Planococcus ficus and the spread of grapevine leafroll disease in vineyards: a 30-year-long case study in north-West Spain

Abstract

The mealybug Planococcus ficus is one of the main vectors of Grapevine leafroll associated virus-3 (GLRaV-3), which was commonly detected in cv “Albariño” planting material before certified stock was available. Mealybug infestations were rare in vineyards in southern Galicia (NW Spain) during the 1990s (2.2% of the vineyards surveyed) and are still rare in inland zones. However, mealybug infestations have spread since 2000, with 15% of surveyed vineyards infested in 2004 and 80% of surveyed vineyards infested in 2016. The spatial and temporal distributions of plants infected with GLRaV-3 were quantified over a 30-year period in an experimental plot established in 1989. The disease progress curve (DPC) was linear for 25 years, with a slow constant rate of spread of less than one newly infected plant per year (0.6%). Since 1992, >82% of infected plants were located on the west side of the plot as were 84% of newly infected plants. Newly infected plants were in contact with infected plants, suggesting vector-mediated transmission, but no potential vectors were found. In 2013, a small mealybug infestation was detected and identified as Pl. ficus. Between 2014 and 2016, the infection rate increased to >21% per year, and in 2019 all plants tested positive for GLRaV-3. This is a valuable case study illustrating how changes to the vector fauna can increase the rate of spread of an economically important virus of grapevine.

Assessment of Symptoms of Grapevine Leafroll Disease and Relationship with Yield and Quality of Pinot Noir Grape Must in a 10-Year Study Period

“…Grapevine virus diseases are generally only of concern for growers when very striking symptoms appear in the field, especially those affecting grape clusters (millerandage), as observed with GFLV and other nepoviruses. Although information has been compiled in the last decades regarding the economic impact of GLD [10,[23][24][25][26][27] winegrowers' concern about GLD does not seem to have increased greatly in traditional vineyards in Europe [28]. Winegrowers do not readily associate loss of yield or quality with GLD symptoms, to the point, that in some cases, leaf rolling and reddening or yellowing are considered characteristic of cultivars and to be a natural process occurring in vineyards in autumn.…”

“…If the infection remained invisible in the field in an indicator, this would surely happen in many red cultivars and in most white ones; there could be a risk in thinking that it will not be a major problem because late or absent symptoms meant an absence of economic losses (Figures 12 and 13). However, these plants will still be sources of GLRaV-3 to be transmitted by mealybugs that do not require heavy infestations for the virus to spread rapidly [31] and such transmission could "create" plants with more aggressive combinations of viruses. Making decisions about roguing infected plants can be based on direct observation of GLD symptoms or tele-detection of symptoms [32] at least in red cultivars [13].…”

“…[1] pointed out that much research had focused on the viruses, but limited attention had been given to the disease itself and the factors affecting disease development, which may vary in relation to the different viruses and also different climates and growing conditions. However, several recently published studies have considered different aspects of the GLD together with the associated viruses [4,11,13,31].…”

Climate Change and Pathways Used by Pests as Challenges to Plant Health in Agriculture and Forestry

“…Other observational studies have investigated species along latitudinal or elevational gradients as a proxy for changes in climate over time. In addition to these empirical approaches, "theoretical" approaches have also been adopted, such as the meta-analysis of published results [49,50] or the analysis of long-term datasets [51,52]. Finally, some studies have drawn upon expert opinion or have generated simulation models to predict how projected changes in climate or atmospheric composition will alter the distribution, prevalence, severity, and management of pests and other organisms [13].…”

Summary of the worldwide available crop disease risk simulation studies that were driven by climate change scenarios and published during the past 20 years

“…For example, Chaloner et al (2021) reported that they did not consider RH in their model due to paucity of data concerning RH requirements of many pathogen species, as well as large uncertainties over future global RH projections. Uncertainty of disease risk simulations is also true for respective plant pathogen species that are strongly affected by interactions with other organisms such as insect vectors (Cabaleiro et al, 2022), unless their interactions are well studied (Juroszek & von Tiedemann, 2013a), and thus fairly predictable (Gimenez‐Romero et al, 2022; Godefroid et al, 2022).…”