Suppression of Plodia interpunctella moth populations infesting wheat warehouses in Israel using mating disruption

Abstract: Indian meal moth (IMM) Plodia interpunctella is a common and harmful insect pest in stored grain and dry food in Israel. Usually, chemical treatment, such as fogging, residual insecticides or fumigation is used for IMM control. Despite the high efficacy of these traditional measures, their disadvantages, particularly their negative impact on the environment and public health have led to intensive research focused on safe and eco-friendly alternatives. In recent years, the use of sex pheromone for mating disruption of IMM was suggested. The purpose of the present investigation was to study the efficacy of mating disruption of P. interpunctella using sexpheromones in suppressing moth populations in wheat warehouses in Israel. The study was conducted in small scale (15 m3 filled with 3 ton of wheat grain) and two commercial scale warehouses (each one of 3000 m3 filled with 2000 ton of wheat grain) in the central part of Israel. The Prescription Treatment® brand ALLURE® MD (Whitmire Micro-Gen Research Laboratories, Inc., MO, USA) with 93% of active ingredient (Z-9, E-12-Tetradecadien-1-yl acetate) was used for mating disruption. Evaluation of IMM populations was performed using two methods: the first, based on pheromone traps containing pheromone dispensers SP LOCATOR (AgriSense BCS Ltd, UK) and the second, based on food traps containing culture media used for IMM rearing. The small scale warehouse was initially tested as a control (without mating disruption) and then as a treatment (1 dispenser per 15 m3). Two commercial warehouses were used for control and treatment (1dispenser per 30 m2) in parallel. It was found that both of the tested methods were suitable for evaluating IMM population levels. In the small scale warehouse experiment, an initial population of 40 introduced pupae, control-treatments resulted in 543 F1 males caught in the pheromone traps, (means of 136 males/trap) with a total F1 population of 1086 (males and females). Using food traps for evaluating population levels, the total number of F1 was 716 (both males and females) (means of 144/trap). On the other hand, after mating disruption the 231total F1 adults were caught (means of 23/trap) resulting in a 70% suppression of IMM in the first generation. However, when higher initial populations were tested (300 introduced pupae), the treatment was ineffective. On testing the efficacy of mating disruption in the commercial scale warehouses, with the initial density of the population of 1 male/pheromone trap, the numbers of trapped males were significantly less compared with the non-treated warehouse after a month of treatment: 1.5 and 7.0 adults per trap, respectively. However, at the end of the second month the numbers of trapped moths in the treated and non-treated warehouses were almost equal: 19.3 and 20.5 adults per trap, respectively. It can thus be concluded that mating disruption can indeed suppress populations of IMM in warehouses, however when populations reach high levels chance encounters prevail and thus mating disruption should be implemented within an integrated pest management program thereby maintaining pest populations at low levels.