Pest Management Alliance Project

Final report for Year 5, 2003

Mario Viveros, Walt Bentley,

Peggy Schrader and Minerva Gonzalez

Introduction:

The purpose of this project was to demonstrate a reduced pesticide input versus a conventional pesticide management program in young orchards for the Southern end of the San Joaquin Valley.  This project was established five years ago in a 160 acre block which was made up of 80 acres of “hard shells” (Butte – Mission – Padre) and 80 acres of “soft shells” (Nonpareil – Fritz – Sonora).  Both “hard and soft” shell varieties were divided into two (20 acres each) conventional and two (20 acres each) reduced input management plots.  For the 2001, 2002, and 2003 season each of the plots in both conventional and reduced input were divided into dormant and non-dormant spray subplots.  This is to say we now have the following treatments:  1) conventional dormant,  2) conventional non-dormant,  3) reduced dormant, and  4) reduced non-dormant.

This report is for data obtained in the 2003 season.  It doesn’t include information from 1999, 2000, 2001, and 2002 seasons.

Cover Crops:

The barley cover crop has been selected because of the saline-alkali and poor drainage conditions of the PMA orchard soil.  The barley was seeded in every middle on one of the 20 acres soft shell blocks.  The planting was done in December at a rate of 80 lbs per acre.  Due to the late rains, there was a good seed germination.

Pest Monitoring:

The setup for pest monitoring was similar to the one we used in 2002.  The reason being that both conventional and reduced input management treatment was subdivided into dormant and non-dormant subplots.

San Jose Scale (SJS).  This pest was monitored using twig samples, pheromone lures and double-sided sticky tape.  The overwinter population on fruiting wood was monitored in December.  Twenty spurs were gathered from each block, concentrating on the susceptible varieties, Padre, Sonora and Thompson.  Ten spurs were gathered low and ten high on the tree.  The fruiting wood was again evaluated in March taking five twig samples in each treatment.  The adult population was monitored by placing one sticky trap with a pheromone lure in each plot.  The trap was placed on the tenth tree in from the end, and six or seven feet high in the northeast quadrant of each tree.  The trap was placed on February 11 and was monitored weekly until the end of November.  Pheromone lures were replaced every four weeks.  Adult San Jose moths were counted as well as the Encarsia and Aphytis adults.  The crawlers were monitored by using double-sided sticky tape which was placed in four trees surrounding the tree that contained the pheromone traps.  Tape was placed March 29, 2002 and was monitored weekly for presence-absence over the course of the season.

Peach Twig Borer (PTB).  This pest was monitored by placing pheromone traps and by larva emergence from hibernacula.  The traps were used for monitoring the adult population.  They were placed in the tenth tree in from the end, six or seven feet high in the northeast quadrant of the tree.  The traps were placed March 21, 2003 and their pheromone lures were replaced every eight weeks.

The PTB larvae emergence was determined by collecting rust-colored hibernacula (minute chimney-like piles of frass and sawdust) from crotches (branch angles) of two year old trees.  With a grafting knife, a pie-shaped wedge containing the hibernacula was cut from tree crotches and placed into a vial.  Ten hibernacula were collected from 10 different areas of an orchard located 9 miles from the PMA orchard.  Under the microscope, the hibernacula was opened with a probe and the presence or absence of the larvae was noted.  Absent larvae meant it had emerged.  Therefore emergence was determined by the number of absent larvae.  Samples were taken, every five days, from January 30 through March 17.

Navel Orangeworm (NOW).  This pest was monitored with egg traps and winter sanitation.  One NOW egg trap was placed in each plot on March 21, 2003.  It was placed in the tenth tree in from the end in the north side of the tree and six or seven feet high.  The traps were black and contained an almond meal mixture.

Winter sanitation was evaluated on February 12, 2003 by counting the number of nuts left from harvest.  These nuts are called mummies.  Forty-five trees in each plot were selected and the number of mummies were counted in each tree.

Mites.  This pest was monitored with soil and leaf samples.  The soil samples were taken in the winter and leaves were sampled during growing season.  Soil monitoring to determine the overwintering female web spinning mite began February 10, 2003 and continued with weekly samples until March 26, 2003.  Soil samples were taken from the base of the trees and placed in eight ounce Styrofoam cups which were filled to the rim.  Then, they were placed on a sticky card and left at room temperature for two weeks.  After two weeks, the overwintering female mites emerged from the soil and got stuck to the cards.  The sticky cards were then read and the overwintering female mites were recorded.

