Task 2:

Butte County

Orchard Specifications

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, a 5-acre dormant organophosphate spray, and a 5 acre dormant and hullsplit organophosphate spray. Traps were placed in the center Nonpareil row on the north side of the same tree and monitored weekly.

Peach Twig Borer

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. Figure 2.1 demonstrates the peach twig borer generations and Table 2.1 shows seasonal total trap counts.

Table 2.1. Butte Co. Seasonal peach twig borer trap captures as of10/5/00.

Peach twig borer shoot strikes were counted on 5/16/00 by inspecting 20 vigorous shoots on six random trees per treatment. No PTB strikes were noted. Shoot strikes were monitored systematically again on 5/23/00 and only 2 PTB shoot strikes were noted on the inspected trees.

Navel orangeworm

Mummy counts on 20 randomly chosen trees in each block were taken in January 2000. An average of these 80 trees indicated there were 3.3 mummy nuts per tree in the orchard. Since this number was too high for navel orangeworm IPM, winter sanitation was indicated. Heavy wind and rain occurred in February and March and another similar mummy count was performed on March 6, 2000. Following the late winter winds and rain, the number of mummy nuts in the entire orchard was less than one per tree. Winter sanitation, either natural or imposed, is the most effective means of controlling 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. Figure 2.2 demonstrates the relatively low numbers of navel orangeworm eggs found of the egg traps as well as the degree-days depicting generations and Table 2.2 shows seasonal totals of navel orangeworm. Overall, there were very few eggs detected on our traps in the orchard. Low populations of navel orangeworm are attributed to winter sanitation.

Table 2.2. Seasonal total of NOW eggs Butte Co. PMA 2000

San jose scale and san jose scale parasite

Dormant 100 spur samples were taken in December 1999 from each of the four blocks and evaluated for san jose scale. These dormant spur samples indicated 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. 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 most male scale and the least number of parasites. The dormant-hullsplit block had the least scale but had many parasites present with 8285 total (Table 2.3).

Table 2.3. Butte Co. Seasonal total of San jose scale males and parasites trapped 2000.

Mites

In 1999, 50% of dormant spurs had European red mite (ERM) eggs present. This year's dormant sample showed a much lower percent of spurs with ERM eggs. Seventeen percent of the grower standard spurs, eighteen percent in the PMA, eight percent of the dormant organophosphate sprayed spurs, and eight percent of the organophosphate dormant and hullsplit treatment had detectable ERM eggs.

Mite monitoring for two spotted mites 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 highest number of beneficial insects/predatory mites observed (Table 2.4). 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 be 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 2.4. Butte Co. 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.

European fruit lecanium

European fruit lecanium, Lecanium corni, populations have been building in this orchard. The scale was not detected in the first year of the project, but a population was first detected during the dormant spur sample inspection at the beginning of the second year. European fruit lecanium (EFL) was on 8% of the dormant 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 exists but a satellite project studying in-season 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 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 from each treatment were chosen and 100 almonds per tree totaling 500 almonds per block were collected. Almonds were cracked out and 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 2.5 and kernel damage in Table 2.6. Quality was outstanding in all four blocks this year.

Table2.5. Hull feeding noted in the Butte Co. Almond PMA site 2000.

Table 2.6. Kernel quality (% damage) from the Butte Co. Almond PMA site 2000.

Economic Data 2000

In Table 2.7 below, the materials and costs for running each of the four treatment programs are calculated and recorded. The grower standard with three sprays is the most economical. The next most economical treatment is the PMA soft treatment that had two total applications but Rally was applied for shothole whereas the grower standard applied Rovral for shothole. The application of Rally increased the treatment cost per acre. However, the least economical treatments were those treatments receiving the organophosphate applications. The dormant organophosphate treatment received three total applications of material at a cost of $119.67 per acre. The organophosphate dormant and hullsplit treatment received four total applications which cost $161.72 per acre.

