Butte County Almond Pest Management Alliance

2003 Final Report

Year 5

Joe Connell, UCCE Farm Advisor, Butte County; Carolyn Pickel, Area IPM Advisor; Sara G. Smith, Field Scout, UC IPM; Nick Bertagna, grower; Richard Gregor, pest control advisor.

Butte County Objectives:

1. To scientifically evaluate the success and profitability of managing arthropod pests with less broadly toxic pesticides in a commercial almond orchard. 
2. To demonstrate and facilitate adoption of integrated pest management monitoring techniques and decision making processes to growers and pest control advisors.

This report summarizes our progress through the fifth year of the project.  The Butte County site is an orchard of 49 acres and originally contained four different treatment blocks plus an untreated check of ½ acre added in 2001.  The PMA I block is a “typical” soft treatment with Bacillus thuringiensis used for lepidopteron control, the OP Dorm block is treated with an organophosphate pesticide plus oil during dormancy, and the OP Dorm/HS block is treated with an organophosphate plus oil during hullsplit as well as during dormancy.  The PMA II block is the grower’s standard practice.  However, no insecticide treatments (except for the section treated with Clinch ant bait) were applied to the PMA I in either 2001, 2002, or 2003 so it was the same as the untreated control.  Starting in 2002, chemical inputs were reduced even more in the PMA II block (Grower Standard) with no further insecticide treatments ; making this orchard an excellent demonstration of the long term effects of an economically viable and environmentally friendly farming system.  The two “OP” blocks mentioned above have received a dormant application each year, and the OP Dorm/HS block received an insecticide at hullsplit every year except 2002.  Pest control has been supplemented with three species of beneficial insects released by a private Pest Control Advisor, Richard Gregor.  In 2003, a satellite trial was conducted in portions of the PMA I and OP Dorm blocks.  These were treated with a reduced risk ant bait for comparison purposes.  The entire orchard was treated with a reduced risk fungicide and also an herbicide for weed control.  Treatment details for 2003 are as follows:

1.      PMA I and PMA II, 39 acres total.  Grower’s standard practices- no insecticide sprays applied.

2.      OP Dorm, 5 acres.  Diazinon (4 pts/acre) plus oil (4 gal/acre) applied mid January.

3.      OP Dorm/HS, 5 acres.  Diazinon (4 pts/acre) plus oil (4 gal/acre) applied mid January, and Imidan (5 lbs/acre) applied at hullsplit July 19.

Clinch ant bait was applied on July 21, after sampling to determine the areas with the highest population.  The treatment area was approximately the eastern 8 acres of the PMA block and the eastern 3 acres of the OPD block, for a total of about 11 acres.  The application rate was about 0.9 lbs per acre and was applied with a spreader specifically for use with Clinch.

Beneficial insects were released evenly throughout the orchard, in all the treatment blocks, starting in April 2003.  Lacewing species, Trichogramma species, and Goniozus legneri were released approximately every week throughout the summer until harvest.  Fungicide treatment and weed management was the same across the whole orchard, with two applications of Vanguard @ 5 oz/acre, one each in February and March.  Herbicide was applied to the strip (in the tree row) in April and July with Roundup @ 2 pints/acre and Goal @ 5.5 oz/acre.  The middles were treated in August and September with Roundup @ 3 pints/acre.  Additional weed control was achieved by mowing.  The orchard floor was mowed every other row 6 times.

Monitoring:

This trial is monitored for peach twig borer, naval orangeworm, web spinning mites, San Jose scale adult males, and San Jose scale parasitoids (Encarsia and Aphytis), and ants from late winter through October.  In each treatment pheromone traps were placed in the center of the block and monitored weekly for peach twig borer and San Jose scale.  Naval orangeworm is monitored with an egg trap baited with almond meal.. Lures  and bait were changed as recommended by the manufacturer. Weekly trap counts were shared with growers, Farm Advisors, and PCA’s.  Degree days for each of these pests were calculated to determine biofixes and to provide treatment timing for those in the area who might need it.   Weather data and degree day calculations were obtained at no cost from www.Fieldwise.com using the Durham station.  Beginning in June, plots were monitored every other week for mites using the presence / absence sampling technique.  Each treatment block was surveyed for shoot strikes in June and in July.  Sampling for ants took place in Mid July using the hot dog baiting method.