Leaf monitoring for mites on Nonpareil and Butte varieties began on April 2, 2003.  Leaf samples were taken at random from five trees in each plot.  The tree location changed every week.  Ten leaves were selected from each tree.  Initially, only interior leaves were selected, however, by mid-May, half of the leaves were selected from the interior and half from the exterior of the tree.  Leaves were brought back to the lab, in an ice chest, and examined under a microscope.  The presence-absence method was used.  Only web spinning mites were considered.  European red, predatory mites and sixspotted thrips were noted.

On March 26, 2003, twigs were selected from trees to evaluate the movement of overwintering females.  Five twigs were gathered from five different trees in each plot.  Twigs were selected from inside of major branches and only the lower parts of the branches were sampled.  The twigs were brought back to the lab and examined under a microscope.

Ants.  This pest was monitored by the “hot dogging” method on May 14, June 27, August 11 and October 31, 2003.  Half-inch hot dog slice (Bar-S brand containing beef, pork, and chicken) was placed in a snap-cap vial.  These vials were distributed in the orchard in the morning when ant activity is at its maximum.  The vials stayed on the orchard floor for a period of two hours, then picked up and stored in the freezer until counting.  The ants were removed from vials by washing them on to a petri dish.  The ants were separated with a glass rod and counted.

Nutrients.  The nutrient levels were monitored by June-July leaf samples.  The samples were washed in distilled water.  They were allowed to dry and then ground through a Wiley mill.  The samples were then sent to the ANR Laboratory at U.C. Davis for analysis.

Production.  Yields of Nonpareil and Butte from both conventional and reduced input systems were taken at harvest.  In addition, yields were taken from dormant and non-dormant sprayed plots from both conventional and reduced input systems.  Furthermore, yields were also taken from the Fritz variety to evaluate yield’s response to SJS infestation.

Treatments:

Dormant Sprays.  The conventional and reduced input systems were subdivided into sprayed and non-sprayed.  The conventional sprayed treatment was sprayed with five pints of Diazinon® plus six gallons of oil mixed with 200 gallons of water per acre.  The reduced input treatment received six gallons of oil in 200 gallons of water per acre.  The spray was applied December 18, 2003.

Winter Sanitation.  By February 7, both conventional and reduced input treatment were mechanically shaken for mummy removal.

May Spray.  This spray was skipped this year.  The reason was due to the ineffectiveness of May sprays.

Hull Split Spray.  This spray was done on July 11, 2003, at the on-set of hull split for the control of NOW.  The conventional (dormant and non-dormant) was sprayed with Imidan® 5 lb per acre in 200 gallons per acre.

Mite Sprays.  The conventional received the following treatment. Agri-Mek® (10.1 oz.) + 1% oil (4/30 and 6/11) then 2% oil in every middle (7/2).  The reduced input was divided into predatory mite and no predatory mite treatments.  In the predatory mite treatment, 2500 mites per acre were released May 13 and June 5.  Oil at 2% was sprayed (6/16) every other middle then 2% oil was sprayed in every middle in July 2.  The reduced input without predatory mite releases consisted of the following: Agri-Mek® (10.1 oz.) plus 1% oil sprayed May 13, two percent oil was sprayed every other middle in June 5, then a 2% oil was applied in every middle in July 2.  Please note that all these sprays were applied with 200 gallons of water.

Ant Sprays.  The conventional-dormant was sprayed on July 27 with 4 pt. Lorsban® in 100 gallons of water per acre.  Reduced-dormant received 1.5 lb. Distance® per acre on June 19.  The reduced-nondormant received one pound of Clinch® per acre on July 9.  There was an untreated control.

Results:

San Jose Scale.  The San Jose Scale continues to increase in the plots that were left unsprayed for three seasons.  The populations exploded in the plots where no dormant oil was applied and a hull split organophosphate insecticide was applied for NOW control.  Table 1 shows the percent of SJS infestation.  The no dormant treatment shows the greatest percent of infested twigs with live SJS.  The reduced input shows the least amount of SJS infestation.  This may mean that the organophosphate insecticide applied at hull split may be affecting the natural enemies of SJS.

Table 1.  Percent of twig infestation with both live and dead SJS in reduced input, conventional and no dormant treatments.

Reduced Input                                                        1.2            24.8                             74.0

Conventional                                                           4.4            35.2                             60.4

No dormant                                                           32.5           21.2                             46.3

The SJS adult population from reduced and conventional treatments from plots that received dormant and no dormant oil sprays is found in Figure 1.  The population was monitored from March to November.  However, the only difference in the population is found in early March.  Where no dormant oil was applied, we have a greater SJS population in the reduced input than on the conventional.  This is expected since no dormant oil was applied.  However, where a dormant spray was applied the reverse occurred.  The conventional treatment showed a greater SJS population than the reduced treatment.  This can be due to the effect of organophosphate spray at hull split.  The spray may have eliminated SJS natural enemies.  SJS populations can be detected by using the adult traps.  However, orchard infestation can be best determined by sampling spurs in the dormant season.

