Vine mealybug Planococcus ficus Signoret (Hemiptera: Pseudococcidae) is an important phloem-feeding pest species in many grapevine producing areas worldwide. The economic damage of P. ficus is thought to be mainly caused by sooty mould on infested grape clusters and transmission of plant viruses. Direct damage caused by mealybug feeding to grapevine plants (Vitis vinifera, L.) has only been vaguely described or otherwise completely discarded. The present study is the first to give an insight into the direct impacts of P. ficus on vegetative growth and biomass dynamics of grapevine plants. In a screenhouse, three-year-old, potted grapevine plants were infested with mealybugs at two different densities, imitating high and low field infestation levels. Mealybug numbers, plant biomass, leaf area, leaf size and leaf number were monitored over six months and compared to a control treatment without mealybugs. High infestation levels reduced leaf and stem biomass by one third, while low levels of P. ficus impacted only stem biomass, indicating a higher sensibility of the perennial parts of the plant or a reallocation of biomass. Leaf area, size and number were not affected by mealybug feeding.In conclusion, grapevine response to P. ficus is gradual and involves different plant parts depending on the severity of the attack. Contrary to previous assumptions, this study demonstrates considerable direct impacts of mealybug feeding on temporal and perennial parts of grapevine plants.

Carbon dioxide (CO₂) is one of the primary factors driving climate change impacts on plants, pests, and natural enemies. The present study reports the effects of different atmospheric CO₂ concentrations on the vine mealybug Planococcus ficus (Signoret) and its parasitoid wasp Leptomastix dactylopii (Howard). We investigated the life-history parameters of both species on grapevine Vitis vinifera (L.) plants grown under elevated (eCO₂) and ambient (aCO₂) CO₂ levels in a greenhouse and in a vineyard free-air carbon dioxide enrichment (FACE) facility. The greenhouse experiments with an eCO₂ level of around 800 ppm showed a significant increase in survival rates, a strong trend towards declining body size, and an increasing fecundity of female mealybugs, while fertility and development time did not change. However, none of these parameters were altered by different CO₂ concentrations in the VineyardFACE facility (eCO₂ level around 450 ppm). On the other hand, the parasitism success, development time and sex ratio of L. dactylopii, reared on P. ficus under eCO₂ or aCO₂, varied neither in the greenhouse nor in the FACE facility. These results suggest that future CO₂ levels might cause small-scale changes in vine mealybug fitness; however, this is not necessarily reflected by parasitoid performance.

The invasive Argentine ant causes ecological and economic damage worldwide. In 2011, this species was reported in vineyards of Cafayate, a wine-producing town in the Andes, Argentina. While the local xeric climate is unsuitable for Argentine ants, populations could establish in association with vineyards where human activity and irrigation facilitate propagule introduction and survival. In 2013–2014, we combined extensive sampling of the area using ant-baits with monitoring of the change in land use and vineyard cultivated area over the past 15 years. Our results revealed that the species has thus far remained confined to a relatively isolated small area, owing to an effective barrier of dry shrublands surrounding the infested vineyards; yet the recent expansion of vineyard acreage in this region will soon connect this encapsulated area with the rest of the valley. When this happens, vulnerable ecosystems and the main local industry will be put at risk. This case provides a rare opportunity to study early invasion dynamics and reports, to the best of our knowledge, for the first time, the Argentine ant in high altitude agroecosystems.

Leafcutter ants are a major pest in vineyards in Argentina, but their damage to vine plants has not been sufficiently quantified. Biological control against leafcutter ants has not been successful so far. Sugary rewards can trigger ants to act as plant bodyguards against a wide range of herbivores. The Argentine ant Linepithema humile (Mayr) is a common invader of vineyards worldwide and has a strong preference for carbohydrates. In a first 10-week field experiment, we attracted L. humile ants to a group of plants using sugar feeders, while no feeders were used for a second group. Ant-excluded control plants were also deployed. We quantified the damage inflicted by the leafcutter ant Amoimyrmex bruchi (Forel) on potted vines with and without L. humile ants. In a second short field experiment, we evaluated the impact of L. humile on A. bruchi foraging through the quantification of foraging activity and the amount of transported material as a function of L. humile presence. We found that A. bruchi caused >90% leaf area reductions in plants without L. humile, while plants where the species was present were rarely attacked and leaves developed similar to those of ant-excluded controls. Active interaction with L. humile decreased A. bruchi’s foraging activity and the amount of material transported by it. This is the first report of A. bruchi as a vineyard pest and the first quantification of the damage inflicted by a leafcutter ant on organic grapevines. We demonstrate that L. humile defends vine plants against herbivore pests and artificial sugar sources boost can this defense service. The development of biological control strategies that include the ecological services of ants as natural enemies of herbivorous pests could become a useful tool in sustainable viticulture and horticulture.