Apple Maggot Emergence and Seasonal Activity In Wisconsin1

Abstract

Adult emergence of the apple maggot, Rhagoletis pomonella (Walsh), was studied from 1958 through 1963 and its seasonal activity during 1961 and 1962. There was 41% emergence of adults from a potential of 9072 larvae entering the soil to pupate. First emergence ranged from June 26 to July 17, and the last from August 15 to September 20. Peak emergence ranged from 9 to 12 days after emergence. Two peaks were recorded during 3 of the 5 years with the first peak the major one. Females dominated before emergence peaks and males afterward. The period of adult emergence ranged from 42-65 days with an average of 55. Carryover emergence was 15% and 5% during 1962 and 1963, respectively. Temperature had the greatest effect on emergence with higher than average mean temperatures causing earlier emergence. High temperatures and low rainfall tended to result in early emergence and a shorter emergence period. There was a better correlation between adult emergence and rainfall early in the season than late, with the latter having practically no effect. Adults tended to emerge earlier, reach a peak sooner, and have a shorter emergence period where the larvae developed in early maturing apple varieties than they did following development in later varieties. There was no significant difference in adult activity as related to the four quadrants of a tree, although more flies were usually trapped on the south side. Adults were more active between noon and 7:00 PM than between 7:00 AM and noon, and almost no activity occurred between 7:00 PM and 7:00 AM.