Central Oregon

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Late Aug/early Sep is the time to scout for Mint Root Borer (MRB) larvae in the soil if fall control is being considered.

Larvae are generally too small to see in August, while sampling in late September is too late as damage is done.

Control treatments must be applied before larvae form hibernacula (overwintering, soil-based cocoons). Based on the insect development model, 5% hibernacula formation is expected September 3 near Powell Butte, and occurred on August 19 near Madras.

Sampling Recommendations for MRB larvae:

  • Sample 1ft2 of soil to a depth of 2-3” (include rhizomes)
  • 2 samples taken every 2-3 acres
  • Minimum 25 samples per field
  • Screen samples in the field or with Berlese funnels in the laboratory

Treatment threshold = average of 2-3 larvae/ft2 sample

Central Oregon – August 25

Central Oregon – August 3

Central Oregon – July 26

Central Oregon – July 20

Central Oregon – July 12

Central Oregon – July 5

Central Oregon – June 30

Central Oregon – June 23

Archived Reports – 2022

August 31, 2022   

August 10, 2022

August 4, 2022

July 28, 2022

July 20, 2022

July 15, 2022

July 6, 2022

June 29 2022

June 24 2022

Archived Reports – 2021

Central Oregon Mint Pest Alert Newsletter – August 28

Time for fall treatment.

Central Oregon Mint Pest Alert Newsletter – July 30

Plan to sample early for larvae in soil.

Central Oregon Mint Pest Alert Newsletter – July 23

MRB captures can vary a lot between fields, so be sure to scout your fields.

Central Oregon Mint Pest Alert Newsletter – July 16

Optimum application window closed/closing.

Central Oregon Mint Pest Alert Newsletter – July 10

The optimum application window for MRB and VC control with Coragen or Vantacor is ending soon.

Central Oregon Mint Pest Alert Newsletter – July 3

The optimum application window for MRB and VC control with Coragen or Vantacor is now.

Central Oregon Mint Pest Alert Newsletter – June 25

Upcoming heat wave moves up optimum application window for Vantacor or Coragen

Central Oregon Mint Pest Alert Newsletter – June 18

6 MRB were found in 1 field

Mint Pest Alert Newsletter – June 11

No MRB were found in traps this week, and no insects of interest were found in sweep net samples.

Mint Pest Alert Newsletter – June 4

Two MRB were found in a trap on June 3. First moth catch was expected on June 4.

Archived Reports – 2020

Central Oregon Mint Pest Alert Newsletter- September 11

Late Aug/early Sep is the time to scout for Mint Root Borer (MRB) larvae in the soil if fall control is being considered (i.e. Lorsban, Mocap, nematodes). MRB larvae drop from the foliage to the ground in August and tunnel into rhizomes, where they will feed into the fall. Larvae are generally too small to see in August, while sampling in late September is too late as the damage is done.
Control treatments must be applied before larvae form hibernacula (overwintering, soil-based cocoons). Based on the insect development model, hibernacula formation in Madras/Culver will reach 50% by Sept 17th. Prineville/Powell Butte should expect 5% hibernacula by Sept 16th.

Central Oregon Mint Pest Alert Newsletter- August 28

Control treatments must be applied before larvae form hibernacula (overwintering, soil-based cocoons). Based on the insect development model, hibernacula formation in Madras/Culver should be 5% by Aug 31st and will reach 50% by Sept 22nd. Prineville/Powell Butte should expect 5% hibernacula by Sept 22nd .

Central Oregon Mint Pest Alert Newsletter-August 7

According to the GDD models, optimal application timing for in-season control of Mint Root Borer (MRB) and Variegated Cutworm (VC) has passed in Madras and Powell Butte area. Coragen or Orthene application now may still control VC in Powell Butte/Prineville area. Average MRB moth counts decreased between the last two trapping events, suggesting we are past peak moth catch. According to the model, VC are past or entering 5th instar, after which they will drop to the ground to pupate and cannot be controlled with sprays.

