Practical Winery
65 Mitchell Blvd, San Rafael, CA 94903
phone: 415-453-9700 ext 102
email: Office@practicalwinery.com
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MARCH/APRIL 2010
GRAPEGROWING
European grapevine moth pupa inside partially open cocoon found under the bark. Photo Jack Kelley Clark, courtesy of UC Statewide IPM Program.
Ground surveys for immature insects by vineyard, regulatory, and UC Cooperative Extension personnel were more fruitful. Almost 30 individual properties inNapa County are now presumed positive for at least one life stage of L. botrana. By November 2009, trapping efforts had ended for the season, concurrent with the lack of a population in the adult stage.
In late winter/early spring 2010, trapping efforts will resume in Napa County, and expand throughout California to determine statewide distribution of L. botrana. Considering its status as one of the most damaging pests of grape berries in the Mediterranean region, and its recent rapid spread in Chile, this state-wide monitoring effort will be critical to delimit populations to track the pest’s spread and damage in California vineyards.
Currently, the European grapevine moth has been classified as a Q-rated pest by the CDFA, a temporary rating pending determination of a permanent rating. Once adequate information has been collected on its statewide distribution, L. botrana will then be assigned an A, B, or C rating.
Pests with an A-rating are organisms of recognized economic importance that are subject to state-enforced action involving eradication, quarantine regulation, containment, or rejection; B-rated pests generally have established, but not widespread populations, are recognized as economically damaging, and are subject to regulatory action at the discretion of the Agricultural Commissioner at the local level. C-rated pests are recognized as generally distributed, and are therefore not subject to regulatory action except to retard spread, and at the nursery level to assure pest-free plants.
During the 2009 harvest, quarantine zones and compliance agreements established for the light brown apple moth (Epiphyas postvittana) in Napa County may have limited the movement of European grapevine moth.
Geographic distribution
L. botrana was first described by biologists Denis and Schiffermüller in 1775 in Vienna, from samples collected in Italy, and was classified as a pest in Austria in 1800. It was reported from several European countries and Russia in the 1800s and has since spread to North and West Africa and the Middle East. It was introduced into Japan before 1974 and recently into Chile.
Climates in the area occupied by the pest can be characterized generally as dry or temperate. The currently reported global distribution of L. botrana suggests that the pest may be most closely associated with habitats classified as montane scrub, Mediterranean scrub, and temperate broadleaf and mixed forest.
The Chilean department of agriculture, Servicio Agrícola y Ganadero (SAG), issued the first report on L. botrana in the Americas on April 23, 2008. Surveys conducted in 2008 and 2009 showinfestations in all grapegrowing regions of Chile, a spread of approximately 1,500 kilometers (930 miles).
Hosts
European grapevine (Vitis vinifera), American bunch grape (V. labrusca), and spurge laurel (Daphne gnidium), a common shrub inMediterranean Europe, are the main hosts. Some researchers theorize that D. gnidium constitutes the original host of L. botrana and its adaptation to grapes is a relatively recent event.
The larva feeds on all cultivated grape varieties, although they develop better on some than on others. Females lay eggs almost exclusively on flower clusters and berries.
The literature includes about 25 hosts other than grape, however Lobesia is found only very rarely or accidentally on other hosts with the exception of D. gnidium. Vitis vinifera constitutes the main food resource.
L. botrana is considered a major pest only on grapevines. In olive, only the flowers are infested, never the fruit; therefore, olive trees next to vineyards may constitute an important source of infestation of nearby vines by moths in the late spring.
Females select plants to lay eggs on by flying upwind following olfactory cues.Once they land on a plant they also taste the surface with contact chemoreceptors before laying their eggs. Plant surface chemicals stimulate or deter egg laying. The host-plant range in California will need to be studied to establish the role that alternate hosts play in the life cycle of L. botrana.
Identification
The adult moth is approximately ¼ inch long. Female moths tend to be slightly larger, although both sexes have mosaic-patterned wings. The first pair of wings is tan-cream and mottled with gray-blue, brown, and black blotches. The second pair of wings is gray with a fringed border.
Unlike other common vineyard tortricids, which lay eggs in overlapping masses, L. botrana lays single, elliptical, and flat eggs (0.03 inches in diameter). As it ages, the iridescent, creamy white egg turns yellow, and later blackens as the head of the developing larva forms. The larva hatches from the edge of the egg, leaving the translucent egg shell attached to the plant.
Both sexes have five larval instars; fully grown larvae are approximately ½ inch long with dark thoracic legs. First-instar larvae are creamy white with a black head. Older larvae have lighter, yellowish-brown heads with a dark border at the rear edge (closest to the body) of the prothoracic shield (segment behind the head; see photo). Young larvae have tan bodies, whereas older larvae take on the color of their gut contents and food source (from dark green to shades of maroon).
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