Task 3  Kern County Site

Pest Management Alliance Project, Kern County

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 three 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 season each of the plots in both conventional and reduced input was divided into dormant and non-dormant spray subplots to better assess the impact of dormant sprays.  Thus, there are now 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 2001 season.  It doesn’t include information from 1999 and 2000 seasons.

Cover Crops:

A 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 both “soft” and “hard” shell blocks, at a rate of 80 lbs. per acre.  The seeding was done in December.  In previous years, insectary mixes were also planted at this time.  However, this has been discontinued.  Lack of success was attributed to poor germination and plants that bloomed too late to be of benefit for the control of key pests.

Pest Monitoring:

The setup for pest monitoring was modified for 2001 because each 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 over-wintering SJS population in the orchard was monitored by randomly selecting 20 spurs from each plot.  These spurs were sampled in early December.  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 28 and was monitored weekly until the end of November.  Pheromone lures were replaced every four weeks.  Adult SJS 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 April 4, 2001 and was monitored weekly for presence-absence until the biofix occurred.

Peach Twig Border (PTB).  PTB was monitored by the placement of 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 April 4, 2001 and their pheromone lure 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 a few 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, twice a week, from early February through mid-March.

Navel Orangeworm (NOW).  NOW was monitored using egg traps and an evaluation of winter sanitation practices.  One NOW egg trap was placed in each plot on April 4, 2001.  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 7, 2001 by counting the number of mummies, the nuts left from harvest.    Forty-five trees in each plot were selected and the number of mummies was counted in each tree.

Mites.  Mites were 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 2, 2001 and continued with weekly samples until April 11, 2001.  Soil samples were taken from the base of the trees and placed in eight ounce Styrofoam cups, filled to the rim with the soil.  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 became 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 11, 2001.  Leaf samples were taken at random from five trees in each plot.  The tree location changed every week.  One week the trees were located at the extreme ends of the orchard, but on the following week, they were located through the middle of the two blocks.  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.

Ants.  Ants were monitored by the “hot dogging” method on May 26 and June 25, 2001.  Half-inch hot dog slice (Bar-S brand containing beef, pork, and chicken) was placed in a snap-cap vial; 10 vials were distributed in a diagonal pattern across each block.  Vials were distributed in the orchard during early morning ant activity for duration of two hours, then picked up and stored in the freezer until counting.  Sample processing involved removing ants from the hot dog and vial by washing them into a petri dish for counting.  All ants per vial were individually separated 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.

Treatments:

Dormant Sprays.  For the 2001 season, the conventional and reduced input systems were subdivided be dormant spray, i.e., sprayed and non-sprayed.  The conventional sprayed treatment was sprayed with five pints of Diazinon® plus six gallons of oil mixed with 250 gallons of water per acre.  The reduced input treatment received six gallons of oil in 250 gallons of water per acre.  The spray was applied January 23, 2001.

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

May Spray.  A May spray was done for control of SJS.  The biofix for male adult moths occurred March 21, 2001 and for crawlers it occurred March 26, 2001.  Degree-day calculations indicated that the optimum time for spraying was during the second week of May (from the 7th to the 15th.)

The orchard was sprayed May 8.  The conventional dormant treatment plots were sprayed with Esteem® at a rate of 14 oz. In 200 gallons of water per acre.  The non-dormant conventional treatment plots were left unsprayed.  The reduced input treatment (dormant oil only) was sprayed with two gallons of oil in 200 gallons of water per acre.

Hull Split Spray.  This spray was done June 27 before hull split took place.  It was timed for the control of PTB in the soft shell plots.  The conventional plots were sprayed with Imidan® at a rate of four pounds in 200 gallons of water per acre.  The reduced input was sprayed with 16 oz. of Confirm® in 200 gallons of water per acre.  The hard shell blocks were left unsprayed.

Mite Sprays.  The conventional (dormant spray) plots were sprayed with Omite® at a rate of 4 pts. in 200 gallons of water per acre on May 30.  The conventional (non-dormant spray) plots were sprayed with 12 oz. Agri-Mek® plus 2 gallons of summer oil in 200 gallons of water.  This spray was also applied to the non-dormant spray reduced input plots.  The Agri-Mek® spray on both of these plots was applied May 31.  Predatory mites were released in the reduced input (dormant oil) plot June 1.  There were two predatory mite releases in the reduced input (non-dormant) plot, one May 16 and the second, June 1.  Each release was 2500 mites per acre.

