University of Florida

Regardless of whether you have already decided to use windbreaks and are searching for additional information or you are about to make your initial decision, here are some considerations to help guide those decisions.

Among the various types of windbreaks, all windbreaks share several generally known and well-established advantages. These include:

  • Reduce the spread of canker disease and its severity.
  • Wind scar reduction.
  • Provide wildlife habitat (living windbreaks).
  • Reduce wind/soil erosion (living windbreaks).
  • Environmental cleanup (living windbreaks).
  • Windbreaks also have certain disadvantages such as:
  • They occupy space that may be otherwise used for income.
  • They shading adjacent crops and may reduce productivity.
  • They can compete with crop plants for water and nutrients.
  • They have establishment and possibly maintenance costs.
  • They can complicate or interfere with equipment movement.
  • There may be effects on microclimate and pest populations.

The balance or tradeoffs between the advantages and disadvantages should be the foundation of any individual decision.

A primary reason for using windbreaks is to manage canker disease. Successful management of this disease will depend on the integrated effectiveness of three tools – resistant scion varieties, copper sprays and windbreaks.

 

In a field study conducted by Drs. Tim Gottwald and Pete Timmer, the relative importance of the latter two tools was compared.

An experiment was established in a nursery to evaluate the effect of windbreaks and copper sprays on the spread and severity of citrus canker. Several nursery rows were used for each of the following treatments: 1) windbreak 2) copper sprays 3) windbreaks and copper sprays and 4) untreated control. An 8-ft tall artificial windbreak was constructed around 3 sides of the rows used in the windbreak treatments and those with copper treatments were sprayed monthly with a copper product. In all cases 3 seedlings heavily infected with canker were planted at the beginning of each nursery row. Spread and disease severity were monitored periodically. In the graphs below, disease severity is indicated on the vertical axis and distance of spread with time on the horizontal axes.

The main conclusions from this study were:

1) Windbreaks almost completely stopped the spread of canker from the infected plants at the beginning of the row.

2) Copper sprays did not limit the distance of spread of the disease compared to the control, but did reduce disease severity somewhat.

3) Copper sprays to the trees within the windbreak provided little additional control

In addition, Pete Timmer conducted studies in grapefruit groves in Argentina where the windbreak effect of the tree itself was evaluated. In one study, lesions on the leaves and fruit on the wind exposed side of the tree (SW) were counted and compared with lesion numbers on the leeward side (NE) and the lateral quadrants (NW and SE) of trees in a widely spaced grapefruit planting. Lesion counts were as follows:

 

Lesions

Sector

Leaves

Fruit

SW

8.2

82

NW

2.5

43

SE

2.9

15

NE

1.1

6

Thus, just from one side of the tree to the other, the wind-exposed side had ten times more canker than the protected side of the tree.
Lesions on entire trees in different rows in the grove were counted to compare canker incidence among trees in a row exposed to the prevailing winds, a row on the opposite side of the block, and in three internal rows. Counts were as follows:

 

 

Lesions

Row

Exposure

Leaves

Fruit

A

Prevailing winds

5.0

91

B

Internal

5.2

23

C

Internal

1.1

19

D

Internal

2.7

9

E

Opposite, exposed

4.3

32

These results show that external windbreaks reduce canker severity, but the citrus trees themselves can provide some protection for internal rows. Windbreaks help reduce the spread of canker. However, more important, they reduce the amount of infection in infested groves by lowering wind velocity and decreasing the penetration of bacteria into stomates and wounds.

Here are some key questions related to windbreak decisions.

For more comprehensive information, see Design and Management.

Q. Should windbreaks be used for all varieties everywhere?

A. Windbreaks will be advantageous in most situations, but their value varies depending on the circumstances. Highly susceptible varieties like grapefruit and navel oranges grown for the fresh market will definitely require windbreaks, probably surrounding each 5- to 10-acre block. In many situations, a row of windbreak trees about every 300 ft or so planted parallel with the rows of citrus trees should be sufficient. Such windbreaks may require removal of trees. However, for the present time, we are recommending that growers plant windbreaks wherever they have sufficient space along fence rows, ditches, edges of wetlands to put them in. As we gain more experience with the severity of canker under Florida conditions and the beneficial effects of windbreaks in our situation, we'll have a better idea of the need for windbreaks.

Q. What is the relationship to field conditions in your neighborhood to deciding whether to use windbreaks?
A. Obviously extensive flat areas planted uniformly with citrus will call for more windbreak protection. Some groves in wooded or hilly areas already have some protection.

Q. Are windbreaks appropriate for juice fruit groves or only fresh fruit?
A. Windbreaks will probably be needed for both, but the susceptibility of the variety is a key factor. Early oranges will probably need at least some windbreak protection even when grown for juice. Valencia oranges are more tolerant and perhaps windbreaks will not be needed.

Q. Are windbreaks important for newly planted trees and mature trees?
A. Windbreaks are helpful in both situations. With newly planted trees, sugarcane or other tall grasses provide good temporary protection. It is important to keep canker to a minimum on young trees to allow them to develop rapidly and to prevent buildup of large amounts of inoculum.