Occurrence of peach mealy aphid Hyalopterus persikonus in the spring in Zhengzhou and resistance evaluation of peach and its relatives

Abstract:【Objective】Peach mealy aphid, Hyalopterus persikonus belongs to Hyalopterus genus and is one of the three mealy aphids in Prunus plants. It is very similar to Hyalopterus amygdale and Hyalopterus pruni morphologically. Peach mealy aphid was seldom studied as a distinguished species in the past. As one of major worldwide pests occuring in the spring, it was very difficult for chemical insecticides to deal with the aphid due to a layer of wax powder on the body. Meanwhile, the use of chemicals could not only increase the production cost, pollute the environment and bring potential risk to food safety, but also kill the natural enemies and destroy the biodiversity. However, occurrence regularity of peach mealy aphid was scarcely known in many regions in China, especially in Zhengzhou. Moreover, till now rare resistant germplasms to peach mealy aphid has been reported. Recently, the occurrence range of peach mealy aphid fast expanded and the damage was gradually aggravated. New effort is needed to face the situation. We aimed at investigating the occurrence and the damage of peach mealy aphid on peaches in the spring in Zhengzhou, and identifying the resistant germplasms from different peaches and their wild relatives in order tosupply a foundation for scientific management of peach mealy aphid and resistance breeding in the future.【Methods】27 peach accessions from species of Prunus mira, Prunus davidiana, Prunus kansuensis,Prunus persica and Prunus ferganisis and 18 populations derived from different peaches and its wild relatives including materials from species P. mira, P. davidiana, P. kansuensis, P. ferganisis, P. triloba, P.tangutica, P. mongolica, P. cerasifera and P. salicina were planted in nursery of Zhengzhou Fruit Research Institute for resistance identification, and all trees were four or five years old. The seedlings of each population came from the seeds of open pollinated mother trees. The occurrence, colony development and damage of H. persikonus on peaches and its relatives were investigated every five days from late February. The aphids from the infested peach trees were collected for incubating the above materials. For each plant, five new shoots were chosen and excessive peach mealy aphids were incubated before bagging with40 mesh silver insect net. Seven days later, the resistance grades of different plants were scored by the aphid number on the shoots and the damage to the shoots. Five grades were divided for the different germplasms according to the damage degrees grade 1, 2, and 3 indicated highly resistant, middle resistant and slightly resistant, respectively, whereas grade 4 and 5 meant susceptible and highly susceptible. For the population evaluation, disease index(DI) was used to grade, DI≤20% as highly resistant,20%P. triloba) showed highly resistance with disease index(DI) of 21.2%, the population of‘Menggubiantao 1'(P. mongolica) and‘Sidaoling wild plum'(P. salicina) showed resistance with DI of38.9% and 44.9%, respectively, and‘Guizhou maotao 4'(P. persica) showed medium resistance with DI of 56%; Whereas the rest populations belonging to P. kansuensis, P. davidiana, P. mira or P. tangutica respectively, showed no resistance. P. mongolica, and P. cerasifera were newly found susceptible to the peach mealy aphid.【Conclusion】The occurrence and damage characteristics of the peach mealy aphid on peaches and relatives in the spring in Zhengzhou were basically clarified, which would be helpful for controlling the aphids in orchard. We found that plants of P. mongolica and P. cerasifera were good hosts for the peach mealy aphid, which expanded the understanding of host range of the peach mealy aphid. The population of‘Flowering almond 1'‘Menggubiantao 1'‘Sidaoling wild plum'and‘Guizhou maotao 4'were identified to possess resistance to the peach mealy aphid, which could be used in the resistance breeding program.