Addition of Pear Ester With Sex Pheromone Enhances Disruption of Mating by Female Codling Moth (Lepidoptera: Tortricidae) in Walnut Orchards Treated with Meso Dispensers.

We evaluated the low-density application of 50 dispensers per hectare, in contrast to the traditional >800 dispensers per hectare in apple orchards, to achieve disruption of communication of adult codling moth, Cydia pomonella (L.), in walnuts, Juglans regia (L.), using several methods. These methods included cumulative catches of male moths in traps baited with sex pheromone (Ph) or codlemone, (E,E)-8,10-dodecadien-1-ol, or a combination of codlemone, pear ester (PE), ethyl (E,Z)-2,4-decadienoate, and acetic acid, and by examining the mating status of females. These data were collected from 2011-2014 in nontreated plots and in similar plots treated with Meso dispensers loaded with codlemone (Ph Meso) or codlemone and PE (Ph + PE Meso). Male moth captures in both the Ph and combination lure traps reduced by 88-96% and 72 to 77%, respectively, compared with traps in the nontreated plots. A significantly higher proportion of female moths were nonmated in plots treated with Ph + PE Meso dispensers (33%) than in plots treated with Ph Meso (18-26%), or left nontreated (13%). In addition, significantly fewer multiple-mated females were trapped in the Ph + PE Meso-treated plots (6%) than in either Ph Meso-treated (13-18%) or nontreated plots (23%). These data suggest that the addition of PE can effectively improve Ph-based disruption of C. pomonella in walnut orchards. In addition, these data suggest that the use of low-density hand-applied dispensers can be an effective and lower-cost approach to manage this pest in the large canopy presented by walnut orchards.

Does use of pesticides known to harm natural enemies of spider mites (Acari: Tetranychidae) result in increased number of miticide applications? An examination of California walnut orchards.

Integrated pest management (IPM) offers guidelines to reduce spider mite (Acari: Tetranychidae) outbreaks by avoiding pesticides known to be harmful to the natural enemies of spider mites. However, in practice, these guidelines can be inconsistent in their effectiveness. The project examined whether California walnut (Juglans L.) growers, following IPM guidelines to avoid pesticides harmful to the natural enemies of spider mites, achieved lower miticide use. Significant statistical tests suggested that fields with harmful applications were 40% more likely to have a miticide application than fields without. Although the IPM guidelines achieved the goal of reducing miticide use, further analysis of other potential causal mechanisms behind outbreaks could strengthen the effectiveness of the guidelines, potentially increasing IPM adoption.

Developing Drosophila suzukii management programs for sweet cherry in the western United States.

BACKGROUND: The spotted wing drosophila, Drosophila suzukii Matsumura (Diptera: Drosophilidae), is a newly introduced pest of sweet cherry on the west coast of North America which produces about 97% of the value of the US sweet cherry crop. D. suzukii initially caused considerable economic loss to cherry growers, who were unaware of this new pest. Little control information was available at the time of initial infestation. Pest control studies were initiated to examine the materials, timings and application methods to control D. suzukii in three major cherry-producing states (California, Oregon and Washington). RESULTS: Three classes of registered insecticides, organophosphates, pyrethroids and spinosyns, have demonstrated good topical or residual activity against D. suzukii. Neonicotinoids and the systemic organophosphate dimethoate appear to be able to kill eggs or larvae in fruit. Preliminary timing studies indicate that at least two preharvest insecticide sprays are required to obtain control of D. suzukii in California cherry orchards. Aerially applied malathion ULV (ultra-low volume) appears to be a viable control tactic for this pest. CONCLUSION: The results presented here form the basis for developing D. suzukii management programs in the western United States. Additional studies are needed to refine management practices for the different growing regions and conventional versus organic production requirements. Cherry growers will likely need to apply broad-spectrum insecticides in a prophylactic manner until treatment thresholds and monitoring methods have been developed and validated.

The role of tyloses in crown hydraulic failure of mature walnut trees afflicted by apoplexy disorder.

In the Central Valley of California, mature walnut trees afflicted with apoplexy disorder exhibit rapid and complete crown defoliation within a few weeks of symptom initiation. Symptoms are typically found throughout the entire crown and are initially expressed as wilting and chlorosis followed by scorching of leaves. Since the cause of apoplexy disorder is unknown, we set out to elucidate the water relations physiology underlying this condition. Stem water potential (Psi(s)) of healthy, asymptomatic trees remained high throughout the 2007 growing season, while that of apoplexy-afflicted trees decreased significantly with the onset of symptoms for both healthy-appearing and symptomatic portions of these trees. Psi(s)s were significantly reduced by at least 0.7 MPa in the lower, middle and upper portions of the symptomatic canopies compared with those from asymptomatic trees. Heat pulse velocities measured in the main trunk at three radial depths consistently decreased prior to the onset of symptoms and eventually reached zero with complete crown defoliation. Comparison of sap flow with predicted water use based on walnut evapotranspiration suggests that stomata of symptomatic trees were closing at higher evaporative demand prior to symptom formation. Specific hydraulic conductivity (K(s)) of symptomatic stems was significantly lower than that of asymptomatic stems, and no detectable K(s) could be measured on several of the symptomatic stem samples. However, shallow root K(s) did not significantly differ between symptomatic and asymptomatic trees, suggesting that hydraulic failure was isolated to the crown of these grafted trees. Light and scanning electron microscopy of stem and trunk sapwood revealed extensive tylose development in vessels throughout the crown of symptomatic trees. Analysis of the formation of tyloses on multiple dates revealed rapid development of these vessel occlusions in conjunction with visual symptom formation and dramatic decreases in sap flow. In 2008, tylose development was associated with elevated ethylene production in the active sapwood of symptomatic trees. The cause of elevated ethylene associated with tylose production and symptom formation is yet to be determined.