Description of the Pest
Liriomyzid leafminer adults are small, shiny black flies with a bright yellow triangular spot on the upper thorax. Eggs are white and oval and laid within the leaf. Larvae feed between leaf surfaces, creating meandering tracks or mines. Mature larvae leave the mine and drop to the ground to pupate. The life cycle takes only 2 weeks in warm weather; there can be many generations a year.
Damage
Larvae mine between upper and lower leaf surfaces, creating winding, whitish tunnels that are initially narrow, but then widen as the larvae grow. Leaves injured by leafminers drop prematurely; heavily infested plants may lose most of their leaves.
Management
Leafminers are rarely a problem in the Imperial Valley. In other areas, regular monitoring for leaf mines is important in detecting damaging populations of this pest. Avoid the use of early-season applications of broad-spectrum insecticides (dimethoate, esfenvalerate, methomyl) for control of other pests, in order to conserve natural enemies of the leafminer.
Biological Control
Natural enemies, primarily parasitic wasps in the Diglyphus genus, often control leafminers. When parasites are killed by pesticides, leafminer outbreaks are common.
Organically Acceptable Methods
Biological control and sprays of azadirachtin and the Entrust formulation of spinosad are acceptable for use on organically certified produce.
Monitoring and Treatment Decisions
Regularly check leaves for leaf mines, especially between bloom and fruit development. Most mines occur on older bottom leaves and some mines are most obvious from the underside of the leaf. Also look for dead larvae, which is a sign of parasitism. If parasitism levels are at least 50%, the crop will most likely tolerate damage. However, if leafminer populations build up to high levels, a chemical treatment may be necessary. Avoid early-season applications of broad-spectrum insecticides for other insects, because they may cause leafminer outbreaks to occur.
Pesticides and Natural Enemy Releases
Not all registered pesticides are listed. The following are ranked by their IPM value, with the most effective and least harmful to natural enemies, honey bees, and the environment listed at the top of the table. When choosing a pesticide, consider information related to water and air quality, resistance management, and the pesticide's properties and application timing. Use PestManage to compare summarized management options for different pests in the same crop. Always carefully read the label of the product being used and take all necessary precautions when handling pesticides.
| Rank | Active ingredient | Example trade name | Group | Group Order | MoA 1 | Amount per acre | REI (hours) ‡ | PHI (days) ‡ | Comments | Selectivity 2 | Bees 3 | Predatory mites 4 | Predators 5 | Parasitoids 5 | Residue duration 6 | Leaching(fish) 7 | Adsorbed runoff(fish) 8 | Solution runoff(human) 9 | Leaching(human) 10 | Solution runoff(human) 11 | Last updated 12 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
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|
Agri-Mek SC | Application Timing Varies (See UC IPM Pest Management Guidelines and Label) | 8 |
6 |
1.75–3.5 fl oz | 12 | 7 | Do not apply at less than 7-day interval... | moderate | moderate | low | moderate/high | moderate to predatory mites & affected insects | high | low | extra high | low | intermediate | 06/2016 | ||
|
|
Neemix 4.5 # | Application Timing Varies (See UC IPM Pest Management Guidelines and Label) | 8 |
UN |
4.0–7.0 fl oz | 4 | 0 | Must be consumed by larvae; kills leafmi... | broad | moderate | low/moderate | low/moderate | short | intermediate | high | intermediate | very low | very low | 06/2016 | ||
|
|
Trigard | Application Timing Varies (See UC IPM Pest Management Guidelines and Label) | 8 |
17 |
2.66 oz | 12 | 0 | Do not make more than two sequential app... | narrow | low | low | low | short | very low | low | low | low | low | 06/2016 | ||
|
|
Radiant SC | Application Timing Varies (See UC IPM Pest Management Guidelines and Label) | 8 |
5 |
6–10 fl oz | 4 | 1 | Is more efficacious and has longer resid... | narrow | moderate | moderate 13 | low/moderate | moderate 14 | low | low | low | very low | low | 06/2016 | ||
|
|
Entrust # | Application Timing Varies (See UC IPM Pest Management Guidelines and Label) | 8 |
5 |
2–3 oz | 4 | 1 | Best control is achieved when aimed at n... | narrow | moderate | moderate 13 | low/moderate | moderate 13 | very low | low | low | very low | low | 06/2016 | ||
|
|
Success | Application Timing Varies (See UC IPM Pest Management Guidelines and Label) | 8 |
5 |
6–10 oz | 4 | 1 | Best control is achieved when aimed at n... | narrow | moderate | moderate 13 | low/moderate | moderate 13 | very low | low | low | very low | low | 06/2016 |
Legend
- ‡ a b Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without personal protective equipment. Preharvest interval (PHI) is the number of days from treatment to harvest. In some cases, the REI exceeds the PHI. The longer of the two intervals is the minimum time that must elapse before harvest.
