Mszyca ziemniaczana średnia

It is occasionally found on potato plantations in Poland, and according to studies at the Bonin Institute, it is declining. It has forms reproducing both anholocyclically and holocyclically. The species is not abundant but appears early on plants, sometimes just after emergence. It is polyphagous, feeding on many plant species as secondary hosts. In Europe, its occurrence increases eastward. Its origin is likely European. In the USA, it is an important vector of potato viruses, introduced from Europe.

Biology

• Eggs – can overwinter on many plant species.
• Larvae (harmful stage) – 1.9–2.6 mm long, pear-shaped, very delicate, wingless, shiny yellow to green nymphs (photo: 1). Light spot at the base of siphons. Antennae longer than body. Pale, long siphons with dark tips. Aphids mainly inhabit the underside of leaves. Juveniles resemble adults. Characteristic feature: segmented antennae. Piercing-sucking mouthparts (stylets), sap-sucking. Parthenogenetic development through multiple generations of viviparous females on potato (secondary host).
• Adults (harmful stage) – winged form, green, body length up to 3 mm (photo: 2). Dark antennae and siphons, dorsal pattern: transverse stripes. Summer generation (migratory) is an active vector of viruses (PLRV, PVY, PVM) transmitted to potato plants.

Life cycle

This is a polyphagous aphid living on 48 plant species. In temperate climates, most populations overwinter as wingless nymphs, especially on potato sprouts and various greenhouse and wild plants.

In the field, it has many secondary hosts (including potato, other Solanaceae crops, and weeds). Holocyclic development with viviparous females, winged individuals, and a sexual generation laying eggs on weeds occurs only in some forms. They overwinter in shelters or greenhouses. In spring (April), they migrate to crops and produce generations of viviparous females (stem mothers), which colonize young shoots. Winged individuals (migrants) then migrate to summer hosts such as potato, beet, and Solanaceae, where several generations of wingless viviparous females and winged forms develop. Under dry and warm conditions, new colonies quickly establish on newly infested plants, aided by wind-dispersed migrants. In autumn, sexual generations return to the greenhouse. In Europe, anholocyclic reproduction prevails – females overwinter on tuber sprouts in storage or in greenhouse plants and migrate to fields in spring in search of hosts.

Occurrence and damage

This species occurs rarely in Poland, mainly in warm years and where secondary hosts or greenhouses are present.

A. solani are primarily vectors of viruses that cause degradation of seed material and cultivated varieties. A. solani is an active vector of Potato leafroll virus (PLRV), Potato virus M (PVM), and Potato virus Y (PVY), currently the most economically important potato virus in Poland. Pressure from this aphid is variable and generally low due to decreased potato cultivation and climate changes, but it is still “important” for transmitting viruses to potatoes. Adults and nymph colonies directly damage green parts of potato plants by sap-sucking and, in greenhouses, can cause leaf curling and deformation.

Economic threshold

The economic threshold is 20 aphids per 100 leaves. Even a single winged aphid on a plantation can be a threat as it may transmit non-persistent Y and M viruses and persistent PLRV to healthy plants via stylets.

Monitoring can be done through frequent field inspections after planting and during summer growth. Aphids can be mechanically removed using a Johnson aspirator. Monitoring can also use yellow traps (for winged aphids) or by counting aphids on the underside of middle canopy leaves (100-leaf method).

Control methods

The primary protection method is seed tuber treatment with an insecticidal seed dressing in spring during planting. Currently, only one such dressing is available – Prestige Forte 370 FS, containing a systemic active substance. The most common treatments are foliar insecticides (aphicides). The first treatment should be applied when the first individuals are observed on leaves or yellow traps. Subsequent treatments should be applied at intervals of 7–14 days, depending on actual threat. Spraying with mineral oils does not effectively control aphids but can reduce their numbers and growth on potato leaves. Mineral oils significantly reduce virus transmission, important in seed potato production.

Avoiding weed growth on plantations is also critical as weeds may harbor viruses and serve as hosts for some aphids, e.g., Aphis fabae. Excessive nitrogen fertilization (>150 kg/ha) promotes lush plant growth, favoring aphid development. Essential oils from plants such as rosemary, lavender, thyme, and peppermint also help repel or control aphids, although application techniques remain challenging.

Other methods to reduce aphid infestations include covering ridges with chopped cereal straw or planting trap crops in strips around fields (soy, sorghum, wheat, oats). These methods reduce potential vectors and significantly lower PVY infection in tubers.

Compiled by: Dr. Eng. Tomasz Erlichowski