In favorable years, it is the most common aphid on potato plantations in Poland. The species consists of small individuals that form numerous colonies on plants. It is particularly abundant in areas where buckthorn is widespread as a shrub. In Europe, its occurrence increases eastward. It is also found in America (in the USA it is a vector of potato viruses), Asia, and sporadically in Africa.

Biology

• Eggs – small, laid on the bark of common buckthorn, the winter host (overwintering occurs in this stage).
• Larva (harmful stage) – length 1.2 mm, body oval, very delicate, wingless nymphs lemon-yellow (photograph 1). Short cauda and siphunculi. Forms compact colonies, mainly on the underside of older lower leaves; juvenile individuals, though wingless, resemble adults. Piercing-sucking mouthparts (stylets), extract sap. Parthenogenetic development through multiple generations of viviparous females (several generations per season) on potato (secondary host). Often similar to A. frangulae, forming mixed colonies on potato, making field identification difficult.
• Adult (harmful stage) – winged form, dark thorax with light green rings between wing bases and head, lateral spots on the abdomen light brown, and 1-2 transverse stripes behind siphunculi; body length 1.4–2.1 mm (photograph 2). No dark spot between siphunculi bases. Cauda and siphunculi brown with uniform pigmentation. Summer (migratory) generation is an active vector of PVY, PVM, and PVS transmitted to potato. Researchers suggest it may also transmit PLRV.

Life Cycle

The buckthorn-potato aphid is a heteroecious species. It inhabits the primary host (common buckthorn Rhamnus cathartica) and secondary hosts (potato and other Solanaceae, weeds of Polygonum, Fagopyrum, Nasturtium). Its development is holocyclic (complete) with viviparous females, winged individuals, and a sexual generation (egg-laying). Females lay eggs in autumn on the bark of the winter host, overwintering in this stage. In spring (April), eggs hatch into generations of viviparous females on buckthorn, colonizing young shoots. Winged migrants then move to summer hosts, where several generations of wingless viviparous and winged individuals develop. In dry and warm conditions, new colonies rapidly establish on newly colonized potato plants. In autumn, the sexual generation (males and females) returns to buckthorn, where mating occurs and fertilized eggs are laid in bark crevices and at the base of buds.

Occurrence and Damage

The species is widespread and abundant in Poland, mainly in warm years and where the winter host (common buckthorn) occurs.

A. nasturtii aphids are primarily virus vectors, causing degradation of seed and cultivated potato varieties. They actively transmit potato viruses M (PVM), S (PVS), and Y (PVY), currently the most economically important potato viruses in the country. Aphid pressure in Poland varies and remains at a moderate level, but it is a significant pest in virus transmission, especially where the peach-potato aphid is absent. Potato vegetative reproduction (through tubers) increases virus accumulation annually, leading to yield reductions. Therefore, it is important to frequently replace seed material with new qualified stock depending on varietal susceptibility. Adults and colonies (nymphs) also directly damage green potato parts by sap extraction, 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 by transmitting transient Y and M viruses to healthy plants.

Frequent field observations after planting and during summer growth are sufficient for aphid monitoring. Mechanical collection can be done using a Johnson aspirator. Monitoring can also be performed using yellow traps (winged aphids) or by counting aphids on the underside of middle-tier leaves (100-leaf method).

Control Methods

The primary control method is seed tuber treatment with a systemic insecticide at planting. Currently, only Prestige Forte 370 FS is available, containing a systemic active ingredient. Foliar insecticide applications (aphicides) are more common. The first treatment should be applied when the first aphids appear on leaves or yellow traps. Subsequent treatments should follow at intervals of 7–14 days, depending on actual threat. Mineral oil sprays generally do not control aphids but can reduce their numbers and influence growth on potato leaves. Mineral oil significantly limits virus transmission, making it important in seed production.

Avoiding weed infestation is critical because viruses may persist in weeds, which are also secondary hosts of certain aphids, e.g., Aphis fabae and A. nasturtii (Polygonum sp.). Excessive nitrogen fertilization (>150 kg/ha) causes excessive vegetative growth, favoring aphid development.

Essential oils from certain plants have significant potential for aphid control through repellent or lethal effects. Literature reports satisfactory efficacy of rosemary, lavender, thyme, and peppermint oils, though application methods remain technically challenging.

Other measures to reduce aphid colonization include covering ridges with chopped cereal straw or using trap crops sown around plantations (soy, sorghum, wheat, oats). Both methods limit potential virus vectors and reduce PVY tuber infection.

Eliminating the winter host (buckthorn) and avoiding planting seed potatoes nearby is also crucial in controlling A. nasturtii.

Compiled by: Dr. Tomasz Erlichowski