1a. Objectives (from AD-416):
1. Evaluate the correlation of leafroller adult catches in traps baited with pear ester and acetic acid with local larval populations within orchards. 2. Evaluate the relative attractiveness of other host plant volatiles in combination with acetic acid for both leafrollers and codling moth.
1b. Approach (from AD-416):
Orchards with known leafroller populations will be identified in the Wenatchee and Yakima Valleys. Blocks will be monitored with traps baited with acetic acid and pear ester. Leafroller larval populations and fruit injury will be sampled and correlated with moth catches. Replicated trials will be conducted in a few sites to compare the attractiveness of several different host plant volatiles plus acetic acid.
3. Progress Report:
The work summarized in this progress report relates to objective number 3 in the Project Plan for 001-00D: 3. Discover and develop chemical attractants for codling moth, fruit flies, pear psylla, and other insect pests of temperate tree fruits and their natural enemies. The addition of acetic acid to a sex pheromone-pear ester combination lure increased codling moth catches, especially females. A commercial acetic acid lure was developed by Trécé Inc as a result of this research. The optimal daily release rate of acetic acid from lures required to be effective for leafrollers was found to be higher than for codling moth. A lure comprised of 6 plant volatiles combined with codling moth sex pheromone and acetic acid attracted Pandemis and oblique banded leafrollers. Pear ester provided the highest catch of codling moth, especially of female moths. A new attractant (International patent pending) developed in New Zealand was more (2 to 7-fold) attractive than pear ester when used with acetic acid for both leafroller species and the eye-spotted bud moth. Field studies with both species of leafrollers found that a single trap baited with codling moth pheromone, pear ester, and acetic acid provided useful information about the presence of local infestations of leafrollers. Several factors were of concern with the use of this monitoring approach. ‘False negatives’ where the trap fails to catch adult leafrollers and larvae were detected in a few sites with the presence of overwintering larvae and no subsequent adult catches. This was likely due to the use of control tactics against the spring generation of leafroller larvae which eliminated the subsequent emergence of the summer generation adults in the orchard. No cases occurred where traps failed to catch moths and larvae from the subsequent generation were detected. The occurrence of ‘false negatives’ also appeared to have occurred in some pear blocks where the eye-spotted bud moth was present and injured fruits were misclassified as oblique banded leafroller damage. ‘False positives’ where the trap catches leafroller adults but no larvae are found was more common and always occurred in blocks with adjoining cherry blocks. Due to the immigration potential of leafroller adults from cherry these catches are considered to be useful information for apple and pear growers to assess their risk. Growers need to sex moths to ascertain if females are moving into the orchard. In the great majority of orchards the use of the CM-DA Combo lure with acetic acid caught one or more leafroller adults when leafroller pressure was ranked as moderate to high (based on the presence of larvae or injury); and traps failed to catch any adult leafrollers when the pest pressure was rated low to nonexistent.