San Jose scale pheromone traps were placed in the orchard on February 21 and checked weekly for the presence of male scales.  The SJS traps were also checked for parasitic wasps of the scale, Encarsia perniciosi and Aphytis species which are also attracted to the SJS lure and get stuck on the trap.  The first scales were found in the traps March 26 and increased dramatically on April 8, which turned out to be the highest population all season.  After this date, the male scale reappeared sporadically in low numbers all season.  Parasitoids were also detected on the traps beginning March 26 and were most always present whether or not scale was caught on the traps.  The peak population of Encarsia occurred on April 24, and Aphytis catches were highest on June 12 as shown in the three graphs below.

PTB pheromone traps were hung March 26 and checked twice a week to establish the first biofix.  The weather data and degree day modeling available on the UC IPM website http://www.ipm.ucdavis.edu/index.html, used in conjunction with actual trap catches helps to identify the biofixes during the season.

The upper portion of the canopy was inspected for shoot strikes (SS) at the beginning of PTB generations.  Five trees per treatment block were examined.  Shoots with damage were clipped with a pole pruner and split down the center to verify presence and identification of larvae.  In previous seasons, few if any shoot strikes were ever found, making the high level of strikes found in 2003 unusual.  When larvae were present, they were identified, but if the strike was already vacated, no attempt was made to determine whether the damage was done by Peach Twig Borer or Oriental Fruit Moth.  The following data was collected on June 12, 2003:

In 2003, much higher SS counts occurred in all of the treatment blocks. From 1998 through the 2002 season, shoot strike counts were never more than 1 per tree. In most years we would find only one or two shoot strikes in each block. In spring 2003, the dormant spray treatment had 1.9 shoot strikes per tree which was less than the 4.4 strikes per tree in the no dormant spray treatment.  None of the shoot strikes in the dormant treatment were PTB and the shoot strikes in the no dormant treatment were predominately OFM.

The Naval Orangeworm egg traps were filled with ground almond bait and placed in each treatment block on April 8.  Due to repeated rainy weather and molding of the almond bait, the traps were removed, refilled, and replaced on May 13.  The only NOW eggs found on the egg traps all season were in the week of September 8, when there were 8 eggs on the trap in the Untreated check, and 5 on the trap in the PMA I block.

Cumulative trap catches through October 23, 2003 for peach twig borer, San Jose scale males, Encarsia, Aphytis, and naval orangeworm eggs for the four treatments and check are listed below.  It is worth noting that both PMA I and II had zero sprays of organophosphates, the OP Dorm block had one spray, and the OP Dorm/HS block had two insecticide sprays.

In previous years, ants were monitored to determine species present in each of the treatment blocks, but no attempt was made to quantify the ant populations.  The species found in the orchard were Southern Fire Ant and Pavement Ant.  The harvest samples from 2001 and 2002 were damaged mostly by ants even though the damage level was very low. 

Therefore, ant sampling was conducted in both 2002 and in 2003 to measure population levels and densities of ants throughout the entire orchard.  Vials were numbered, baited with pieces of hot dog and placed, open, at the base of every 15^th tree.  This was done in every fifth row.  The vials were capped, collected, and frozen after 1.5 hours.  Later, the vials containing ants were counted to determine whether any areas of the orchard would have to be baited for ant control. The data, following, shows a range of population densities which could be due to location in the orchard.  The data also shows an increase in the ant populations since last year in all areas of the orchard, hence the treatment decision described near the beginning of this chapter.

Dormant spur sampling is conducted before the growing season begins, most recently on Jan 15, 2004.  Spurs were taken from each treatment block and inspected for mite eggs, predatory mites, San Jose scale, parasitized SJS, and European Fruit Lecanium crawlers.  Counts were tabulated and compared to the four previous years of the PMA project to determine if levels are increasing or decreasing and if the treatment threshold for any of the listed insects had been reached.  Dormant spur sampling has continued in this orchard beyond the five years of the PMA for use in future research projects, for a total of six years of dormant sampling data.

 ALMOND PMA 2003 Counts from Dormant Spurs for Six Consecutive Years

This orchard has had evidence found in the dormant spur sample of parasitism of the San Jose scale and also of the European Fruit Lecanium.

