Aphid damage on Solanaceae

Solanaceae of large-scale crops (potato, tobacco)

Several viruses transmitted by aphids can infect potato. The most economically important is potato virus Y (PVY), known under the name mosaic, crinkle or mottling. It is non-persistent virus transmitted by different species of aphids. The initial inoculum can come from diseased plants from the same plot or from neighbouring plots, infected regrowth areas, other cultivated Solanaceae (tobacco, tomato, pepper) or weed species (black nightshade). The green peach aphid (Myzus persicae) remains the main vector of this virus followed by the buckthorn aphid (Aphis nasturtii). However, alates from other species not always dependent on potato can also transmit the virus. If these alates are highly abundant, they can play an important role as vectors of the viruses and therefore in the development of the disease. The potato leaf roll virus (PLRV) is also prominent. It is transmitted through the persistent mode, essentially by the aphid Myzus persicae. Other species like the foxglove aphid (Aulacorthum solani) and potato aphid (Macrosiphum euphorbiae) can also transmit this virus, but less effectively.                                        

Other than their role as vectors of plant viruses, aphids cause direct damage by extracting a substantial amount of sap. Three species are currently found on potato. Myzus persicae have a preference for colonizing the lower leaves. Macrosiphum euphorbiae are located rather on flower spikes where colonies cluster round like a sleeve when their population proliferates. Finally, Aulacorthum solani develops on leaves at lower and intermediate levels. Since 1996, in Champagne-Ardenne, Picardie and Nord-Pas-de-Calais, large numbers of two other species have been reported on foliage. These sightings involve Aphis nasturtii and the alder buckthorn-willowherb aphid (Aphis frangulae). The first individuals of Aphis nasturtii are seen in June and colonies develop on lower leaves in July where they can proliferate. In regions with a warm climate, Aphis frangulae can be replaced by the -cotton aphid (Aphis gossypii) which belongs to the same group of species.

The viral diseases of tobacco prove to be a significant factor behind limited production in certain regions. Large-scale implantation of blond tobacco varieties has changed the incidence of these diseases. The Virginie and Burley types are more sensitive to viruses than the brown tobaccos. Two viruses transmitted by aphids are predominant on tobacco: the potato virus Y (PVY) and the cucumber mosaic virus (CMV). More rarely the alfalfa mosaic virus (AMV) is also transmitted by aphids in the tobacco crops located nearby lucerne fields. The principal vectors of these viruses are the cotton aphid (Aphis gossypii) and the green peach aphid (Myzus persicae). These diseases are responsible for diminished yields and altered leaf quality leading to possible downgrading of the crop. Whatever viruses are present in the plant, the nature and intensity of their symptoms can vary with the type of tobacco grown, the variety but above all on the character of the viral strains. In any case, colonies of Myzus persicae induce crinkling of the foliage.

Solanaceae of market-garden crops (tomato, peppers, aubergine)

Tomato can be attacked by several viruses. Such infections have been advancing for several years. They can lead to considerable damage in plants having no genetic resistance. The cucumber mosaic virus (CMV) and potato virus Y (PVY) are transmitted by means of the non-persistent mode by several aphids, including the green peach aphid (Myzus persicae) and the cotton aphid (Aphis gossypii). The leaves formed after CMV infection are reduced to their veins, then the leaves that follow are severely lacerated to resemble fern leaves. Growth is slowed down and the affected plants produce little fruit. Myzus persicae also causes direct damage, shown by leaf rolling and deformation. Colonies of the potato aphid (Macrosiphum euphorbiae), which develop on stems, can weaken the plants and taint them with sooty mould.

Most diseases and pests of tomatoes are also capable of targeting crops of aubergine and peppers which are particularly sensitive to a number of aphid-transmitted viruses: cucumber mosaic virus (CMV), alfalfa mosaic virus (AMV) and potato virus Y (PVY) which is a serious threat to peppers. On those plants, the presence of aphids can also stimulate the formation of abundant sooty mould which degrades the harvest.

Integrated control management against aphids in the greenhouse requires the introduction of several  predators or parasitoids.