Arias Giralda, A., Nieto Calderon, J., 1979.
Hatching of the winter eggs of the fruit red spider mite Panonychus ulmi Koch, in the Guadiana Plains (Badajoz), 1970-78. Boletin del Servicio de Defensa contra Plagas e Inspeccion Fitopatologica, 5: 177-194.
Abstract
Analysis of the hatching dates of the winter eggs of Panonychus ulmi (Koch) on peach, pear, apple trees in the Province of Badajoz, Spain, over a period of 8 years (1970-78) showed that the eggs hatched between late February and early May, and that 80% hatched between 20 March and 20 April. At the time when 50% of the eggs had hatched, late-flowering peach varieties and middle-flowering pear varieties were at the petal-fall stage and late-flowering pears and Starking apples were in full flower. The eggs tended to hatch earlier on peach than on apple, the 50% hatch occurring some 7 days apart. It was not found possible to use the sum of effective temperatures to predict the hatching dates sufficiently accurately to form the basis of treatment recommendations. Two applications of specific acaricides with no or little ovicidal effect are recommended (at an interval of 10-12 days) when the 50 and 80-85% hatching levels have been reached. It is concluded from the records of average temperatures in August (23.9 deg C), September (21 deg C) and October (16.7 deg C) in the Guadiana Plains, Badajoz, that the effect of the photoperiod inducing the production of winter eggs (which is LD 13:11 to 15:9 at 15 deg C) is modified by the temperature.