There were additional mite sprays in June-July.  Three out of the four Omite® plots (conventional dormant-spray) and one reduced input plot (where mites were released June 1) were sprayed using 2 gallons of oil in 200 gallons of water per acre.

Ant Sprays.  Clinch® was applied to the reduced input plots at a rate of one pound per acre.  There was no spray on the conventional plots.

Results:

San Jose Scale.  Shoot samples have been showing an increase in infestation.  Table 1 shows that shoots from reduced input plots were more infected than shoots from the conventional plots.  For this reason, the crawlers in half of the reduced and half of the conventional were treated with oil and Esteem® respectively.

Table 1.  Percent of infested shoots from conventional and reduced input treatments.

Conventional 1                             Sonora                              0                                        0

Reduced Input 1                          Sonora                             45                                       0

Conventional 2                         Butte/Padre                          0                                       25

Reduced Input 2                       Butte/Padre                          0                                       10

Conventional 3                              Butte                               0                                       10

Reduced Input 3                            Butte                               0                                       40

Conventional 4                             Sonora                              0                                        5

Figure 1 and 2 show the number of SJS male from February to November.  The number of males was higher in the no-dormant than on the dormant plots.  The population was higher on the conventional than on the reduced input plots (Figure 1).  However, this was not the case for the dormant spray plots.  Both conventional and reduced plots show no differences in SJS (Figure 2).  Figure 1 and 2 show no male SJS population after April 14.  This was before a crawler spray was applied.

Figure 1.  Average number of male SJS per trap, where no dormant spray was applied, from February to November.

Figure 2.  Average number of male SJS per trap, where dormant spray was applied, from February to November.

Peach Twig Borer.  Figure 3 shows the PTB emergence for 2001.  PTB emergence doesn’t correspond to bloom development.  Full bloom of Nonpareil occurred February 26.  At this time there were no PTB emergence.  The treatment level occurred March 8 or 12 days after full bloom (Figure 3).

Figure 3.  Percent of PTB emergence for 2001.

The number of shoot strikes in both May and June readings were not large.   In the May reading, shoot strikes were greater in the reduced input (dormant oil treatment) than conventional dormant treatment (Diazinon® and oil). The same relationship can be seen in the July readings (Table 2).

Table 2.  Average number of PTB strikes per tree in conventional and reduced input plots treated and non-treated with dormant sprays.

Figure 4 shows the adult population of PTB from February to November in the no dormant spray for both conventional and reduced input treatments.  The adult population for the conventional and reduced input plots differs at the beginning of the third flight and continue in this manner until the end of October.  There were no sprays on these plots.  This was not the case in Figure 5, which shows the PTB adult population from the dormant spray of both conventional and reduced input.  The dormant spray received an Imidan® and Confirm® spray on June 27.

Figure 4.  Average number of PTB per trap, where no dormant spray was applied, from February to November.

Figure 5.  Average number of PTB per trap, where dormant spray was applied, from February to November.

The percent rejects due to PTB is shown in Table 3.  The rejects were very low in 2001 in both Nonpareil and Butte.  Either spray, Confirm® or Imidan®, had little effect in reducing reject levels in the Nonpareil.

Table 3.  Percent of reject levels due to PTB from conventional dormant and non-dormant also from reduced dormant and non-dormant sprays.

Navel Orangeworm (NOW).  Mummy counts showed that all conventional and reduced input management plots had less than one mummy per tree by February 15.

Figure 6 shows number of eggs per trap of NOW where no dormant spray was applied for both conventional and reduced input management treatment.  There were no differences between conventional and reduced.  This is expected since no spray was applied.  In contrast, there was a marked difference in the number of eggs between conventional and reduced input plots when they were dormant sprayed (Figure 7).  There were more eggs in the reduced input dormant-sprayed plot than the conventional dormant-sprayed treatment.

Figure 6.  Average number of NOW eggs per trap, where no dormant spray was applied, from February to November.

Figure 7.  Average number of NOW eggs per trap, where dormant spray was applied, from February to November.

