1a. Objectives (from AD-416):
1) Characterize seasonal abundance of navel orangeworm in southern Central Valley walnuts, and compare these data with codling moth abundance and walnut infestation by these two pests. 2) Estimate the relative contribution of residents and immigrants to navel orangeworm populations in orchards in this region. 3) Examine the impact of mating disruption on reproduction and damage of navel orangeworm in the southern Central Valley.
1b. Approach (from AD-416):
For objectives 1 & 2, female-baited and oviposition traps will be used to compare abundance of navel orangeworm males and eggs, respectively, between the center and edges of walnut orchards with historically high damage, and also to compare these codling moth and navel orangeworm abundance with infestation by these pests in harvest samples. For objective 3, mating disruption for navel orangeworm will be applied to orchard with historically high damage. Impact of mating disruption will be assessed based on the ability of males to locate live females in traps, oviposition by females, and infestation at harvest by navle orangeworm and codling moth.
3. Progress Report:
This new subordinate project in walnuts is a logical extension of objective 4C (Develop models for almonds relating navel orangeworm damage to males captured in pheromone traps within the same year) in the parent project, 5302-43000-033-00D. It is a more direct extension of objective 5 (Determine the role played by NOW movement among multiple hosts on the efficacy of the new management practices demonstrated) from the Navel Orangeworm Area-wide suppression project, 0500-00044-023-00D, which was also under the auspices of the research 5302-43000-033-00D. The navel orangeworm (NOW) is a key pest for some walnut growers. NOW infestation is often seen as secondary to codling moth (CM); however, in the central San Joaquin Valley (i.e., Tulare, Kings, and Fresno counties), NOW has historically been more abundant and there has been greater expansion of other tree nut crops (pistachios and almonds) that can support high NOW abundance. The objectives of this project are: 1) compare phenology and damage between NOW and CM; 2) estimate the relative contribution of residents and immigrants to NOW populations in orchards in this region; and 3) examine the impact of mating disruption on reproduction and damage by NOW in walnuts. Cooperators were identified for 10 sites in Tulare County, with two additional sites monitored in Kings and Fresno counties. Navel orangeworm was monitored weekly at each site using egg traps (24-30 per site) and pheromone (female-baited) traps (1-2 per site). Timed-release aerosol mating disruption dispensers (Puffers) were placed at four of the sites in Tulare County. Both pheromone and egg traps indicated abundant overwintered NOW at most sites. The number of males captured in mating disruption plots comprised 79% of those captured in non-mating disruption sites before treatment started, but 0.1% of those in non-mating disruption sites after treatment began. There were also significantly fewer eggs in mating disruption plots compared to non-mating disruption sites after mating disruption treatments began, indicating impact on female fertility (objective 3). The findings to date indicate walnuts can support high abundance of NOW independent of other crops (objective 2), and NOW has potential for damage independent of CM in some walnut orchards, depending on management (objective 1).