Turfgrass-Sod webworm

Includes

Cranberry girdler (Chrysoteucia topiaria)
Larger sod webworm (Pedasia trisecta)

Pest description and crop damage The larger sod webworm (LSW) and cranberry girdler (CBG) are larvae of "lawn moths." The moths are characterized by wings that are partially folded around the body giving the moths a very slender appearance as well as a pronounced "snout." The LSW is one of the larger webworms with a wingspan of 21 to 35 mm, while the CBG is smaller with a wingspan of 20 to 25 mm. The wings are usually white, grey or tan, and may have patterns of silver, gold, copper or other colored scale. Larvae can cause considerable damage to turf areas if conditions favor their development. However, due to the high natural mortality of small larvae, damage is seldom severe. Presence of larvae is indicated by dying back of grass shoots until irregular brown spots occur. Close examination usually shows leaf blades chewed off at base of plant.

Biology and life history Webworms overwinter as larvae in the soil. Adults emerge in late May through June. Moths have erratic flight, move freely over lawn about dusk, and are attracted to light. Adults lay eggs shortly after emergence. Eggs hatch in 5 to 14 days and the young larvae feed on the tender young grass leaves, spinning a protective silky web. As the larvae mature, they construct subterranean burrows and feed only at night. CBG will burrow into the crown and feed on plant roots, and is often referred to as the subterranean webworm. In the PNW, the larval stage lasts through the winter and may involve as many as 8 instars.

Scouting and thresholds Worms or worm droppings can be detected by breaking apart a section of dying sod. Thresholds for larval numbers have not been established in the PNW.

Management-biological control

Disease, insect predators and especially bird predation exact a very high toll on larvae, and collectively reduce larval populations up to 90%.

  • Bacillus thuringiensis-Some formulations are OMRI-listed for organic use.
  • beneficial nematodes-Read label carefully for application procedures, timing and appropriate soil temperatures for best efficacy.

Management-chemical control: HOME USE

To protect bees, mow lawns before treatment to remove any bloom that might attract them.

Insecticides listed below are to prevent larval injury to lawns. The insecticides will not greatly reduce the number of moths present at the time of application. Moths will migrate into treated lawns from surrounding areas. Do not permit children or pets on the treated turfgrass until it has been watered to wash the insecticide into the turf and the grass is completely dry. Most insecticides are toxic to bees exposed to direct treatment or to residues on blooming weeds/ flowers in lawns: mow and remove clippings prior to applying insecticides.

  • azadirachtin (as a mix with pyrethrins)-Some formulations are OMRI-listed for organic use.
  • bifenthrin (often as a mix with other active ingredients)
  • carbaryl
  • deltamethrin
  • fenvalerate
  • gamma-cyhalothrin
  • indoxacarb
  • lambda-cyhalothrin
  • permethrin
  • phenethyl propionate (as a mix with other active ingredients.)-Some formulations are OMRI-listed for organic use.
  • plant essential oils (clove, garlic, thyme, etc.)-Some have demonstrated efficacy against Lepidopteran larvae. Some formulations are OMRI-listed for organic use.
  • pyrethrins -Some formulations are OMRI-listed for organic use.

Management-chemical control: COMMERCIAL USE

To protect bees, mow lawns before treatment to remove any bloom that might attract them.

Insecticides listed below are to prevent larval injury to turf areas. The insecticides will not greatly reduce the number of moths present at the time of application. Moths will migrate into treated turf stands from surrounding areas. Do not permit children or pets on the treated turfgrass until it has been watered to wash the insecticide into the turf and the grass is completely dry. Most insecticides are toxic to bees exposed to direct treatment or to residues on blooming weeds/ flowers in lawns: mow and remove clippings prior to applying insecticides.

  • acephate (Orthene Turf Tree & Orn. WSP)
  • azadiractin (Nemix 4.5 IGR)-OMRI-listed for organic use.
  • beta-cyfluthrin (Tempo SC Ultra Insecticide,)
  • bifenthrin (Talstar S, Select Insecticide, multiple label names) at 0.05 lb ai/a or 10 fl oz/a. Can be applied up to 0.1 lb/ai/a per treatment. Bifenthrin is highly toxic to bees and other pollinators exposed to direct treatment or residues on blooming crops or weeds. Do not apply bifenthrin or allow it to drift to blooming crops or weeds if bees or other pollinating insects are foraging in the treatment area. Extremely toxic to fish and aquatic invertebrates. Do not apply if rain is expected within 24 hr or whatever time is necessary for product to dry
  • bifenthrin + imidacloprid (Allectus G Insecticide)-Note: Neonicotinoid pesticides have been banned from use on public properties in some towns and counties (check with local authorities).
  • carbaryl (Sevin Brand RP4 Carbaryl, Lebanon Sevin 7G Granular Insect Control, Sevin SL Carbaryl Insecticide)
  • chlorantraniliprole (Acelepryn Insecticide, Acelepryn G Insecticide) at 0.1 to 0.2 lb ai/a
  • chlorpyrifos (Andersons Golf Products Insecticide III, Dursban Pro Dursban 50W In WSP Speciality Insecticide, Hatchet Insecticide, Nufos 4E Insecticide, Vulcan, Quali-Pro Chlorpyrifos 4E Insecticide, Warhawk, Warhawk Clearform)-Retail sale of products containing chlorpyrifos for residential use ended 12/31/01. RESTRICTED USE IN OREGON.
  • clothianidin (Arena 0.25G Insecticide, Arena, 50 WG Insecticide, Arena 50 WDG Insecticide)-Apply as soon as overwintering adults are seen in the spring. Note: Neonicotinoid pesticides have been banned from use on public properties in some towns and counties (check with local authorities).
  • clothianidin + bifenthrin (Aloft GC G Insecticide, Aloft GC SC Insecticide, Aloft LC G Insecticide, Aloft LC SC Insecticide)-Restricted use.
  • cyantraniliprole (Exirel WG)
  • cyfluthrin (Tempo 20WP Golf Course Insecticide in WSP, Tempo 20 WP Insecticide)
  • cypermethrin (Demon WP Insecticide)-Highly toxic to fish.
  • deltamethrin (Deltagard G Insecticide, D-Fense SC Insecticide, Suspend SC Insecticide)-For adults.
  • dinotefuran (Zylam)-Note: Neonicotinoid pesticides have been banned from use on public properties in some towns and counties (check with local authorities).
  • esfenvalerate + prallethrin + piperonyl butoxide (Onslaught FastCap Spider and Scorpion Insecticide)
  • gamma-cyhalothrin (Optimate CS Controlled Release Insecticide)
  • indoxacarb (Provaunt, ,)-For larvae.
  • lambda-cyhalothrin (Scimitar, Demand CS Insecticide, Demand EZ Insecticide, Demand G Insecticide, Cyonara 9.7 Insecticide, Cyzmic CS Controlled Release Insecticide, Exile 9.7, Patrol Insecticide)
  • methomyl (Lannate, Lanox, Nudrin)
  • mint oil, geraniol + oil of rosemary (Keyplex Ecotrol Plus Insecticide/Miticide, Essentria IC3 Insecticide Conc.)-OMRI-listed for organic use.
  • spinosad A & D (Conserve SC Turf & Ornamental Insect Control) -Some formulations are OMRI-listed for organic use.
  • thiamethoxam (Meridian 0.33G Insecticide, Meridian 25WG Insecticide, Flagship 25WG Insecticide)-Note: Neonicotinoid pesticides have been banned from use on public properties in some towns and counties (check with local authorities).
  • trichlorfon (Dylox 6.2 Granular, Dylox 420 SL Turf & Ornamental)-For larvae.