Pest and Disease Management for Crop Production inside Greenhouses

A.R. Syed
MARDI Cameron Highlands, 39000
Tanah Rata Cameron Highlands, Pahang
Malaysia

Keywords: greenhouses, protective cultivation, pest and diseases, biological control,

integrated pest management
Abstract
The warm humid conditions and the abundance of food in greenhouses and
protective structures are ideal for occurrence and development of pests and diseases.
Problems can be chronic unless recognized and corrected. There are several major
pests and diseases caused by living organisms belonging to several groups including
arthropods, acarina, mollusks and microbial causal organisms like fungi, bacteria
and viruses. The common and important pests are spidermites, thrips, whiteflies,
leafminers, aphids, lepidopteran larvae, slugs and snails. The common diseases of
economic importance include powdery mildew, downy mildew, damping-off, root
rots, late blight disease, gray mold, sclerotinia stem rots, and a wide range of viral
and bacterial diseases. There are several steps before control and management tactics
are employed for the reduction or elimination of the pest and disease problem in a
particular greenhouse or protective structure. The preliminary steps are (1) clean
production area, (2) select clean resistant quality seeds and plants, and (3) early pest
and disease detection with regular inspection using sticky and pheromone traps. The
next stage is to consider all management and control tactics available for the
particular pest and disease detected. The control options should take into considera-
tion economic aspects, toxicological and environmental effects of the management
tool to be employed. The control options available include (1) cultural, (2) physical,
(3) mechanical, (4) biological, and (5) chemical control. The more appropriate
approach in pest and disease management would be to utilize all possible options with
reduction of pesticide usage and making biological control as core component of the
management programme. This control tactic is generally termed as integrated pest
management or IPM.
INTRODUCTION
Crop production in greenhouses and protective structures has gained popularity in
many countries. This is evident by the increase in production area in several countries in
Europe, United States of America and Asia (Robinson, 1991; Jensen, 1999). The crops
grown generally are vegetables, ornamentals and fruit crops. In Europe, the Netherlands
has one of the biggest vegetable and ornamental crop industry under protective cultivation
with an area of 10,526 hectares. With the development in the last 10 years, China has
emerged to have the largest protective cultivation areas, 68,000 hectares in 1986 to 1.3
million hectares in 1999 (Cantliffe and Vansickle, 2003). There are several types of
protective structures developed and being continuously improved to adapt to
environmental conditions. In the tropics, protective structures generally are the naturally
ventilated types with plastic roofs often termed as rainshelters and netted structures and
modification and variations of the two types.
The advantages in protective cultivation of crops include virtual indifference to the
seasons, control of the environment necessary for crop growth, increase of yield and
quality of produce and ease of mechanization and automation in the greenhouses. The
advantages are further enhanced with the use of hydroponics over soil culture. The
additional benefits include better management of soil-borne pathogens, direct and
immediate control of nutrient requirements of the crop, increase of yields possible using
new cultivars especially bred for such systems, efficient use of space with high density

