Certified Arborist Practice Exam

The correct answer is Bacillus thuringiensis. This is a well-known microbial pesticide that produces proteins toxic to certain insect pests. These proteins are derived from the bacteria and are selectively harmful to specific groups of insects when ingested. Bacillus thuringiensis is commonly used in organic gardening and agricultural practices due to its effectiveness and minimal impact on non-target species, making it a favored choice among those looking to manage pest populations sustainably.

The other options listed do not function in the same way. For instance, Streptomyces avermitilis is known for producing avermectin, which has different modes of action and is used in some pest control formulations but does not target insects in the same manner as Bacillus thuringiensis. Similarly, Penicillium notatum and Aspergillus niger are fungi primarily recognized for their roles in antibiotic production and decomposition, rather than being utilized as insecticides.