Ever since man began storing food, insects of many kinds have been known to exploit and feed in the man-made environments, since these artificial habitats provide the insects with nearly unlimited food resources. These insects, called pests for being not wanted, imply great costs for agricultural and food industries every year. Control of the pest species has traditionally meant excessive use of toxic and unhealthy insecticides greatly affecting non-target organisms and humans. Therefore there is a restrictive use of insecticides in many countries and the need for alternative control methods has increased. As a result Integrated Pest Management (IPM) was developed as a concept to control pests, where hazardous insecticides are replaced by biological and physical control methods (Trematerra, 1997). Much work has been devoted to develop the use of pheromones in IPM. For example, for pest moths the sex pheromones of females have been used to monitor the density of males of a pest population and for an early detection of a pest infestation (Phillips, 1994). In direct control of an infested area, with the aim to lower the pest density, two pheromone-based methods, mass trapping and mating disruption, have been succesful. Mass trapping is a straightforward method with the aim to catch as many insects as possible, whereas mating disruption is a method where males are confused with a permeated atmosphere of female sex pheromone, and thus being unable to find a partner. Most of this research has produced good results when trying to capture and disrupt males whereas the females are left unaffected. This is a great disadvantage, since males can mate with multiple females and the pest population density can be maintained although a substantial part of the males are killed. In order to control females, for a more effective impact on the population, research work is done on finding substances attractive to females. Accumulations of food are potential ovipositional sites for stored product pests and since females obviously colonize and infest food resources, the existence of food attractants is evident. In my Ph D studies I will concentrate on these food attractants in order to:
In the stored product pest research not much has been reported on work to find a stimulus attractive to females. However, in a study on Plodia interpunctella it was found that both food conditioned by larval secretion and food alone were highly attractive to gravid females (Phillips & Strand, 1994). The food consisted of corn meal, chick starter mash and glycerol, indicating that at least one of these constituents contains substances attractive to females. Food attractants of Tribolium beetles have been reported as fatty acids; especially palmitic acid seem to evoke aggregation and feeding for both T. confusum females and males (Loschiavo, 1965). Extracts of a blend of dried seeds and fruits (cashew nuts, groundnuts, carobs, maize, almonds, raisins, wheat, rye, barley, oats, millet) are attractive to both sexes of adult T. castaneum (Levinson & Levinson, 1978). In a study with the European corn borer, Ostrinia nubilalis, the trap efficiency increased when baited with both phenylacetaldehyde, an O. nubilalis food attractant, and pheromone, indicating synergism (Maini & Burgio, 1999). The functionality of this phenomenon was also suggested by Levinson & Levinson (1995): "optimal attraction of certain storage insect species to their male aggregation pheromones depends on simultaneous availability of appropriate feeding stimuli ". Furthermore, food attractants have other advantages; their ability to attract several generalist species make them ideal for multi-species traps and their attractiveness to both larval and adult stages, both factors being of economical importance (Chambers, 1990). Also larval secreted substances can be useful as means of female control. In Ephestia kuehniella high concentrations of larval secretions have proven highly deterrent for ovipositing females (Corbet, 1973)
The target species of my project are the Indian meal moth (Plodia interpunctella), the Mediterranean flour moth (Ephestia kuehniella) and the almond moth (Ephestia cautella). All three belong to the family Pyralidae and are common pests in storage facilities all over the world. The larvae of these species are polyphagous and feed on stored grains, nuts, dried fruits, legumes and other stored food products (Phillips & Strand, 1994). The confused flour beetle (Tribolium confusum) and the rust-red flour beetle (Tribolium castaneum ) are also included in the project. These two beetle species are cosmopolitan and feed on the same types of food as the moths, implying that some food attractants may be shared and can be used in IPM for both beetles and moths.
I. Attraction of different pest species to different diets
I will conduct behavioural studies in a wind tunnel with different kinds of food stimuli. In the windtunnel I will try to establish a good response to food for each species and evaluate different diets´attractivity on the target species.
II. Identification of food attractants/ Attractive dose optimization of food components
By using GC-EAD/GC-MS technique the attractive compound can be identified. The identified substances can be evaluated in behavioural tests in a wind tunnel.
III. Practical utilization of food attractants
Behavioural and field studies, in collaboration with cereal industry, with traps baited with food attractants and pheromones will be done.
IV. Practical utilization of larval-secreted attractants.
Traditional identification of previously reported attractive secretions, including GC-EAD, GC-MS and behavioural stuides. Investigation of relevant doses and mixtures.
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Chambers, J. 1990. Overview on stored-product insect pheromones and food attractants. J. Kansas Entomol. Soc. 63(4): 490-499.
Corbet, S. A. 1973. Oviposition pheromone in larval mandibular glands of Ephestia kuehniella. Nature 243: 537-538
Levinson, A. R. & Levinson, H. R. 1995. Reflections of structure anf function of pheromone glands in storage insect species. Anz. Schädlingskunde,. Pflanzenschutz, Umweltschutz 67: 99-118.
Levinson, H. Z. & Levinson, A. R. 1978. Dried seeds, plant and animal tissues as food favoured by storage insect species. Ent. Exp. appl. 24: 305-317.
Loschiavo, S. R. 1965. The chemosensory influence of some extracts of Brewer´s yeast and cereal products on the feeding behavior of the confused flour beetle, Tribolium confusum (Coleoptera: Tenebrionidae). Ann. Ent. Soc. Amer. 58: 576-588.
Maini, S. & Burgio, G. 1999. Ostrinia nubilalis (Hb.) (Lep., Pyralidae) on sweet corn: relationship between adults caught in multibaited and ear damages. J. Appl. Ent. 123: 179-185.
Phillips, T. W. 1994. Pheromones of stored-product insects: current status and future perspectives. In: E. Highway (ed.). Proceedings of the 6th International working conference on stored-product protection, Canberra, Australia. Wallingford: CAB International. pp. 479-486.
Phillips, T. W. & Strand, M.R. 1994. Larval secretions and food odors affect orientation in female Plodia interpunctella . Entomol. Exp. appl. 71: 185-192.
Trematerra, P. 1997. Integrated pest management of stored-product insects: practical utilization of pheromones. Anz. Schädlingskde., Pflanzenschutz, Umweltschutz. 70 (3):41-44.
