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Mimosa Webworm

| By | Pests

Mimosa Webworm (Homadaula anisocentra)

GDD Window (base 50): 880-1200 (1st gen egg hatch), 1800-2100 (2nd gen egg hatch)

Overview:​​​

  • Overwinters as pupae in cocoons, and within bark flaps and cracks of the trunk  ​
  • Cocoons are bright white and have the appearance of puffed rice, often occurring in masses  ​
  • Emerge as adults in June and lay small, pearly-white, oval-shaped eggs on leaflets or small twigs of honeylocust trees  ​
  • Adults are silver-gray moths and have black speckles, growing to 3/8” long, and are mostly nocturnal ​
  • Early instar larvae feed by etching the undersides of leaflets, and begin as only 2mm long  ​
  • Mature caterpillars reach about ¾” long, and have a brownish body with five white stripes running along the length of their bodies
  • They use webbing to bring leaflets together to create protective feeding areas. The webbing becomes larger and denser as the larvae grow.  ​
  • Mature first generation larvae will pupate within the webbing where they will emerge as adults  ​
  • The 1st generation does most of its feeding in July  ​
  • When 1st generation adults emerge, they will lay eggs within the previous webbing and the 2nd generation will expand the damage  ​
  • Webbings form at the outer edges of the leaf canopy, and can expand throughout the entire crown  ​
  • Late instars skeletonize leaves and eventually consume entire leaflets  ​
  • Feeding symptoms are more pronounced during the 2nd generation in August/September  ​
  • Cause leaf browning, and the tree may appear to be scorched by a fire ​
  • Host plants: mimosa and honey locust trees

Management:

Cultural Practices:
  • Natural predators:  parasitoids, stink bugs, assassin bugs, green lacewings, birds, lizards ​
  • Killed by cold temperatures, and urban environments can enhance survival​
  • Trees located along streets and paved areas will experience the highest populations​
Materials:
  • Contact insecticides:​
    • Spinosyns [5]: spinosad​
    • Pyrethroids [3A]: –thrins ​
    • Carbamates [1A]: carbaryl​
  • Systemic insecticides:​
    • Diamides [28]: chlorantraniliprole​
    • Acephate (translaminar)​
    • Abamectin​
  • Considerations:​
    • Successful suppression of 1st generation will reduce the emergence of the 2nd generation ​
Biorationals:
  • Bt [11] Bacillus thuringiensis​
    • Work best against young instars ​
  • Spinosyns [5]: spinosad​
  • Azadiractin ​
  • Diflubenzuron (IGR)

Management:

Mimosa Webworm Activity Begins – PPA

Landscape Pest Notes for Late June 2023 – PPA

 

As the mimosa webworm webbing becomes more dense, then insecticide controls will become more difficult. (Photo Credit: Steven K. Rettke, Rutgers Coop. Ext.)
Females lay exceptionally small, oval, pearly-white eggs on leaves or small stems. 2nd generation eggs are often laid on previous webbings made by the 1st generation. (Photo Credit: Steven K. Rettke, Rutgers Coop. Ext.)
The adult mimosa webworm moth has a steel gray appearance with black speckles. (Photo Credit: Dan McCord, Indiana State Coop. Ext.)
The 1/4-inch brown pupal skins are numerous as mimosa webworm adults emerge. (Photo Credit: Steven K. Rettke, Rutgers Coop. Ext.)
A close-up of the unusually extreme population of overwintering mimosa webworm pupal cocoons. The cocoons have the appearance of puffed-up white rice as they are massed together in groups. (Photo Credit: Steven K. Rettke, Rutgers Coop. Ext.)
The overwintering pupal cocoons are not difficult to find with extreme populations. (Photo Credit: Steven K. Rettke, Rutgers Coop. Ext.)
Mimosa webworm overwintering pupal cocoons attempt protection within bark flaps & crevices of honeylocust tree trunks. (Photo Credit: Steven K. Rettke, Rutgers Coop. Ext.)
Mimosa webworm have better winter survival in urban areas such as along paved streets or near buildings. (Photo credit: Steven K. Rettke, Rutgers Coop. Ext.)
As mimosa webworm infestations become extreme, then the tree canopy will have a bown, burnt appearance as if scorched by fire. (Photo Credit: Steven K. Rettke, Rutgers Coop. Ext.)
Disclaimer – Materials do not cover all possible control scenarios and are intended for licensed professionals. Tradenames do not imply endorsement and are used as examples. You must strictly follow the label for each compound prior to use. Rutgers is not responsible form is used materials or damages thereof. The label is the law. Labels will provide detailed information on use and restrictions. Additionally, application intervals, compatibility, surfactant use, PHI, PPE, important and other key information is described in detail. Always discuss treatments with your local agents. Note: Neonicotinoids can only be legally applied in commercial agriculture settings by licensed applicators. Guidelines and recommendations made in this presentation are specific to the state of New Jersey.