Green Peach Aphid
Wingless Colour - Normally waxy green but can vary from shining yellow to mid green or orange red.
Winged Colour - Almost black.
Length - 1.2 to 2.3 mm long. Average is 1.9 mm.
In general most of green peach aphids do not have a resting stage, such as eggs to carry them from year to year. When their host crop dies off, all aphids disperse or die. They persist from one growing season to the next in low numbers on suitable surrounding hosts. Winged aphids fly back to infest their winter host, canola, lupins or pasture during early autumn depending on the season. Aphid populations are favoured by a mild wet summer followed by an early break and mild autumn and winter with a cool, mild spring. This enables numbers to build up rapidly.
In stone fruit, in spring, the aphids multiply rapidly and can cause serious damage to young foliage. In early summer as growth is hardening off they migrate from trees to various weeds and cultivated plants such as potatoes. They spend the summer on these alternate hosts - until late autumn when they fly back to the peach or nectarine trees.
In a few inland regions where extreme cold temperatures occur the female aphid produces a generation of wingless egg laying females. These mate with males and lay over wintering eggs from May to mid July.
Late flowering canola crops are usually affected more than early flowering crops.
Habitats:Origin and History:
The green peach aphid is a pest of a wide range of crops including lupins, canola, potatoes, Brassica species, peaches and nectarines. The aphid infests the young leaf growth of stone fruit during October to November. As a result leaves can curl and shrivel and in severe situations trees are left unproductive.
On crops such as lupins and canola the green peach aphid can cause damage feeding on the growing tips of young and flowering plants. Direct feeding in large numbers can slow growth, distort flowers and reduce pod set and fill. They do not often form large dense colonies. Generally they are widely distributed through the crop in low numbers, rather than in well defined patches. The green peach aphid is considered to be the most effective aphid for transmitting viruses including cucumber mosaic virus and bean yellow mosaic virus. These viruses result in stunting, leaf yellowing and significant yield losses.
Management and Control:Recent studies have shown that some green peach aphid populations have developed resistance to dimethoate and pirimicarb insecticides. Methamidophos (Nitofol) is still an effective control agent. This occurrence highlights the importance of only using insecticides when pest pressure demands. Alternating types of insecticides used helps prevent or delay the onset of resistance. Green peach aphid resistance kits are available to determine whether infestations have developed resistance. This is essential information for determining what insecticide can be applied for successful control.
Thresholds:On Canola, if aphids cover a 25 mm length of flowering stem on most plants and biocontrol agents (such as ladybirds, lacewings, hover fly larvae, wasps and fungi) are not active then it is usually worth spraying. (Hart et al 1995). In WA this rarely occurs and spraying is rarely worthwhile. Monitor from late winter to the end of flowering. Check under the bottom leaves.
Yellow lupins are more sensitive than Narrow-leaved Lupins which are more sensitive than White Lupins to aphid damage.
On lupins, if 30% of the growing tips have more than 30 aphids then
a) on varieties with moderate or greater aphid tolerance. apply a single spray, one to two weeks after reaching this threshold or
b) on varieties with less than moderate tolerance, apply a spray immediately and a follow up spray in two weeks time if necessary.
See Pest Susceptibility of Lupin Varieties for rankings of varieties.
On Faba Beans and Lentils, aphid infestations probably have to be very heavy or early before it is worth spraying.
Insecticide ResistanceSome populations are resistant to pirimicarb, synthetic pyrethroids and organophosphates. The level of resistance to organophosphates appears to have plateaued.
Related Species:Similar Species:
See Significance: under the Description for Aphids for a key to distinguish different species that are common on canola.
References:WADA Bulletin 4179 "Producing Lupins in W.A".
NSW Department of Agriculture Bulletin "Green Peach Aphid".
Francoise Berlandier, Agriculture WA (pers. comm.)
David Pfeiffer, Agriculture WA (pers. comm.)
Collated by HerbiGuide. Phone 08 98444064 or www.herbiguide.com.au for more information.