Mass releases of commercially produced Trichogramma wasps can be used to reduce damage from codling moth by 60% in walnut and pome fruit orchards in California. Results from field trials indicate that release rate and evenness of distribution are important factors influencing the effectiveness of wasp releases, and that damage reduction is more effective in walnuts and pears than in apples. Because the environmental risks of large-scale releases of Trichogramma wasps are likely to be small, wasp releases could be integrated with pheromone-based mating disruption for effective management of codling moth.
The Walnut Pest Management Alliance (PMA) for a tenth year continued work to reduce pesticide inputs in California walnuts and demonstrate and increase implementation of pest management strategies based on various formulations of pheromone mating disruption (PMD). Three long-term, area-wide projects continued in 2008 with aerosol pheromone puffers for codling moth (CM) control and three additional sites and an expansion area were created. The majority of the PMD acreage in this project in 2008 did not need supplemental insecticides to control CM, but some blocks did need treatments to control walnut husk fly and navel orangeworm which are not affected by the pheromone program. Several years of using PMD over a large area demonstrate the benefits of this system which include reduced crop damage, reduced CM populations which can be managed using fewer insecticide sprays, reduction of broad spectrum insecticides and a move to softer insecticides to supplement PMD. Data collected from the same locations over several years allows measurement of these reductions. The trial locations are independent and the results are not meant to be compared to each other. Monitoring data from several of the puffer sites was compared to a non-pheromone treated orchard and the resulting graph (Figure 1) was shared regionally. The success of this program depends on the inputs from many collaborators including pest control advisors (PCAs), UCCE Farm Advisors, Suterra LLC, Trece Inc, USDA-ARS, Ca. Dept. of Pesticide Regulation, UC IPM, Walnut Marketing Board, Walnut Entomology Workgroup, growers, and several field assistants. The project is supported by grants from: • Walnut Marketing Board, $23,000 • Western IPM, $55,000 • USDA areawide project, $49,000 • UC IPM Demonstrations, $10,000 OBJECTIVES 1. Validate pheromone application technology required for control of codling moth with an emphasis on “area-wide” control over multiple years. Continue using aerosol puffers at sites in San Joaquin, Glenn, and Butte Counties and expand acreage of SJ site to take advantage of area-wide CM suppression. 2. Create new sites where growers have shown interest in Yolo, and Tehama Counties to increase local visibility and experience with the pheromone puffers. 3. Demonstrate the use of monitoring CM to watch for population increases and to determine spray timings. Monitor damage to the crop with in-season surveys of nuts in the canopy. Over time, the need for supplemental sprays should be decreased and eliminated with CM population reductions.
ABS TRACT Essentially a continuation of the Walnut Pest Management Alliance (PMA), this project continued for a seventh year efforts to reduce pesticide inputs in California walnuts and demons trate and increase implementation of pest management strategies based on various formulations of pheromone mating disruption (PMD). Si x long-term, area-wide projects continued in 2011 with aerosol pheromone „puff ers‟ for codling moth (CM) control. Two of these sites, San Joaquin and Glenn, have successfully used puffers for seven years as the primary CM management tool. The majority of the PMD acreage in this project did not need CM insecticide treatments in 2008 or 2009, but in 2010 and 2011 supplemental sprays were required at some sites. Several years of using PMD over a large area demonstrates the benefits of this system including reduced crop damage, reduced CM populations which can be managed using fewer insecticide sprays, reduced broad spectrum insecticide applications, and a move to softer insecticides as supplements for PMD. As PMD becomes better understood, the research and implementation effort shifts focus from managing the primary walnut pest, CM, to managing navel orangeworm (NOW) considered a secondary pest. The success of this program is the result of input from many collaborators including growers, pest control advisors (PCAs), UCCE Farm Advisors, Suterra LLC, Pacific BioControl Corporation, Trece Inc, USDA-ARS, Ca. Dept. of Pesticide Regulation, the UC Integrated Pest Management Program, and the California Walnut Board.
The walnut PMA work plan continues with the broad based implementation project designed to encourage adoption of reduced-risk pest management programs in walnuts statewide. The focus of this project is to continue current efforts to demonstrate economical reduced-risk management strategies on walnuts and to improve communication and cooperation among the different groups involved. The PMA project has evolved into a broader program than originally envisioned with individual researchers working closely with the PMA in the area of codling moth and blight. This research feeds directly into the PMA project, allowing the PMA project to better focus on testing and demonstration that are near term. Several factors have increased the prospects for development of reduced risk practices for codling moth, which is the primary target for broad spectrum insecticides in walnuts. These factors include the documentation of resistance to the most commonly used insecticides and the development of newer pheromone application technologies such as sprayable pheromone and puffers. This coupled with the development of new, more selective insecticides that can help provide control without disruption of naturally occurring biological control. The codling moth PMA project in 2003 again demonstrated pheromone mating disruption at the five sites with the using two different rates of Suterra CM-F in the sprayable formulation. Since sprayable pheromone is more practical for walnut growers to apply, there is a higher probability that growers will incorporate it into their existing codling moth control programs. In addition, the project expanded to include 18 grower implementation sites throughout the walnut growing region. The implementation sites were managed by the grower and PCA using protocols written by the walnut PMA. The PMA sites used the newest technology in a lure for monitoring with traps that contains a kairomone instead of a pheromone, and catches both males and females. The PMA has continued to test Xanthocast, the walnut blight model, as well as helping growers learn to use the model. A satellite project using reduced risk materials for walnut husk fly management was conducted in as well. The PMA will continue to develop management techniques from research funded by the Walnut Marketing Board, using UC IPM monitoring programs refined by the walnut PMA, and outreach programs that will result in increased adoption of a reduced-risk walnut program to decrease the use of pesticides in walnuts.
Prune ( Prunus domestica ) producers have an increased incentive to produce larger fruit. Potassium is thought to be critical in prune production and the fruit utilize large amounts of K. Growers have been fertilizing heavily with K to maximize fruit size. We conducted a survey of 16 `French' prune orchards in 1998 and 1999 growing seasons. Low (≈1.0% mid-July) leaf K concentration is associated with leaf chlorosis, early leaf drop and shoot dieback, with symptoms pronounced in the upper canopy, particularly with heavy cropping. The survey orchards were chosen to represent a range of leaf K within and among orchards, and among counties. At harvest, fruit drying ratio, dry yield per tree, and dried fruit size were determined in order to develop relationships between fruit quality and yield, and leaf K over the growing season. To date we have determined the following: 1) spring (May 1998 and April–May 1999) leaf K concentration is correlated with mid-summer (mid-July 1998) and early summer (late June 1999) leaf K concentration, respectively; 2) mid-April to mid-May leaf K concentration is being maintained by growers due to thinning and fertilizing, and to light cropping in 1998, at adequate to above adequate levels (2%) that increase through the growing season; 3) no beneficial relationship between fruit size, drying ratio or dry yield has been found with spring or summer (June or mid-July) leaf K concentration above 2%, either when evaluating all surveyed orchards together or as individual orchards.