New Invasive Leafhopper Species

Recently, a new invasive leafhopper species, known as Ligurian leafhopper (Eupteryx decemnotata Rey, Hemiptera: Cicadellidae) was reported by Bill Gerth, OSU Plant Clinic . This insect species is of Mediterranean origin and is a pest of many plants in the family Lamiaceae which include peppermint, sage, basil, oregano, rosemary, lemon balm, and other culinary herbs.

Ligurian leafhoppers are tiny, less than 3mm long or 0.12 inches, yellowish-green leafhopper (see image) with a characteristic pattern of spots on the head and the wings.

Ligurian leafhopper - Eupteryx decemnotata

The Ligurian leafhopper is an important pest in cultivations of plants from the family Lamiaceae. Just like other leafhoppers, they are sap-feeding insects causing damage by puncturing cells and removing their contents. The characteristic stippling is produced (see image) when pest density is high. The damage can be mistaken for thrips or mite injury. Occurrence in Central OR mint production systems and damage potential is still unknown.

Ligurian leafhopper - Eupteryx decemnotata

Central Oregon Mint Pest Alert Newsletter- July 24 

Peak moth catch was last week in Madras, which is supported by our trap counts decreasing this week. In-season control for Variegated Cutworm (VC) with Coragen or Orthene is most effective at early instar stages. Peak 3rd instar of VC in Madras was July 19, and is now in PB area. VC larvae should be controlled before 5th instar when they drop to ground and become difficult to control. Treatment threshold is 0.6 larva/sweep or 1.3 larvae/sq ft.

Central Oregon Mint Pest Alert Newsletter- July 17th

We are now in the best application window for the in-season management of MRB and variegated cutworm.

Central Oregon Mint Pest Alert Newsletter- July 9th

The optimal window for insecticide application and peak moth flight is beginning next week.

Central Oregon Mint Pest Alert Newsletter- July 2nd

Trap counts remain high again this week with peak flight fast approaching in the coming weeks.

Central Oregon Mint Pest Alert Newsletter- June 26th

High number of MRB (33 moths) were captured this week. Peak flight is approaching fast.

Central Oregon Mint Pest Alert Newsletter-June 19th

Few MRB adults (9 moths) were captured in the pheromone traps this week.

Central Oregon Mint Pest Alert Newsletter- June 12th

The first flight of MRB adults was predicted this week for Central Oregon and we captured 4 moths in the pheromone traps.

Archived Reports – 2019

Central Oregon

Central Oregon Mint Pest Alert Newsletter – August 29th


Central Oregon Mint Pest Alert Newsletter – August 7th


Central Oregon Mint Pest Alert Newsletter – August 1st


Central Oregon Mint Pest Alert Newsletter – July 24th


Central Oregon Mint Pest Alert Newsletter – July 17th

According to the growing degree day model, peak moth flight of MRB was reached on July 15th in Culver/Madras area, and will be reached July 23rd. Moth counts in the Culver/Madras area decreased from an average of 4 moths/trap on July 11th, to 3 moths/trap on July 18thThis indicates the model prediction is in line with what we are finding in the field.

There was a minor increase in moth counts this week in the Powell Butte area. We continue to find alfalfa loopers in the field and small populations of cutworms. Continue scouting your own fields to make management decisions. If control is needed, now is the optimal time to apply Coragen for control of MRB, loopers and cutworms in the Culver/Madras area. See newsletter for more information.


Central Oregon Mint Pest Alert Newsletter – July 11th

Adult MRB counts in pheromone traps are picking up, with some sites at 8/trap while others remain at less then 5/trap. Reports in Central Oregon are also finding areas with increased MRB flight activity. Alfalfa loopers are showing up more frequently in sweep net samples, so please continue to scout fields over the next week to determine if populations are increasing in your fields.


Central Oregon Mint Pest Alert Newsletter – July 5th

Third week of trapping continues to find low adult MRB and cutworm/looper numbers – less than one per trap on average.


Central Oregon Mint Pest Alert Newsletter – June 28th

Second week of trapping has found very low adult MRB numbers, a total of four (4) have been collected in the last week. A few alfalfa loopers have also been found.


Central Oregon Mint Pest Alert Newsletter – June 19th