Managing Your Tropical Fruit Grove
Under Changing Water Table Levels.

C.F. Balerdi, J.H. Crane and B. Schaffer, University of Florida

This fact sheet has been prepared by IFAS staff working with tropical fruit crops in an effort to help growers manage their groves under conditions of flooding or high water tables.  Although weather events cannot be controlled, becoming familiar with the effects of high water table on tropical fruit crops can help growers survive these events with minimal or no damage.  However, this process will be impacted by water levels, which are managed in South Florida and thus are dependent on water management decisions.

Recovery from Flooding Stress

Tree symptoms of flooding stress

Symptoms progress from 1 to 3.

  1. leaf wilting and browning (scorching)
  2. fruit drop and leaf chlorosis and leaf abscission (drop)
  3. stem dieback, limb dieback, tree death

Documentation and reporting

  1. Report damage to the Farm Service Agency (FSA) (tel: 305-242-1197) as soon as possible after the event.  Ask FSA is it is ok to begin repair and recovery of trees.
  2. Photograph flooding and damage to the trees.

Steps in recovery

  1. Allow the flood-water to subside.
  2. Remove a portion of the tree canopy.  This will reduce the transpirational load on the root system.
  3. Removing fruit from the tree may decrease stress.
  4. If registered for your crop and symptoms appear apply fungicide according to label instructions.

    Note: Damage may be more severe on young trees than on large mature trees.  Trees with fruit tend to have a more severe negative reaction to flooding than trees without a fruit load.
  5. Wait several weeks to evaluate the extent of damage or tree death.  This is because it takes time for trees to recover or for trees to decline from flooding.  As an example, sometimes trees may lose leaves or have scorched leaves but the tree recovers.

Disease Control

Under flooding/high water table conditions root diseases proliferate.  This is specially true of the disease causing "water molds" - Pythium and Phytophthora.  For groves that are located in low, flood prone areas or areas of high water table, the grower has to be aware that, these fungi can attack tree roots and cause severe losses.  These diseases spread very fast and growers cannot afford to wait for a long time before taking remedial actions.  Two fungicides are commonly used to stop the spread and the damage of these diseases - Ridomil and Aliette.  Ridomil is usually drenched around the root area and Aliette is sprayed on the foliage or injected into the trunk.  However, these fungicides are only registered for citrus and avocados.  Timely use of these compounds on labeled crops can be very effective in avoiding extensive damage.  On the other hand, repeated, preventative treatments should be avoided as resistance to these products can develop, as it is already happening with Ridomil on citrus in some areas of Florida.

Replanting

In previously planted groves that were recently flooded or suspected to be subject to flooding in the future we recommend replanting those trees that have died on 3 ft high mounds or higher.  If you lose entire rows you should consider making a 3 ft high beds.  You may also want to consider replanting with flood tolerant tropical fruit crops (see Table 1).

Geographic Location - Site Selection

Before you purchase land find out what the elevation the property has.  This information may be obtained from the land title, or the Natural Resources Conservation Service in Florida City has topography maps with land elevations.  Elevations at or below 4-6 feet may be subject to periodic flooding in some areas.  In addition, view adjacent property for what agricultural activity is occurring, e.g., container nursery, fruit crop, vegetable crop and potential signs of flood damage (e.g., dead plants).  Speak with potential neighbors concerning past conditions of the land you intend to buy as to flooding. You may also want to contact the Dade County Cooperative Extension Service and speak with an agent about the property.

Soil Types

There are two basic soil types in most of the land in South Dade, the dark marls and the rock soils.  Tropical fruit trees should only be planted in rock soils.  There are very few cases where some tropical fruit groves have been planted in marl.    The soil going into the planting hole must be the same soil that was removed from it.  Do not add any other soil to the planting hole!  Muck, marl, peat, etc. hold a lot of water and provide a good environment for root disease development.  There are some poorly drained sandy soils in the north end of Dade County.   Although there is no commercial agriculture in this area the same principles apply for dooryard plantings.

Tropical Fruit Crops Flood and Drought Tolerance

Tables 1 shows the relative sensitivity of tropical and subtropical fruit crops to flooding or high water table and drought, respectively.  For south Miami-Dade, flooding tolerance may be more important than drought tolerance.  This information was compiled from several sources.  Flood tolerance is dependent upon crop species, prior plant stress (e.g., freezing weather, drought), crop load, air temperatures (warm\hot temperature more detrimental), soil type, flooding depth and flooding duration.

