Erol, T., & Yaşar, B. 1999 [Investigations on natural enemies, some biological characteristics and population fluctuations of Lepidosaphes ulmi (L.) (Homoptera, Diaspididae) and Palaeolecanium bituberculatum (Targ. and Tozz.) harmful to apple trees in Van Province].. Turkish Journal of Agriculture and Forestry 23: 2, 151-164.

Notes: [Original title: Van ili elma agaclariinda zararlii Lepidosaphes ulmi (L.) (Homoptera, Diaspididae) ile Palaeolecanium bituberculatum (Targ. and Tozz.) (Homoptera, Coccidae)'un populasyon degisimleri, bazii biyolojik ozellikleri ve dogal dusmanlarii uzerinde arastiirmalar.] A study was carried out from 1991 to 1993, in Van province (Erciis, Edremiit, Gevas), Turkey, with the aim to determine population fluctuations, some biological characteristics and natural enemies of Lepidosaphes ulmi and Palaeolecanium bituberculatum which are pests of apple trees. Samples were collected periodically every 15 days from 7 trees (variety Starking) in orchards in Gevas, Edremiit and Erciis. L. ulmi and P. bituberculatum overwintered as eggs on apple trees in Van province. They reproduced sexually and had one generation a year. The average number of eggs laid per female for L. ulmi and P. bituberculatum were determined as 50 and 259 eggs, respectively. The mobile nymphs of the two species, which were the most susceptible stage to insecticides, were found in orchards in May. Aphytis mytilaspidis and Hemisarcoptes malus were found to be the most effective natural enemies of L. ulmi. The parasitoid Coccophagus palaeolecanii was obtained from P. bituberculatum, but its population was very low.