Development of an 'attract and kill' strategy for effective management of citrus leafminer (Phyllocnistis citrella Stainton) in Texas

Citrus is an evergreen plant which is usually found in tropical and subtropical climates. Most of the commercial citrus in Texas is grown in the Lower Rio Grande Valley, and fruit are destined essentially to the fresh fruit market. Due to warm climatic conditions in which citrus is grown and because of its evergreen nature, citrus production faces many biotic and abiotic challenges. Among the biotic challenges of citrus in Texas, arthropod pests are of the greatest concern. All citrus plant parts are attacked by arthropod pests. In Texas, growers consider arthropod pests as the most important impediment to citrus production. Control of these pests increases production costs to growers, and negatively impacts their profit margins. The use of chemical pesticides can potentially impact non-target organisms and the environment. Thus, to avoid losses to farmers and to meet the demand of higher food product output while protecting our environment, an innovative and effective way to control pests needs to be developed that is sustainable and environmentally-friendly. Hence, in the current research we investigated a new strategy termed "attract and kill" for the control of citrus leafminer (CLM) in Texas. This approach utilizes the mate finding behavior of adult CLM to lure adult males onto a baited target, thus reducing their population and the need of insecticidal sprays for their control. MalEx, a new research product has CLM pheromone to attract CLM adults and an insecticide as active ingredient to do the killing. Adult CLM dies when it comes in contact with the MalEx formulation, thus MalEx does the mating disruption by significantly reducing CLM male population and disrupting subsequent successful mating by females. The result is a dramatic reduction of oviposition of fertile eggs and larval populations. To compare the effectiveness of MalEx, a foliar imidacloprid (Provado) was used as standard in field tests. MalEx formulations with different active ingredients and in different concentrations were tested in mature sweet orange and grapefruit orchards. Field experiment results showed that of all MalEx formulations, 'MalEx 14 imidacloprid' without oil was equally effective as foliar spray of Provado in reducing both CLM adult populations and larval damage levels on leaves. Results of the present study also showed that the flight activity of CLM starts in May in south Texas, and populations rapidly increased during the summer months, and declined by the end of November. No CLM flight activity was recorded from December until early April, probably because of hibernal conditions and the lack of young flush for the most part of this period. Hence, we suggested initiating CLM control by the beginning of May to prevent rapid population increase in citrus. 'MalEx 14 imidacloprid' can be a very good candidate for the novel attract and kill approach for effective management of CLM populations in Texas.