DEVELOPING IMPROVED METHODS FOR THE RELEASE OF MACROLOPHUS PYGMAEUS (RAMBUR) (HETEROPTERA: MIRIDAE) IN SARDINIAN TOMATO GREENHOUSES

Abstract

The release of biocontrol agents for the management of arthropod pests on greenhouse tomatoes is an increasingly widespread technique in Europe. The predatory mirid Macrolophus pygmaeus was initially used for control of the greenhouse whitefly, Trialeurodes vaporariorum, but its range of application expanded when it was found to have the potential for management of the tomato leafminer, Tuta absoluta. One of the constraints that still limits the use of this beneficial in Sardinian greenhouse crops is its slow population growth, frequently responsible for unsatisfactory control of target pests. To evaluate the effects of two innovative release methods on the establishment and population build-up of M. pygmaeus in tomato crops, experiments were carried out under semi-field and field conditions. The two techniques tested for the introduction of the mirid were pre-plant release and release in confined areas. Pre-plant releases were done in the nursery, while confined area releases were done in the production greenhouse where the mirid was introduced on plants covered with a non-woven film for six weeks and provided with a food source (Ephestia kuehniella eggs). In both cases, approximately 0.8 adult mirids per plant were released. The experiments were conducted in glasshouses where spring tomato crops were grown for up to four months. The method that achieved the most promising results in terms of mirid population build-up (up to 9.6 individuals per plant) was the introduction in confined areas. However, when the insects used were purchased through ordinary retail channels, insufficient population growth and inadequate control of target pests were observed. The pre-plant release method failed to significantly enhance the build-up of M. pygmaeus population, and the peak density observed by eight weeks after its introduction was 1.1 individuals per plant for predators introduced in both a heated and unheated nursery.