Definitions used for flood tolerance are:

  1. Tolerant - Flood tolerant fruit crops may survive excessively wet (high water table) and flooded conditions for several days to a few weeks.  However, the stress of wet conditions may reduce tree growth and fruit production.  In addition, root diseases may develop resulting in tree damage or death.
  2. Moderately Tolerant - Moderately flood tolerant trees may survive several days of excessively wet or flooded soil conditions.  However, the stress of wet conditions may reduce tree growth and fruit production.  In addition, root disease may develop resulting in tree damage or death.
  3. Not Tolerant - Trees not tolerant of wet or flooded soil conditions may sustain heavy damage or be killed by a day or few days of wet soil conditions.

Drought tolerance is dependent upon crop species, prior plant stress, and crop load.  Drought reduces growth and yields of tolerant and non-tolerant crop species.

  1. Tolerant - Tolerates lack of water for a few days to several weeks.  However, drought stress may reduce tree growth and yields.
  2. Moderately Tolerant - Trees may withstand several days of drought.  However, drought stress may reduce tree growth and yields.
  3. Not Tolerant - Trees may survive a few days of drought however, this may result in severe leaf drop, poor vegetative growth, and a large reduction in yield.

Land Preparation Practicies

Owners of land in areas that are subject to flooding, excessively wet soil conditions, or that have a low elevation (4-7 ft) should seriously consider planting trees on beds or mounds.  This will increase the chances that part of the root system is above flooded or wet soil conditions in the event of flooding.  To create enough soil to bed trees, deep scarification with a "rock plow" or asphalt scrapper is needed.  We recommend enough soil be "created" to make beds or mounds 3 ft high (there will be some settling with time).  We have observed some bedded avocado and lime and mounded mamey sapote groves that have survived periodic flooding in the past.  (Caution:  This is not to say all trees survived or that they will survive future flooding events).

Irrigation

Irrigation is needed for the well-being of tropical fruit tree groves in both, high and low elevation land.  Irrigation (or some way of watering) is essential in newly planted and young groves.  Depending on the species planted, as groves mature, less water may be needed though many species will benefit from irrigation from fruit set to harvest.  Excesses of water can create problems, besides being wasteful and expensive.

The choices of an irrigation system for tropical fruit trees in high or low elevation land are: microsprinklers and regular high volume over or under tree sprinklers.  The formers are more efficient in water use, thus recommended in areas with scarcity of water.  A good microsprinkler system could also be used for cold protection although this has not been tested.  High volume systems use quite a bit more water but give better cold protection.  Naturally, in the same area, the soil of bedded or mounded groves will dry faster than that of flat planted groves where the water table is closer to the roots so more frequent irrigation may be needed.

Nutrition

Tropical trees in flood prone/high water table areas may need special fertilizer considerations.  Because in these areas water is so close to the surface, growers should consider increasing the frequency of fertilizer applications but reducing the amount applied each time provided that the total recommended amount is applied to each tropical fruit crop.  Also consideration should be given to not applying fertilizers during rainy periods to avoid fertilizer leaching.

 

Table 1.  Flood tolerance of some tropical fruit crops.

FLOOD TOLERANCE*

TOLERANT

MODERATELY TOLERANT

NOT TOLERANT

Guava

Lychee

Avocado

Sapodilla

Longan

Papaya

Caimito

Tahiti Lime

Mamey sapote

Coconut

Canistel  

Sugar apple (anon)

Grafted citrus

Mango, Carambola, Banana

Atemoya, Passion fruit, Jackfruit

 

DROUGHT TOLERANCE*

TOLERANT

MODERATELY TOLERANT

NOT TOLERANT

Grafted citrus

Avocado

Air layered citrus

Sapodilla

Mamey sapote

Papaya

Mango

Passion fruit

Banana

Canistel

 

 

Lychee, Longan, Carambola, Caimito, Coconut, Guava, Jackfruit, Sugar Apple, Atemoya

 

 

 

Based on experiments with containerized plants, field observations and literature.