Symphylan control in seed crops

The garden symphylan, Scutigerella immaculata Newport, is a serious soil arthropod pest whose root-feeding affects yield potential and survival of several high-value crops in Western Oregon during crop establishment. The broad host range includes grass grown for seed, vegetable seed crops, and other specialty crops such as peppermint and strawberries. Previously, symphylans have primarily managed using Lorsban (chlorpyrifos) as pre-plant incorporation (PPI). Now that chlorpyrifos is being phased out, growers will have limited chemical control options (pyrethroids only) as no clear path for registration exists for alternate chemistries (e.g., Mocap and Ethoprop). In this study, we aimed to evaluate the efficacy of new and existing insecticides and to identify potential options to support the product registration process.

Winter cutworm egg-laying activity has been recently reported as shown in the pictures taken on host plants as well as on non-plant structures in and around farms in Western Oregon. This insect lays its eggs in flat sheet clusters. The eggs are spherical in shape, ribbed and reticulate, and cream-colored to yellow, but darken over time. One female moth can deposit up to 2,000 eggs in her lifetime. Eggs hatch after 2 to 4 weeks, depending on the weather conditions. Field collected eggs were viable and no parasitization was noted when brought to the lab early this week.

We recommend destroying the egg masses as you encounter them in your fields or farm structures by either crushing using sharp objects or smashing to allow a promising physical/mechanical control before they get to hatch and disperse in the field and cause damage this fall.

For further information on this pest, please refer to resources below:

PNW Insect Handbook Chapter: Grass Seed-Winter Cutworm

OSU Extension Publication: Winter cutworm, A new pest threat in Oregon

Our program is testing commercial traps ( to capture flight activity of few noctuid species that can cause economic damage in grass crops grown for seed production. Above is the picture of a trap set up in a tall fescue field. These traps are fully automated,  self-cleaning units with a funnel housing a pheromone lure to attract male moths.  These traps provide a real time information on insect capture and weather data via a smart phone friendly app.

Dr. Seth Dorman, research entomologist at USDA-ARS Forage Seed and Cereal Research Unit in Corvallis, OR is leading a collaborative effort to establish a noctuid pest monitoring network in tall fescue and perennial ryegrass crops for seed production in Willamette valley. This study will help identify local and regional drivers of pest outbreaks in grass seed systems and serve as a decision-support system. We would like to expand this network based on the industry’s needs and intend to start a weekly pest alert newsletter in the near future.

Heat maps on insect trap capture for two lepidopteran insect species during June 18- July 9, 2021, are presented below:

A slide deck for Important lepidopteran insect pest species of grass seed crops in Oregon (Author Dr. Amy Dreves, University of Virgin Island)

Larva and pupae (Flaxseed) of Hessian fly (pointed by yellow arrows).


Hessian fly is known to exist in the Willamette Valley several decades ago but has not been identified as an agronomic problem in the region for many years.  There have been recent identifications made in infected fields of both spring and winter wheat crops in Polk and Washington counties.

Scout within the wheat field for stunted plants with dark and wider leaves. Leaves may appear thickened, erect, and bluish-green in color. In cases of heavy infestations, the central stem is often missing. Infested stems usually break over at the time of head formation. Grain yields can be greatly reduced. The economic loss probably occurs when from 15 to 30 percent of the tillers are infested.

Look for small larvae that are small ~3/16 inch, greenish-white, legless, headless maggots underneath lower leaf sheaths. The pupal stage ~3/16 inch is represented by brown seed-like cases containing a maggot, often referred to as a “flaxseed.” The maggots or “flaxseeds” (puparium) present beneath the leaf sheath above the surface of the ground, as high as the second or third joint, are signs of Hessian fly. Adult flies have a red-brown to dusky-black body and dusky wings. They resemble mosquitoes in form and are about 1/6 inch long.  They are short-lived and could be hard to find in the fields.

