Title: Minimizing damage to nursery crops after prolonged heavy rains
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Title: Minimizing damage to nursery crops after prolonged heavy rains
Physical Description: Book
Creator: Burch, Derek George,
Publisher: Agricultural Research and Education Center, IFAS, University of Florida
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Bibliographic ID: UF00076423
Volume ID: VID00001
Source Institution: University of Florida
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Resource Identifier: oclc - 141258005

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MINIMIZING DAMAGE TO NURSERY CROPS
AFTER PROLONGED HEAVY RAINS







BY




Derek Burch and Ra A ano
HUjE ULRAry

University of Florida':j 0 C1c5

Institute of Food and Agr :.Fleual ?jeen orideF_
Agricultural Research and Education Center
Fort Lauderdale, Florida


JUNE 1982
FL-82-2









MINIMIZING DAMAGE TO NURSERY CROPS

AFTER PROLONGED HEAVY RAINS


DAMAGE FROM LONG PERIODS OF RAIN TAKES THREE FORMS:

1. A potting medium or field soil that is saturated with water

for a long time is poorly aerated. The plant roots cannot

get the oxygen that they need to stay alive and cannot get

rid of the carbon dioxide that is produced as a waste product

from the activities of their cells. Under these conditions

many roots die and those surviving become more susceptible

to root rots.

2. Extremely humid air and leaves which remain wet provide good

conditions for the growth of bacteria and fungal spores that

infect the leaves. Any preventive sprays of fungicide or

bactericide on the leaf surfaces are washed off by frequent

heavy rains leaving the foliage unprotected and allowing rapid

spread of disease.

3. Another form of damage results from the leaching of nutrients

from the root zone which may upset the nutritional balance and

hence the growth of the plant.

If the rain is severe enough to cause flooding, there are the additional

problems of physical damage to plants which are tipped over, loss of soil from

pots and the deposition of mud or debris on the plants. Leaves brought into

contact with the soil or surface water may develop diseases which they might

not otherwise get.

STEPS TO MINIMIZE DAMAGE:

If flooding has occurred, get container material out of the water and

upright as soon as possible. With field grown plants it will, of course,








not be possible to do anything until the water subsides. Even then it may

be better to avoid possible compaction of the soil that could result from

working around the plants by leaving the area alone until the soil is no

longer saturated. It is probably safe to work when the soil no longer

sticks to boots or tools in large lumps. Set plants upright, stake if

necessary and prune tops by thinning out some whole branches and shortening

others. Removing about 20% of the topgrowth will lighten the head and make

the plant less likely to fall over again. This also leaves less leaf surface

to be supplied by roots weakened by mechanical damage or flooding. Later

treatment after these first emergency operations is the same as for pots or

field areas that have not been flooded but have been subjected to extended

heavy rain.

Experience has shown that root rot organisms, especially the watermolds,

increase during periods of prolonged rains and increase the danger of rots

that may attack roots weakened by poor soil aeration. Fungicide drenches

are frequently effective in preventing root rots and new systemic fungicides

may even provide some therapeutic activity where infections-have already

occurred. However, drenching with fungicides is an expensive treatment and

is only effective when the chemical can reach all parts of the root zone before

plants are too severely damaged. Under saturated field condition adequate soil

penetration may not be possible. The nurseryman must weigh all factors cost

of treatment and the possibility that the treatment may not be effective versus

the value of the plants and their susceptibility to disease.

Commonly available fungicides are listed below with the organisms against

which they are effective. Use all chemicals with caution and in accordance

with the label instructions.








Fungicides to treat against Watermolds (Pythium and Phytophthora):

Banrot 40% WP

Subdue 2E

Terrazole 35% WP, 25% EC

Truban 5G, 30% WP, 25% EC

Fungicides to treat against Fusarium, Rhizoctonia, Sclerotinia, others:

Banrot 40% WP

Benomyl 50% WP

To combat leaf diseases the usual sprays must be applied as soon as the

weather allows and repeated as often as necessary to keep an active layer of

the chemical present on all leaf surfaces.

Many plants, including palms, crotons, and dieffenbachias, which seldom

show foliar attacks by watermolds under normal growing conditions, may be

badly damaged by these organisms if they have been in contact with flood water

or soil debris.

A soil analysis will be valuable in bringing nutritional levels back to

normal. Foliar feeding may be useful at this time both to stimulate new root

growth and to supplement what the weakened root system is able to draw from

the soil.
















Use of trade names in this publication does not imply endorsement or exclusion

of other similar products








Fungicides to treat against Watermolds (Pythium and Phytophthora):

Banrot 40% WP

Subdue 2E

Terrazole 35% WP, 25% EC

Truban 5G, 30% WP, 25% EC

Fungicides to treat against Fusarium, Rhizoctonia, Sclerotinia, others:

Banrot 40% WP

Benomyl 50% WP

To combat leaf diseases the usual sprays must be applied as soon as the

weather allows and repeated as often as necessary to keep an active layer of

the chemical present on all leaf surfaces.

Many plants, including palms, crotons, and dieffenbachias, which seldom

show foliar attacks by watermolds under normal growing conditions, may be

badly damaged by these organisms if they have been in contact with flood water

or soil debris.

A soil analysis will be valuable in bringing nutritional levels back to

normal. Foliar feeding may be useful at this time both to stimulate new root

growth and to supplement what the weakened root system is able to draw from

the soil.
















Use of trade names in this publication does not imply endorsement or exclusion

of other similar products




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