Comparison of Various Pest Management Techniques in a Commercial Almond Orchard in Butte County, CA October, 2000

Joe Connell, Farm Advisor Butte Co. UCCE, Carolyn Pickel, Sacramento Valley IPM Advisor, and Nicole Darby, Field Technician Sacramento Valley

Butte County Almond PMA

This orchard is approximately 49 acres. The grower standard block is 27 acres, the PMA block is 22 acres divided into a 12 acre soft treatment and a 10 acre organophoshpate dormant treatment. Five of these 10 acres received an organophosphate hullsplit spray, the other five acres does not receive an organophosphate spray. Traps were placed in the center Nonpareil row on the north side of the same tree and monitored weekly. This is the end of the second year of a three year project. Year four funding is pending. As of this date, information regarding spray application rates and date and economic data are not available.

Peach Twig Borer

Dormant 100 spur samples were taken in December 1999 from each of the four blocks and evaluated for peach twig borer hibernacula. No hibernacula were present in any of the blocks. Peach twig borer traps were placed in the Butte County Pest Management Alliance orchard on March 22, 2000. One trap was placed in each of the four blocks: grower standard, soft chemical, dormant spray, and dormant-hullsplit spray. Traps were monitored weekly, lures changed every two weeks, and liners changed as necessary. The first biofix occurred on April 4, 2000. Subsequent biofix dates are: July 5, August 3, and September 19.

Table 1. Seasonal peach twig borer trap captures as of10/5/00.

Navel orangeworm

Navel orangeworm traps were placed in trees on April 25, 2000. The biofix for this orchard occurred on April 25, 2000. The second biofix occurred on 6/29, the third biofix occurred on 8/5, and the last biofix occurred on 8/23. Overall, there were very few eggs detected throughout the orchard. These low populations are attributed to winter sanitation. Mummy counts taken in January 2000 showed that out of 20 randomly chosen trees in each block that the orchard may be susceptible to navel orangeworm damage later in the season. A total of 80 trees were examined for mummies and the orchard average was 3.3 mummy nuts per tree. Since this number is unacceptable for IPM practices on navel orangeworm control, another mummy count was performed, using the same protocol as in January, on March 6, 2000. Due to winter winds and rain, the number of mummy nuts in the entire orchard was less than one per tree. Winter sanitation is the most effective means of controlling navel orangeworm.

Table 2. Seasonal total of NOW eggs Butte Co. PMA 2000

San jose scale and San jose scale Parasite

Dormant spur samples taken in December 1999, showed that less than 10% had scale or parasitized scale in each block. San jose scale traps were placed in the orchard on March 17, 2000. New traps were placed in the tree weekly as the old traps were collected, wrapped in plastic wrap, and brought back to the laboratory to be evaluated under a microscope. The male scale and the parasites were counted using the random blocks provided on each trap. The first biofix for San jose scale was on 3/27, approximately three weeks earlier than in 1999, and populations grew until April 10, 2000. After this date, the male scale reappeared sporadically in low numbers on 5/10, 6/20, and 7/11. Parasites were present starting on 3/27.These numbers grew through 4/10 and then dropped significantly. However, when male scale was detected on the traps, the parasite was most often detected as well. Season totals show that the grower standard block had the least number of male scale and parasites. The dormant-hullsplit block had a season total of 85 scale but had the most parasites present with 3335 total (Table 3).

Table 3. Seasonal total of San jose scale males and parasites trapped 2000.

Mites

Dormant samples showed much lower mite eggs than in 1999 where the samples showed that over 50% of the spurs had mite eggs. This dormant sample showed that the grower standard spurs had 17%, the PMA had 18%, the dormant organophosphate spray only had 8%, and the organophophate dormant and hullsplit had 8% detectable mite eggs. Mite monitoring began on June 1, 2000 and continued weekly until August 16, 2000. At each sampling, five trees per block were chosen randomly and fifteen leaves from each of the five were collected and inspected for red mites, two-spot mites, beneficial mites, and beneficial insects. Differentiation between two-spot mites and red mites were not noted. The total season count shows that the grower standard block had the least mites and the second highest number of beneficial insects observed (Table 4) and. There was an increase of mites and their predators on 8/8/00 and the orchard was monitored again on 8/11. However, on 8/11/00, harvest had begun and a mite treatment could not have been applied. Since the population increase occurred late in the season, and defoliation was minimal, these mites will not be detrimental to tree performance next year.

Table 4. Seasonal total of leaves with predator mites/beneficial insects and european/two-spot mites 2000.

Ants

Ant traps were placed in each block in the orchard on 8/8/00. Baited with dried almonds collected from the orchard, weekly monitoring detected no ant activity. No ant activity was detected during weekly monitoring.

Peach Twig Borer Shoot Strikes

Shoot strikes were monitored on 5/16/00 by inspecting 20 vigorous shoots on six random trees per treatment. No PTB damage was noted. Shoot strikes were monitored again on 5/23/00 and only 2 PTB shoot strikes were noted in the entire orchard.

Europoean fruit lecanium

European fruit lecanium, Lecanium corni, populations have been building in this orchard. It was not detected in the first year of the project, yet signs of a population was detected during the dormant spur sample inspection. During the dormant samples, European fruit lecanium, EFL, was in 8% of the spurs in the grower standard and in 15% of the spurs in the PMA soft treatments. Populations were not detected in the two treatments receiving a dormant spray, the organophosphate dormant treatment and the organophosphate dormant and hullsplit treatment. No monitoring protocol was developed however, a satellite project studying oil sprays for the control of EFL was conducted in Butte County and the results are pending.

Diseases

(shothole, scab, anthracnose)

Diseases were monitored by visual inspection and disease presence was to be reported immediately. There were no major disease outbreaks throughout the orchard this year.

Harvest

Harvest samples were collected from Nonpareil trees in the trap row on August16, 2000. Five trees were chosen and 100 almonds collected totaling 500 almonds per block were collected. Almonds were inspected for peach twig borer, navel orangeworm, oriental fruit moth, and ant damage. The almonds were first inspected for hull damage and then meats further inspected for damage. Hulls were inspected for OFM and PTB damage but not differentiated unless a larva was detected. The meats were inspected for PTB, OFM, NOW, and ant damage. Hull damage observed is expressed in percent in Table 5 and meat damage in Table 6. Quality was outstanding in all four blocks this year.

Table 5. Harvest results from the hulls in Butte Co. Almond PMA site 2000.

Table 6. Harvest results from the almond meats in Butte Co. Almond PMA site 2000.

Comparison of 1999 and 2000 Results from Butte County

The Almond Pest Management Alliance has just completed the second year of studying reduced risk techniques. Whereas no statistical information is drawn, a direct comparison between the two seasons are noted. In most instances, there was an increase in the total seasonal in the second year pest numbers but not in the harvest damage.

Table 7. Seasonal peach twig borer total counts for 1999 and 2000.

Table 8. Seasonal male San jose scale total counts for 1999 and 2000.

Table 9. Seasonal prospaltella counts for 1999 and 2000.

Table 10. Seasonal navel orangeworm counts from 1999 and 2000.

Table 11. Seasonal counts of leaves with European red mites or webspinning mites from 1999 and 2000.

Conclusion

We had another very successful season with the Butte County Almond Pest Management Alliance. Our spring meeting was very well attended and interest in adopting reduced risk practices remains in the forefront for growers. We were able to monitor using the exact same techniques as the first year, thus helping to ensure that reduced risk practices are being researched accurately. The key to reduced risk practices is intensive monitoring. We will continue to monitor intensively to ensure that pests do not cause economic damage. We look forward in continuing to study reduced risk practices.