05 October, 2006
Prevention of early aphid populations is absolutely essential in the control of this important cotton pest, according to the CSD extension and development team.
CSD agronomist, David Kelly, said aphid populations are troublesome because they reduce yields, degrade lint quality by producing honeydew, and can act as a vector for Cotton Bunchy Top (CBT).
He said aphids are becoming more difficult to manage because of increasing insecticide resistance, and because the low spray regime in Bollgard II® crops means they are not being controlled incidentally by Heliothis insecticides, as was the case in conventional cotton.
“Understanding the aphid life cycle helps explain why aphids can be such a difficult pest to manage. Cotton aphid usually produces asexually – females give birth to live female young without having to mate.
“This results in aphid ‘clones’- the young are the same as their mother, including being resistant to an aphicide if their mother is.If you apply an aphicide to a field and kill 95 per cent of the aphids, the surviving 5 per cent will be resistant because there is no outcrossing.
“Also, aphids do not go into a dormant phase such as heliothis pupae. They can only survive on a living plant host. This produces both a threat and an opportunity in terms of control measures.
“All sources of aphids should be removed before this year’s cotton crop is established. The highest priority should be ratoon (regrowth) cotton plants within fields.
“We’ve looked at a lot of these plants this year, and all of them have had aphids on them. As the young cotton plants around them become established, these aphids can move straight across, and you’ve got a problem from day one.
“Fields should also be carefully scouted for early aphid populations, but only count plants infested if there are non-winged aphids present. Aphid hotspot areas should also be identified and checked for Bunchy Top symptoms,” David Kelly said.
He noted that further information on aphid control can be found in “IPM Guidelines for Cotton Production Systems in Australia” which is accessible on the Cotton CRC website at (http://www.cotton.crc.org.au/), on CSD’s ‘Facts on Friday’ newsletter, and in archived Web on Wednesday video transcripts on the CSD website at www.csd.net.au.
CSD, Wee Waa – 02 6795 0000
James Quinn, Moree – 0428 950028
Craig McDonald, Narromine – 0428 950015
David Kelly, Goondiwindi – 0428 950021
Rob Eveleigh, Narrabri – 0428 915921
John Marshall, Dalby – 0428 950010
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