Aphids are a big problem in the horticultural sector. Through their enormous reproductive capability, aphids can cause severe damage to several crops. Resistance to pesticides is increasing. Important aphids occurring in glasshouses are: the cotton aphid Aphis gossypii, the glasshouse potato aphid Aulacorthum solani, the potato aphid Macrosiphum euphorbiae, the green peach aphid Myzus persicae var. persicae and the tobacco aphid Myzus persicae var. nicotianae.
In glasshouses aphid population always consists of viviparous females. Young aphids are born and immediately start feeding on plant sap. They grow quickly and moult four times before they become adult.
The resulting characteristic white skins betray the presence of aphids. Winged aphids develop at high densities, enabling rapid spread through the glasshouse from hot spot areas.
Nymphs and adults feed on plant sap. This halts growth, causing curled leaves. Sometimes yellow spots appear. Aphids excrete honeydew. Sooty moulds can develop, soiling the crop. Photosynthesis is reduced, and consequently growth and production. Toxic substances can be brought into the plant, causing strong allergic reactions in the plant. Plant pathogenic substances, particularly viruses, can be brought into the plant.