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.
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 .
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.
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.
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.
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.
We are now in the best application window for the in-season management of MRB and variegated cutworm.
The optimal window for insecticide application and peak moth flight is beginning next week.
Trap counts remain high again this week with peak flight fast approaching in the coming weeks.
High number of MRB (33 moths) were captured this week. Peak flight is approaching fast.
Few MRB adults (9 moths) were captured in the pheromone traps this week.
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
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 18th. This 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.
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.
Third week of trapping continues to find low adult MRB and cutworm/looper numbers – less than one per trap on average.
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.