Test Bench for the Mechanical Distribution of Predators to Control Insect Pests

In agriculture, chemical insecticides are widely used to protect crops from insect pests. Over a period of years, some insects such as Colorado potato beetle （CPB） succeed in developing resistance to most of the registered chemical insecticides. Consequently, heavy applications of chemical insecticides to control this pest become ineffective on a long-term basis and can lead to serious health and environmental problems. The use of natural enemies to control CPB is an interesting alternative to chemical means However, hand release of predators is not feasible on a large scale in the field. The main objective of this research study was to design and build a test bench to investigate the technical feasibility of mechanically releasing predators. The test bench consisted of a vertical chain conveyor mounted on two vertical shafts driven by an electric motor. Since the predators are small and fragile, they were placed in a specially designed container to preserve their physical integrity. Trials using this test bench showed that a carrier material was required, because most of the predators remained inside the container. The success of this mass predator release system will be highly valuable for the biological control of insect pests in many crops.

Design of a Mechanical Release System of Predator Insects to Control the Colorado Potato Beetle, Leptinotarsa Decemlineata （Say）

The CPB （Colorado potato beetle）, Leptinotarsa decemlineata （Say）, is the major insect pest of potato crops in North America, Europe and Asia. Large amounts of chemical insecticides are used to control this insect pest. Also, the CPB has developed over the years a resistance to most of the registered chemical insecticides, including those that were effective at one time. One of the most promising alternatives to chemical insecticides consists of taking advantage of natural enemies. The use of the stinkbug predator Perillus bioculatus to control the CPB has been successful at small scale. However, this natural enemy is not abundant in the nature and its hand release at large scale is not realistic. To remedy to this problem, predators must be massively released in potato fields using a mechanical distributor. Such a machine has been successfully designed and built at the Department of Soils and Agri-Food Engineering of University Lavak In this distributor, masses of predators are placed in small containers and mixed with a carrier material. In the field, the containers are mechanically opened at different locations, based on a source-point mass release option. These locations are determined in advance following a field monitoring of the populations of CPBs. Field trials proved that the mechanical distributor is reliable and ease of use. Its efficiency in releasing insect predators is high and comparable to that obtained in previous laboratory tests.

Control of the Colorado Potato Beetle, Leptinotarsa decemlineata （Say）, Using Predator Insects Released by a Mechanical Prototype

The CPB （Colorado potato beetle） is unquestionably the major insect pest of potato crops in North America, Europe, and Asia. The use of chemical insecticides to control this insect pest started in the 1860s. To date, no registered chemical has been capable of effectively managing this agricultural pest. Moreover, the CPB has developed over the years a resistance to most of the registered chemical insecticides. The biological control through manual release of natural enemies of the CPB has been successful at small scale. However, hand release of these predators at large scale is not realistic. The objective of this study was to investigate the effectiveness of controlling the CPB through mechanical release of predator insects under real conditions in a potato field. Obtained results indicate that the mechanical release of predator insects resulted in a better control of the CPB populations and egg masses than the manual release. The success of this mechanical release of predator insects in potato fields will be highly valuable for the biological control of insect pests in many other row crops such as strawberry, lettuce, etc..

CHARACTERISTICS OF ARTHROPOD COMMUNITY AND THEIR DIVERSITY RESTORATION IN LEAFY VEGETABLE FIELDS

The effect of chemical insecticides on the structure and diversity of arthropod communities in various vegetable fields and the restoration of their biodiversity after stopping application of chemical insecticides were studied. The results showed that the effect of chemical insecticides on the arthropods in vegetable fields could be characterized the species structure, the diversity index and the evenness of species distribution. Components of arthropod species depended closely on the species number of insect pests, predatory natural enemies and spiders. Investigations showed that the numbers of species in the vegetable fields managed with chemical insecticides were obviously reduced, and their diversity indices were lower comparing with that without chemical insecticides. When the applications of chemical insecticides were stopped in vegetable fields, the index of population trend ( I ) of dominant insect pests decreased greatly, the control effect of natural enemies on major insect pests increased, and the diversity index of arthropod increased at the same time. Thus, limiting the application of chemical insecticides, resuming the environment of vegetable fields destroyed by using chemical insecticides, escalating the control ability of natural enemies on main insect pests will play an important role in the ecological control of insect pests in vegetable fields.