Stanislaus County Almond Pest Management Alliance Project. 

2003 Final Report.

Roger Duncan, UCCE Farm Advisor, Stanislaus County; Walt Bentley, IPM Advisor, UC Kearney Agricultural Center, Parlier; Merlyn Garber, grower; Art Bowman, PCA, Salida Ag Chem

Objectives of the Stanislaus County Almond Pest Management Alliance project:

·        To scientifically evaluate the long-term effectiveness and economic viability of less broadly toxic pest management programs.

·        To extend research-based information to the almond industry.

·        To demonstrate IPM monitoring techniques and decision-making processes to local growers.

We have completed our fifth and final season in the Stanislaus County PMA trial.  The original three pest management regimes were maintained similarly to the first two years (grower’s standard practice and two “reduced risk” treatments).  Because reject levels were very low for all pest management regimes, a fourth, “untreated” program was added in 2001.  Each pest management program is replicated three times within a 120 acre Nonpareil orchard west of Modesto.  Each plot is approximately 13.5 acres in size.  The treatments are:

1)                  Grower’s Standard Practice: (fairly common in the Northern San Joaquin Valley).

¨       A dormant application of Asana^® (a pyrethroid), 6 gallons of oil, & 8 lb. Kocide^®.

¨       A May spray with an organophosphate (Lorsban).

¨       Lorsban for ant control.

2)                  Soft Program #1:

¨       A dormant application of copper & oil (no insecticide).

¨       A “bloom” spray of Confirm^® at ~ 30% PTB emergence (piggy-backed with fungicides).

¨       A May spray of Success^®.

¨       Clinch^® (Abamectin) bait for ants if monitoring deems necessary.

3)                  Soft program #2:

¨       A dormant application with oil only.

¨       Two “bloom” applications of Bt (@ ~20% PTB emergence & ~ 80% emergence).

¨       Two May sprays of Bt (300-350 & 450-500 DD after biofix).

¨       Esteem^® bait for ants if monitoring deems necessary.

4)                  “Untreated”:  only mites and ants are controlled if necessary. 

¨       No dormant copper, oil, or insecticide application.

¨       No bloom insecticide applications.

¨       No May or hull split sprays.

¨       Esteem^® bait for ants if monitoring deems necessary.

Overwintering nuts (“mummies”) were removed and destroyed in all treatments to reduce overwintering naval orangeworm.  Cover crop management, fertilization, and fungicide treatments were the same for all treatments other than no dormant copper was applied in “soft program #2” and the “untreated” areas.

Monitoring:

Each plot had two PTB pheromone traps, two San Jose Scale pheromone traps, and two NOW egg traps.  Peach twig borer and naval orangeworm traps were checked twice weekly while San Jose scale pheromone traps were monitored bi-weekly throughout the season (March through September).  In addition, mites and mite predators were monitored bi-weekly with the presence / absence leaf sampling technique.  In the fall, spurs were sampled to monitor San Jose scale populations.

Results:

PTB.  For the first time in this trial there were more peach twig borer moths caught in the untreated areas than in treated areas (Fig. 1).  Untreated areas had 28% more male PTB moths caught than the standard treatment (627 moths and 491 moths, respectively).  The largest difference in moth catches occurred in the last flight which peaked after the Nonpareil had been harvested (Fig. 2).  There were no differences in PTB caught between the standard treated areas and the two “reduced risk” pesticide treated areas.

San Jose scale.  Once again, San Jose scale populations were very low in 2003 in all treatments (Fig. 3).  In addition, scale parasites were again much lower in the areas treated with the grower’s standard insecticide program compared to untreated areas.  For unknown reasons, the areas treated with Success and Confirm had lower scale parasites than the Bt-treated and untreated areas in 2003. The ratios of scale parasites to San Jose scale were again very high in the untreated areas and the Bt-treated areas. For the first time in this trial San Jose scale was found on fall-sampled spurs.  Scale were only found in the untreated areas.  Numbers were well below the treatment threshold.

For reasons unknown, Encarsia numbers have declined substantially in all treatments during the five years of this trial (Fig. 4).  In 2003, Encarsia numbers were extremely low with only about 25 wasps caught on average in the grower’s standard treatment.  Aphytis was the most commonly recovered scale parasite. 

NOW, ants and spider mites.  Almost no navel orangeworm eggs were found on traps in any treatment.  The grower did a great job with orchard sanitation and therefore reduced overwintering NOW populations.  There were no differences among treatments in web spinning mite populations according to the presence / absence sampling technique.  Mite numbers stayed well below treatment thresholds in all areas.  Ants were not monitored in 2003 and no treatments were applied for ant control.

Insect Damage at Harvest.  Three hundred nut samples were collected from windrows at harvest in each plot (total of 900 nuts per treatment). Nuts were cracked by hand and examined for feeding damage by navel orangeworm, peach twig borer and ants (Table 1).  Overall insect damage was very low and there were no significant differences among treatments.

Treatment costs.  Although there was no difference in pest pressure or insect feeding damage at harvest among treatments, there was a significant cost difference (Table 2).  The Confirm / Success treatment cost an extra $21.70 per acre.  The Bt treatment cost an additional $37.10 per acre.  From an economic view point, there is no incentive for growers to use reduced risk materials like Success, Confirm or Bt. If a grower needs to apply a dormant oil for scale control, it makes better economic sense to apply something for PTB at that time.  If a dormant oil spray for scale is not necessary, a grower may choose to apply one of these reduced risk materials at bloom for PTB if necessary.   Of course the least expensive program is one where no insecticide is applied.  However, few growers may choose to take that risk.

*Bt application timing did not coincide with fungicide bloom sprays in 2003.  Therefore an additional application cost of $13.65 is included.