Biology, ecology and integrated pest management of the white mango scale, Aulacaspis tubercularis Newstead, a new pest in southern Spain - a review

Highlights

• Aulacaspis tubercularis Newstead is considered one of the most important pests of mango crops around the world.

• A reduced number of insecticides are being mainly used for managing white mango scale, but their effectiveness is limited.

• Biological control, involving parasitoids and predators, has played a key role in suppressing A. tubercularis.

• Development of sustainable strategies to carry out an Integrated Pest Management program are discussed.

Abstract

Aulacaspis tubercularis Newstead (Hemiptera: Diaspididae) is a tropical, cosmopolitan, polyphagous armored scale which is considered one of the key pests of mango crops around the world, because it produces conspicuous pink blemishes on the mango fruits, which depreciate their commercial value and make them unacceptable for export markets. If no control measures are taken, the pest can cause up to 90% yield losses in mango groves and may pose a threat to sustainability mango production. At present, control of A. tubercularis is based on the application of a reduced number of insecticides, most of which show a limited efficacy and are disruptive to beneficial insects. Considering the current European regulations on the sustainable use of phytosanitary products, the application of other management alternatives, such as the use of cultural control measures or biological control agents, is a priority. However, despite its economic importance, there is limited information on control methods for A. tubercularis, and most of the literature has focused on the description of its biological cycle and natural enemies in different mango producing regions. This report is an updated review on its biology, ecology and sustainable control measures, aimed to help in the development of integrated management strategies of this pest in the main mango growing areas of Spain and other countries of the Mediterranean Basin.

Introduction

Mango (Mangifera indica L.) ranks as the fifth most consumed fruit in the world, after citrus, banana, grapes and apple with an estimated harvested global area of 5.68 million hectares and a global production of 50.64 million metric tons (FAO, 2019). Mangoes are grown under very diverse climatic conditions in tropical and subtropical regions. Asia is the dominant producing region, with over 74.4%, followed by the Americas and the Caribbean (13.1%), Africa (12.4%), and Oceania (0.1%) (FAO, 2019). Mango is not produced commercially in continental Europe except in Spain, which has approximately 4200 ha of plantations, and a total production of 28000 tons in 2016 (MAPA, 2018), representing only 0.06% of the world's mango production. However, in the last 15 years, there has been a substantial development of this crop in the south of Spain becoming, after avocado, the most important subtropical crop. This increase is mainly due to the privileged climatic conditions for this crop (absence of winter frosts and dry-sunny summers), which allow the production of a high-quality fruit, and the growing demand of this fruit from the main European markets (Hermoso et al., 2018). Most of the Spanish mango production is located on the Andalusian Mediterranean coast (Málaga and Granada provinces) and in the Canary Islands, being exported mainly to other European Union countries such as Portugal (28%), France (27%) and Germany (17%) (Junta de Andalucía, 2017). Until a few years ago, Spanish mango production was characterized by a minimal application of phytosanitary products, which allowed rapid access to the European market with a high-quality product and optimum ripeness.

Mango crops present numerous phytosanitary problems, favored by the special climatic conditions in the producing regions (Peña et al., 1998). Among them, the Mediterranean fruit fly Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) and the white mango scale, Aulacaspis tubercularis Newstead (Hemiptera: Diaspididae) stand out in Spanish mango groves for their constancy and economic importance due to the serious damage they cause to the fruit (Boyero et al., 2017). This has led to an increasing dependence on the use of insecticides, with an increase in associated costs and risks, among them the potential imbalance of secondary pests (Boyero et al., 2017). Scale insects, especially diaspidid scales, are among the most important pests of mangoes in some parts of the world (Waite, 2002). In the case of A. tubercularis, this species is considered one of the key pests of mango crops around the world (Nabil et al., 2012; López-Guillén et al., 2017), because it causes conspicuous pink blemishes on the mango fruits, which depreciate their commercial value and make them unacceptable for export markets (Porcelli, 1990; Nabil et al., 2012). This damage has a significant economic importance, because it can lead to the loss of up to 90% of economic value production if the pest is not controlled in time, mainly in organic crops (Hodges et al., 2005; Urías-López, 2006).

There is currently limited information on A. tubercularis, with most published scientific studies focused on the description of its biological cycle and natural enemies, specifically in South Africa (Daneel and Dreyer, 1997, 1998), Egypt (El-Metwally et al., 2011; Nabil et al., 2012; Abo-Shanab, 2012) and Mexico (Urías-López et al., 2010). In Spain, Arteaga et al. (2003) studied the presence of the pest in the Canary Islands and described the damage. Likewise, Vela et al. (2015) report on the phenology of A. tubercularis and its natural enemies complex in Andalusia. In addition, the efficacy of eco-compatible active substances has been determined (Bienvenido et al., 2017) and the bases for control of A. tubercularis using sexual pheromone have been developed (Ortiz et al., 2017). The present report is an update of the currently available information, aimed to help in the development of integrated management strategies of this pest in the main mango growing areas of Spain and other regions of the Mediterranean Basin.