Characteristics and Pest Description

It is rarely observed in Poland on potato plantations. It belongs to the largest potato aphids. Due to its inability to overwinter and relatively slow development, it appears late, approximately in mid-summer. The species is not very numerous, but it persists on plants the longest – sometimes until the first frosts. It is polyphagous, feeding on many plant species as secondary hosts. In Europe, its occurrence increases eastwards. Originating from America (where it is a vector of potato viruses in the USA), it has been introduced to Europe and other temperate countries. In America, it has a holocyclic development; in other regions, anholocyclic.

Biology

• Eggs – small, white.
• Larva (harmful stage) – 2.5-3.2 mm long, oval body, very delicate, wingless nymphs, green with a distinct stripe on the abdomen (photo 1), occasionally pink forms. Found mainly on the underside of older leaves of the lower plant tiers; juvenile individuals (nymphs) resemble adults despite being wingless. Piercing-sucking mouthparts (stylet), feeding on sap. Parthenogenetic development through several generations of virgin females (multiple generations per season) on potatoes (secondary host).
• Adult insect (harmful stage) – winged form (photo 2), dark thorax with light green stripe, very long legs, green abdomen, body length up to 3.3 mm. 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 about 200 plant species. In the field, it has many secondary hosts (including potato and other Solanaceae, weeds from the Chenopodiaceae family). Holocyclic development (complete), with virgin females, winged individuals, and sexual generation (laying eggs on weeds in autumn) is observed only in America. In spring (April), eggs on weeds hatch to produce generations of virgin females that colonize young shoots, then winged individuals (migrants) move to summer hosts such as potato, beet, Solanaceae, cabbage, where several generations of wingless virgin females and winged individuals develop. In dry and warm weather, new colonies rapidly develop on newly colonized sites (potatoes) with migrants flying over long distances (with the wind). In autumn, the sexual generation (males and females) returns to weeds, copulates, and lays fertilized eggs in bark crevices and at the base of buds. In Europe, an anholocyclic life cycle occurs – females overwinter on tuber sprouts in storage or on greenhouse lettuce. In spring, they fly to fields in search of secondary hosts.

Occurrence and Harmfulness

The species is rare in Poland, mainly in warm years and where secondary hosts or greenhouses are present.

The aphid M. euphorbiae is primarily a virus vector that causes degradation of seed material. It 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. The pressure of this aphid in Poland is low and remains at a minor level (mainly due to decreased potato cultivation), but it is an important aphid in infecting potatoes with these viruses. Vegetative reproduction of potato (through tubers) increases virus load annually, causing further yield reduction. Therefore, depending on variety susceptibility, seed material should be frequently replaced with new, certified stock. Adults and colonies (nymphs) also directly damage green parts of potato plants, sucking phloem sap, rarely causing leaf curling or deformation.

Economic Threshold

The threshold is 20 aphids per 100 leaves. Even a single winged aphid on a plantation can pose a potential threat (as it can transmit non-persistent viruses Y and M, as well as PLRV, directly via its stylet).

Monitoring can be done through frequent field observations after planting and during summer growth. Mechanical removal can use a Johnson aspirator. Monitoring may involve yellow traps (winged aphids) or counting aphids on the underside of leaves in the middle tier (100-leaf method).

Control Methods

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

It is also crucial to prevent weed growth in plantations, as weeds can harbor viruses and serve as secondary hosts for certain aphids such as Aphis fabae. Excessive nitrogen fertilization (over 150 kg/ha) promotes plant overgrowth, creating favorable conditions for aphid development. Essential oils from rosemary, lavender, thyme, and peppermint have shown promising aphid-repellent or insecticidal effects, although application methods remain challenging.

Other methods to reduce aphid infestations include covering ridges with chopped cereal straw or planting trap crops around plantations (soy, sorghum, wheat, oats). Both methods limit potential vectors, significantly reducing PVY infection in tubers.

Compiled by: Dr. Eng. Tomasz Erlichowski