Stanislaus County Status Report

April 2000

Few significant changes have been made for the second season of the Stanislaus County PMA research trial. As in 1999, the trial is being conducted in the same 120-acre orchard (Nonpareil: Carmel) west of Modesto. Three insect pest management programs are again fully replicated three times within the trial. The treatments are:

Grower’s Standard Practice: This pest management program is fairly common in the Northern San Joaquin Valley. While many growers in this area apply a hull split spray for Naval Orangeworm control, our cooperator elects to target Peach Twig Borer with a May spray. Specifically, pesticide treatments will include:

• A dormant application of Asana XL (a pyrethroid) @ 8 oz, copper (Kocide DF) @ 8 lb, and oil (Gavicide 440) @ 6 gallons.

• A May spray of Lorsban 4E (an organophosphate) @ 4 pints. The spray will be timed for 400-500 degree days after biofix of peach twig borer.

• Omite for mite control if shown necessary through monitoring.

• Lorsban @ 4 pints for ant control if shown necessary through monitoring.

Intermediate Program: In these areas, "reduced risk" pesticides are used. Specifically, pesticide treatments will include:

• A dormant application of Success @ 6 oz, copper (Kocide DF) @ 8 lb, and Gavicide Super 90 @ 6 gallons.

• A May PTB spray of Success @ 6 oz timed for 400-500 degree days after biofix of peach twig borer.

• Agri-Mek 0.15 EC @ 10 oz & Gavicide 440 oil @ 1 gallon for mite control if shown necessary through monitoring

• Abamectin bait (Clinch) @ 1.5 pounds for ant control if shown to be necessary through monitoring.

Soft program: Treatments include:

• A dormant application of oil only (Gavicide 440 @ 6 gallons).

• Two spring applications of Bt (Dipel DF @ 1 lb.). These were tank mixed with normal fungicide and foliar nutrient applications and therefore did not necessitate additional application costs.

• Two May PTB sprays of Bt (Dipel DF @ 1 lb.) timed for 300-350 & 450-500 degree days after biofix of peach twig borer.

• Agri-Mek 0.15 EC @ 10 oz & oil @ 1 gallon for mite control if shown necessary through monitoring

• Abamectin bait (Clinch) @ 1.5 pounds for ant control if shown to be necessary through monitoring.

Dormant sprays were applied on February 1 in 100 gallons of water per acre. Mummies were removed and destroyed in all treatments. Mummy removal was evaluated on February 17 by examining five randomly selected trees per plot. Mummy counts ranged from 0-8 per examined tree but averaged 1.9 mummies per tree throughout the trial. This falls just below the established UC threshold of less than two mummies per tree.

We attempted to time the two spring Bt sprays with 20-40% and 80% twig borer emergence from their hibernacula. In an attempt to prevent additional application costs and to mimic what most growers do, we attempted to apply these sprays with regularly scheduled fungicide and foliar nutrient sprays. Unfortunately, the first spray was probably applied too early at about 5% emergence. The second application went on at about 60-70% emergence. Due to the cold spring, PTB emergence was prolonged. Three Bt applications were probably necessary to adequately cover PTB emergence this year.

Monitoring: In each treatment replication there are two PTB pheromone traps, two S.J. scale pheromone traps, eight S.J. scale crawler sticky tape traps, and two NOW egg traps for a total of 126 traps in the trial. PTB pheromone traps were hung March 16 and checked every other day to establish the first biofix. Biofix for the overwintering generation of PTB has been established as March 30. The first Naval Orangeworm egg was detected on March 20. The orchard will be monitored twice weekly through the season for PTB and NOW. Trap catches and the degree-day phenology model will be used to determine application timings for May PTB sprays. San Jose scale pheromone and sticky tape traps are being checked weekly. Male San Jose scale, Encarsia, and Aphytis populations are recorded from pheromone traps. Beginning in May, plots will be monitored weekly for mites using the presence/absence sampling technique. Ants will be monitored occasionally using the hot dog baiting method.

Cumulative trap catches through April 4 for S. J. scale males (pheromone traps), Encarsia, Aphytis and Naval Orangeworm are listed below for the three treatments.

Although it is still very early in the season, we are once again beginning to see approximately twice as many Encarsia scale parasites in the soft program verses the program with the dormant pyrethroid treatment. So far there is no difference in San Jose scale male populations. It will be interesting to see if the higher scale parasite numbers will keep the San Jose Scale under control.

The next progress report will include estimated costs associated with each treatment.