Proc. IS on Greenhouses, Environmental Controls & In-house Mechanization

for Crop Production in the Tropics and Sub-tropics 89
Eds. Rezuwan Kamaruddin, Ibni Hajar Rukunuddin & Nor Raizan Abdul Hamid
Acta Hort. 710, ISHS 2006
planting, better management in cleaning and sterilizing of the system to manage pests and
diseases, and higher quality of produce due to optimum use of nutrients.
The greenhouse or protective structure is a perfect habitat for many types of
arthropods and pathogenic microorganisms that cause damage and diseases on the
cultivated crops. Some of the common pests are whiteflies, aphids, thrips, spider mites,
snails, slugs, pathogenic fungi, bacteria and viruses. The cost of pest and disease
management was generally estimated to be in the range of $0.80USD to $1.00USD per
plant per growing season. It is therefore important for effective management of pests and
diseases to ensure high yields and profits.
MAJOR PESTS AND DISEASES
The major pests and diseases generally occurring in glasshouse and protective
cultivation are shown in Tables 1 and 2. The common pests are the two-spotted spider
mites, thrips, whiteflies, leafminers, aphids, lepidopteran larvae, snails and slugs. The
common fungal diseases are powdery mildew, downy mildew, damping off, late blight
disease of solanaceous crops, gray mould and sclerotinia stem rot. The virus diseases
commonly found were those spread by insects. These were impatiens necrotic spot virus
(INSV), cucumber mosaic virus (CMV), tobacco mosaic virus (TMV), tomato ringspot
virus (TomRSV), tomato spotted wilt virus (TSWV) and tobacco ringspot virus (TRSV).
The major bacterial diseases in greenhouses and in crops cultivated under protective
environment were black rots caused by several subspecies of Xanthomonas campestris,
bacterial leaf spot caused by Pseudomonas maculicola, bacterial soft rot caused by
Erwinia carotovora in vegetables and E. chrysanthemi in ornamentals, bacterial wilt
caused by Pseudomonas solanacearum and bacterial specks caused by P. syringae. A
short description of the major pests and diseases is given below.
Mites
The most important among the mites is the two-spotted red spider mite (TSRM),
Tetranychus urticae (Syed, 2004). The TSRM is a web-forming mite that pierces plant
cells and removes their content. It is easily identified by two distinct dark markings on its
abdomen. The life-cycle ranges from 8 days at temperatures above 25°C to 28 days at
temperatures below 18°C. The stippling and sucking of leaf juices cause the leaves to turn
yellow with bronzed or brown areas; damaged leaves frequently die. Infested plants are
generally stunted in growth. The TSRM attacks a wide range of vegetables, ornamentals
and strawberries (Kim, 2001; Coop et al., 1997).
The other important mite species in protective cultivation is the cyclamen mite,
Steneotarsonemus (Phytonemus) pallidus. The cyclamen mite is generally found along the
mid-vein of young unfolded leaves and under the calyx of newly emerged flower buds.
When populations increase, these mites may be found anywhere on non-expanded plant
tissue. They are less than 0.3 mm in size and not visible to the naked eye. Matured mites
are pinkish orange and shiny. They are a major pest of strawberry and ornamentals like
dahlia, geranium, chrysanthemum, begonia and snapdragon. Heavily infested plants are
stunted and crinkled resulting in a compact leaf mass in the center of the plant (Robb et
al., 2004; Zalom et al., 2004).
Thrips
The important thrips species in greenhouse cultivation are the western flower
thrips (WFT), Frankliniella occidentalis; the greenhouse thrips (GHT), Heliothrips
haemorrhoidalis; and the onion thrips (OT), Thrips tabaci (Robb et al., 2004). The WFT
has three colour forms; the pale form, which is white and yellow, the intermediate colour
form, which has a dark orange thorax and a brown abdomen, and the dark form, which is
dark brown in colour. The WFT usually feeds in enclosed tissues such as flowers, buds or
growing tips. Adults also feed on pollen and spider mites. The prepupa and pupal stages
take place in the soil beneath the infested plants. Development time to complete one
generation of the WFT varies from 11 days to 44 days depending on temperature

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(Driesche, 1999). The GHT is black in colour with whitish wings folded backwards and
produces a globule of fecal fluid at the tip of the abdomen. This fecal matter drops off
with a new one forming, resulting in characteristic spotting of the infested area with black
specks of fecal material. The OT is an important pest of onions. Its size is 0.5 to 1.2 mm,
its body is elongated, elliptical and slender. The immatures are wingless and found
between the young leaf blades at the top of the plant.
The WFT mainly feeds on flowers and sometimes on young leaves, whereas GHT
and OT feed primarily on leaves. Direct feeding damage includes streaking, spotting and
tissue distortion. The WFT and the OT can be vectors of tomato spotted wilt virus and
impatiens necrotic spot virus.
Whiteflies
The major species of whiteflies attacking crops in greenhouses are the greenhouse
whitefly, Trialeurodes vaporariorum; the silverleaf whitefly, Bemisia argentifolii; and the
tobacco whitefly, Bemisia tabaci (Robb et al., 2004). These species of whiteflies attack a
wide range of vegetable and ornamental crops and may cause extensive damage if not
controlled. The whiteflies are also vectors of viruses in many crops. The greenhouse
whitefly adult is 0.9 to 1.1 mm long with four wings, sucking mouthparts and a waxy
coating over the body. Eggs are laid on the underside of leaves, initially yellowish and
closer to hatching turning purplish brown. The first nympal instar is called the crawler
and has functional legs while the remaining instars are attached to the underside of the
leaf and do not move. The generation time of the greenhouse whitefly is 21 to 26 days at
15 to 20°C. The silverleaf whitefly, B. argentifolii is smaller than the greenhouse whitefly
measuring 0.8 to 1.0 mm long. The silverleaf whitefly completes its development from16
to 31 days depending on the environmental temperature.
Whitefly adults and immatures feed on plant sap. As they feed, they excrete
honeydew, a sticky substance that causes unsightly glistening and supports the growth of
black sooty mold on the leaves and fruits. Feeding by the silverleaf whitefly also causes
uneven ripening of tomato fruits. Very large populations of whiteflies cause stunting of
plant growth, and leaves may senesce and die. In recent years, the greenhouse whitefly
has been found to be a vector of tomato infectious chlorosis virus, a virus capable to cause
heavy crop losses. The whiteflies also transmit geminiviruses such as tomato yellow leaf
curl, which may cause high losses in greenhouses (Zalom et al., 2004).
Leafminers
The common leafminers are the serpentine leafminer, Liriomyza trifolii; pea
leafminer, Liriomyza huidobrensis; vegetable leafminer, Liriomyza sativae; and the
garden pea leafminer, Chromatomyia horticola (Jones et al., 1986; Alverson et al., 1982).
Leafminer adult flies are small measuring about 1.8 mm, yellow and black in colour with
clear wings. Females insert their eggs within the leaf epidermis by puncturing the leaf
surface with their ovipositor. The punctures are also feeding sites when eggs are not laid.
Eggs hatch and the larvae mine below the epidermis, increasing in size as they grow.
Larvae have three instars like most dipteran flies. Pupation occurs in the soil or any
surface below the infested plants. The garden pea leafminer pupates in the leaf mines. The
life cycle of most species ranges from 14 to 25 days depending on the temperature (Robb
et al., 2004; Zalom et al., 2004).
When populations are high, stippling, caused by females puncturing the leaves
with their ovipositor to feed and lay eggs, can be serious. However, most of the damage is
caused by the larvae in the mines. Heavy infestation results in leaves with large white
blotches that detract from the aesthetic value of the crop. Leaves injured by leafminers
drop prematurely; heavy infested plants may lose most of the leaves, and if this occurs
yields may be affected.

Aphids
Numerous species of aphids infest economic cultivated crops, however, the most

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common and important species are the melon aphid, Aphis gossypii; the green peach
aphid, Myzus persicae; and the potato aphid, Macrosiphum euphorbia. Melon aphids are
typically dark green with red eyes and antennae. The green peach aphids vary in colour
from yellowish green to rose pink. Aphids exhibit polymorphism. This means that the
adults may be winged (alates) or wingless (aptera), depending on the circumstances.
Alates generally occur when there is overcrowding or when there is a change of host
plant. They can then move to another plant. Aphids give birth young, generally when they
are 7 to 10 days old (Robb et al., 2004).
Aphids like whiteflies excrete honeydew, a sweet, sticky substance that they
produce as they feed on the plants. Black sooty mold grows on the honeydew and this
detracts the appearance of the plant and fruits. Heavy feeding can cause the foliage to
become yellow, and feeding on newly developing tissues can cause those parts to become
twisted and deformed. The melon aphids are known to transmit 44 plant viruses, while the
green peach aphids are known to transmit more than 100 plant viruses (Greer, 2000).
Lepidoptera
This group of insects are the moth and butterflies. The most important
lepidopterans infesting greenhouse and protective crops are the diamondback moth,
Plutella xylostella; beet armyworm, Spodoptera exigua; cabbage looper, Trichoplusia ni;
and the fruit borers, Helicoverpa spp. and Maruca testulalis (Robb et al., 2004). This
group undergoes four life stages; the egg, the caterpillar (larva), the pupa and the adult.
The eggs are laid on the leaves or glass or any greenhouse material, usually in groups or
singly. The larva has a well-developed head with strong biting and chewing mouthpart,
and feeds vigorously generally on foliage (Robb et al., 2004). The fruit borers like
Helicoverpa spp. and Maruca testulalis bore into the fruits and pods and sometimes
remain inside until time for pupation. Pupation generally occurs in the soil or any suitable
place to spin a cocoon. The generation time of this group varies with species and the
surrounding temperatures. As an example the diamondback moth takes 14 days in the
humid tropical lowland areas, and takes about 28 days in the cool highland areas.
Slugs and Snails
Slugs and snails are the most bothersome pest in many greenhouses and protective
structures like rainshelters and netted houses. The common species are the brown garden
snail, Helix aspersa; white garden snail, Theba pisana; gray garden slug, Agriolimax
reticulates; and field slug, Deroceras reticulatum. The biology of the slug and snail is
similar, except the slug lacks the snail’s external spiral shell. Slugs and snails are
hermaphrodites, so all have the potential to lay eggs. Slugs and snails are most active at
night and on cloudy or foggy days. On sunny days they seek hiding places out of the heat
and light, often the clue to their presence are their silvery trails and plant damage. In the
tropics the slugs and snails are active throughout the year.
On plants they chew irregular holes with smooth edges in leaves and flowers and
can clip succulent plant parts. They are also a serious pest of ripening fruits such as
strawberries and tomatoes (Flint, 2004; Speiser et al., 2001).
Powdery Mildew
Powdery mildew is the name given to diseases resulting from infection by fungi
that produce a white, powdery appearance on the surface of leaves, stem and flower buds.
The common fungi as causal agents of this disease are Erysiphe spp., Sphaerotheca spp.
and Oidium neolycopersici. Some of the fungi that cause the disease are highly specific in
nature in terms of pathogenicity. For example, the powdery mildew that infects squash
plant will infect plants from the cucurbit family, but will not infect roses, and the powdery
from roses will not infect zinnias and vice versa, although the fungus that infects zinnias
also infects many other members of the compositae family. The powdery mildew fungi are
obligate parasites; that is they can only grow on living plant tissue. When the infected plant
part dies so does the fungi, unless the fungi resting spores are formed (Davies et al., 2004).

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 Powdery mildews are favoured by warm days and cool nights and moderate
temperatures (15 to 22°C). Greenhouse conditions are usually ideal for the development
of the powdery mildew fungi (Raabe et al., 2004).

Downy Mildew
The common fungi species causing downy mildew are Peronospora spp. and
Plasmopara spp. The name downy mildew is somewhat a description of the appearance
of the white, tan, lavender and purple colouration that occurs on the underside of infected
leaves. Downy mildew infections are sometimes angular in shape and delimited by veins.
When young shoots are infected the resultant growth is stunted, malformed and
discoloured. The downy mildews are more specific as to hosts than the powdery mildews,
but the big difference between the two organisms is that downy mildews require very wet
conditions to flourish. Spores of the fungi usually are short-lived and infection occurs 8 to
12 hours after contact with a suitable host. The fungi produce sexual spores that can
survive dry conditions, without the host. Growth of the disease is favoured by moist and
cool conditions of 10 to 20°C (Raabe et al., 2004).
Damping-off and Root Rots
The most common fungi that cause damping-off and root rots are Rhizoctonia
solani and Pythium spp. The fungi attack juvenile tissues such as the root tip. After
gaining entrance to the root the fungus may cause a rapid black rot of the entire primary
root and may even move up the stem tissue. The situation is brought about by poor soil
drainage or excess irrigation. Rhizoctonia can cause disease under somewhat drier and
warmer conditions. The fungus causes serious problems on young germinating seedlings.
Pythium can survive for long periods in soils and substrates in the form of sexual resting
spores called oospores. Some species form non-sexual resting spores called
chlamydospores, which can survive under adverse conditions (Raabe et al., 2004).

Late Blight Disease

The late blight disease is caused by a fungus, Phytophthora infestans. This fungus
attacks all solanaceous crops like tomato, capsicum and potato. It is one of the most
serious diseases of tomatoes grown in greenhouse and protective structures. Leaf
symptoms of late blight first appear as small, water-soaked areas that rapidly enlarge to
form purple-brown, oily-appearing blotches. On the lower side of the leaves, rings of
grayish white mycelium and spore-forming structures may appear around the blotches.
The entire leaf dies and infection quickly spreads to the petioles and stems. Infected fruits
e.g. in tomato, turn brown but remain firm unless infected with secondary organisms. Late
blight is found when humid conditions coincide with mild temperatures for prolonged
periods. When humidity is above 90% and the average temperature is in the range of 14 to
18°C, infection occurs in about 10 hours. The fungus overwinters in plant parts and
possibly in the soil. The infectious spores of the fungus are easily spread by wind to other
plants (Davies et al., 2004; Syed et al., 2003).

Gray Mold
The gray mold disease is caused by a fungus, Botrytis cinerea. It is one of the most
destructive plant pathogens and attacks a wide variety of plants. Fruits that are ripening
are particularly susceptible to infection. Under condition of high humidity, the fungus
sporulates on infected tissue and produces masses of characteristic gray or brownish
spores that become airborne and are the primary means by which the fungus is dis-
seminated. With the presence of moisture the spore germinates and starts a new infection.
Botrytis does not invade healthy leaves unless an injured or dead area is present. Botrytis
causes wet lesions on most cultivated flower petals resulting in huge losses to the
floriculture industry. The optimum temperature range for growth of the fungus is 18 to
22°C (Raabe et al., 2004).

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Sclerotinia Stem Rot
The sclerotinia stem rot is caused by the fungus, Sclerotinia sclerotiorum. The
fungus attacks a wide range of vegetables including crucifers, eggplant, tomato, lettuce
cucumber and squash. In greenhouses it is a disease of tomatoes. It occurs during moist,
cool periods. The disease can be recognized by a soft watery rot with white, moldy
growth on stems, petioles, and leaves. If condition remains moist, a large amount of
cottony, moldy growth can be seen on the dead tissue. As this growth progresses, hard
black, irregularly shaped bodies called sclerotia form on the surface or in the pit of the
stem. The fungus overwinters as sclerotia in the soil and may survive up to 7 years in dry
soil. When moisture and temperature are suitable the sclerotia form many mushroom-like
bodies called apothecia. The apothecia produce an enormous number of spores that are
blown about and cause primary infections. Disease is dependent on high moisture and
cool temperature (15 to 20°C) (Averre, 2000).

Virus Diseases
Virus diseases of crops grown in greenhouse and protective structures result in
substantial economic losses to growers each year. There are several varieties of viruses
that can infect the crops, which are transmitted from plant to plant by insects. The
common virus diseases are impatiens necrotic spot virus (INSR), cucumber mosaic virus
(CMV), tobacco mosaic virus (TMV), tomato ringspot virus (TomRSV), tobacco ringspot
virus (TRSV) and tomato spotted wilt virus (TSWV). Symptoms are associated with
viruses and the host that is affected (Nameth, 2004). The same virus can cause different
symptoms in different hosts. Symptoms such as mosaic, ringspot, necrotic spot, leaf
blistering and deformation are all symptoms associated with plant viruses. Other
symptoms like yellowing, stunting and wilting may be confused with other plant diseases
caused by other causal agents or physiological disorders. The typical symptoms of the
viral diseases need to be clearly recognized (Averre et al., 2000).

Bacterial Diseases
Bacterial diseases are not as common as fungal diseases, but they can be very
destructive and are difficult to control in the greenhouse and in protective structures. The
common bacteria that cause the diseases are Xanthomonas campestris (several sub
species), Pseudomonas solanacearum, P. maculicola, P. syringae and several species of
Erwinia. Xanthomonas campestris generally causes black rots and bacterial blights e.g.
black rot of cabbage and Xanthomonas blight of geraniums. The Pseudomonas spp.
causes bacterial wilt of several vegetables and ornamentals. Most species of Erwinia
cause soft rots of vegetables and ornamentals (Chase, 1999).

