. Untersuchungen im Feld von Bacillus thuringiensis zur Steuerung von Western Hemlock looper. Hemlock looper Kontrolle; Bacillus thuringiensis. Während der Testperiode, Juli und August, ein Nebel oder niedrige bedeckt die meisten jeden Tag anhielt; stand Temperaturen in der Regel zwischen 55° bis 65° F., REACH-ing 70° bis 72° auf die paar Tage mit Sonnenschein. Relative Luftfeuchtigkeit 60 bis 70 Prozent in midafternoon, erhöht um 90 bis 100 Prozent bei Nacht. Ziele Das allgemeine Ziel der Prüfung war es, festzustellen, ob die wirtschaftliche Kontrolle des Western Hemlock looper mit B. thuringiensis sofort machbar war. Speci

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. Field testing of Bacillus thuringiensis for control of western hemlock looper. Hemlock looper Control; Bacillus thuringiensis. During the test period, July and August, a fog or low overcast persisted most of each day; stand temperatures usually ranged from 55° to 65° F. , reach- ing 70° to 72° on the few days with sunshine. Relative humidity was 60 to 70 percent in midafternoon, increasing to 90 to 100 percent at night. OBJECTIVES The broad objective of the field test was to determine whether economic control of the western hemlock looper with B. thuringiensis was immediately feasible. Specific objectives were to: A. Determine when larval mortality commenced, reached a peak, and ended and how much mortality occurred. B. Relate spray deposit and spray distribution to total looper mortality at the end of a 20-day period. C. Test the frass-drop method as means for evaluating looper mortality. D. Deduce indirect effects of spraying on larval development and biotic control agents. E. Evaluate population trends and tree damage occurring 1 and 2 years after spraying. ASSESSMENT OF LARVAL MORTALITY Methods Test and check areas were sampled by means of systematically located plots. Each plot consisted of three codominant hemlocks which were sampled for living larvae; a cloth-bottomed tray was placed under each tree to collect dead larvae and frass falling from trees (fig. 2). In the test area, 20 plots were located along five east-west lines, which were about 180 yards apart. In the check area, 10 plots were equally divided between two north-south lines about 150 yards apart. In both areas, plots were located at 150- to 160-yard intervals along lines. Figure 2.—Sample tree at plot used to evaluate larval mortality from spraying with B. thuringiensis. Note dense underbrush.. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly rese

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