Developing Integrated Pest Management (IPM) Tools For Managing Thrips and TSWV in Pepper
Aziz Baameur, Farm Advisor
UC Cooperative Extension, Santa Clara County 1553 Berger Dr., Bldg. 1
San Jose, CA 95112
Phone/Fax: (408) 282-3127 / (408) 298-5160
Shimat Joseph & Steven Koike, Farm Advisors Monterey County
Background and Rationale
Although virus disease incidence and severity vary greatly from season to season, viruses have been a perennial problem in pepper production fields in the Central Coast of California. In the Gilroy/Hollister area, Tomato spotted wilt virus (TSWV) remains the persistent and dominant virus problem in pepper fields.
In this proposed project, we will explore different integrated pest management (IPM) strategies to manage this virus. We will employ timely chemical treatments to suppress thrips, selected TSWV-resistant pepper cultivars, and thrips and disease monitoring strategies. Because Impatiens necrotic spot virus (INSV), another thrips-vectored virus, has been confirmed in peppers in Georgia (Naidu, 2005) and here in coastal California (Koike, unpublished), we will also monitor pepper fields for this pathogen.
- Assess the usefulness of differently timed insecticide treatments in delaying and/or reducing virus occurrence in pepper.
- Plant selected peppers with the resistance gene to TSWV to ascertain their usefulness in coastal California.
- Test methods for monitoring thrips populations as they develop in pepper fields.
Materials and Methods
The study will have two factors: pepper varieties and insecticide treatments. The three pepper varieties will be: 1) standard local commercial variety, 2) resistant variety (with the sw-5 gene that confers resistance to TSWV), and high yielding commercial variety (without the sw-5 gene). Resistant pepper cultivars to TSWV are available and in use in other regions. However, they were not developed for our area and may not fit the needs of our growers. Yet, their inclusion in this work would be informative and useful to test their performance under our conditions and when exposed to local strains of viruses (TSWV, CMV, and INSV).
The insecticide treatments will be as described in the table below:
|Treatment 2||Cyazypyr*||At transplanting|
|Treatment 3||Cyazypyr||At transplanting & at 10, 20, 30 days after transplanting|
|Treatment 4||Grower's treatment||Grower's standard treatment|
* The Cyazypyr treatment will be drenched at the maximum label rate.
The experiment will be a randomized block design replicated 4 times (3 variety treatments x 4 chemical treatments x 4 replicates = 48 plots total). Beat-cup samples for thrips will be collected until 90% of the plants start flowering; at this point in the crop development, blossom samples will be collected and assayed for thrips. Beat-cup sampling (Joost and Riley 2004) involves bending the plant foliage into a large styrofoam cup and shaking vigorously for 5 seconds; thrips that fall into the cup are then collected for counting and identification. Beat-cup samples will be taken for 10 randomly selected plants per row per week so as to monitor when thrips begin to be found in the crop. Sticky traps will be placed at the edges of the study plots as additional indicators of insect presence.
Blossom sampling (Riley and Pappu 2004) will consist of collecting a single pepper blossom from the top third of the plant; blossoms are collected from 10 randomly selected plants per plot and placed into a vial containing an alcohol-water solution. In addition, a single cylindrical yellow sticky trap for thrips will be set up in the center of the plot approximately 12 inches above the ground on stakes. Traps will be exposed for a week for the first month after transplanting, will be exposed at tri-weekly intervals until harvest. Adult thrips trapped by both methods will be identified to species using key characteristics from published dichotomous keys (Oetting et al. 1993, Stannard 1968) under stereomicroscope.
Infected and/or symptomatic plants will be assayed for the three viruses (TSWV, INSV, and CMV). A field assistant will be scouting the plots on a weekly basis and replacing sticky traps.
Our main goal is to verify the impact and usefulness of the above-described tools to:
- Test the effectiveness of insecticide treatment and timing in suppressing thrips (virus vectors) in pepper fields.
- Verify the usefulness of variety of pepper with TSWV-resistant gene (sw-5) under our conditions and as exposed to virus strains in our region.
- Share information with growers at pepper next pepper grower's seminar in 2014.
Proposed budget for 2013 virus project
|Testing Kits for TSWV & CMV||$1,500|
Joost, P. H., and D. G. Riley. 2004. Sampling techniques for thrips (Thysanoptera: Thripidae) in pre-ßowering tomato. J. Econ. Entomol. 97: 1450-1454.
Naidu, R. A., Deom, C. M., and Sherwood, J. L. 2005. Expansion of the host range of Impatiens necrotic spot virus to peppers. July 27. Online. Plant Health Progress doi:10.1094/PHP-2005- 0727-01-HN.
Oetting, R. D., R. J. Beshear, T.-X. Liu, S. K. Braman, and J. R. Baker. 1993. Biology and identification of thrips on greenhouse ornamentals. Georgia Agricultural Experiment Station. Res. Bull. 414.
Riley, D. G., and H. R. Pappu. 2004. Tactics for management of thrips (Thysanoptera: Thripidae) and Tomato Spotted Wilt Virus in tomato. J. Econ. Entomol. 97: 1648-1658.
Stannard, L. J. 1968. The thrips, or Thysanoptera of Illinois. Ill. Nat. Hist. Surv. Bull. 29: 215-552.