Aphids

Aphids are small insect pests with oval-shaped green, brown or black bodies. Often occurring in colonies, aphids suck on sap, causing loss of vigour, and in some cases yellowing, stunting or distortion of plant parts. Honeydew secreted by the insects can cause sooty mould to develop on leaves. When aphids transmit viruses, the impact on crop growth and yield can be significant. The earlier the transmission of virus, the greater the potential impact.

Direct aphid feeding rarely causes major damage to broadacre crops, and control measures are generally unnecessary, as parasitoids and predators keep populations in check. Exceptions occur when aphid populations are extreme (particularly early), a previous application of broad-spectrum pesticide has impacted beneficial populations, or the compensatory ability of the crop is compromised by stress (particularly moisture stress). Under these scenarios, aphid impact on flowering or pod set/fill may be significant, although in a stressed crop, the lower yield potential needs to be taken into consideration when calculating economic thresholds.

See also the following pages

• Aphids in canola
• Aphids in winter cereals
• Aphids in pulse crops
• Parasitism of aphids
• GPA insecticide resistance management strategy

Life cycle diagrams (in pdf) are available for the following aphid groups: Cabbage aphid | Cereal aphid | Green peach aphid | Turnip aphid | Winter cereal aphid

Aphid species	Crops infested	Alternative hosts	Virus transmission	Impact on crop
Turnip aphid	Canola (generally restricted to cruciferous crops and weeds)	Wild radish and wild turnip		Reduced pod set, pod fill and seed quality.
Cabbage aphid	Canola (generally restricted to cruciferous crops and weeds)	Wild radish and wild turnip		Reduced pod set, pod fill and seed quality.
Blue green aphid	Canola Pulses Pastures	Pasture legumes, incl medic, subclover & Lucerne	Cucumber mosaic virus (CMV)	Lucerne and pasture: damages terminal buds, upper leaves and stems.
Green peach aphid	Canola	Wild radish and wild turnip, lupins, capeweed plus others	Beet western yellows virus (BWYV)	Early season pest, with potential to impact on yield through transmission of BWYV. Rarely persists to cause direct yield loss. View GPA insecticide resistance management strategy
Cowpea aphid	Pulses	Pasture legumes (incl medic & vetch) potatoes	Cucumber mosaic virus (CMV) in lupins, lentils, faba beans, chickpeas Bean yellow mosaic virus (BYMV)in faba beans, lupins Alfalfa Mosaic virus (AMV) in lentils, lupins, chickpeas	Early infestation and virus transmission has the greatest impact on crops. Infestations can occur during flowering, reduce pod set and pod fill.
Oat aphid	Winter cereals	Pasture grasses	Barley yellow dwarf virus (BYDV)	Early infestation and virus transmission poses greatest threat to yield. Direct feeding by aphids can retard plant growth, but the impact on yield in not well understood.
Corn aphid	Sorghum Winter cereals	Pasture grasses	Barley yellow dwarf virus (BYDV)	Sorghum: Adults and nymphs suck sap and produce honeydew. Honeydew can cause grain stickiness at harvest if aphids persist. Cereals: Aphids feed on stems, leaves and heads, but the impact on yield is not well understood. Very early infestations can retard plant growth
Rose grain aphid	Winter cereals	Grasses	Barley yellow dwarf virus (BYDV)	Tend to be a later season infestation. Colonies are common on leaves, however their impact on yield is unclear.
Russian wheat aphid	Barley and wheat highly susceptible. Oats tolerant. Other winter cereal crops intermediate.	Grasses. Not known to build up in sorghum	Can transmit BYDV, but not as effective a vector as the other cereal infesting aphid species.	Yield loss as a result of reduced photosynthetic capacity of infested plants. Whitening of leaves and rolling reduce effective leaf area. In very severe infestations, seedlings may die. Infestation at head emergence can result in rolling of the flag leaf, trapping the emerging head and significantly affecting yield.
Soybean aphid	Soybeans		Not known to transmit virus within Australia. In China, soybean aphid transmits soybean mosaic virus, which can cause yield loss and decreased seed quality.	Infested plants can have distorted leaves and may be covered in sooty mould. Heavy infestations can reduce yield and delay harvest maturity
Pea aphid	Faba beans Field peas Lucerne	not common in pea crops	Cucumber mosaic virus (CMV) Pea seed-borne mosaic virus (PSbMV) Bean yellow mosaic virus (BYMV)	Can cause misshapen leaves, yellowing and stunting
Faba bean aphid	Faba bean and vetches	Lucerne	Bean leaf roll mosaic virus (BLRV) Pea seed-borne mosaic virus (PSbMV)	Intensive infestations can cause necrosis, wilting, stunting and defoliation

Further information

• Aphids and Viruses in Pulse Crops (GRDC)
• Aphids in field crops (DAF Queensland)
• Pestnotes: aphids (cesar)