Lobesia botrana Denis & Schiffermüller 1775
The European Grapevine Moth (EGVM, Lobesia botrana) is a serious pest of grape (Vitis vinifera), a preferred host, although it is reported from other cultivated and wild hosts as well. Although native to southern Italy, this moth was first described from Austria and is now distributed throughout Europe, North and West Africa, the Middle East, and eastern Russia. More recently, it was inadvertently introduced to Japan. In 2008, it was reported from Chile and in 2009 from the Napa Valley in California (U.S.A.). (Varela et al. 2009)
In laboratory wind tunnel tests, mated females (but not males or virgin females) were attracted to the leaves, berries, and flowerbuds of grapevines (Vitis vinifera). This pattern of responsiveness is presumably due to the need for mated females to locate appropriate oviposition (egg laying) sites (Masante-Roca et al. 2007).
Moreau et al. (2008) investigated the question of whether oviposition behavior of Lobesia botrana females is affected by the host on which they were reared. In this study, females that had never experienced grapes were able to discriminate among three different grape (Vitis vinifera) cultivars: Pinot, Chasselas, and Chardonnay. In a choice situation, they preferentially selected Pinot as an oviposition substrate. Furthermore, this "naive" preference of oviposition could be modified by larval environment. Females raised on grapes as larvae preferred to lay eggs on the cultivar they had already experienced. (Moreau et al. 2008)
The European Grapevine Moth has two generations in northern Europe and three generations in southern Europe; it is reported to have a partial fourth generation in warmer regions of Spain, Greece, Jordan, and Egypt. The first generation population tends to be the largest, although it is not the most damaging. Pupae overwinter in diapause (a resting state) inside silken cocoons under the bark, in soil cracks, or in hidden places on trellis posts. Adults of the first generation emerge when air temperatures exceed a threshold of 10° C for a period of 10 to 12 days. Adult males emerge about a week before females. The first male flight may begin as early as bud break and continue for 4 to 5 weeks. Adults remain hidden during the day, emerging to fly at dusk if temperatures are above 12º C. Mating occurs in flight. The majority of females mate only once, although they are capable of mating multiple times. (Varela et al. 2009) Work by Torres-Vila et al. (2005) indicates that large females that fed on ripe grapes exhibited significantly higher levels of polyandry (mating with more than one male) than did smaller females that fed on inflorescences, with females that fed on unripe grapes showed intermediate levels of remating (polyandry also tended to increase later in each flight period).
Egg laying begins one or two days after mating. Eggs of the first generation are glued singly on flat surfaces on or near the flower cluster. A female can lay as many as 35 eggs a day for about 6 days, with a mean of 80 to 140 eggs laid per female, depending on the generation. Adult lifespan is from 1 to 3 weeks, depending on climatic conditions. Egg hatch depends on temperature, and ranges from 3 to 5 days under optimal conditions in summer to 10 to 11 days in spring when conditions are less favorable. The first generation larvae web flower parts together and feed on individual flowers and pedicels (flower stalks); they may enter the fruit stalk, causing the bunch to dry up. Like other tortricid larvae, when disturbed they will wiggle and drop on a silken thread. Larval development is completed in 20 to 30 days, depending on temperature. Pupation occurs inside a webbed cocoon that may be found on the flower cluster, under the bark, or in soil cracks. Adults emerge 6 to 14 days after pupation. The adult and egg stages are considered the most vulnerable to environmental factors. (Varela et al. 2009)
The second- and third-flight female moths lay eggs individually on shaded grapes. Shortly after the larva emerges, it enters a grape and hollows it out as it feeds. A single bunch may be infested with several larvae. Webbing, frass, and fungal infection may result in extensive contamination of the bunch. (Varela et al. 2009)
The lower and upper developmental thresholds are 10° C and 30° C, respectively although some authors report that the lower threshold is as low as 7° C. Optimal development conditions are 26 to 29° C and 40 to 70% humidity. Shorter day lengths and cooler temperatures initiate diapause. Although larvae may die when temperatures fall below 8°C, a diapausing pupa can withstand even the cold northern European winters. Some authors report that larvae die when the temperature exceeds 34°C.
The first generation is shorter than the summer generations. Using the 10°C and 30° C lower and upper developmental thresholds, eggs hatch in about 66 degree-days Celsius (DDC). Larvae feeding on flower clusters are reported to develop faster than those feeding on grape berries later in the season, and this influences generation time. Non-diapausing pupae require about 130 DDC to develop. Adult females may lay eggs about 61 DDC after emergence. Estimates of DD for a generation vary considerably in the literature, from 427 DDC to 577 DDC in the first generation to 482 DDC to 577 DDC in later generations. For European Grapevine Moths in California, good data on developmental time are not yet available, but Varela et al. (2009) estimate that it would be around 463 DDC for the first generation and 502 DDC for the second generation. (Varela et al. 2009)
The eggs of the European Grapevine Moth are elliptical and flat. They are very small (0.6 to 0.8 mm in diameter), but visible to the naked eye. Initially they are iridescent creamy white, but they turn yellow as the embryo develops and later black when the head of the developing larva is formed. The larva emerges from the edge of the egg and leaves the translucent, iridescent chorion (outer shell) attached to the grape. (Varela et al. 2009)
Amsellem et al. (2003) developed Lobesia botrana microsatellite markers potentially useful for studying the population structure of this moth.
