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Title: LABORATORY BIOASSAY OF BACILLUS THURINGIENSIS AND AN ORGANOSILICONE SURFACTANT AGAINST THE CITRUS LEAFMINER, PHYLLOCNISTIS CITRELLA STAINTON (LEPIDOPTERA: PHYLLOCNISTIDAE)

Author
item Shapiro, Jeffrey
item Schroeder, William

Submitted to: Florida Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/28/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: Larvae of the citrus leafminer, Phyllocnisitis citrella, live and feed in mines in young citrus leaves, causing extensive damage to the leaves. The layer of epithelial cells covering the leaf mine protects the leafminer and complicates biological or chemical control. This study developed two separate tests (assays), one for lethality of biological control agents to the leafminer larvae and another for penetrability of leaf mines by active agents. Several preparations of a bacterium commonly used for biological control of other insects, Bacillus thuringiensis, were active against the leafminers. An organosilicone surfactant, Silwet L-77, killed leafminers at moderate to high concentrations and enhanced the penetration of mines by Bacillus thuringiensis. These tests indicate the feasibility of biological control of the citrus leafminer with the economical, safe, and commercially available insect pathogen Bacillus thuringiensis, with the addition of an organosilicone surfactant to enhance penetration of leaf mines.

Technical Abstract: Two bioassays were developed for testing insect pathogens for biological control of larval citrus leafminers, Phyllocnistis citrella, in isolated citrus leaves. One assay tested the virulence of an agent by measuring larval mortality following injection of a test mixture into mines. The other assay tested penetrability of mixtures by measuring larval mortality following topical treatment of the mine with an active mixture. The nematodes Heterorhabditis bacteriophora and Steinernema riobravis, the bacterium Bacillus thuringiensis (Bt), and a nuclear polyhedrosis virus, the celery looper virus, were tested. An organosilicone surfactant, Silwet L-77, was tested for lethality and ability to enhance leaves in water at concentrations greater than 0.01%, and at lower concentration when injected into mines. Topically applied at high concentrations, commercial Bt preparations in water were slightly active against CLM, but L-77 significantly enhanced activities when added to Bt at a low concentration.