Figure 1.  Average number of SJS adult males from reduced and conventional treatments from plots that received dormant and no dormant oil sprays.

                                            No Dormant Spray

                                                Dormant Spray

Peach Twig Borer.  The PTB emergence in relation to air and bark temperature is found in Figure 2.  The bark temperature is higher than the air temperature but both run parallel to each other.  Furthermore, they don’t appear to have an effect on the rate of emergence of PTB.

The rate of emergence coincides with bloom development.  The beginning of Nonpareil bloom was February 12, at this time PTB emergence was 22%.  PTB reached 80% in March 13, at this time Nonpareil was at the end of petal fall.  When PTB emergence coincides with bloom, one can control bloom diseases and PBT by mixing a fungicide and Bt in the same sprayer’s tank.

Figure 2.  Peach Twig Borer emergence in relation to air and bark temperature.

Figure 3 shows the PTB moth population from reduced and conventional treatments where dormant and no dormant sprays were applied.  The moth population was lower in the no dormant treatment than on the dormant treatment.  This was especially true early in the season.  In August 24 both show a definite peak and another peak appears in October 17.  The late season increase in population may explain the high reject level of late maturing varieties.

Figure 3.  Average number of PTB moths per trap from reduced and conventional treatments where dormant and no dormant sprays were applied.

                                        No Dormant Spray

                                           Dormant Spray

Table 2 shows the number of strikes in June.  The number of strikes was very low in the orchard.  At this level one should not expect much nut meat damage.  The reduced input plus oil in the dormant spray had the highest number of strikes.  However, both the conventional sprayed with Diazinon® plus oil and conventional with no spray had the same number of strikes per tree.  This means that Diazinon® and oil did not reduce the number of PTB strikes per tree.

Table 2.  Average number of PTB strikes per tree from different dormant treatment in both conventional and reduced.

Conventional                                     Diazinon + Oil                                                   0.4

Conventional                                     No treatment                                                     0.4

Reduced Input                                   Oil only                                                             2.4

The percent of rejects due to PTB is shown in Table 3.  The reject level in Nonpareil was below one percent and it was zero for Butte for all management systems.  This means that Diazinon® and oil had no effect in reducing nut meat damage.

Table 3.  Percent of rejects due to Peach Twig Borer in Nonpareil and Butte under different management systems.

Navel Orange Worm (NOW).  Mummy counts showed that both conventional and reduced input had less than one mummy per tree by February 12.

The average number of NOW eggs per trap from conventional and reduced input were very low in both dormant and non-dormant treatments early in the season.  No major peaks were detected until early September.  The no dormant conventional treatment had Imidan® at hull split.  The dormant spray conventional had a Diazinon® at dormant and a Imidan® at hull split.  Over all there were less eggs on the dormant spray treatment than on the non-dormant spray.  The third generation peaks (late august early September) were about the same.  However, the eggs in the conventional treatments peaked at a higher level.

This year growers complained about the high reject levels of the late maturing almond varieties.  This may be due to the third generation peak which coincide with the hull split of these varieties.

Figure 4.  Average number of NOW eggs from reduced input and conventional treatments where dormant and non-dormant treatments were applied.

                                          No Dormant Spray

                                                Dormant Spray

NOW rejects can be found in Table 4.  The reject levels of Nonpareil in 2003 were very similar to the reject levels of 2002.  The highest one was 1.13% which occurred in the non-dormant spray (no Diazinon®) and no hull split spray.  The conventional (Diazinon® in dormant and Imidan® at hull split) had a 0.90% reject level.  This means that the conventional only gave us a 20% control.  The reject levels of Butte were below one percent.  The reject levels in the conventional treatment were higher than on the reduced inputs.

Table 4.  Percent of rejects due to NOW damage in Nonpareil and Butte under different management systems.

Mites.  The 2003 season was a mite year due to the high temperatures in June.  The mites were kept under control with predatory mite releases, Agri-Mek® sprays and oil sprays.  Table 5 contains the different mite spray treatments that were required to control the mites this year.

Table 5.  Management treatments for the control of mites in 2003.

Conventional               Agri-Mek® @ 10.0 oz. & !% oil per acre in 200 gallons of water were

                                   sprayed 4/30 & 6/11.  Then 2% oil was sprayed July 2.

