- Wallner, William E.
Department of Entomology, Michigan State University
Helicopter application of concentrated and dilute chemicals and biological sprays was used to suppress 4 lepidopterous hardwood defoliators. Evaluations were based upon larval catches on three 1010 ft polyethylene tarps within treatment blocks. A pyrethrin mist-blower spray was applied 1 week following treatment to the tree canopy above the tarps to detect surviving larvae and other organisms. Trichlorfon concentrate and trichlorfon and carbaryl diluted sprays reduced survival of 2nd-stage fall cankerworm and spring cankerworm to less than 0.5%. Carbaryl-oil concentrate spray had the highest larval survival percentage of any treatment, because of clogging of nozzles by the formulation. One year following applications a pyrethrin must-blower evaluation of treated and untreated blocks showed little population change. After 2 years, the entire population collapsed. The decline was not attributed to the impact of chemical sprays but to natural factors which caused a similar collapse throughout Michigan.
Second instars of the forest tent caterpillar were limited to survival with 1 application of carbaryl-oil concentrate. Dilute sprays pf either carbaryl plus ponolene or Bacillus thuringiensis car. thuringiensis (Berliner) gave acceptable suppression in spite of 1/4 inch of rain 10 hours after application. Trichlorfon concentrate and dilute sprays showed activity but failed to give larval reductions comparable to other treatments.
Less than 0.25 and 3rd instars of the saddled prominent, Heteracampa guttavilla (Walker), survived a carbaryl-4-oil concentrate spray. Trichlorfon-oil concentrate caused larval reduction comparable to the carbaryl-oil, but significantly fewer survivors than a dilute spray of either trichlorfon or carbaryl. Dilute sprays of B. thuringiensis var. thuringiensis and B. thuringiensis var. kurslaki De-Dajae gave unacceptable larval reductions. Adults of predatory beetles Calasoma Scrtator F. and C. calidum F. were affected adversely by the dilute carbaryl spray, whereas other treatments, including carbaryl-oil concentrate showed no effect. No treatment had any apparent effect upon a predator erythracid mite Leptus sp. which attacks the saddled prominent.