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Potato Aphid

Macrosiphum euphorbiae

Potato Aphid

A close up of a green potato aphid macrosiphum euphorbiae on a plant to scale
Photo by Jesse Rorabaugh (CC0)
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Macrosiphum euphorbiae, commonly called the Potato Aphid, is a sap-sucking true bug. They're not just pests of potato, but many other commercially important crops and ornamental plants, such as rose. These insects can survive on over 200 species of plants across 20 plant families! Their favoured plant hosts are those found in the Nightshade family (Solanaceae). The species can give rise to multiple colour morphs, including yellow, green, pink and purple. Their colour is dictated by where they have been feeding on the plant. The severity of an infestation is influence by factors such as temperature, rainfall and abundance of natural enemies. It's recommended to only use pesticides wherever necessary so that beneficial insects can are sustained, to help control garden pests. Populations begin to peak in gardens from May to August.

Traits

Aphids produce honeydew which may attract ants and black mould.
Aphids are predated by other insects and garden wildlife.

Appearance

Adults: Aphids may be green, yellow, purple or brown. They're pear-shaped and can either have wings or be wingless. Nymphs: Very similar to adults but smaller, wingless and sometimes paler. Eggs: The eggs look like tiny white dots, and laid beneath the leaves of the host plant.

Symptoms

Yellowing of leaves. Colonies of aphids on new growth. Leaf and stem distortion. Honeydew can attract ant colonies and black mould. Premature leaf and flower bud fall. Reduced flower quality.

Activity

Diurnal

Personality

Order

Hemiptera

Family

Aphididae

Metamorphosis

Incomplete

Distribution

North America and temperate parts of Europe and Asia

Biological treatment

General good housekeeping can help prevent any insect pest infestation. Before planting, be mindful of the space you leave between crops and shrubs. Weeds and plant debris can facilitate a bad pest infestation. Planting strong-smelling herbs such as basil, chive, Allium and mint are believed to deter aphid activity. Aphids aggregate in areas of new growth, so be sure to check in all the nooks of plants, including beneath the leaves. Aphids can also be treated with a strong jet of water to dislodge them from the plant; or, a light, soapy mixture applied to the plant or even just squashing them. Alternatively, garlic or chilli-based spray diluted with water is thought to act as a natural insect repellent. Aphids can sometimes attract ants to the infested area because of the honeydew they produce. An ant colony will protect aphids so they can farm their honeydew. Placing ant traps near infested plants will help to prevent any secondary infestations. Aphids possess an array of natural enemies (ladybirds, wasps and lacewings, to name a few!). These can be attracted into the garden by planting a selection of indigenous plants, incorporating an insect hotel, or by letting some bits of the garden grow wild.

Chemical treatment

Wherever possible, aphids should be tolerated on plants because they are food for other wildlife. Aphid populations tend to peak during spring, but die off when natural enemies become more apparent later in the summer. For outdoor plants, assess the level of damage for the time of year before taking action with chemicals When using chemicals, it’s always best to act when nymphs (immature aphids) are most active, which tends to be in the spring. Assess the plants' size. Full pesticide coverage for trees and large shrubs is expensive, if not impossible, to achieve. Likewise, apply pesticides before flowering occurs. Sprays can be indiscriminate killers, killing the useful insects as well as the bad. Killing the beneficial insects can make pest problems worse in the years to come! Contact insecticides containing natural plant oils can be more environmentally benign than synthetic pesticides. Look out for products containing natural pyrethrums, fatty acids and plant oils. Any product containing oil should be applied during colder periods of the day. Synthetic pyrethroids that are available for home use include ingredients: deltamethrin, lambda-cyhalothrin and cypermethrin. These can be applied less frequently. Likewise, if you intend to eat your crop, be sure it is listed on the bottle and follow directions carefully.

Attracts

Particularly drawn to plants in the NIghtshade family (Solanaceae).
A red rose on a Rosa plant

Rose

Rosa spp.

Some red Solanum lycopersicum tomatoes in a garden

Tomato

Solanum lycopersicum

A close up of a white and yellow Solanum tuberosum flower

Potato

Solanum tuberosum

Cabbage

Brassica oleracea (Capitata Group) 'Cabbages'

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