Spatial and temporal distribution of airborne Bacillus thuringiensis var. kurstaki during an aerial spray program for gypsy moth eradication.

Abstract

We measured airborne exposures to the biological insecticide Bacillus thuringiensis var. kurstaki (Btk) during an aerial spray program to eradicate gypsy moths on the west coast of Canada. We aimed to determine whether staying indoors during spraying reduced exposures, to determine the rate of temporal decay of airborne concentrations, and to determine whether drift occurred outside the spray zone. During spraying, the average culturable airborne Btk concentration measured outdoors within the spray zone was 739 colony-forming units (CFU)/m3 of air. Outdoor air concentrations decreased over time, quickly in an initial phase with a half time of 3.3 hr, and then more slowly over the following 9 days, with an overall half-time of about 2.4 days. Inside residences during spraying, average concentrations were initially 2-5 times lower than outdoors, but at 5-6 hr after spraying began, indoor concentrations exceeded those outdoors, with an average of 244 CFU/m3 vs. 77 CFU/m3 outdoors, suggesting that the initial benefits of remaining indoors during spraying may not persist as outside air moves indoors with normal daily activities. There was drift of culturable Btk throughout a 125- to 1,000-meter band outside the spray zone where measurements were made, a consequence of the fine aerosol sizes that remained airborne (count median diameters of 4.3 to 7.2 microm). Btk concentrations outside the spray zone were related to wind speed and direction, but not to distance from the spray zone.

Of Pesticides and Men: a California Story of Genes and Environment in Parkinson’s Disease

“…[27–29] Some agricultural use pesticides are highly persistent and can be found in treated soils and dust even decades after application, indoors [30–32] and in ambient air. [33,34] A California central valley study assessed inhalation risks from airborne agricultural pesticides and concluded that agricultural applications of organophosphates and their oxon products may have substantial volatization and off-field movement.…”

Spread of a Gammabaculovirus within Larval Populations of Its Natural Balsam Fir Sawfly (Neodiprion abietis) Host Following Its Aerial Application

“…Aircraft wakes typically sink at 0.3–1.0 m/s [ 32 ], pushing the smaller (40–80 μm) droplets downward into the forest canopy [ 33 ]. Following the dissipation of the aircraft wake, spray droplets are affected by wind, air temperature, humidity, and characteristics of the ground cover [ 34 ], and small droplets may remain in the air column for hours after application [ 35 ]. As a result, active ingredients can be found hundreds of meters from the point of application [ 36 , 37 , 38 , 39 , 40 , 41 ].…”

A Four Dimensional Spatio-Temporal Analysis of an Agricultural Dataset

“…Within the context of two spatial dimensions × time much work is largely descriptive. For example, Teschke et al [ 36 ] and Bell et al [ 37 ] use maps at several timepoints, with the maps essentially being descriptive devices. The more complex models are generally Bayesian and use either geostatistical methods or the convolution CAR prior of [ 8 ].…”