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Light infestations of A. solani can severely injure potato foliage. Its feeding causes discoloured spots on tobacco, and heavily infested plants can show large necrotic areas, sometimes resulting in the senescence of the entire leaf. Feeding also causes irregular curling of young potato leaflets and it is speculated that growth of the leaflet is hindered as a result of the feeding puncture. In potato stores, A. solani can attack potato sprouts.
Indirect damage is caused by honeydew production and virus transmission. Honeydew, a sticky liquid excreted by the aphid, covers the foliage and is often colonized by black saprophytic fungi, hampering respiration and photosynthesis.
Selection of growing area
Because virus spread is related to aphid populations, seed production areas should be selected on the basis of aphid population studies. Aphid populations are generally low in areas with low temperature, abundant rainfall and high wind velocity. Within a potato growing area, to reduce dissemination of viruses through viruliferous aphids, seed potato fields should be located upwind from commercial potato fields and alternative host crops. Seed production areas ideally should be completely separated from commercial potato production.
The timing of aphid migration may be more important than the total number of aphids trapped, as aphid flights often reach definite peaks at certain times of the year. Virus spread early in the season is more serious than later on, as young plants are generally more susceptible. Furthermore, plants that are infected early become more efficient sources for further virus spread than plants infected later in the season.
Primary hosts of the virus should be eliminated. Within a seed field, eliminate infected potato plants as early as possible. Yellow, flowering weeds and any other host plants within and around the field should also be removed.
After a viruliferous aphid has fed on potato foliage, the virus requires time to infect the tubers. In order to avoid this, highest-grade seed potatoes should be harvested no later than 8 to 10 days after population studies reveal a critical aphid build-up or increase.
Aphids readily colonize tuber sprouts and so potato tubers must be protected during storage by preventing access of aphids and by using aphicides. Seed potatoes are very susceptible to infection at this stage, and so potato stores should be fumigated when migration has finished, ensuring even distribution of smoke.
Glandular pubescence, a non-specific arthropod resistance mechamism in the wild potato, Solanum berthaultii, has been used in potato breeding as a defence against a variety of insect pests, including potato aphids, the potato leaf hopper (Empoasca fabae) and the potato flea beetle (Epitrix cucumeris). Mizukoshi and Kakizaki (1995) reported the trapping of early instars of A. solani in the trichomes of Phaseolus vulgaris, resulting in differential mortality between cultivars. Obrycki et al. (1983) reported that glandular pubescent potato cultivars and naturally occurring predators and parasitoids are compatible and complementary methods for managing aphids on potatoes. Gibson (1971) reported A. solani resistance in three Solanum species.
Soybean cv. Adams is tolerant to infection by Soybean dwarf virus (SbDV) in the field and exhibits antibiosis to A. solani, which transmits SbDV (Takahashi et al., 2002; Ohnishi et al., 2012).
Snowdrop lectin (Galanthus nivalis agglutinin, GNA) has been shown to have insecticidal effects against A. solani when incorporated in artificial diet and/or expressed in transgenic potato (cv. Desireé) (Down et al., 1996).
Due to the variable regulations around (de-)registration of pesticides, we are for the moment not including any specific chemical control recommendations. For further information, we recommend you visit the following resources:
A. solani is becoming an increasingly economic important pest of several agricultural crops worldwide and has recently undergone a status change from an occasional pest to a serious pest of vegetables and ornamental plants in greenhouses of North America and the UK (Jandricic et al., 2010, 2014a). A. solani was first recorded on citrus in the north of Iran in 2003-2004 (Alavi and Rezvani, 2007).
In most potato growing areas, A. solani is one of the most economically important pests, causing injury either directly by their feeding punctures or indirectly by spreading virus diseases. With the use of organic insecticides, direct feeding damage has become less serious. However, more stringent permitted levels of virus infection in seed potato certification programmes has increased the importance of aphids as virus vectors, since a very small percentage of infection can lead to rejection of an entire seed lot.
A. solani is an important vector of Potato virus Y, Potato virus A, Potato virus X and Potato leafroll virus (Culjak et al., 2013). The aphid also transmits other viruses, including Cucumber mosaic virus (Contangelo et al., 1994), Soybean dwarf virus (Honda et al., 1996; Ohnishi et al., 2012), Bean yellow mosaic virus (Yahia et al., 1997), Turnip yellows virus (Schliephake et al., 2000), Zucchini yellow mosaic virus (Katis et al., 2006) and Johnsongrass mosaic virus (Mariño et al., 2010).
The economic injury level (EIL) for A. solani on greenhouse pepper (Capsicum annuum) was estimated at 57 cumulative A. solani-days and the economic threshold was established at 20 cumulative A. solani-days to prevent aphid density from reaching the EIL between sampling periods (Sanchez et al., 2007). In another study on greenhouse pepper, the EIL obtained was so low that treatment was required as soon as aphids were detected to prevent economic losses (Hermoso de Mendoza et al., 2006).