8.2 Pests Flashcards
What is phylloxera?
- Aphid-like insect that feeds on and lays eggs on the roots of grape vines.
- Weakens vine roots and causes swellings and cracks, which then lead to rot.
How does phylloxera spread?
- Crawling
- Flying
- Transported by humans
What are the 5 main symptoms of phylloxera?
- Vines die of drought in patches that increase in size year by year
- Vine roots are covered with the insects surrounded by yellow eggs
- Swellings on older roots
- Pale green leaf galls on the under-surface of the leaves
- Slow, stunted shoot growth and leaf yellowing appears in around three years, the plant dies after around five years.
When was phylloxera identified? Where? Where did it originate?
- Identified: 1863
- Identified in: Europe
- Originated in: USA
What was the effect of phylloxera on Europe?
Destroyed two-thirds of the European vineyard in the late nineteenth century.
What was the effect of phylloxera on USA?
Nothing. American species were naturally resistant.
What types of soil is immune to phylloxera?
Sandy
What are management options for phylloxera?
- Planting American vine species (not ideal)
- Grafting European varieties onto rootstocks from single American vines (not ideal)
- Grafting European varieties onto rootstocks hybrids from multiple American vines (ideal)
Name the 3 American vine species that offer the most protection against phylloxera.
- V. berlandieri
- V. riparia
- V. rupestris
Describe how the American vine species protect against phylloxera.
They form hard, corky layers that surround the eggs, sealing the wounds and preventing invasion by bacteria or fungi.
Why aren’t American vine species typically used? What are they typically used for?
They produce different and undesirable aromas in the resulting wine. The solution was to graft European varieties onto rootstocks from American vines.
What tends to happen when grafting onto the rootstocks of single American varieties? Why?
- Soils of Europe are typically calcareous
- American varieties have little lime tolerance
- Thus, vines suffered from chlorosis turning the leaves yellow, halting photosynthesis and reducing yields and quality
How does one choose which rootstock to use?
- There are many rootstocks, often with complex parentage, that can deal with a number of problems
(phylloxera, nematodes, extremes of soil pH, water stress, salinity) - Goal is to match the appropriate rootstock to:
1. the vineyard soil
2. the pests to be combatted
3. the level of vigour desired
What is a main disadvantages of planting on rootstocks?
Significantly more expensive than on the vines own roots
What are nematodes?
Tiny worms that live in the soil, typically too small to be seen by the naked eye.
How are nematodes harmful to vines?
- Feed off vine roots
- Transmit viral diseases
Name 2 of the most commonly occurring nematodes.
- Root-knot nematode
2. Dagger nematode
How do nematodes spread?
- present in the soil already
- unclean nursery stock
- irrigation water
- vehicles
How can nematodes be eliminated?
They can’t. They can only be managed.
How are nematodes managed? What happens first? What is typically the best solution?
Soil samples are analysed in a lab to determine the number and type of nematodes present.
- Leave the soil fallow for a number of years (costly, no crop)
- Fumigate the soil.
- Plough in a cover crop of mustard plant, which contains compounds that work as biofumigants, killing nematodes.
- For most, the best solution is the use of nematode-resistant rootstocks
What are grape moths and how do they affect vines?
- Many species of moths that feed on flowers and grapes, damaging vines
- Wounds created are then vulnerable to further attack from bacteria and fungi, including botrytis
Name the 3 most common types of grape moths and the regions they affect.
- Light brown apple moth (Australia)
- European grapevine moth (southern Europe)
- Grape berry moth (central and eastern North America)
What happened to Napa Valley in 2009?
- European grapevine moth was introduced accidentally
- Eradicated in 2016
How are grape moths managed?
- Biological controls include the use of:
- - the bacterium Bacillus thuringiensis (which produces substances that are toxic to the moths)
- - use of pheromone capsules to disrupt mating (‘sexual confusion’)
- - natural predators (parasitic wasps, green lacewings, some spider species). - Insecticides can be used.
