Vine mealybugs disrupt biomass allocation in grapevine

Maria Schulze-Sylvester,José Antonio Corronca,Carolina Ivon Paris

doi:10.20870/oeno-one.2021.55.1.4458

Maria Schulze-Sylvester, José Antonio Corronca + Show 1 more

Open Access

https://doi.org/10.20870/oeno-one.2021.55.1.4458

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Abstract

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.

Highlights

Insect herbivory is often associated with a leaf‐chewing feeding mode, but in viticulture and many horticultural systems sap-sucking insects, such as mealybugs, scale insects, aphids and leafhoppers are a much bigger concern
The present study investigates the effects of different P. ficus densities on vegetative growth parameters of grapevine plants over the growing season
No significant differences between treatments were found for the leaf area, leaf size and leaf number per plant during the course of the experiment at any time (Figure 1)

Summary

Introduction

Insect herbivory is often associated with a leaf‐chewing feeding mode, but in viticulture and many horticultural systems sap-sucking insects, such as mealybugs, scale insects, aphids and leafhoppers are a much bigger concern. The vine mealybug, Planococcus ficus Signoret (Hemiptera: Pseudococcidae), is an invasive phloem-feeding insect from the Mediterranean area, which has become a serious pest in many grape‐growing regions worldwide (Daane et al.,2012; Mansour et al, 2017; Walton and Pringle, 2004). Mealybug infestation has been shown to affect wine and must quality, but the underlying mechanism is unclear; it may be linked to the presence of mealybugs in the grape bunches (i.e., the “mealybug flavour”), to the honeydew and fungus associated with their feeding, or to changes in the plant’s physiology (Bordeu et al, 2012; Chiotta et al, 2010; Viglianco et al, 2016). Other studies used 3 or 5 minutes counts of the whole plant during spring, detecting up to 40 mealybugs per plant (Geiger and Daane, 2001) or classified mealybug densities as high (> 10 individuals), moderate (0-10) or low (0) (Walton et al, 2006)

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