Harvest Reject Levels

At harvest, 100 almonds were randomly collected from each of five trees in each of the treatment blocks for a total of 500 per treatment.  Due to the portions of the orchard blocks treated with Clinch bait for ants, additional samples were collected for ant damage comparisons.  Nuts were inspected for damage, and an attempt was made to identify the insect which had caused the damage.  It is difficult to distinguish OFM from PTB worm damage to the nut, if no larvae or pupae parts were found, it was classified as “PTB/OFM”.  Percent damage to each treatment block was calculated.  This year, the harvest sample contained more insect damage than any of the previous years of the Almond PMA, a situation which was seen throughout the state.  The Harvest Damage Table is expressed in percent damage.

The blocks with and without dormant insecticide treatments were compared, in the first graph below, for peach twig borer (PTB), oriental fruit moth (OFM), stink bug, navel orangeworm (NOW), undifferentiated worm damage (PTB/OFM), and total worms (sum of OFM/PTB+PTB+OFM). The dormant spray treatment reduced the amount of PTB damage but had little effect on OFM damage. It also did not reduce stink bug, navel orangeworm, or ant damage.  It is clear from this data that a dormant spray would have only reduced the rejects by a small amount.  There were no treatments receiving only a hull split spray.  Comparing damage in the treatment receiving dormant plus hull split insecticide sprays versus treatments receiving no hull split spray in the second graph below, it can be seen that the hull split spray reduced the PTB, OFM, NOW, and total worm damage. The hull split treatment did not reduce ant or stink bug damage.

Although damage from ants was again less than 1% in 2003, we saw less damage in the Clinch-treated area, as shown below.

Costs Associated with Almond Pest Management Programs

The costs of the different insect pest management programs are discussed below.  Fungicide and weed control are the same throughout the entire orchard, so are not compared in the table below.  The beneficial insect releases were covered by the PCA’s flat rate of $43/acre.  The plots with an application of Clinch are listed separately from the main treatment blocks to separate out the additional cost.

ALMOND PMA 2003 Pest Control Treatments

Treatment costs are meant to represent an average grower in this area.  Prices for materials are from the 2003 UC publication Sample Costs To Establish An Almond Orchard And Produce Almonds in the South San Joaquin Valley because it is the most recent and up to date cost study.  Application costs for the orchard sprayer are directly from the grower to more closely represent the region, and include labor, fuel, lube and repairs.  The treatment block that received treatments at dormant and at hullsplit is by far the most expensive, but it also had much less damage from PTB due to the hullsplit spray.  Most years the worm damage is very low in all blocks, but in 2003, the hullsplit spray reduced worm damage to 1.6%, and the other blocks without a hullsplit treatment averaged 6.33% damage from worms (OFM / PTB).

Conclusions

Historically, the Butte County Almond PMA has been quite successful in showing that there is no more pest damage in the PMA blocks which had zero pesticide applications, than there is in the treatments with organophosphate sprays.  Clearly, in 2003 we had the highest population of OFM that we have seen in 5 years of monitoring this orchard. We suspect that these high populations along with the unusually cool weather allowed OFM to feed in the green nuts resulting in unexpected damage. A prophylactic hull split spray was applied in July to one treatment in the Butte Almond PMA orchard and it resulted in the lowest worm damage this year.  The subsequent unseasonably cool weather conditions also delayed harvest which undoubtedly contributed to an increase in all types of damage.  The unusual circumstances that led to damage this year would have been difficult if not impossible to anticipate.  It is unlikely that the ongoing expense of annual hull split insecticide treatments (which have not shown benefits in this orchard in previous years) could be justified on the basis of these relatively rare events.

Our spring field day and winter dormant meeting were well attended and interest in adopting reduced risk practices remains in the forefront for growers.  The outreach and education portion of this project emphasizes that the key to successful reduced risk practices is intensive monitoring.  We will continue to monitor to follow insect populations to see what if the unusual pest pressures of 2003 will be repeated.  The Almond Pest Management Alliance has been active for five years in California.  Interest in reduced risk farming practices has increased as the economic viability of the methods has been demonstrated.  The PMA demonstration in Butte County has been beneficial for growers, industry, and the environmental and regulatory community.