The Hessian fly usually has two to three partial generations per year, one to two in the spring and one in the late summer or early fall. Occasionally a second generation will occur in the spring. Usually, the flaxseed of the spring generation spends the summer in wheat stubble to produce another emergence of flies in late summer or early fall. Fall-generation flies deposit eggs on volunteer wheat or early-sown winter wheat. Larvae from such eggs overwinter in the flaxseed stage and produce flies in the spring.

Predisposing factors. Rain in late August or September, accompanied by cooler temperatures, are key factors that prompt pupation and adult emergence in the fall. In the spring a mean temperature of 50° F. is usually required before fly emergence begins. In most year’s very little emergence occurs before April. Warm weather emergence occurs before April. Warm, wet weather in early spring can lead to a heavy infestation in wheat seeded in late February or March.


  1. Planting resistant cultivars is the most effective approach to minimize losses to this pest. Consult your crop advisor, extension educator, or specialist to select recommended varieties for planting in your region.
  2. Deep plowing soon after harvest is helpful if soil conditions permit this practice. Plow wheat stubble soon after harvest to bury the flaxseed. Deep plowing prevents flies from emerging in the fall. Wheat stubble is a primary site where the Hessian fly both overwinters and over summers. It is most responsible for the spring populations. Plow under any volunteer wheat on which fall generation flies may deposit eggs.
  3. Use fly-free planting dates. Winter wheat seeded after mid-October is usually free of this pest. Spring wheat seeded behind failed fall-seeded wheat is especially prone to attack. Time fall-seeded cereals so that they do not emerge until after the Hessian fly flight period has ceased. Generally, wheat planted after the second week in October will avoid Hessian fly damage. Fall-seeded wheat usually suffers less injury than spring-seeded wheat. Generally, the fly prefers barley less than wheat.
  4. Seed treatments applied to wheat and barley seed may help control the Hessian fly. Please refer to PNW Insect Management Handbook for chemical control recommendations.

Aphid management in grass grown for seed production

Aphid flights occurring in spring & fall each year can infest newly planted grass seedlings and established fields. Winged forms colonize fields in irregular patterns, often according to prevailing wind direction and wind-blocking features along field margins. We recommend regular scouting in April-May. Inspect seedling grasses for aphid colonies by visual exams; installing water traps for winged adults in spring, fall; and using sweep net samples. Consult PNW Insect Pest Management Handbook for available chemical control options.


  • Treat if 10 aphids for every two- to six-leaf seedling.
  • Treat if 10–20 aphids per stem or head (from boot to heading stage).

Prevention and management

  • Consider beneficials (parasitic wasps, syrphid larvae (hoverflies), lacewing larvae, lady beetles) when deciding whether or not to apply an insecticide. Individual aphids that are parasitized appear brown to gold.
  • Removal of volunteer plants that may act as insect reservoirs when crop host is not present.
  • Avoid planting into the previously infested ground; allow two weeks before planting.
  • Aphid populations are susceptible to rainy, windy weather, and sudden cold. Unseasonal high temperatures from April through June can reduce aphid populations quite effectively.

2021 Aphid Efficacy Trial

This is the second year of field evaluation of Transform® WG insecticide at two rates 0.75 and 1.5 oz/acre vs potential competitors (e.g. Sivanto) for aphid management in grass grown for seed. Data collected during Spring 2020 indicated that both rates of Transform® WG insecticide rapidly knocked down the aphid populations with a consistent low aphid counts in treated plots for up to four weeks after application. Data collection during Spring 2021 is underway. Results will be available soon!

Spring 2021 Aphid Efficacy Trial in Tall Fescue.


An update on the Oregon Seed Council and the Western IPM Center-funded project to conduct an area-wide survey of commercial grass seed fields. Our goal is to determine what species of entomopathogenic or insect parasitic nematodes and or other beneficial microbes occur in grass seed production systems and if these organisms have the potential to become promising biological control agents against soil-dwelling insects -like sod webworm, billbugs, and cutworms.

