Elena Martínez-Villar, elena.martinez@daa.unirioja.es1, Fernando Moreno, fernando.moreno@daa.unirioja.es1, Francisco J. Sáenz-de-Cabezón, fjsaenzdecabezon@ucdavis.edu2, E. García-Ruiz1, Vicente Marco, vicente-santiago.marco@daa.unirioja.es1, and Pérez-Moreno Ignacio, ignacio.perez@daa.unirioja.es1. (1) Universidad de La Rioja, Unidad de Protección Vegetal. Departamento de Agricultura y Alimentación, Madre de Dios, 51, Logroño, La Rioja, Spain, (2) University of California Davis, Entomology, One Shields Avenue, Davis, CA
The effect of photoperiod and time of maintenance at different temperatures on diapause termination in overwintering eggs of the phytophagous mite
Panonychus ulmi (Koch) (Acari: Tetranychidae) was determined.
Eggs collected in the beginning of the diapause from pear trees in La Rioja (Spain) were maintained in a growth chamber in dark conditions at three different temperatures: 2, 4 and 8 ºC for different time intervals: 10, 20, 40, 60, 80 and 100 days. After each time period, eggs were transferred to a growth chamber at 20 ºC constant temperature, and two different photoperiods (16:8 and 8:16 L:D respectively). Hatching percentage was recorded daily.
Temperature had not a significant effect on hatching percentage. Photoperiod and duration of maintenance at the different temperatures influenced the percentage of hatching for P. ulmi diapause eggs. Hatching percentage was affected by photoperiod when diapause eggs were reared for 10 to 40 days under low temperatures. Time periods at low temperatures exerted a detrimental effect on hatching percentages (being 6.3 ± 1.2 and 59.5 ± 4.1 after 10 and 100 days respectively). Diapause termination in 50% of the eggs (T50%) was strongly influenced by the time that eggs were maintained under low temperatures.
Acari Tetranychidae
Panonychus ulmiKeywords: overwintering eggs, diapause termination
