Dispersal of potato tuber moth estimated using field application of Bt for mark‐capture techniques

Abstract

A new mark‐capture technique involving field applications of Bacillus thuringiensis Berliner (Bt) to study the dispersal of potato tuber moth, Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae), was investigated as a tool to improve information on the potential impact of insect pest dispersal on crop infestation and insecticide resistance. The acquisition and persistence of Bt on moths were characterized and potential contamination of moths from naturally occurring Bts was examined. This mark‐capture technique was developed to mark larger numbers of moths than had been previously achieved with laboratory marking using fluorescent dyes in mark‐release‐recapture experiments. Applications of commercial preparations of Bt to 0.3 and 1.0 ha potato fields were estimated to have marked ca. 50 000 moths in each experiment. Pheromone trap catches of potato tuber moths in the Bt‐sprayed fields and in potato fields at distances of ca. 80, 200, 350, and 750 m were assayed for the Bt marker using selective microbiological media and identification of characteristic Bt crystal inclusions. Marking rates of moths were 78–100% in the sprayed fields and, compared with our previous mark‐release‐recapture studies, marking at ca. 200 m was increased by 15–18‐fold to >3.0 moths per trap. This capture rate allowed the calculation of a dispersal curve that improved the reliability of estimates of movement at farm‐scale distances. These estimates indicated that 10% of the population dispersed to 240 m in 3 days, and suggested that moths can potentially disperse throughout a typical potato‐growing area in one growing season. This level of dispersal has implications for the spread and management of potato tuber moth populations, especially if insecticide resistance is present.

Farm‐scale dispersal of Bactericera cockerelli in potato crops measured using Bt mark‐capture techniques

“…These markers have been shown to be suitable for a range of insects (Hagler & Jones, ) including small parasitoids (Hagler et al., ) and psyllids (Boina et al., ). We have used similar mark‐capture techniques based on the application of a microbial marker, Bacillus thuringiensis Berliner (Bt), using normal spray equipment in field‐sized crops (Cameron et al., ). Bt was applied as a marker with no intent to control insects.…”

“…Our use of Bt markers has extended dispersal measures for P. operculella to ca. 350 m in 3 days (Cameron et al., ), a distance that is relevant beyond single fields to farm‐scale management of potato crops. Although longer distance migratory movements are generally credited for arrival of B. cockerelli in potato crops in the northern USA, alternatively, survival on various plant species may contribute to the successful overwintering of adult psyllids during the winter months (Butler & Trumble, ; Swisher et al., ).…”

Area-wide monitoring of potato tuberworm (Phthorimaea operculella) by pheromone trapping in Northern Italy: phenology, spatial distribution and relationships between catches and tuber damage

“…Geostatistical analysis carried out with respect to the percentage of damage at harvest resulted in maps not supported by cross‐validation. However, because of the low dispersion range of PTW adults (Cameron et al , ) in relation to the whole scale of sampling and because of the positive correlation between trap catches and damage, contour plots drawn on captures from hilling to harvesting could provide an indication of the risk of damage. This assumption is corroborated by observations reporting that farms with higher damage were located generally in areas where maps indicated higher adult infestation.…”

Estimating survival and transition probabilities from aggregate sightings of animals

“…In laboratory applications, we frequently see the use of fluorescent dyes or powders (e.g. Schneider 1999;Maciel de Freitas et al 2008), but various other marking techniques have been proposed, such as quick-drying paint (Miyatake et al 2000), or (in the field) ''self-marking'' by stable isotopes (Macneale et al 2005), chemicals (Scarratt et al 2008) or bacterial infection (Cameron et al 2009). Hagler and Jackson (2001) provide a review of marking techniques.…”