California Pepper Commission


California Pepper Commission Summer 2007 Pepper Weevil Project, Piru, California

California Pepper Commission Summer 2007 Pepper Weevil Project, Piru, California
Final Report
Prepared By: David Holden
Holden Research and Consulting
December 2007


In a randomized complete block design (RCBD) trial, eight different insecticide treatments were evaluated against an untreated check, to screen for efficacy against Pepper weevil (Anthonomus eugenii). Pepper weevil adults were routinely caught in pheromone traps set up around the field, yet at no time during the course of this trial were any weevils found infesting the mature peppers. Data was also collected for Western flower thrips (Frankliniella occidentalis) and Potato Psyllid (Paratrioza cockerelli). No significant control of either of these pests was observed with any of the applications. All data rated as significant was done so utilizing the New Duncanís Multiple Test Range at a 95% confidence level.

Methods and Materials

Test Location: Piru, CA

Planting Date: April 5, 2007 Transplanted

Start Date: May 31, 2007

Harvest/Completion Date: August 15, 2007

Final Report Date: December 2007

Number of Treatments: Nine

Application Method: Solo Backpack airblast sprayer

Water Source: Local Well Water

Spray Volume: 50 and 100 gal/acre

Treatment Timing: See Table 1 below.

Planting Density: Approximately 26,000 plants per acre

Data Collection: Insect numbers and damage

Statistical Analysis: Duncanís Multiple Range Test (DMRT)

Plot Size: 10 feet (three beds) by 20 feet

Data Analysis Package: Gyllings Data Management Agricultural Research Management Software, Version 7.2

Discussion of Methods

This trial was laid out as a Random Complete Block Design (RCBD) of eight treatments and a water check control. Each treatment consisted of four replicates each measuring ten feet (three beds) by twenty feet in length. Data was collected from the center bed of the three beds utilizing the two outer beds as buffers. Treatments were applied in the morning. All treatments went on in the equivalent of 50 or 100 gallons of water per acre. The following table shows the treatments and dates for each treatment called for in the original protocol.

Table 1: Treatments and schedule (A=May 31, B=June 11, C=June 20, D=June 27, and E=July 10, 2007)

No.NameRateRate UnitStgCodeDescription
1Untreated Check     
2Warrior3.84FLOZ/APREHARABCDERaise app rate to 100 gpa late
4Provado 1.66.2FLOZ/APREHARACE 

No deviations occurred from the above treatment schedule. All applications were applied as directed foliar treatments using a Solo Backpack Airblast Sprayer with a two line Gearmore Nozzle.

No phytotoxic effects to the peppers were ever observed from any of the treatments over the course of this trial.

Results and Discussion

The test area was managed for nutrients and pests in the same manner as the surrounding fields except no Pepper weevil insecticides were applied to the test area, except for the test materials. The test area was monitored for pest development on a regular basis once treatments had begun. Though the test was designed to evaluate current conventional insecticide efficacy for the control of Pepper weevil, data was also collected for other insect pests observed to be present. Incidence for Western flower thrips activity was collected at four days post first treat, two days post second treat, and two days post third treat. The thrips were rated by slapping five plants three times each onto a count tray and reporting the average number of thrips found per plant. Thrips damage was rated later by collecting twenty-five fruit per replicate (100 per treatment) and rating for the incidence of thrips damage to that fruit along with a severity rating for that damage. Severity was based on a zero to three scale for damage, zero being no damage, and a three would cause the pepper to be considered a cull. Potato psyllid was also observed in the field. Data for this pest was collected by sampling ten leaves per replicate (forty per treatment) and counting the total number of nymphal psyllids found on the undersides of the leaves, then reported as the average number found per leaf. Finally Pepper weevil incidence was collected by harvesting twenty-five fruit per replicate (100 per treatment), cutting the fruit open and observing for damage or incidence of weevil larvae or adults. This analysis was conducted twice just prior to harvest.

Charts 1 shows the average number of thrips found per plant per rating date along with the average for all rating dates. As can be seen by this data, the thrips incidence was very low and no significant differences in thrips population densities were observed through the use of any of the test materials. Chart 2 shows the average incidence rating for peppers with thrips damage and though there were no significant differences observed in thrips populations in the field, the Dimilin treatment did show significant reductions in thrips damaged fruit, while all other treatments showed numerical reductions in the percent of fruit with thrips damage over the untreated check.

Chart 3 show the average number of Pepper psyllids found per leaf per rating date, along with the final post treat averages. As can be seen in this data no significant differences in Potato psyllid control were observed with any of the treatments.

Finally, as mentioned in the abstract, no Pepper weevils were ever found in any of the peppers on any of the rating dates for this pest. Pepper weevils were routinely found in traps set up around the perimeter of the field early in the growing period, but not found as often during the bloom period.

All data rated as significant was done so utilizing the New Duncanís Multiple Test Range at a 95% confidence level.


Due to the low incidence of Pepper weevils and other pests present in the field, no firm conclusions regarding the efficacy of the test materials for control of these pests could be drawn from this years testing.

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