- # a b Acceptable for use on certified organic crops. Check with your certifier to confirm before application.
- 1 ↩ Group numbers for insecticides and miticides are assigned by the Insecticide Resistance Action Committee (IRAC). Insecticides with unknown modes of action are assigned mode-of-action group numbers (MoAs) that begin with UN. Rotate pesticides with a different mode-of-action group number, and do not use products with the same mode-of-action group number more than twice per season to help prevent the development of resistance. For example, the organophosphates have a group number of 1B; insecticides with a 1B group number should be alternated with insecticides that have a group number other than 1B.
- 2 ↩ Range of insect and mite groups affected by a pesticide. Broad means the pesticide affects most groups of insects and mites; narrow means the pesticide affects only a few specific groups.
- 3 ↩ Risk of harm to honey bees. For more information, see Bee Precaution Pesticide Ratings.
- 4 ↩ Risk of harm to predatory mites. Toxicities are generally to western predatory mite, Galendromus occidentalis. Where differences have been measured in toxicity of the pesticide-resistant strain versus the native strain, these are listed as pesticide-resistant strain or native strain.
- 5 a b Risk of harm to parasitoids and general predators. Toxicities are averages of reported effects and should be used only as a general guide. Actual toxicity of a specific insecticide depends on factors including the application rate, environmental conditions, and the life stage and species of a parasitoid or predator.
- 6 ↩ Length of time residue affects natural enemies. Short means hours to days; moderate means days to 2 weeks; and long means many weeks or months.
- 7 ↩ Risk of harm to fish from leaching, based on USDA Natural Resources Conservation Service Windows Pesticide Screening Tool (WIN-PST).
- 8 ↩ Risk of harm to fish from adsorbed runoff, based on USDA Natural Resources Conservation Service Windows Pesticide Screening Tool (WIN-PST).
- 9 ↩ Risk of harm to fish from solution runoff, based on USDA Natural Resources Conservation Service Windows Pesticide Screening Tool (WIN-PST).
- 10 ↩ Risk of harm to humans from leaching, based on USDA Natural Resources Conservation Service Windows Pesticide Screening Tool (WIN-PST).
- 11 ↩ Risk of harm to humans from solution runoff, based on USDA Natural Resources Conservation Service Windows Pesticide Screening Tool (WIN-PST).
- 12 ↩ Date information was last updated in the UC IPM Pest Management Guidelines.
- 13 a b c d e Toxic to some natural enemies (lacewing and syrphid fly larvae, predatory beetles, and thrips) when sprayed and up to 5 to 7 days after.
- 14 ↩ Residual is moderate if solution is between a pH of 7 and 8.
UC IPM Pest Management Guidelines: Peppers
UC ANR Publication 3460
E.T. Natwick (emeritus), UC Cooperative Extension Imperial County
J.T. Trumble, Entomology, UC Riverside
J.L. Aguiar, UC Cooperative Extension Riverside County
Acknowledgement for Contributions to Invertebrates
W.J. Bentley (emeritus), UC IPM and Kearney Agricultural Research and Extension Center, Parlier
W.E. Chaney (emeritus), UC Cooperative Extension Monterey County
R.L. Coviello, UC Cooperative Extension Fresno County
C.F. Fouche, UC Cooperative Extension San Joaquin County
C.G. Summers (emeritus), Entomology, UC Davis and Kearney Agricultural Research and Extension Center, Parlier
