Cluster Thinning

Question 1

Cluster thinning is a reduction of fruit load by removing: (3)

Answer 1

1. a proportion of clusters
2. a portion of individual clusters (mainly for table grapes)
3. individual berries (table grapes, chemical thinning)

Question 2

5 Reasons why a vine overcrops

Answer 2

➢ Wrong, poor, inadequate winter pruning!
➢ Objective high bud fruitfuilness
➢ Cluster size
➢ Conditions favoring bud induction
➢ The grapevine suffers from “alternate bearing” as other fruit trees!

Question 3

Cluster thinning should be done among _________ of the total crop, otherwise it could be too light. Why?

Answer 3

30 % and 60 %

because we have compensation from the remained clusters and so totally useless.

Question 4

Chemical cluster thinning may be performed using ____________ in pre-bloom

Answer 4

gibberellins

Question 5

What is alternate bearing?

Answer 5

meaning one-year high crop, the next one low crop and so on, sometimes it happens in grapevine and once it happens is very difficult to be adjusted.

Question 6

Crop thinning can be executed at three points, list them and discuss the best philosophy for this

Answer 6

1. Fruit set
2. Cluster pre-closure
3. Veraison

The sooner we solve the overcropping the better

Question 7

When does cluster thinning usually happen?

Answer 7

In general, the cluster thinning done around veraison is more frequent than an earlier cluster thinning.

Question 8

Describe the graph

Answer 8

In situation A, the ratio is too low, meaning that I have an overcrop, so doing cluster thinning we move towards A position and the ratio is going to increase as well as the quality.

In situation B we are already in an optimal ratio so when we crop thin here we are losing yield without gaining quality

Question 9

Discuss the results of the Cluster thinning trail on Prosecco (three years)

Answer 9

The key take away is that when we are trying to force the vine to stay artificially at a lower level of yield, there is overtime a reaction trying to replenish the initial level. (rebalancing)

Question 10

What do we see when we compare Pre-flowering defoliation to traditional cluster thinning

Answer 10

We see that defoliation is more recommended. The overall quality stayed consistent between the two however with defoliation there was higher yield and less compactness for the clusters. This treatment is also more mechanizable

Question 11

Remember those big scary tables: what did they basically say?

Answer 11

That late thinning is has very little if any improvement

Question 12

Too much crop can…

Answer 12

Delay ripening

Question 13

Need ______ leaf area to ripen of _________ of fruit
- One leaf feeds ________

Answer 13

1. 10-15 cm2
2. 1 g
3. 5-10 berries

Question 14

Growing shoot tips compete with ___________.
→ Limit _________ growth after veraison

Answer 14

1. ripening berries
2. (lateral) shoot

Question 15

4 main reasons why we crop thin

Answer 15

• Regulates crop load (fine-tuning) → Prevents overcropping
• May improve fruit composition
• Can increase berry size
• May promote shoot growth

Question 16

Early fruit thinning leads to…

Answer 16

An increase in shoot growth

Question 17

Late fruit thinning leads to…

Answer 17

Greater effect on yield