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The rosy apple aphid Dysaphis plantagineaThe rosy apple aphid Dysaphis plantaginea is a specialized host-alternating holocyclic, species since plantain (Plantago spp.) and dock (Rumex sp.) are its host plants in summer, whereas apple (Malus sylvestris Mill.) is the main plant host in autumn, where this aphid species over winters as eggs on apple branches.
The eggs laid in the fall are yellow and about 0,5 mm long. A very wet and rain full autumn result in a small number of eggs followed by a slight attack the next season.
Eggs hatch just before beginning of apple flowering and the newly hatched nymphs immediately begin to feed on newly developed leaves and buds. Each female produces about 150 to 200 nymphs and a rapid buildup of generations can occur due to the short developing time of this species (only 2-3 weeks).
D. plantaginea secrete large quantities of honeydew which provides a substrate for a black sooty fungus which can affect fruit quality. However, the most serious effect result from the translocation of saliva from the leaves to the fruit. This causes the apples to remain small and deformed and renders them unmarketable. Systemic effects of the toxic saliva include reduced growth of roots and other woody tissue.
D. plantaginea populations are generally controlled by insecticides, which are applied as soon as one fundatrix is observed. However, since rosy apple aphids live within curled leaves, they could be protected from direct sprays.
Winged morphs of D. plantaginea can be present in asexual clones and interestingly it has been observed that the infection of Dysaphis plantaginea densovirus (DplDNV) results in a significant reduction in aphid reproduction rate, but such aphids can produce the winged morph, even at low insect density, which can fly and colonize neighboring plants suggesting that a mutualistic relationship exists between the rosy apple aphid and its viruses.
The parthenogenetic females of D. plantaginea showed a chromosome number of 2n=10.