Influence of Bacillus thuringiensis application timing on population dynamics of gypsy moth in Mediterranean cork oak forests

Abstract

BACKGROUND The gypsy moth, Lymantria dispar, is one of the main pests of oak forests worldwide and causes extensive defoliation during its periodic outbreaks. In the Mediterranean region, control of gypsy moth populations in cork oak forests is based on application of Bacillus thuringiensis serovar kurstaki (Btk) formulations. This research investigated the effects of Btk applications carried out in two different population development phases on gypsy moth population dynamics. With this aim, temporal and spatial fluctuation patterns of L. dispar egg density were monitored in cork oak forests treated with Btk applications from 2004 to 2009 in Sardinia (Italy). RESULTS Applications undertaken during the progradation and culmination phases protected the oak canopies equally in the year of application, leading to a similar decrease in pest population density in the following year. However, the medium‐term effectiveness of Btk differed between the two application timings, because only applications in the culmination phase caused a gradual decrease in L. dispar infestations throughout subsequent years. By contrast, when the application was undertaken during the progradation phase, population density increased again after 2–3 years. Moreover, Btk applications in the culmination phase reduced significantly the number of years in which gypsy moth density was damaging compared with those done in progradation. CONCLUSIONS Our results indicate that Btk applications during the culmination phase were more effective than those in the progradation period, because application in the latter case did not suppress the population, but only postponed the outbreak peak by 2–3 years. © 2019 Society of Chemical Industry

Gypsy Moth Management with LdMNPV Baculovirus in Cork Oak Forest

“…While a good baculovirus efficacy was achieved in these experiments, larval mortality was significantly lower in comparison with plots treated with Btk, which was confirmed to be a powerful bioinsecticide against gypsy moth [22,23].…”

Potential Differences and Methods of Determining Gypsy Moth Female Flight Capabilities: Implications for the Establishment and Spread in Novel Habitats

“…A study by Lentini et al [37] found that outbreaks are generally more frequent in overexploited forests and woodlands (<25% canopy cover rate) than natural ones. Moreover, gypsy moth population dynamics may be further subjected to changes depending on control measures [15]. A study by Mannu et al [15] found a forward shift in abundance peak with early Btk applications during the population growth, leading to postponed outbreak peak by two to three years, whereas Btk applications during the culmination phases were found to be more effective in suppressing gypsy moth populations.…”

“…Moreover, outbreaks in established areas are now better regulated in a density-dependent form by two host-specific pathogens, (1) the fungus Entomophaga maimaiga Humber, Shimazu, and Soper (Zygomycetes: Entomophthorales) and (2) a nucleopolyhedrosis virus, LdNPV [13,14]. In addition, aerial application of Bacillus thuringiensis Berliner serovar kurstaki (Btk) is currently the most effective control method to suppress gypsy moth outbreaks in Europe [15]. In areas with established gypsy moth populations, outbreaks generally occur every five to ten years [16] and last between one and three years [17,18].…”

Development of Enumerative and Binomial Sequential Sampling Plans for Monitoring Lymantria dispar (L.) (Lepidoptera Erebidae) in Mediterranean Oak Forests

“…Lymantria dispar population dynamics is described by a typical fluctuation pattern with a starting period of low-density population (latency), after which the pest density increases (progradation), reaches a peak (culmination), and then decreases until returning to low levels (retrogradation) [1,8]. Periodic density fluctuations cause severe outbreaks at regular intervals, which occur from 6 to 13 years, depending on the geographical area and anthropogenic pressure [6,[9][10][11].…”