Effects of Citrus Overwintering Predators, Host Plant Phenology and Environmental Variables on Aphid Infestation Dynamics in Clementine Citrus

Abstract

The Spirea citrus aphid, Aphis spiraecola Patch, and the cotton aphid, Aphis gossypii Glover (Hemiptera: Aphididae), are key pests of clementine mandarines in the Mediterranean basin. Severity of aphid infestations is determined by environmental variables, host plant phenology patterns, and the biological control exerted by their associated natural enemies. However, there is no information about the role these limiting and regulating factors play. Aphid densities, citrus phenology, and associated predators that overwinter in the crop were monitored weekly throughout two flush growth periods (February to July) in four clementine mandarin groves; relationships between these parameters and environmental variables (temperature and precipitation) were studied. Our results show exponential increase in aphid infestation levels to coincide with citrus phenological stages B3 and B4; shoots offer more space and nutritional resources for colony growth at these stages. Duration of these phenological stages, which was mediated by mean temperature, seems to importantly determine the severity of aphid infestations in the groves. Among those studied, the micro-coccinellids, mostly Scymnus species, were the only group of predators with the ability to efficiently regulate aphid populations. These natural enemies had the highest temporal and spatial demographic stability. Aphid regulation success was only achieved through early presence of natural enemies in the grove, at the aphid colonization phase. Our results suggest that conservation strategies aimed at preserving and enhancing Scymnus sp. populations may make an important contribution to the future success of the biological control of these key citrus pests.

Aphid predators in citrus crops: the least voracious predators are the most effective

“…Experiments were conducted in four clementine mandarin (Citrus clementina) plots in the Valencia Region of Spain during the spring of 2015 and 2016. This region has a Mediterranean climate with mild (mean temperature of 12 °C) and relatively humid winters and hot (mean temperature of 26 °C) and dry summers that limit citrus growth in that period of the year (Bouvet et al 2019b). The two experimental plots employed were as follows: Moncada (39°35'17.43″N/0°23′53.28″O) (0.40 ha) and Castellon (39°59′29.92″N/0°4′12.77″O) (0.11 ha) belonging to the Instituto Valenciano de Investigaciones Agrarias and to the Jaume I University, respectively.…”

“…Experiments were started when approximately 5% of citrus shoots in the plots were occupied with aphid infestations (beginning of exponential growth of plot infestation (Bouvet et al 2019b)). A randomize complete design was used in each exclusion experiment.…”

“…Nevertheless, aphidophagous predators are abundant and diverse but usually arrive late to the colonies (Gómez-Marco et al 2016). The Micro-coccinellids, Scymnus interruptus Goeze and Scymnus subvillosus Goeze (Coleoptera: Coccinellidae) were the only predators found in sufficient numbers at the end of winter to provide effective aphid regulation at early infestation stages (Bouvet et al 2019b). However, aphid suppression by the aphidophagous predators has not been quantified.…”

Economic value of conservation biological control for management of the Asian citrus psyllid, vector of citrus Huanglongbing disease

“…The holistic nature of IPM demands an extensive knowledge of the agroecosystem in order for it to be successfully implemented. Insufficient knowledge of the ecological processes which modulate the pest demography and the shortages of economic evaluations to the benefits of IPM implementation are the main causes of its shortcomings …”

“…4 The holistic nature of IPM demands an extensive knowledge of the agroecosystem in order for it to be successfully implemented. Insufficient knowledge of the ecological processes which modulate the pest demography [5][6][7] and the shortages of economic evaluations to the benefits of IPM implementation are the main causes of its shortcomings. 1,4 Of all the management tools available in IPM, biological control (BC) seems to be the most important and the one with the highest returns on investment.…”