Improving stored products pest management: Biological control and methods for pest detection in stored rice

Abstract

Arthropod pests in stored products represent a significant economic and food safety challenge for the agro-industry as they compromise post-harvest food production and damage the final product. Although the problem is mainly managed with pesticides, Integrated Pest Management (IPM) offers a more sustainable alternative. Biological control with natural enemies is a promising IPM strategy. However, more knowledge is required on its effective implementation and success in different storage environments, in addition to improving pest prevention and detection techniques. This PhD thesis focuses on improving alternative methods for controlling major pests of stored food products, particularly in bulk rice, through the development of biological control strategies with parasitoids and predatory mites and the improvement of pest detection by molecular methods. Chapter 1 studies the use of three generalist predatory mites, Blattisocius tarsalis, Cheyletus malaccensis and Amblyseius swirskii, as biocontrol agents for the control of major stored product pests. Potential preys were tested in two arenas of different complexity. The effect of weekly releases of these mites, individually or combined, on populations of the common rice pests, O. surinamensis and Sitotroga cerealella, was evaluated in medium-sized rice arenas over 10 weeks. Only B. tarsalis and C. malaccensis were able to significantly consume these pests, reducing their population by half, with no additional benefit from combining the two species. Chapter 2 evaluates the suitability of the parasitoid Cephalonomia tarsalis, very little studied, as a natural enemy of the sawtooth grain beetle, Oryzaephilus surinamensis, in rice and explored the potential enhancement of pest control by combining it with the predatory mite, B. tarsalis. The ability of the parasitoid to locate and parasitize its host was tested in 150 cm long PVC pipes filled with rice, while the combination of natural enemies was assessed in medium-sized arenas. Cephalonomia tarsalis move freely through the rice up to 150 cm deep and can reduce pest population by up to 60%. In the medium-sized arena, a single release of the parasitoid nearly completely suppresses the pest for three months, while releases of B. tarsalis every two weeks suppress the pest population by half. Combining both natural enemies does not enhance pest reduction produced by the parasitoid. Chapter 3 assesses the effectiveness of the well-studied parasitoid Anisopteromalus calandrae in controlling one of the main rice pests, Sitophilus zeamais in the presence of the alternative host pest, Rhyzopertha dominica. Trials in laboratory and commercial big bags with different proportions of both pests were conducted to determine host preference. Anisopteromalus calandrae prefers S. zeamais as a host, regardless of host proportions and arena size, and the presence of R. dominica does not alter its control. Finally, in Chapter 4, a method based on real-time qPCR using universal arthropod primers is developed to detect rice contamination by the most common pest species of this cereal in a single analysis, avoiding the use of specific primers for each pest species separately. The method could detect pests at an infestation level as low as 0.0052 g of arthropod biomass per kg of rice. The findings of this PhD thesis represent an important advancement in optimizing the management of stored products pests and contribute to the development of more sustainable control strategies.

Date of Award	8 Nov 2024
Original language	English
Supervisor	Cristina Castané Fernández (Director) & Jordi Riudavets Muñoz (Director)