a fine, whitish powder. Given the late stage of canola crops (with many crops already windrowed), it is very unlikely that applying chemical sprays now will be economically viable.

Snails can cause contamination issues in grain when they are present above cutting height in the canopy (or in windrows) and harvested along with the grain. This can lead to clogging of machinery and/or quality downgrades. A series of wet winters and moist summers have resulted in snail numbers increasing in many regions of Victoria and New South Wales. Harvester modifications and grain cleaning will help to ensure grain is successfully delivered, but these usually incur some grain wastage. Identifying snail species and monitoring numbers before harvest, and before and after control operations is essential. For further information refer to GRDC FactSheet – Snail Management.

Rutherglen bugs (Nysius vinitor) are native insects that attack a wide range of weeds and crops. They are well adapted to dry warm weather and are often most damaging to moisture stressed plants. Adults can also become a grain contaminant when in high numbers. Highest numbers of Rutherglen bugs are often observed along crop perimeters. Numbers will increase with the warmer weather conditions and can reach damaging levels very quickly. Check crops over the coming weeks, particularly canola, linseed and sunflowers. Click here for images of Rutherglen bugs.

Native budworm moths are still being observed in some regions of northern Victoria and southern New South Wales. Egg laying by these moths should not pose any risk to crops which are rapidly maturing and nearing harvest. Growers with caterpillars presently in their crops need to be mindful of insecticide withholding periods close to harvest and remember that windrowing is classified as harvest. Some insecticide products have quite long withholding periods (e.g. alpha-cypermethrin in canola, 21 days). Click here for further information on the native budworm.

 

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