aphids
Beginner
Scientific Name: Amphorophora agathonica, A. sensoriata, Aphis rubicola (Order: Homoptera; Family: Aphididae)
Identification:
- Three most common are the large raspberry aphids, Amphorophora agathonica and Amphorophora sensoriata, and the small raspberry aphid, Aphis rubicola. Small raspberry aphids are rare in Ontario.
- All three species are small, pear-shaped, and soft-bodied.
- Two cornicles, or “tail pipes”, stick out from the posterior end of their bodies.
- Generally slow-moving and may drop off plants when disturbed.
- Large raspberry aphids are about 3 mm long, some can reach up to 9 mm. Aphis rubicola measures about 1.5 mm in length.
- Amphorophora agathonica is of a yellow-green colour, A. sensoriata is pale bluish-green and Aphis rubicola is pale yellowish-green.
- Generally found in colonies on the underside of leaves or on growing tips of canes, especially primocanes and new lateral shoots on fruiting canes.
Often Confused With
Tarnished Plant Bug nymphs
Potato Leafhopper
Poor Pollination-causing sooty mould on collar of fruit
Period of Activity
Aphids hatch from their eggs in spring, around May, and are present throughout the summer and fall. Cool, dry weather allows aphid populations to soar, but very hot conditions or strong downpours of rain will negatively affect aphid populations and drive down their numbers.
Scouting Notes
Start in May, search for mainly wingless aphids on the underside of leaves and on shoot tips of primocanes and new lateral shoots on fruiting canes. Choose leaves from the top, middle and bottom of each plant you examine. Use a hand lens to better identify the insects. Be careful not to confuse moulted, cast skins and dead aphids with live ones. Scout for symptoms of aphid feeding, such as curled, deformed or discoloured leaves and sticky residue, called honeydew, on leaves and fruit. Check fruit and leaves for the characteristic dark growth of this sooty mould growing on the honeydew. Check for the presence of beneficial predators that feed on aphids, such as lady beetles, lacewings and predatory wasps.
Thresholds
None established. If high populations are causing significant visual plant damage or fruit are becoming contaminated with honeydew or sooty mold, treatment may be warranted.
Advanced
Scientific Name: Amphorophora agathonica, A. sensoriata, Aphis rubicola (Order: Homoptera; Family: Aphididae)
Identification:
There are several species of aphids that affect raspberries; however the three most common are the large raspberry aphid, Amphorophora agathonica and Amphorophora sensoriata, and the small raspberry aphid, Aphis rubicola. Small raspberry aphids are rare in Ontario.
Raspberry aphids feed on plant sap using straw-like piercing and sucking mouthparts. They pierce the vascular tissue and the high pressure inside phloem forces the plant sap into the aphid. The aphid excretes excess sugars from the sap at its posterior end. This exudate, commonly known as honeydew, is a sticky, sweet substance that attracts ants and promotes fungal growth. Dark sooty mould fungi can grow on the honeydew, cover leaves and fruit, and make the fruit unfit for sale.
Aphid feeding removes nutrients from the plant and leaves can become deformed, curled and discoloured. This feeding damage is not significant if the infestation is moderate. The most significant damage is the potential for transmission of viruses.
A virus infection can cause stunting, discolouration of the leaves, distortion, and may reduce fruit production. The mosaic virus in particular, can have devastating effects as it may cause the loss of over 50% of harvest yields. For more information on these viruses, please refer to the Virus infosheet in the Diseases and Disorders section.
All three species of aphids are small, pear-shaped, and soft-bodied wiith piercing-and-sucking mouthparts. Their head is small relative to the remainder of their bodies. Two cornicles, or “tail pipes”, stick out from the posterior end of their bodies. Aphids are generally slow-moving and may drop off plants when disturbed.
Large raspberry aphids are about 3 mm long, but some can reach up to 9 mm. Amphorophora agathonica is of a yellow-green colour and A. sensoriata is pale bluish-green. Aphis rubicola measures about 1.5 mm in length and is pale yellowish-green.
Aphids are generally found in colonies on the underside of leaves or on growing tips of canes, especially primocanes and new lateral shoots on fruiting canes. Both winged and wingless aphids exist and as they cast their skins and moult to the next stage, flimsy frail white exoskeletons may be found on the leaf. Aphids have a number of natural enemies, such as lady beetles, lacewings and parasitic wasps. Aphids which have been parasitized are beige, brittle, and balloon-like in shape.
