Description of the Pest
Wings are cream colored at the base and a mixture of rust-orange and dark brownish-gray toward the wing tip. Wings are also marked with dark lines. The wingspan is approximately 0.8 in (20 mm). Males and females appear nearly identical, although the front wings of females have slightly more orange patches.
Eggs are laid along the veins on either side of leaves. They are oval, flat, and transparent to white and turn greenish-brown prior to hatching. Depending on the temperature, eggs hatch in approximately 5 to 10 days.
Larvae feed on leaves for 2 to 4 days then drop to the soil surface and burrow into a rhizome. Mature larvae are white or tan with a reddish-brown head and are about half an inch long. In October, larvae leave the rhizomes to overwinter in hibernacula just below the surface (2–4 cm below). Larvae pupate in spring.
Adult mint root borers start emerging between early and mid-June, with peak emergence occurring from mid- to late July. Mint root borers have one generation per year.
Damage
Larvae bore into and feed on rhizomes of peppermint. Economic loss is due to decreased oil yield, reduced quality of oil, and shorter productive expectancy of mint stands.
Management
Biological Control
Parasitic nematodes can be released through irrigation at 2 billion infective juveniles per acre.
Cultural Control
Tillage can be effective in late fall or spring when the mint root borer is overwintering or before adults emerge in June. Rotation with a non-host crop is also a possibility.
Monitoring and Treatment Decisions
- Sample for mint root borer larvae from September through October.
- Take at least two soil samples (1 ft2 x 3 inches deep) for every 2- to 3-acre area (minimum of 25 samples per field).
- Examine soil, roots, and rhizomes, and record the number of larvae found. In addition, roots and rhizomes can be placed in a Berlese funnel for approximately 24 hours or until dry to extract larvae.
- Consider a postharvest treatment if two or more larvae are found per sample.
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(fish) 9 | Leaching(human) 10 | Solution runoff(human) 11 | Last updated 12 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
|
Coragen | Application Timing Varies (See UC IPM Pest Management Guidelines and Label) | 8 |
28 |
3.5–5.0 fl oz | 4 | 3 | — | narrow | low | low | low/moderate | short | — | — | — | — | — | 08/2012 | ||
|
|
Mocap 15% Granular | Application Timing Varies (See UC IPM Pest Management Guidelines and Label) | 8 |
1B |
3 lb a.i. | 48–72 | 225 | Broadcast and incorporate to a depth of... | narrow | low | low | low | — | high | intermediate | high | extra high | extra high | 08/2012 |
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.
- 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.
UC IPM Pest Management Guidelines: Peppermint
UC ANR Publication 3457
K.E. Tollerup, UC IPM and Kearney Agricultural Research and Extension Center, Parlier
