VectoMax FG Bti - 7 lb./acre

OH OH

VectoMax FG Bti

The Collier Mosquito Control District (CMCD) carries on extensive spraying of VectoMax FG

in Collier County residential areas.

Fiddler's Creek	6/27/2025
Sabal Palm Rd and east of the Florida Sports Park	6/30/2025
Lely Resort, Naples Lakes and Naples Mano	7/2/2025

VectoMax FG (formerly CG) is an advanced biological mosquito larvicide based on BioFuse™ technology — a patented formulation and manufacturing process that combines the time-proven and environmentally compatible bacterial active ingredients Bacillus thuringiensis subsp. israelensis (strain AM65-52) and Bacillus sphaericus 2362 (strain ABTS 1743) into a single microparticle.

The mosquito larvae get a dose of a carefully selected ratio of both toxins when VectoMax particles are ingested.

Consisting of only Bti, Bs, and food-grade (USEPA list 4) inert ingredients, VectoMax FG has received approval for application in organic crops (U.S.: Organic Materials Review Institute [OMRI] approved) and sensitive habitats in various countries around the world. The product has a potency of 50 Bs International Toxin Units (Bs ITU) per milligram against Culex quinquefasciatus larvae. The size, shape, and density of VectoMax FG lessen the potential for off-target application due to aerial drift and enable good penetration of dense vegetation.

How VectoMax FG works

VectoMax FG contains two bacteria that specifically target mosquito larvae: 

• Bacillus thuringiensis israelensis (Bti): This bacterium produces toxins that create holes in the gut wall of feeding mosquito larvae.

• Bacillus sphaericus (Bs): The Bs component offers more long-lasting control of mosquito larvae. 

The toxins are only activated in the alkaline conditions of a mosquito larva's gut, and other insects like dragonflies, with their different digestive systems, are unaffected. 

Indirect effects and ecosystem impact

Because VectoMax FG reduces the population of mosquito larvae, it removes a food source for dragonfly nymphs. This could potentially have a negative impact on dragonfly populations, although it would not be from direct poisoning. The severity of this indirect effect depends on several factors: 

• Availability of other prey: If other food sources are abundant, the impact on dragonflies may be minimal.

• Scale of application: Larger, more widespread treatments would have a greater effect on the food chain than smaller, isolated applications.

• Local conditions: The overall ecosystem health and availability of other insect populations will affect how dragonflies are impacted.

• 
  

What the evidence shows

• Laboratory studies: Studies in laboratories have shown no lethal effect on dragonfly nymphs (naiads) when they were fed mosquito larvae that were infected with the VectoMax FG ingredients (Bti and Bs).

• Manufacturer claims: The manufacturer, Valent BioSciences, states that VectoMax FG is not harmful to non-target organisms.

• Uncertainty remains: An independent study of an area treated with Bti noted a decline in the local dragonfly population but could not definitively link it to the larvicide. Researchers suggested further study was needed to test the hypothesis of indirect harm caused by the disruption of the food chain.

• Potential for resistance: In areas where Bti and Bs are used regularly, the combined effect of the two bacteria in VectoMax FG has also been studied to address the development of resistance in mosquito populations, which could affect the product's long-term effectiveness. 

However:

“While the gut of the dragonfly nymph may not produce the deadly conditions that the gut of the mosquito larvae does in the presence of Bti, that same toxin is being ingested by the dragonfly nymph when it feeds on the larvicide-exposed mosquito larvae as a food source. A further study is indicated before I can completely abandon that there is no relationship between the decline of the dragonfly presence at Madrona Marsh and the recent dosing of Bti.”

Reference

chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://csef.usc.edu/History/2014/Projects/J1732.pdf

Bti CRG does not directly poison dragonflies. However, by eliminating the larvae of mosquitoes and other Diptera that serve as a primary food source, widespread or repeated Bti application can indirectly threaten dragonfly populations by causing a severe reduction in their prey.