of Zoological Horticulture 1991 Conference Proceedings
elegans photographed at Parrot Jungle Island, Miami Florida
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Integrated Pest Management (IPM) program is evaluated, the use of beneficial
insects and disease-resistant plants are usually acknowledged as the main
tools of such a program.
methods, such as controlled watering, pruning, and mulching, are not covered
very well in texts about IPM (Yepsen 1985, Horn 1988, Olkowski et al 1991).
This article will attempt to show how cultivation techniques can aid in
pest and disease control.
the amount and quality of water a plant receives is important not only
from the aspect of plant growth but also to prevent insect and fungal
problems. Stress caused by wilting has the same effect as senescence.
Moisture deficiency accelerates leaf protein breakdown, causing an increase
in the nitrogen content of the phloem sap and in starch hydrolysis which
increases the sucrose content of the phloem (White 1984, Smith 1989).
These reactions have shown to be a critical factor in the population growth
of many insect herbivores (Holtzer et al 1988).
plants to wilt has shown an increase in the development and survival of
plant feeding aphids (Smith 1989). Stress through summer drought and excess
soil water in winter was implicated in the increased survival of larval
looper caterpillars (White 1974). Fungal problems in plant roots are often
caused by excessive watering and poor drainage which can be alleviated
by a more porous soil medium. High amounts of soluble salts can build
up in the soil due to poor water quality affecting plant health.Specimen
or bedding plants can be permanently grown in containers to allow the
horticulturist to change a display often without damaging the plants.
is insufficient light or cool temperatures causing damage, containerization
will facilitate the easy movement of the plant to the nursery where it
can be grown under optimum conditions. Because commercial soil mixes with
peat moss and pine bark tend to break down and hold water within a year
under tropical conditions, a special soil mix must be prepared. This helps
reduce fungal problems on the roots. Also since many tropical plants come
from acidic areas, these conditions must be duplicated in a medium that
will not readily break down. Well-broken down soil produced from a compost
pile, with some extra sand for better drainage, will do the job. Although
heavier than a commercial mix, this will not break down after a couple
cv. Orange Christmas
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plants to become potbound will improve drainage, further reducing fungal
problems. Many tropical plants including bromeliads, crotons, heliconias,
gingers, etc., will do very well under potbound conditions as long as
adequate water and fertilizer is supplied. Growth and reproduction of
herbivorous insects and mites is dependent upon the state of growth, or
level of soluble nitrogen, in their host plant (Price 1984, White 1984,
Dixon 1985). The onset of senescence brings about a breakdown of protein
to soluble amino acids in the senescening tissue. This soluble nitrogen
is translocated via the phloem to sites of storage (seeds) or new growth
and mites tend to specialize in the plant parts upon which they feed (Horn
1988). Phytophagous mites normally colonize senescent tissue to feed on
the nutritious phloem sap (White 1971, Shimonski 1991). Homopterans, as
a group, seem to be more versatile. Scale insects are mostly found on
older or senescent foliage, whereas aphids, tended by ants, are found
on new growth of inflorescences (personal observation on tropical plants).
pruning to control phytophagous mites and Homopterans is a viable tool
in the IPM program. It has been shown removal of presenescent foliage
on Musoid plants can control phytophagous mites almost to the point of
eliminating the use of chemical controls (Shimonski 1991). Controlling
aphids and scale on palms, as well as the subsequent sooty mold, can also
be achieved by selective pruning. Aphids are often found on inflorescences
being tended by ants. If the ants cannot be controlled, they will protect
aphids from predators and increase their rate of reproduction (Holldobler
and Wilson 1990). Removal of the inflorescence upon emergence will alleviate
this problem. Older or senescent fronds being colonized by scale or other
Homopterans should be cut off.
the green tissue from a plant obviously has its drawbacks. Reduced photosynthetic
surface and loss of stored nutrients will affect the growth of the plant.
In one study, complete removal of leaves had the effect of suppressing
reproduction in some tropical trees (Rockwood 1973). It has been shown,
however, that prior wounding by insect or mechanical means induces increased
resistance (inducible defenses) of many crop plants and trees to insect
damage through production of allelochemicals (Howe and Westley 1988),
complete leaf removal on transplanted Sabal palmetto palms has shown to
be the best method for transplanting this species (Broschat 1991). Chamaedorea
tepejilote palms responded to experimental defoliation by producing two
to three times more new leaves than did controls (Oyama and Mendoza 1990).
Selective pruning may not be the best method for controlling herbivorous
insects and mites on all plants but it seems to work well on tropical
T. (1991). Effects of Leaf Removal on Survival of Transplanted Sabal Palms.
University of Florida, IFAS TropicLine. Vol. 4, Number 3
(1985). Aphid Ecoloqy. Blackie and Son Ltd., Glasgow.
(1980). The Remobilization of Nutrients from Leaves. J. Plant Nutrit.
B. and E.O. Wilson. (1990). The Ants. Harvard University Press, Cambridge.
T.; T. Archer; J. Norman. (1988). Host Plant Suitability in Relation to
Waterstress in Plant Stress.
E.A. Heinrichs, ed. Wiley-lnterscience, New York.
(1988). Ecoloqical Approach to Pest Manaqement. The Guilford Press, NewYork.
and L. Westley. (1988). Ecoloqical Relationships of Plants and Animals.
Oxford University Press, New York.
W.; S. Daar, and H. Olkowski. (1990). Common Sense Pest Control. The Taunton
and A. Mendoza. (1990). Effects of Defoliation on Growth, Reproduction,
and Survival of Neotropical Dioecious Palm, Chamaedorea tepejilote.- Biotropica
(1984). Insect Ecology. Wiley-lnterscience, New York.
L. (1973). The Effects of Defoliation on Seed Production of Six Costa
Rican Tree Species. Ecology 54: 1363-1369.
J. (1991). An Integrated Pest Management Plan for the Control of Phytophagous
Mites (Tetranychidae) on Musoid Plants (Scitaminae). Heliconia Society
Int. Bulletin. Vol. 5, No. 2
(1989). Plant Resistance to Insects. Wiley-lnterscience, New York.
(1971). Lerp Insects (Homoptera, Psylliadae) on Red Gum (E. camaldulensis)
in South Australia, S. Aust. Nat. 46:20-23.
(1974). A Hypothesis to Explain Outbreaks of Looper Caterpillars with
Special Reference to Populations of Seidosema suavis in a Plantation of
Pinus radiata in New Zealand. Oecoloqia. 16:279-301.
(1984). The Abundance of Invertebrate Herbivores in Relation to the Availability
of Nitrogen in Stressed Food Plants. Oecoloaia. 63:90-105.
(1985). The Encyclopedia of Natural Insect and Disease Control. Rodale