Lobesia botrana

Inspection of Grapevine Reproductive Organs
Inspect inflorescences and look for eggs or larvae on flower buds or glomerules. Inspect grapes and look for eggs or larvae, or damaged berries. It is easier to look for larval damage rather than for eggs, because detection of eggs is very tedious and time-consuming, especially under field conditions. Egg detection is always preferable when an insecticidal control has to be programmed.
Corrugated Paper Bands
This technique has sometimes been employed to trap and quantify overwintering pupae. Bands are placed around grapevine trunks or primary branches, and diapausing larvae pupate inside. However, this method is only useful in the last generation, and its reliability is uncertain.
Light Traps
Their lack of specificity makes their use inadvisable when the adult trapping methods described below are available. EGVM flight activity mainly occurs at dusk (Lucchi et al., 2018c);this negatively affects the visibility of the light traps, impacting on their efficiency.
Feeding Traps
These traps were largely used in the past before sexual traps were developed, but may still be useful in particular situations. Trapping females with food-baited traps is a valuable tool to predict the onset of oviposition, an event used to properly time insecticide treatments (Thiéry et al., 2006). An earthen or glass pot is baited with a fermenting liquid (fruit juice, molasses, etc.) and the scents produced attract adults which are then drowned;the population may be estimated by counting. Practical problems include irregularity in trapping because fermentation strongly depends on seasonal temperature, trap maintenance (lure replenishment and foam elimination), and low selectivity. Terracotta pots baited with red wine have been used in Spain to assess the L. botrana mating ratio in mating disrupted vineyards (Bagnoli et al., 2011).
Sexual Traps
Pheromone traps are easier to use compared to feeding traps. They are a sensitive tool to monitor flight of males exclusively, but can be useful to time an ovicidal treatment, and to properly schedule scouting activities in the vineyard. Sexual traps were first suggested by Götz (1939). Chaboussou and Carles (1962) designed traps baited with living L. botrana females, which became increasingly important for monitoring. To obtain a large number of females to bait traps, laboratory rearing methods were improved both on natural substrates (Maison and Pargade, 1967;Roehrich, 1967a;Touzeau and Vonderheyden, 1968), and on synthetic or semi-synthetic media (Moreau, 1965;Guennelon et al., 1970, 1975;Tzanakakis and Savopoulou, 1973). However, sexual trapping became more efficient when the major compound of the L. botrana sex pheromone, (7E, 9Z)-7, 9-dodecadienyl acetate, was described (Roelofs et al., 1973), identified from the female sex gland (Buser et al., 1974), and synthesized (Descoins et al., 1974). In traps, females were promptly replaced by dispensers impregnated with synthetic pheromone, which had essential practical advantages for monitoring. It has now been shown that the L. botrana sex pheromone is a blend of 15 compounds (Arn et al., 1988), but for economic reasons commercial traps incorporate only the major pheromone compound, which has a satisfactory trapping specificity for L. botrana. In Italy, males of few species of non target moths are sometimes captured in L. botrana pheromone traps (Ioriatti et al., 2004).
A major limitation of L. botrana sexual trapping (as often occurs in other insect pests) is the lack of a clear relationship between the number of males trapped and the damage done by their offspring, given the high number of other uncontrolled ecological factors involved. The correlation between these variables has been partially improved by diminishing the pheromone dose in traps (Roehrich et al., 1983, 1986). According to Roehrich and Schmid (1979), only a negative prediction can be made when male catches in traps are sporadic (or nil) can one expect minimal (or even no) damage to be caused by offspring on the crop;but if catches are moderate or high, the damage caused by offspring is unpredictable. Nowadays, the variable performance of the traps on the market, the influence of the trap placement and of the wind direction on the number of catches, make it still difficult to find a strict relationship between catches and infestation, especially when the catches are low.
Scouting
Forecasting models and moth trapping alone do not provide sufficient population density information and need to be supplemented with appropriate field scouting of eggs and young larvae (Shahini et al. 2010).
Insecticides are applied according to action thresholds (AT) on the basis of the resulting infestation assessment (percentage of injured clusters, number of nests per inflorescence, number of eggs and larvae per cluster, number of injured berries per cluster). The action thresholds vary widely depending on the generation, susceptibility of the cultivar to subsequent infection by B. cinerea, and whether berries are being produced for table grape, raisins or wine production.
Modelling
Predictive mathematical models have been developed and tested to forecast the life cycle of L. botrana, integrating both biological and climatic information. Temperature-based models, both linear (degree-days accumulated above a lower threshold) and non-linear (deterministic) have been generated in Switzerland (Schmid, 1978), France (Touzeau, 1981), Slovakia (Gabel and Mocko, 1984b, 1986) and Italy (Caffarelli and Vita, 1988;Baumgartner and Baronio, 1989;Cravedi and Mazzoni, 1990). Major problems affecting the correct inference of tortricid populations using modelling are summarized by Knight and Croft (1991) - it should be noted that prognosis is usually only qualitative. However, modelling can be a useful implement in L. botrana management programmes. Time of the first appearance of adults and hatching of the first eggs can be forecasted by predictive models based on temperature requirements of individual instars and critical conditions for oviposition (Moravie et al., 2006). Unfortunately, forecast models based on Degree Days are empirical and their robustness is strongly dependent on the environment in which they have been validated. Alternative forecasting techniques are currently under development, such as the evaluation of larval age distribution during the previous generation in order to predict the distribution of female emergence (Delbac et al., 2010).