All these spray programs controlled mites.  However, from them we can conclude the following:  1) An Agri-Mek® spray can be saved, if one waits until mites are present.  However, one should not wait past May 15 to apply it.  Past this date Agri-Mek® may not be effective.  2) Predatory mite releases can be used to manage mite resistance and  3) Oil sprays (up to 2%) can control mites as long as sixspotted thrips are present in the orchard.

The average number of overwintering female mites are found on Table 6.  The two reduced input treatments have a greater number of overwintering female mites than any other management system.  When the movement of mites from the orchard floor to the tree scaffolds was evaluated by twig samples, no movement was detected from any of the treatments.

Table 6.  Average number of overwintering female mites in each sampling date.

Ants.  This insect can cause more damage to almond meats than NOW and PTB.  Orchards that are harvested early and/or have a good cover crop or resident vegetation are most susceptible to ant damage.  The ant treatments can be found in Table 7.

Table 7.  Ant treatments for 2003.

Lorsban®                                          4 pints per acre                                              July 27

Clinch®                                             1.0 pounds/acre                                              July 9

Distance®                                         1.5 pounds/acre                                             June 19

control                                               untreated

The ant population (ants per vial) can be found in Figure 5. There were no differences in the ant population due to treatment.  The population in all treatments decreased in June 27.  This corresponds to the 100^oF temperatures that occurred in the last week of June.  This is not unusual.  It has happened in the past.

Figure 5.  Average number of ants from each sampling date.

The reject levels due to ants are found in Table 7.  Clinch® and Distance® didn’t provide a good ant control.  Lorsban® appears to be a better choice.  However, it was not better than the control.  Ants have been the most difficult pest to control in the PMA orchard.  The reasons may be due to the barley cover crop and the timing of the applications of both Clinch® and Distance®.  Temperatures may play a role.  When temperatures are high ants don’t forage.  This will make bait materials, such as Clinch and Distance ineffective.

Table 8.  Percent damage due to ants from four different treatments.

Clinch®                                                                                    2.50

Distance®                                                                                2.90

Lorsban®                                                                                 1.56

control                                                                                      1.48

Shell Seal.  We have been evaluating shell seal in the PMA orchard.  In 2002 there were no differences in shell seal and crop load.  This year shell seal was evaluated on Nonpareil and Butte under the different management systems.  The data is found in Table 9.

Table 9.  Percent of open shell seal in 2002 for Nonpareil and 2003 for Nonpareil and Butte under different Management Treatments.

Yields.  The yield date is found in Table 10.  The Nonpareil yields were affected by the management system.  The lower yield was on the reduced inputs, where oil and no spray was applied in the dormant season for SJS control.  This may indicate that SJS can have a major impact on yields.  The yields on the Butte variety however, were not impacted by the management system.

Table 10.  Yields (pounds per acre) of Nonpareil and Butte under different Management Systems.

The Fritz variety showed severe spur and shoot die back in the reduced input with no dormant spray.  The yield data on Table 11 strongly suggests that SJS has a major impact on yields.

Table 11.  Fritz’ yields (meat pounds per acre) due to SJS treatments.

Conclusions:

1.         Monitoring is essential for pest management.

2.         San Jose Scale is a key pest in almonds.  It is very difficult to manage it, when inseason organophosphates are applied in the orchard.  It is a pest that can decrease yields.  This year the yields of both Nonpareil and Fritz decreased due to SJS.  The best way to assess SJS infestation in an orchard is by determining infestation of spurs and shoots.  SJS adult trapping only determines its presence.

3.         The dormant spray (Diazinon® and oil) didn’t appear to control Peach Twig Borer strikes nor did it appear to have any impact on reject levels.

4.         NOW egg traps showed a definite increase in number of eggs in early September.  This may explain high reject levels in late maturing varieties in Kern County.  Hull split spray (Imidan®) resulted in a 20% reduction in NOW damage.

5.         Predatory mites can be used to manage mite resistance to mitecides.  Also they can control mites provided the orchard is heavily monitored.  Oil sprays can be effective in controlling mites provided that sixspotted thrips are present in the orchard.

6.         It has been difficult to control ants in the PMA orchard.  This may be due to the barley cover crop or due to the high temperatures in late spring which may have interfered with ant’s foraging behavior.

Acknowledgements

We wish to thank Thomas Vetsch of Vetsch Farms of California, Inc. for providing and maintaining the study site, and for providing labor when needed.  We appreciate the donation of predatory mites by Matt Billings of Sterling Nursery, and Clinch® and financial support from Syngenta.  This study was supported by a grant from the California Almond Board Pest Management Alliance.  Thank you for your support.