Stanislaus County Almond Pest Management Alliance Project Progress Report May 19, 2000

Walt Bentley, IPM Advisor, Kearney Agricultural Center, Parlier

Roger Duncan, UCCE Farm Advisor, Stanislaus County

Lonnie Hendricks, UCCE Farm Advisor, Merced County

Cara Cross, Field Technician, Stanislaus County UCCE

Merlyn Garber, grower

Art Bowman, pest control advisor

The Stanislaus County Almond PMA site is a research trial as well as a demonstration. This is a summary halfway into the second year of a 3-4 year project. The trial is being conducted in a uniform 120-acre orchard (Nonpareil:Carmel) west of Modesto. Three insect pest management programs are fully replicated three times within the trial. Few significant changes have been made for the second season. Each plot is approximately 13.5 acres in size. The treatments are:

1. Grower’s Standard Practice:

• A dormant application of 8 oz. Asana XL (a pyrethroid), 8 lb. copper (Kocide DF), and 6 gallons of oil (Gavicide 440).
• A May spray of 4 pints Lorsban 4E (an organophosphate). The spray was applied 400-500 degree days after biofix of peach twig borer (May 7-8).
• Omite for mite control if shown necessary through monitoring.
• Lorsban @ 4 pints for ant control if shown necessary through monitoring.

1. Intermediate Program: In these areas, "reduced risk" pesticides are used.

• A dormant application of 6 oz SuccessÒ , 8 lb. copper (Kocide DF), and 6 gallons of oil.
• A May PTB spray of 6 oz SuccessÒ applied 400-500 degree days after biofix of peach twig borer (May 8-9).
• 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 necessary through monitoring.

1. "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.
• Potassium nitrate & oil for mite control if shown necessary through monitoring
• Abamectin bait (Clinch) @ 1.5 pounds for ant control if necessary.

Dormant sprays were applied on January 12-13 in 100 gallons of water per acre. Mummies were removed and destroyed in all treatments. Mummy counts 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% peach twig borer emergence from their hibernacula. In an attempt to prevent additional application costs and to mimic what most growers do, we applied 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 was 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 were 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 periodically for mites using the presence / absence sampling technique. Ants will be monitored occasionally using the hot dog baiting method.

Cumulative trap catches through May 11 for peach twig borer, S. J. scale males (pheromone traps), Encarsia, Aphytis and naval orangeworm eggs 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 programs verses the program with the dormant pyrethroid treatment. So far San Jose scale numbers are very low in all treatments. It will be interesting to see if the higher scale parasite numbers in the "soft" treatments will keep the San Jose Scale under control as well or better than the grower’s standard practice.

Although peach twig borer counts are not very high in any treatment, here appears to be more moths caught in the "soft" treatment than the other two treatments. This may be because our first Bt application was a little earlier than it should have been. Also, because PTB emergence was slow and erratic this spring, a third Bt application may have helped.

Mites:

Leaves were sampled on May 4 to determine whether mite populations were high enough to warrant inclusion of a miticide in the May sprays. The presence / absence method was used to determine levels of mite infestation. When using the presence / absence method, leaves are examined for the presence of mites and mite eggs. If a leaf has one or more mites or mite eggs, it is rated as a +. If no mites or eggs are present, it is given a – rating. Mite predators are also noted. If mite predators are not present, a treatment threshold is reached if approximately 1/3 of examined leaves have mites or eggs. If predators are present, the threshold is adjusted to approximately 50% or more of sampled leaves with mites or eggs.

In this trial, ten leaves from ten trees per plot (100 leaves total) were sampled and examined for mites. Mite levels were below the treatment threshold in all treatments. Although it is too early to draw many conclusions, it appears mites may be building more quickly in the areas treated with the pyrethroid. If this trend continues, it may become necessary to apply a miticide in the grower’s standard treatment while we may be able to avoid one in the "softer" treatments. We will continue to monitor mites through the season.

Conclusions:

It is too early to draw many conclusions from this trial. It is clear San Jose scale parasites are significantly reduced where pyrethroids are applied in a dormant spray. In-season organophosphate sprays also contribute to this. In Stanislaus County, almond and stonefruit orchards rarely have significant damage from San Jose scale whether orchards are treated with insecticides or not. However, in areas where San Jose scale is a serious problem, growers should understand that the use of some insecticides could exacerbate their scale problems.

It has also been well documented that pyrethroid and organophosphate use can lead to an increase in mite populations. This did not occur in 1999 (the first year of the trial). However early season mite counts this year indicate mite numbers may increase more quickly in the standard and intermediate insecticide treatment areas. Although PTB numbers appear to be higher in the Bt treated areas, populations are still low to moderate. It is unknown if this will lead to an increase in worm infestation at harvest.

The cost of the Bt program is almost identical to the grower’s standard pesticide program. This includes the cost of an additional (second) May spray of Bt. No additional application costs are incurred during the bloom sprays if Bt can be applied with regularly scheduled fungicides or other sprays. If Bt timing does not correspond well with other sprays or a third application is necessary, cost of the Bt program will be higher than the standard program. However if pyrethroid or organophosphate sprays increase the likelihood of a mite spray, a Bt program could prove more cost effective.

Program Costs: Estimated cost per acre for each treatment is as follows: