Group Title: ARC-A research report - Agricultural Research Center-Apopka ; RH-78-1
Title: Soil insect pests in production of tropical foliage
Full Citation
Permanent Link:
 Material Information
Title: Soil insect pests in production of tropical foliage
Series Title: ARC-Apopka research report
Physical Description: 5 p. : ; 28 cm.
Language: English
Creator: Hamlen, R. A ( Ronald Alan ), 1940-
Agricultural Research Center (Apopka, Fla.)
Publisher: University of Florida, IFAS, Agricultural Research Center
Place of Publication: Apopka FL
Publication Date: 1978
Subject: Foliage plants -- Diseases and pests -- Florida   ( lcsh )
Soilborne plant diseases -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
Statement of Responsibility: R.A. Hamlen.
General Note: Caption title.
 Record Information
Bibliographic ID: UF00065907
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 70667082

Full Text


The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source

site maintained by the Florida
Cooperative Extension Service.

Copyright 2005, Board of Trustees, University
of Florida



R. A. Hamlen
University of Florida, IFAS
Apopka, FL 32703
ARC-Apopka Research Report RH-78-1

Important soil inhabiting insects that frequently are detected in the

production of ornamental tropical foliage plants are fungus gnats, root
mealybugs and springtails. These are the pests that too often escape

detection during production and then become an enormous problem for the

consumer after sale. This report contains information on their biology

and discusses practices useful in the prevention of these insect problems.

An additional insect, the sugarcane rootstalk borer weevil, is discussed

along with the importance of this pest to the Florida tropical foliage


FUNGUS GNATS Foliage growers frequently become concerned about the tiny

'black flies' that can become quite numerous under greenhouse conditions.
These flies are often the adult stage of the fungus gnat (Sciarids), a pest

that when present in quantity is a real threat to foliage plant production.

The adult is approximately 1/8 inch (3 mm) long and has a delicate pair of

wings, many-segmented, thread-like antennae and long dangling legs. Adults
are weak fliers and are most visible near or running over the soil surface

or even under leaves. The soil inhabiting, immature, legless larva is slender,

white with a black head capsule and is about 1/4 inch (6 mm) long during final

stages of larval development. The larvae are often visible on the soil surface

in the early morning and will rapidly move into the soil if disturbed. In many
species, larvae are saprophagous, feeding on fungi and decaying plant tissues;

however, a few species are primary pests of foliage plants and are capable of

feeding on uninjured plant roots, root hairs and lower stem tissues. Organic

soils of high moisture content or conditions of excessive irrigation appear

to enhance infestations, especially in the presence of decaying plant tissue.

Feeding can be particularly injurious to seedlings, rooted cuttings, or young

plants. Feeding injury also can predispose seedling plants to pathogenic

fungal attack. Peperomia and Schlumbergera appear quite susceptible to larval

feeding injury and severe losses can occur in infested propagation beds.

Injury usually begins at the soil surface and is characterized by destruction

of internal root, stem or leaf tissues with severely injured plants toppling

over onto the soil surface.

The common sciarids which are problems in foliage production are species

of the genus Bradysia. Adult female gnats live for approximately one week

and produce in the crevices of the soil surface 75 to 200 microscopic eggs

which hatch in 4-6 days. At 72F (220C) larval development continued for 2-3

weeks followed by a 4-6 day pupal stage in the soil or on the soil surface.

With increased temperatures, the time of the life cycle will decrease and

several generations will overlap.

Controls are usually directed against the larval stages by applications

of chemical drenches, soil surface sprays or granules to the infested soils

of bench or potted plants. Treatment of walk areas and the soil beneath

benches often will aid in control by reducing the potential for reinfestation

of crop areas due to adult migration. Aerosol applications also have been

effective when directed against adults providing applications are made every

few days over a several week period to eliminate overlapping adult stages.

There are, however, several preventative measures which if followed will

avoid in many cases the need for applications of toxic chemicals. These

preventative measures include: media pasteurization, the avoidance of

accumulating piles of plant debris or refuse, avoidance of over-watering,

careful inspection of plant material and soil media, and very importantly,

avoiding plant disease development.

ROOT MEALYBUGS In addition to the foliar mealybugs which are well known to

most nursery personnel, several small species (Rhizoecus spp. and Geococcus

sp.) approximately 1/16 inch (1-2 mm) long are found below the soil surface

and feed on root and root hair tissues. Infestations are often over-looked

until they are severe and widespread, causing reduced plant vigor, foliar

chlorosis and reduced growth. Careful examination of infested roots will

reveal white, cotton-like masses which contain both eggs and adult females.

Nymphs or immatures are active and may crawl from pot to pot via drainage

holes or are passively disseminated in irrigation water. Populations are

slow to develop and 3 to 6 months may be required before infestations are

easily detected. Populations of the root mealybug may become prevalent in

soil beneath infested plants thereby establishing a source for infestation

of future plantings. Numerous foliage species may become infested but critical

major hosts are Araucaria, Asparagus, Chrysalidocarpus, Chamaedorea, Peperomia,

Nephrolepis, Dieffenbachia, Philodendron, Syngonium, Hedera, Epipremnum, Ficus,

Schlumbergera, Dizygotheca, Hoya, Pilea, Cordyline, Chlorophytum and various


Again, control is largely dependent upon the use of chemicals, usually

applied as drenches or granules to infested soil. Applications are frequently

repeated so that both adults and newly hatched individuals are eliminated. It

must be remembered, however, that it is extremely difficult to free infested

plants of this pest. Careful planning and thorough execution of preventative

procedures is once again the most efficient approach to control. Effective

cultural methods that are essential in preventing infestation include: media


pasteurization; thorough inspection of the roots of newly acquired plants

prior to incorporation into your nursery; sanitation, i.e., no refuse piles

or maintaining of plants which have not responded to previous chemical

treatment; and the use of raised benches for all stock, propagation and

finishing operations. Placing of containers on clean or unused plastic

sheeting will aid in preventing infestations.

SPRINGTAILS Springtails or collembola are small insects usually less than

1/16 inch (1-2 mm) in length. All species are wingless, although certain

species possess a springing organ which enables individuals to jump when dis-

turbed. Springtails are rarely pests, although high populations are frequently

detected in highly organic potting soils, especially on the soil surface

following a thorough watering. The presence of springtails in potting media

frequently causes concern that this pest is injurious. Feeding of springtails,

however, is on organic material in soil and the occurrence of this pest is in

general an aesthetic problem.

SUGARCANE ROOTSTALK BORER WEEVIL Diaprepes abbreviatus (L.), the sugarcane

rootstalk borer weevil, is an important pest of sugarcane, citrus and ornamentals

in the West Indies. In 1964 D. abbreviatus was first detected in the United

States in central Florida. By 1977 ca. 49,000 acres (20,000 ha) of citrus as

well as several ornamental nurseries in central and south Florida were infested.

Adult weevils feed on newly developed foliage whereas the subterranean larvae

feed on root tissue and are the primary cause of plant injury and decline.

Infestations of nurseries result in quarantine restrictions with shipment of

container grown plant material outside of quarantine areas prohibited.

Previous studies for control of D. abbreviatus have included tests for suppres-

sion of adults by foliar insecticides, control of large (late instar) larvae

by insecticide dips, evaluations of ovicidal chemicals and laboratory screening

of insecticides against newly hatched neonatee) larvae. As neonate larvae

drop from oviposition sites within foliage to the soil surface, and then

migrate into soil, larvicidal chemicals contained within the upper levels

of the soil present the best method to prevent infestation. Preliminary

studies have indicated preventative insecticide applications are promising.

Efforts to eradicate late instar larvae from highly organic soils have not

been totally successful, a necessary requirement concerning this quarantin-

able pest. Chlordane is not an effective larvicide and currently heptachlor

is incorporated into soil media as a preventative to infestation. Acceptable

alternatives to the chlorinated hydrocarbons are needed as these chemicals

become limited in usability due to governmental restrictions. Because of the

potential economic impact of D. abbreviatus on the tropical foliage industry,

several cooperative studies between the USDA Weevil Laboratory and ARC-Apopka

have been underway since 1975 to determine alternative methods for certi-

fication of ornamental plant material free of D. abbreviatus infestations.

This public document was promulgated at an annual cost of $18.55 or
3.7 cents per copy to inform county and state extension personnel,
foliage growers, marketers and allied trades of research results
and improved practices in ornamental horticulture.


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