Zoological Studies

Vol. 59, 2020

(update: 2020.05.22; 07.06)
 

Simultaneous Occurrence of Diapause and Cold Hardiness in Overwintering Eggs of the Apple Oystershell Scale, Lepidosaphes Malicola Borchsenius (Hem.: Diaspididae)

Parvaneh Nazari1, Nafiseh Poorjavad2, and Hamzeh Izadi3,*

doi:10.6620/ZS.2020.59-25

1Department of Plant Protection, College of Agriculture, Isfahan University of Technology, P.O. Box 8415683111, Isfahan, Iran. E-mail: parvanehnazari@ymail.com (Nazari)
2Department of Plant Protection, College of Agriculture, Isfahan University of Technology, P.O. Box 8415683111, Isfahan, Iran. E-mail: npoorjavad@cc.iut.ac.ir (Poorjavad)
3Department of Plant Protection, Faculty of Agriculture, Vali-e-Asr University of Rafsanjan, Rafsanjan, Iran. *Correspondence: Tel: +98 34 3131 2012. Fax: +98 34 3131 2042. E-mail: izadi@vru.ac.ir (Izadi)

(Received 27 March 2020 / Accepted 20 May 2020)
Communicated by Benny K.K. Chan

As the key pest of apple fruits, the oystershell scale, Lepidosaphes malicola Borchsenius (Hem.: Diaspididae), overwinters as diapausing eggs under the protective, waxy cover of females. In this research, the effects of diapause development, cold acclimation, and rapid cold hardening were studied on the cold hardiness of the eggs. The changes in some physiological components were also investigated. The results indicated cold exposure to be a prerequisite for the survival of the diapausing eggs of L. malicola. No eggs hatched without exposure to cold. In addition, a direct relationship was observed among cold hardiness, cold acclimation, and diapause of the eggs based on the results. The highest level of hatching (the highest cold hardiness) of the eggs (80%) occurred in the cold-acclimated eggs at the end of diapause (March). Rapid cold hardening also influenced the cold hardiness of the eggs with diapause development. At the end of diapause, the lowest (61%) and the highest (77%) rates of egg survival were observed when the eggs were exposed to 5 and -10C for 24 h, respectively. Cold hardiness of the diapausing eggs of L. malicola was also accompanied by some physiological changes, i.e., a decrease in glycogen content and an increase in simple sugar, lipid, and protein contents. The lowest glycogen content (about 50 μg/g) and the highest amounts of total simple sugars (454 μg/g) of lipids (542 μg/g) and proteins (84 μg/g) were observed in the cold-acclimated eggs at the end of diapause.

Key words: Cold hardiness, Cold acclimation, Diapause, Apple.

Citation: Nazari P, Poorjavad N, Izadi H. 2020. Simultaneous occurrence of diapause and cold hardiness in overwintering eggs of the apple oystershell scale, Lepidosaphes Malicola Borchsenius (Hem.: Diaspididae). Zool Stud 59:25. doi:10.6620/ZS.2020.59-25.