Table 2.7. Economic data for Butte County Almond PMA 2000.

Listed below are the costs for orchard floor management which is the same across all four treatments and the nitrogen costs which are also the same across all four treatments.

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 is noted. In most instances, there was an increase in the total seasonal pest numbers but not in the harvest damage. Table 2.8 through Table 2.13 show the comparisons between the first two years of the Almond PMA.

Table 2.8 Butte Co. Seasonal totals: peach twig borer counts for 1999 and 2000.

Table2.9 Butte Co. Seasonal totals: male san jose scale counts for 1999 and 2000.

Table 2.10 Butte Co. Seasonal totals: Prospaltella sp. counts for 1999 and 2000.

Table 2.11 Butte Co. Seasonal totals: navel orangeworm counts from 1999 and 2000.

Table 2.12 Butte Co. Seasonal totals: number of leaves with European red mites or web spinning mites in 1999 and 2000.

The economic comparisons and the amount of spray applications are noted below in Table 2.13.

Table 2.13. Butte County application and cost comparison 1999 and 2000 Almond PMA.

Conclusion

It was another successful season with the Butte County Almond Pest Management Alliance. The spring meeting was well attended and interest in adopting reduced risk practices remains in the forefront for growers. The project was able to monitor using the same techniques as the first year, thus helping to ensure that the effects of reduced risk practices are being documented. The key to successful reduced risk practices is intensive monitoring. The project will continue to monitor to ensure that the potential for economic damage is minimized.

The Almond PMA has been active for two years in Butte County. Interest in reduced risk farming practices has increased as the economic viability of the methods has been demonstrated. The PMA has been beneficial for growers, industry, and the environmental and regulatory community.

Butte County Pesticide Summary

Butte County almond acreage has remained relatively stable over the past nine years. This trend is seen in Chart 2.1. The information regarding harvested acreage was accessed via the World Wide Web at the California Agricultural Statistical Service (CASS). All pesticide use information was accessed via the World Wide Web on www.ipm.ucdavis.edu and the California Department of Pesticide Regulation, www.cdpr.gov.

Chart 2.1. Harvested Almond Acreage in Butte County 1990-1998.

Organophosphate use in Butte County compared to almond acreage in Butte County is noted in Chart 2.2 below. There has been substantial proactive drive to limit the amount of organophosphates in Butte County. Organophosphates used in this calculation are azinphos-methyl, diazinon, chlorpyrifos, methidathion, parathion, naled, phosmidion, and phosmet.

Chart 2.2. Organophosphate use in Butte County from 1990-1998.

Pyrethroid use in Butte County shows an increase in use throughout 1990-1998. The trend of pyrethroid use is noted in Chart 2.3. Pyrethroids compiled for this report were esfenvalerate, permethrin, and pyrethrin.

Chart 2.3. Pyrethroid applications per acre in Butte County 1990-1998.

Carbamate use in Butte County from 1990-1998 is noted in Chart 2.4. Carbamates compiled for this chart were carbaryl and methomyl. In 1993, only 22 pounds of carbamates were applied in Butte County. However, there has been a steady decrease in the amount of carbamates applied per acre since 1994.

Chart 2.4. Pounds of Carbamates applied per acre in Butte County 1990-1998.

The use of Baccilus thurigiensis (Bt) has grown considerable over the past nine years. For this report all strains of Bt were used. The amount of pounds applied to almonds in Butte County are noted in Chart 2.5. In 1990 and 1991, virtually no Bt was applied to Butte County almonds, however, in 1998, over 1,500 pounds were applied which shows an increase in use from 1992 to 1998.

Chart 2.5. Pounds of Bt applied per acre in Butte County Almonds 1990-1998.

Overall, Butte County harvested acreage has remained steady yet pounds of organophosphates and carbamates has dropped or remained relatively low. The number of applications of pyrethroids rose slightly then has dropped down in 1998. However, the pounds of Bt applied have risen steadily, which is a positive trend.