Abstract
Seed orchards function as the primary source of high-quality seeds for reforestation in many European countries, but their seed yields can be severely reduced due to seed- and cone-feeding insects. We evaluated various parameters of pheromone-based mating disruption for control of the moths Cydia strobilella and Dioryctria abietella, which are major pests in European Picea abies seed orchards. We applied different types of pheromone dispensers (rubber septa or wax droplets) at different densities and heights, and with different amounts of active components, covering whole orchards or part of an orchard. The efficacy of the treatment was evaluated by analysing male captures in pheromone-baited assessment traps, and presence of larvae in cones. A dramatic decrease (94–100%) in capture of males in traps occurred in all pheromone-treated plots compared to control plots for both moth species. In contrast, a subsequent reduction in larval numbers in cones was only achieved when wax droplets were used as the dispensing formulation at high density and at the highest pheromone dose tested, and only in half of the trials for each pest species. Electrophysiological recordings using antennae of male C. strobilella indicated elevated pheromone concentrations in a treated plot versus a control plot. Our results show that mating disruption has potential to reduce cone damage in spruce seed orchards caused by C. strobilella and D. abietella, but optimisation of the technique is required to achieve consistent and efficient population suppression of these pests.
Highlights
In Europe, coniferous seed orchards are the main source for production of high-quality seeds for reforestation (Ruotsalainen 2014)
For C. strobilella, high traps caught on average four times as many males compared to low traps, and for D. abietella, the difference was even more pronounced with 14 times as many males caught in high traps compared to low traps
Cydia strobilella: After the disruption dispensers had been applied at 4 m height in Maltesholm, a drastic reduction in male catches was observed in the treatment area versus the control area, which corresponded to a disruption effect of 99% (Fig. 1a)
Summary
In Europe, coniferous seed orchards are the main source for production of high-quality seeds for reforestation (Ruotsalainen 2014). Trees derived from such seeds are phenotypically superior to trees originating from seeds collected in natural forests. (Tortricidae), and the spruce coneworm, Dioryctria abietella Denis & Schiffermüller (Pyralidae), are severe pests in these seed orchards, and the proportion of cones infested by these species can reach 80–90% (Seifert et al 2000; Rosenberg and Weslien 2005; Rosenberg et al 2015). Females of the diurnal C. strobilella oviposit into female spruce flowers, and larvae mainly feed on seeds and remain inside the cone until adult emergence. The two moths differ in other features such as flight phenology (Annila 1979, 1981)
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