Laboratory and Field Assays with Entomopathogenic Nematodes for the Management of Oblique Banded Leafroller Choristoneura rosaceana (Harris) (Tortricidae)

G. Béair

Abstract


The activity of steinernematid entomopathogenic nematodes against Choristoneura rosaceana was evaluated under laboratory and field conditions. In petri dish trials, all instars were susceptible to Steinernema carpocapsae AII strain with LD[sup5]º values of 13, 5, 3, and 2 infective juveniles for the third-, fourth-, fifth-, and sixth-stage larvae, respectively. Steinernema riobrave 335, S. feltiae UK, S. carpocapsae AII, and S. glaseri 326 caused 85, 55, 45, and 8% mortality of third instars when exposed to the concentration of 25 infective juveniles per dish. When third instars were exposed to S. carpocapsae AII for 0, 1, 4, 8, 12, and 24 hours, larval mortality was 12, 13, 21, 47, 64, and 87%, respectively. At least 8 hours' exposure was required to cause a significant increase in mortality when compared with the control (water) and the 1 and 4-hour exposures. None of the tested adjuvants provided a significant improvement in the average total number and the average number of living S. carpocapsae AII per unit leaf area when compared to the water control. Under field conditions, foliar applications of S. carpocapsae AII at the rate of 2 × 10[sup9] infective juveniles/ha provided 37, 19, and 13% larval control. At present, efficacy level and treatment cost preclude nematode applications as a sole treatment against this pest.

Keywords


apple; biological control; choristoneura rosaceana; entomopathogenic nematode; field; foliar application; lepidoptera; oblique banded leafroller; steinernema carpocapsae; s. feltiae; s. glaseri; s. riobrave; tortricidae

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