Effect of Mediterranean Ants (Hymenoptera: Formicidae) on California Red Scale (Hemiptera: Diaspididae) Populations in Citrus Orchards

Abstract

We conducted an ant-exclusion experiment in a citrus orchard to evaluate the overall impact of three ant species native in the Mediterranean, Pheidole pallidula (Nylander), Plagiolepis schmitzii Forel, and Lasius grandis (Forel), on populations of Aonidiella aurantii Maskell (California red scale). The ant-exclusion was carried out in four experimental plots from March 2007 to November 2008. Another subset of four plots, adjacent to the ant-excluded plots, was used as control. We measured scale densities and percent parasitism on fruits at harvest in 2007 and 2008. Additionally, we sampled the seasonal trend of the scale on twigs and fruits in both treatments during 2008. California red scale densities in the ant-excluded treatment began to be significantly lower than in the ant-allowed control in May (1 mo after ant activity began), and this difference increased until November. Thus, the effect of the ants on California red scale density seems to be accumulative. At harvest, scale densities on fruits were significantly lower in the ant-excluded treatment. However, percent parasitism on fruits was similar between treatments. Finally, scale densities on the fruits of the ant-allowed plots were positively correlated with the number of ants that climbed to the citrus canopy. These results suggest that increases of scale densities induced by Mediterranean ants depend on the intensity of the ant-activity on citrus canopies.

Ants in citrus: impact on the abundance, species richness, diversity and community structure of predators and parasitoids

“…Apparently, ant presence is associated with increased abundances of P. pergandii, as already found for other armored scales (Calabuig et al, 2013;Pekas et al, 2010;Yoo et al, 2013). Other parasitoid species of non-honeydew producers did not follow this trend.…”

“…These results may have practical implications for biological pest control. Despite the fact that ants have no negative impact on the abundance and diversity of predators and parasitoids at the community level their impact on specific natural enemy species may explain the highest pest densities associated with ant presence in citrus (Calabuig et al, 2013;Dao et al, 2014;Pekas et al, 2010;Yoo et al, 2013). This would also highlight the importance of certain species, especially predators, rather than natural enemy assemblages on regulating pest populations as recently was demonstrated in olive groves in the Mediterranean (Paredes et al, 2015).…”

Dispersal of Aphytis melinus (Hymenoptera: Aphelinidae) after augmentative releases in citrus orchards

“…Heavily infested fruit may be downgraded in the packinghouse and, if population levels are high, trees can be seriously damaged. Aphytis melinus effectiveness could depend on the scale careful monitoring, on the use of selective insecticides to control other pests (Grafton-Cardwell et al, 2006;Suma et al, 2009;Planes et al, 2012;Vanaclocha et al, 2012), on the host instars available and their size (Luck & Podoler, 1985;Pekas et al, 2010a), on ant activity (James et al, 1997;Pekas et al, 2010b), on the fitness of the released insects (Vasquez & Morse, 2012) or on environmental conditions (DeBach & Sisojevic, 1960).…”

Ants, pests and natural enemies in Mediterranean citrus. Ecological interactions and practical implications for biological control

“…The invasive Argentine ant, Linepithema humile (Mayr) was associated with higher mealybug densities and fruit infestation in California (Daane et al, 2007) and South Africa vineyards (Mgocheki & Addison, 2010). Moreover, ants have been found to induce populations increases of pests that do not produce honeydew, such as Aonidiella citrina Craw (Hemiptera: Diaspididae) (Flanders, 1945), Aonidiella aurantii Murdoch (Hemiptera: Diaspididae) Pekas et al, 2010b;Dao et al, 2014) and Panonychus citri (McGregor) (Acari:…”

“…one queen per nest), aggressive and dominant species that principally feeds on honeydew (Paris & Espadaler, 2009;Pekas et al, 2011) and has been associated with outbreaks of honeydew producers (Palacios et al 1999;Pekas et al 2011). Interestingly, this species was associated with increased population densities of the nonhoneydew producer A. aurantii (Pekas et al, 2010b).…”