The reject levels for NOW are found in Table 4.  The rejects for Nonpareil are less than one percent.  The rejects from reduced input both from the dormant and non-dormant spray were larger than the conventional dormant and non-dormant.  Please note that both reduced input dormant and conventional dormant received a hullsplit spray on June 27.  Table 4 also shows the reject levels for Butte.  The reject levels for this variety were about one percent.  All treatments were about the same except for the conventional plot, which had less than one percent.

Table 4.  Percent of reject levels due to NOW from conventional dormant and non-dormant also from reduced dormant and non-dormant treatments.

Ants.  Figure 8 shows ant population at May 29 and June 25 from the conventional plots which received no treatment and reduced input plots which received Clinch®.  The population was higher in May 29 and by June 25 had decreased.  There was no marked difference in the population between conventional and reduced input plots.

Figure 8.  Average number of ants per sample on two sampling dates.

Table 5 shows percent rejects due to ants from the conventional and reduced input plots.  The conventional plots were not treated for ants however the reject level is less with the conventional compared to the reduced input treatment.  From the reject level, it appears that the application of Clinch® offered little protection against damage by ants.

Table 5.  Percent rejects due to ants.

Mites.  The 2001 season was a particularly prone to mite infestation this year due to 100 F days during the summer.  The mites were kept under control and none of the trees webbed over or were defoliated during the summer.

Predatory mite releases were unsuccessful in five out of eight plots.  These plots were sprayed with Agri-Mek® or one percent oil when the infestation of the leaves increased to 70%.  These sprays were applied 2 weeks after the predatory mite releases.

Omite® sprays were unsuccessful in two out of four plots.  These plots were re-sprayed with Omite® or one percent oil.

Agri-Mek® worked well in every plot where applied.  One spray done on May 31, 2001.

The female emergence from the soil can be found in Table 6.  There were no statistical differences in the number of females emerging from the soil.  However, when the totals are considered, we can see that there were more female mites emerging from the conventional than from the reduced treatments.

Table 6.  Average number of overwintering female

Reduced

Input                  0.25a      0.10a      0.05a      0.10a      0.05a      0.00a      0.00a      0.05a     .075a*

*value followed by different letters are significantly different at P=0.05.

Yields.  Yields are found in Table 7.  There was a significant difference in yields among in the Nonpareil variety.  The conventional nontreated plot produced more almonds than the reduced nontreated treatment.  There are no significant differences among the treatments in the Butte.

Table 7.  Yields in meat pound per acre for Nonpareil and Butte under different management systems.

*value with same letters are not significantly different from each other.

Reject Levels.  The total reject levels are shown in Table 8.  The reject levels for ants, NOW and PTB are very low and within acceptable levels for growers.

Table 8.  Insect damage (percent) in Nonpareil and Butte due to Ants, NOW and PTB from different management systems.

Orchard Nutrition.  There is no difference in orchard nutrition between conventional and reduced input treatment, as would be expected because there were no differing nutrient applications (Table 9). 

Table 9.  Tree nutrition levels from the conventional and reduced management systems.

Summary and Conclusions:

Monitoring.  Monitoring is a necessity to gain knowledge of pests and diseases in an orchard.  Studies have shown that knowing pest and disease pressures allows the grower to reduce pesticide usage.  Less pesticide use reduces production costs to a grower.

Cover Crops.  The greatest benefit of a cover crop such as barley is an increase in water penetration.  This finding has solid support in literature.

Dormant Sprays.  Dormant sprays control SJS and ants while not controlling PTB.  Esteem® and Oil were effective in SJS control.

Winter Sanitation.  Research has shown that winter sanitation and early harvest reduces NOW nut infestation.  The sanitation was excellent this year, less than one mummy per tree.  The reject levels were less than one percent in all plots.

In Season Sprays.  With reject levels of less than one percent for both NOW and PTB, it is questionable whether in-season sprays are needed.  Also, in season sprays can have a detrimental effect to beneficial insects.

Mite Control.  Mites were controlled by intense monitoring in the orchard, even though more than one spray was applied to some of the plots.  This year predatory mite releases were not always successful, nor was the application of Omite®.  However, Agri-Mek® worked in every plot it was applied.

Shell Seal.  We are expecting a better shell seal this year.  The reject levels were very low in both Nonpareil and Butte.

Acknowledgements

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