Often Confused With
Tarnished Plant Bug nymphs - Tarnished plant bug (TPB) nymphs and aphids can be similar in size and appearance. However, tarnished plant bug nymphs are fast moving, hold their antennae out front to navigate, and have no cornicles. Older nymphs have black dots on their backs and wing pads. Tarnished plant bugs are generally found in fruit and flower clusters. Aphids, on the other hand, are slow moving. Their antennae generally point backwards, and two cornicles stick out from their back ends. They are generally found on new growth, although they can fall into fruit and flower clusters.
Potato Leafhopper- Potato leafhoppers are slender and wedge-shaped, while aphids are pear-shaped. The feeding damage created by both leafhoppers and aphids is similar and both species are most easily found on the underside of leaves. Aphids are generally much slower moving than leafhoppers. Leafhopper nymphs are the only type of insect nymph that scuttle sideways when provoked..
Poor Pollination - In greenhouses and high tunnels, high humidity and a lack of pollinators can cause nectar to build up in blossom clusters. The nectar falls to leaves and surrounding plant tissue, and is colonized by sooty moulds. The effect is similar to that caused by aphid honeydew.
Biology
Aphid development is rapid and they may reach up to 20 generations per year. They over-winter as eggs, hatch into nymphs in the spring and moult into several instars before reaching the mature adult stage. All adults produced from the over-wintering eggs are female. Female aphids give birth to live young. Each female can produce between 50 and 100 young and all of them are female and most are wingless. Later in the summer, winged stages develop and migrate to new plants or new fields. In the fall, males and egg-laying females are born and mating occurs. Females lay their eggs into bud axils on primocanes and the underside of old leaves. The next year’s generation of aphids over-winter in these eggs.
All aphid growth stages are capable of transmitting specific viruses, except for eggs. Large raspberry aphids spread the raspberry mosaic virus complex, while the small raspberry aphid is a vector of the raspberry leaf curl virus. Aphids can pick up these viruses after just 15-30 minutes of feeding on infected plants, and can retain the virus for several hours. The next time the aphid feeds on a plant, it will infect the formerly healthy plant with the virus and the virus spreads throughout the plant via phloem.
Period of Activity
Aphids hatch from their eggs in spring, around May, and are present throughout the summer and fall. Cool, dry weather allows aphid populations to soar, but very hot conditions or strong downpours of rain will affect aphid populations in a negative way and drive down their numbers.
Scouting Notes
Starting in May, search for mainly wingless aphids on the underside of leaves and on shoot tips of primocanes and new lateral shoots on fruiting canes. Choose leaves from the top, middle and bottom of each plant you examine. Use a hand lens to better identify the insects. Be careful not to confuse moulted, cast skins and dead aphids with live ones. Scout for symptoms of aphid feeding, such as curled, deformed or discoloured leaves and sticky residue, called honeydew, on leaves and fruit. Honeydew may allow for the growth of sooty mould. Check fruit and leaves for the characteristic dark growth of this fungus. Check for the presence of beneficial predators that feed on aphids, such as lady beetles, lacewings and predatory wasps.
Thresholds
None established. If high populations are causing significant visual plant damage or the fruit are becoming contaminated with honeydew or sooty mold, treatment may be warranted. In some parts of North America more than two aphids per shoot tip is used as a threshold for applying insecticide to reduce the risk of virus infections. However, in Ontario, in commercial fruiting fields where good virus prevention practices are used, controlling aphids to this threshold is not cost effective.
Management Notes
- Start out with certified, virus-free plants.
- Remove wild brambles near the field.
- Remove all plants exhibiting virus symptoms and destroy them.
- Aphid populations are easily wiped out by a heavy rain. However, spraying down plants with water to remove aphids can ultimately damage the plants if the water pressure is too high.
- Plant aphid resistant cultivars, such as Titan, Glen Ample (susceptible to the virus), and Royalty. Tulameen is resistant to the large raspberry aphid which can transmit the raspberry mosaic virus complex. Autumn Bliss is resistant to the raspberry mosaic virus but not to the aphids themselves.
- Ensure plants receive adequate nutrition. Excessive nitrogen applications lead to high nitrogen content in the leaves and this favours aphid population growth.
- Ants that feed on honeydew will often defend aphid populations from predators and controlling ant populations may keep aphid populations from growing excessively.
- Avoid excessive use of insecticides that kill beneficial insects that prey upon aphids or act as parasites. Often aphid populations increase dramatically after the application of an insecticide as beneficial insects have been killed. Beneficial insects include lady beetles, lace wings, syrphid fly larvae, minute pirate bugs, ground beetles and spiders. Parasitic wasps also help to reduce aphid populations.