A number of other moths in various parts of the world are pests of grapes and some may be known by common names similar to the European Grapevine Moth. In the eastern United States, for example, the Grape Berry Moth (Endopiza viteana) causes damage similar to that of Lobesia botrana, although it differs in life cycle, host range, pheromone composition, and natural enemies (hymenopteran parasitoids in particular). (Varela et al. 2009)
The adult European Grapevine Moth is around 6 to 8 mm long, with a wingspan of about 11 to 13 mm; the female is slightly larger than the male. Both males and females have similar mosaic-patterned wings. The forewings are tan-cream in color, mottled with gray-blue, brown, and black blotches. The hindwings are gray with a fringed border. The wings are held in a bell shape over the abdomen when at rest. (Varela et al. 2009)
The larvae molt through 5 immature stages (instars), with sizes ranging from 1 mm at emergence to around 12 to 15 mm when fully grown. Upon emergence, the larva is creamy white with a black head. As it develops, the head and prothoracic shield (the first segment behind the head) is tan to yellowish brown. The rear edge of the prothoracic shield has a darker brown to black border. In early stages, the body is tan to yellow-brown. In later stages, the cuticle is transparent, such that the body takes on the color of its gut contents (from dark green to shades of dark pink and maroon). White tubercles at the base of the body hairs are quite visible on mature larvae. The thoracic legs are dark brown to black. The anal comb, a toothed structure on the last abdominal segment, has 5 to 6 dark brown teeth. (Varela et al. 2009)
Fifth instar larvae spin a grayish-white silken cocoon in which they pupate. The male pupa is approximately 0.16 to 0.28 inch (4 to 7 mm) long and the female is 0.2 to 0.35 inch (5 to 9 mm) long.
Lobesia botrana is known to use a number of alternative host species in addition to grape (Vitis vinifera). Thiery and Moreau (2005) compared larval performance and several life history traits on three alternative host plants (Daphne gnidium, Olea europaea, Tanacetum vulgare) and three Vitaceae (two cultivars of Vitis vinifera and one wild species, Ampelopsis brevipedunculata), as well as on two control diets (high and low nutritive value) consisting of the feeding medium without any plants material added. Results indicated that L. botrana perform better reared on alternative hosts (at least collectively) than on Vitaceae. Relative to performance on Vitaceae, on alternative hosts larval mortality and development time was reduced, while pupal weight, growth rate, female longevity, female fecundity, duration of laying, and mating success were increased. High quality food ingested
by larvae promotes higher adult body weight and enhances female reproductive output. This suggests that alternative hosts may provide greater nutritional value for L. botrana than do Vitaceae, which may explain the maintenance by L. botrana of a relatively broad host range. (Thiery and Moreau 2005)
Mondy et al. (1998) investigated the relationship between Lobesia botrana moths feeding on grape and the fungus Botrytis cinerea, which infects grape berries and causes them to rot. Lobesia botrana larvae serve as effective dispersal agents for B. cinerea conidiospores and tunneling larvae facilitate rapid penetration and development by the fungal mycelium. It is clear that the B. cinerea fungus benefits from its associaton with L. botrana moths. Mondy et al. found that the moth benefits from this association as well. Female moths preferentially oviposited (laid eggs) on infected grape berry clusters. On infected grape berries development was quicker and mortality lower (this effect was also seen when B. cinerea mycelium was added to an artificial diet). Thus, the relationship between these two serious vineyard pests, L. botrana and B. cinerea, is a true mutualism. (Mondy et al. 1998)
Numerous predators and parasitoids of EGVM in Europe have been reported in the literature. Among the parasitoids are 4 species of tachinid flies and nearly 100 species of parasitic ichneumonid, braconid, pteromalid, and chalicidoid wasps. The parasites that are reported to cause the greatest impact are those attacking the overwintering pupa. In Spain these include the pteromalids Dibrachys affinis and D. cavus, which are reported to cause up to 70% pupal mortality, whereas in Italy the ichneumonids Dicaelotus inflexus and Campoplex capitator are the most important. (Varela et al 2009)
Damage to cultivated grapes (which, to botanists, are technically a type of berry) by the larvae of Lobesia botrana can be severe. In May and June, first-generation larvae web and feed on the flower clusters. Second-generation larvae (July-August) feed on green berries. Young larvae penetrate the berries and hollow them out, leaving the skin and seeds. Third-generation larvae (August-September) cause the greatest damage by webbing and feeding inside berries and within bunches, which become contaminated with frass (excrement). Additionally, feeding damage to berries exposes them to infection by Botrytis and other secondary fungi such as Aspergillus, Alternaria, Rhizopus, Cladosporium, and Penicillium. Secondary pests such as raisin moth (Cadra figulilella), fruit flies, and ants may also be attracted to damaged berries. (Varela et al. 2009)