The objectives of this project are to 1) conduct area-wide surveys in the commercial grass seed production systems to determine the occurrence and distribution of EPN species in western OR, 2) identify the isolated EPNs using molecular techniques and maintain lab cultures for infectivity tests), 3) to conduct infectivity trials using EPN species identified during the survey and comparing their efficacy to the commercially available EPN based products against sod webworm under laboratory conditions.

Watch a short YouTube video for the project activities

  • We collect soil samples (five random locations per site) from commercial field sites (18) on a biweekly basis
  • Soil baiting experiment setup includes using a subsample of field-collected soil and baiting with healthy wax moth larva. EPNs are commonly reared on wax moth larva to maintain EPN culture and mass-produce. Wax moth larvae were ordered from Bassett’s Cricket Ranch (Visalia, CA, USA) through
  • Incubation- One-week incubation under the dark condition at ~22°C
  • Recovery of wax moth larva and transfer to white traps. A white trap is a method of placing infected insects in a small Petri dish inside a bigger Petri dish with a film of water
  • White traps are then incubated at room temperature (~22°C) and observed daily
  • Data is being collected and will be disseminated soon.

A survey is designed to assess current knowledge of biocontrol agents and practices and to evaluate the most critical limitations and knowledge gaps for developing biocontrol strategies for grass seed systems

Western IPM Center-Biocontrol Survey Phase 1

Please help us fill out this survey to collect baseline data on the control methods currently used by grass seed growers to manage soil-borne insect pests; 2) assess the feasibility and ability to integrate biocontrol tactics into existing insect pest management practices. We will distribute two $25 gift cards as raffle prizes. We appreciate your participation in this study!

Please contact Dr. Navneet Kaur or Dr. Betsy Verhoeven if there is any question.

Pocket Guide to Grass Seed Pests and Beneficials

Using the guide

This pocket guide provides information on pests and beneficial organisms
found in grass seed production fields across the state of Oregon.
Pests are organized alphabetically within each category. The guide includes
common occurrences; where pests are found; arthropod pest status;
identification; biology; symptoms of damage; what you might mistake one for;
thresholds, if known; ways to monitor; prevention tools and management; and
a pest scouting calendar based on crop stage.

The current registered chemical management options can be found in the
PNW Insect Management Handbook,

The 2021 version of the PNW Insect Management Handbook is available now at

We greatly appreciate the considerable assistance from experts within the PNW agricultural community who provided information that contributed to the quality of this handbook. These experts include county extension agents and specialists, product representatives, food processing representatives, agricultural experiment station staff, and private consultants.

The sod webworm (SWW), Chrysoteuchia topiaria (Zeller) is a common and damaging species in grass seed, turf, and lawns in western OR. Sod webworm is a persistent but sporadic pest in perennial ryegrass, tall fescue, bentgrass, and orchardgrass; however, the extent of damage is worse and more frequent in older fine fescue stands. Damage is usually first noticed by failures of fall regrowth. Larvae feed on and in crowns and roots of most grasses, and can seriously injure established stands wherever grass is grown for seed. Insecticide options are available, but they are soil active; it is challenging to achieve good efficacy due to the lack of sufficient and timely rainfall that allows the insecticides to reach the targeted pests. A replicated field trial was set up in fall 2020 to evaluate the efficacy of new chemistries against sod webworm; data on herbivory damage, severity, and natural enemy abundance etc. is being collected until spring 2021. The results from this study are expected to generate information for the execution of more accurate chemical management plans. Insect choice and no choice tests were conducted for better
understanding of the sod webworm’s host preference behavior; data are currently being analyzed to determine if the varietal difference in herbivory preference were indicative of differences in plant endophytic associations. Survey results for indigenous entomopathogenic nematode species associated with field-collected sod webworm populations confirmed the presence of an infective strain of Steinernema carpocapsae in at least one field site in OR.

Choice test using grass cultivars
Field collected sod webworm population