Impacts of Argentine ants on mealybugs and their natural enemies in California’s coastal vineyards

Abstract

1. The Argentine ant, Linepithema humile , tends honeydew-excreting homopterans and can disrupt the activity of their natural enemies. This mutualism is often cited for increases in homopteran densities; however, the ant's impact on natural enemies may be only one of several effects of ant tending that alters insect densities. To test for the variable impacts of ants, mealybug and natural enemy densities were monitored on ant-tended and ant-excluded vines in two California vineyard regions.2. Ant tending increased densities of the obscure mealybug, Pseudococcus viburni , and lowered densities of its encyrtid parasitoids Pseudaphycus flavidulus and Leptomastix epona . Differences in parasitoid recovery rates suggest that P. flavidulus was better able to forage on ant-tended vines than L. epona .3. Densities of a coccinellid predator, Cryptolaemus montrouzieri , were higher on ant-tended vines, where there were more mealybugs. Together with behavioural observations, the results showed that this predator can forage in patches of ant-tended mealybugs, and that it effectively mimics mealybugs to avoid disturbance by ants.4. Ant tending increased densities of the grape mealybug, Pseudococcus maritimus , by increasing the number of surviving first-instar mealybugs. Parasitoids were nearly absent from the vineyard infested with P. maritimus . Therefore, ants improved either mealybug habitat or fitness.5. There was no difference in mealybug distribution or seasonal development patterns on ant-tended and ant-excluded vines, indicating that ants did not move mealybugs to better feeding locations or create a spatial refuge from natural enemies.6. Results showed that while Argentine ants were clearly associated with increased mealybug densities, it is not a simple matter of disrupting natural enemies. Instead, ant tending includes benefits independent of the effect on natural enemies. Moreover, the effects on different natural enemy species varied, as some species thrive in the presence of ants.

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

“…The same or even greater variability is reported at the species level; natural enemies, even species belonging to the same taxonomic order, may be affected differently by ants. For example, several studies have shown that ants have a negative impact on certain coccinellid species (Bartlett, 1961;Itioka and Inoue, 1996;Kaplan and Eubanks, 2002), but other coccinellid species are not affected (Flanders, 1958;Vanek and Potter, 2010) or even increase their densities under ant presence (Daane et al, 2007;Völkl and Vohland, 1996). Likewise, the activity of several parasitoid species is disrupted by ants (Bartlett, 1961;Martínez-Ferrer et al, 2003;Mgocheki and Addison, 2009) while others are able to parasitize ant-tended plant feeders (Barzman and Daane, 2001;Flanders, 1958;Völkl, 1994).…”

Pestiferous Scale Insects on Native Epiphytic Orchids in South Florida: A New Threat Posed by Introduced Species

“…Given that P. microcirculus appears to exhibit the same cryptic feeding behavior on orchids in the natural setting, land managers charged with the task of controlling Mealybugs feed on the phloem of their host and secrete honeydew waste that supports the growth of saprophytic fungi (sooty mold) capable of coating the leaves and reducing photosynthesis. Honeydew production also attracts ants whose tending might lead to increases in the mealybug populations (Daane et al 2007). During our sampling, we found that the presence of ants or their debris was a reliable indicator that mealybugs were present (Fig.…”

Foraging Activity and Seasonal Food Preference of <I>Linepithema micans</I> (Hymenoptera: Formicidae), a Species Associated With the Spread of <I>Eurhizococcus brasiliensis</I> (Hemiptera: Margarodidae)

“…One strategy to reduce infestation by E. brasiliensis in vineyards is to control L. micans through the use of toxic baits (Nondillo 2013), as with Linepithema humile (Mayr) (Hymenoptera: Formicidae) in South Africa and California (Addison and Samways 2000;Daane et al 2006Daane et al , 2007Cooper et al 2008;Nyamukondiwa 2008). A basic requirement for success in the use of toxic baits is knowledge of the foraging period and seasonal food preferences, which will guide the choice of attractive ingredients for bait (Markin 1970, Abril et al 2007.…”