Suppression of Four Hardwood Defoliators by Helicopter Application of Concentrate and Dilute Chemical and Biological Sprays1

Abstract

Helicopter application of concentrate and dilute chemicals and biological sprays was used to suppress 4 lepidopterous hardwood defoliators. Evaluations were based upon larval catches on three 10×10 ft polyethylene tarps within treatment blocks. A 1% pyrethrin mist-blower spray was applied I week following treatment to the tree canopy above the tarps to detect surviving larvae and other organisms. Trichlorfon concentrate and trichlorfon and carbaryl dilute sprays reduced survival of 2nd-stage fall canker worm and spring canker worm 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 1% pyrethrin mist-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 1% survival with 1 application of carbaryl-oil concentrate Dilute sprays of either carbaryl plus pinolene or Bacillus thuringiensis var. thuringiensis (Berliner) gave acceptable suppression in spite of ¼ 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 of 3rd instars of the saddled prominent, Heteracampa guttavilla (Walker), survived a carbaryl 4-oil concentrate spray. Trichlorfon-oil concentrate caused larval reductions comparable to the carbaryl-oil, but sig. nificantly fewer survivors than a dilute spray of either trichlorfon or carbaryl. Dilute sprays of B. thuringiensis var. thuringiensis and B. thuringiensis var. kurstaki De-Dajac gave unacceptable larval reductions. Adults of predatory beetles Calasoma scrutator 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 predatory erythraeid mite Leptus sp . which attacks the saddled prominent.