Observations on eggs produced by laboratory-reared Laspeyresia pomonella (L.) in field-oviposition cages provided a practical means for estimating date of 1st egg hatch in the field. Evaluation of timing of the 1st spray application (azinphosmethyl, 1 oz Al/100 gal) showed that under the unseasonably cool weather encountered, sprays could be delayed for more than a month after sex traps began to catch moths. Estimation of date of 1st egg hatch was a useful supplement to sex traps for predicting earliest date that a spray was required.