WSET Diploma D1 Exam Questions with Verified
Answers |2026/2027 Update | A+ Graded
what is the scientific name of powdery mildew? - Answer -Erysiphe necator aka Oidium tuckeri
when was powdery mildew introduced to Europe? - Answer -mid-1800's
which common varieties are particularly prone to powdery mildew? which are not? - Answer --
Chardonnay, Cabernet
- Pinot, Riesling
where is powdery mildew during the winter? - Answer -in buds, on canes
what does powdery mildew attack? - Answer -young green parts of vines
what does powdery mildew look like? - Answer -- starts as dull grey patches that become black
patches as they advance
- patches can damage young shoots, inflorescences and grapes, reducing yield
- grapes can split at véraison and become targets for other infections
1|Page
,what determines the growth rate of powdery mildew? - Answer -Temperature, optimal around
25C
what conditions are favorable to powdery mildew? - Answer -- optimal temperature (25C)
- shade
- can thrive in dry conditions
what causes downy mildew (peronospora)? - Answer -a water mold that lives within vine tissue,
not on the surface
where did downy mildew originate? when was it introduced to Europe? - Answer -- North
America
- late 1800's
what is the main effect of downy mildew? - Answer -attacks green parts of the vines, defoliates
what conditions are optimal for downy mildew? what are its symptoms? - Answer -- rainfall
- temperature = 20C
- yellow, circular 'oil spots' and then white, downy fungal growth on the underside of leaves
2|Page
,how can powdery mildew be managed? - Answer -- Keeping an open canopy to reduce shade
and the density of leaves
- Applications of sulfur
- Systemic fungicides (can become resistant)
how can downy mildew be managed? - Answer -- sprays made from copper salts (Bordeaux
mixture) (protection from these copper sprays only lasts until 20 mm of rain has fallen)
- other fungicides
- good drainage and an open canopy that dries quickly
how can grey rot be managed? - Answer -- Selecting grape varieties that have small grapes with
thick skins and therefore high levels of resistance
- Keeping an open canopy and removing the leaves around bunches
- Traditional sulfur and copper sprays are ineffective, but other fungicides can be used
- Attention has turned to using antagonistic bacteria; for example, Bacillus subtilis and other
forms of biological control
what is eutypa dieback? what does it do? how is it spread? how does it infect? - Answer -- aka
Dead Arm
- fungal trunk disease that leads to rotten wood in vines and can affect whole vineyards
- reduces yields significantly and kills vines over a ten-year period if not tackled
- spread by wind over long distances
- through pruning wounds in moderate temperatures and especially during rain
3|Page
, how can eutypa dieback be managed? - Answer -- pruning late and applying fungicide to
pruning wounds can be effective
- cut back affected trunks 5-10 cm beyond the visible symptoms and treated with fungicide
- Bacillus subtilis
what is pierce's disease? how does it infect? how is it spread? where did it originate? - Answer --
bacterial disease that quickly kills vines
- bacterium lives in the sap channels of vines, which it clogs, leading to shrivelling, dropping
leaves and the death of the vine between one and five years
- bacterium lives in the sap channels of vines, which it clogs, leading to shrivelling, dropping
leaves and the death of the vine between one and five years
- American continent
how can Pierce's disease be managed? - Answer -control is by reducing the number of the
vector (removing vines close to rivers, chemical insecticides, introducing a species of wasp that
feeds on the eggs of sharpshooters
what is fanleaf virus? how was the disease spread enormously? - Answer -- a long-standing
group of diseases (also called Fanleaf degeneration) that is now found around the world-
American continent
- grafted vines following phylloxera and the inadvertent use of infected plant material; also
spread by dagger nematodes
how is leafroll virus spread? what does it do? - Answer -- grafting and mealy bugs
4|Page
Answers |2026/2027 Update | A+ Graded
what is the scientific name of powdery mildew? - Answer -Erysiphe necator aka Oidium tuckeri
when was powdery mildew introduced to Europe? - Answer -mid-1800's
which common varieties are particularly prone to powdery mildew? which are not? - Answer --
Chardonnay, Cabernet
- Pinot, Riesling
where is powdery mildew during the winter? - Answer -in buds, on canes
what does powdery mildew attack? - Answer -young green parts of vines
what does powdery mildew look like? - Answer -- starts as dull grey patches that become black
patches as they advance
- patches can damage young shoots, inflorescences and grapes, reducing yield
- grapes can split at véraison and become targets for other infections
1|Page
,what determines the growth rate of powdery mildew? - Answer -Temperature, optimal around
25C
what conditions are favorable to powdery mildew? - Answer -- optimal temperature (25C)
- shade
- can thrive in dry conditions
what causes downy mildew (peronospora)? - Answer -a water mold that lives within vine tissue,
not on the surface
where did downy mildew originate? when was it introduced to Europe? - Answer -- North
America
- late 1800's
what is the main effect of downy mildew? - Answer -attacks green parts of the vines, defoliates
what conditions are optimal for downy mildew? what are its symptoms? - Answer -- rainfall
- temperature = 20C
- yellow, circular 'oil spots' and then white, downy fungal growth on the underside of leaves
2|Page
,how can powdery mildew be managed? - Answer -- Keeping an open canopy to reduce shade
and the density of leaves
- Applications of sulfur
- Systemic fungicides (can become resistant)
how can downy mildew be managed? - Answer -- sprays made from copper salts (Bordeaux
mixture) (protection from these copper sprays only lasts until 20 mm of rain has fallen)
- other fungicides
- good drainage and an open canopy that dries quickly
how can grey rot be managed? - Answer -- Selecting grape varieties that have small grapes with
thick skins and therefore high levels of resistance
- Keeping an open canopy and removing the leaves around bunches
- Traditional sulfur and copper sprays are ineffective, but other fungicides can be used
- Attention has turned to using antagonistic bacteria; for example, Bacillus subtilis and other
forms of biological control
what is eutypa dieback? what does it do? how is it spread? how does it infect? - Answer -- aka
Dead Arm
- fungal trunk disease that leads to rotten wood in vines and can affect whole vineyards
- reduces yields significantly and kills vines over a ten-year period if not tackled
- spread by wind over long distances
- through pruning wounds in moderate temperatures and especially during rain
3|Page
, how can eutypa dieback be managed? - Answer -- pruning late and applying fungicide to
pruning wounds can be effective
- cut back affected trunks 5-10 cm beyond the visible symptoms and treated with fungicide
- Bacillus subtilis
what is pierce's disease? how does it infect? how is it spread? where did it originate? - Answer --
bacterial disease that quickly kills vines
- bacterium lives in the sap channels of vines, which it clogs, leading to shrivelling, dropping
leaves and the death of the vine between one and five years
- bacterium lives in the sap channels of vines, which it clogs, leading to shrivelling, dropping
leaves and the death of the vine between one and five years
- American continent
how can Pierce's disease be managed? - Answer -control is by reducing the number of the
vector (removing vines close to rivers, chemical insecticides, introducing a species of wasp that
feeds on the eggs of sharpshooters
what is fanleaf virus? how was the disease spread enormously? - Answer -- a long-standing
group of diseases (also called Fanleaf degeneration) that is now found around the world-
American continent
- grafted vines following phylloxera and the inadvertent use of infected plant material; also
spread by dagger nematodes
how is leafroll virus spread? what does it do? - Answer -- grafting and mealy bugs
4|Page