MANAGEMENT AND CONTROL OF PESTS AND DISEASES

A pest management programme should be designed to meet a specific production
objective. In greenhouse production, this objective is usually to produce undamaged pest
and disease free plants. However, in some cases the objective may be to produce
pesticide-free produce. This may allow for some tolerance of minor insect or disease
damage. It is also important to determine the requirements of the clients, for example,
production of ornamental plants and cut-flowers may require absolutely undamaged
plants and flowers, therefore requiring complete control of pests and diseases. In any
case, it is also important to consider control strategies to use low-toxicity pesticides in
regard to the potential contamination of the environment and non-target organisms. There
are several steps that need to be considered before selecting a particular control tactic for
the management of pests and diseases. The steps are:
Clean Production Area
The first step to take in a pest management programme is preventive, and starting
with a clean production area is essential. Greenhouses can be fumigated or otherwise
treated prior to establishment of a new crop to help eliminate pest and disease problems

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from the previous crop. Proper cleaning and sanitation includes removal of debris from
the growing area to eliminate some of the sites that harbour pests and causal organisms.
Weed control in and around the greenhouse and protective structure areas eliminates
alternate host plants for pests and diseases.

Quality Seeds and Plants

The selection of non-infested plants, plugs, cuttings or transplants is critical.
Proper inspection of all planting material is essential, and plants that do not meet the
required specification need to be discarded. When possible, resistant or tolerant cultivars
need to be used to reduce pesticide usage.
Monitoring of Pests and Diseases
Pests and diseases detection procedures need to be established as an early warning
system. There are several tools for the monitoring of pests in a cropping cycle. These
include yellow and blue sticky traps, pheromone traps and visual inspection (Syed et al.,
2001). The yellow sticky traps are suitable for use to monitor movement and populations
of aphids, whiteflies and leafminers (Sivapragasam and Saito, 1986). The blue sticky
traps were found to be more suitable for thrips. Sex pheromone traps were used to
monitor populations of moth and butterfly pests. Regular inspection of plants is also a
form of monitoring. This method is also useful for the detection of early symptoms of
diseases (Robb et al., 2004).
TYPES OF CONTROL AND MANAGEMENT TACTICS

Cultural Control
Cultural control involves providing the conditions that favours the growth,
development and health of the crop, and wherever possible, providing conditions that
work against pests and diseases. Many disease causing fungi and bacteria require moist
conditions for disease development, therefore, maintaining the environment below 85%
relative humidity will help escape or avoid disease problems. This can be achieved by
avoiding wet conditions in the greenhouses, e.g. wet floors, and improving ventilation and
air circulation systems. Proper plant pruning and spacing provide good aeration for the
plants and reduce humidity at the micro-climate level.
Good sanitation is another aspect of cultural control. All crop debris and weeds
should be removed promptly. Pruning tools and other equipments should be cleaned and
disinfected on a regular basis to avoid spread of viral and bacterial diseases.
Physical and Mechanical
Pest infestation can be physically manipulated with light, humidity and
temperature. In greenhouse planting, light quantity and quality affect plant health and
indirectly influence pest population and their damage. For example, ‘bug’ lights used
around plants will not attract insects such as moths, crickets and june beetles. Manipula-
tion of temperature within greenhouses to reduce disease occurrence and increase success
of introduced biological control agents was found to be effective in some cases. There are
several mechanical methods to suppress pests. Screens can exclude pests in greenhouses
or net-houses. High pressure water spray can effectively dislodge spider mites and some
aphids from plants. Traps may be used not only as monitoring device, but also to reduce
populations of pests in an enclosed environment as in greenhouses and net-houses.
Biological
The term biological control refers to the use of natural enemies to suppress pests
to levels below the economic injury level. The goal is to establish a balance between the
pest population and its predators and parasitoids to keep the pest population under
control. Complete eradication of pest is not the goal, a certain level of pest needs to be
present to maintain the natural enemies population. The greenhouse industry has a well

95
established reputation for using biological pest control agents more than any other crop
production industry (Moschetti, 2003; Gilkeson, 1984). The reason for this is that the
growers can manage the environment to favour the biological control agent. The high
value of the greenhouse produce is another reason why the use of biological control is
economical in greenhouse crops. The use of biological control has led to the reduction of
pesticide usage and the industry leads in environmentally responsible, intensive care
production (Robb et al., 2004). A good example would be the use of predator mites,
Phytoseiulus persimilis to control the two-spotted red spidermite, Tetranychus urticae in
several countries (Kim, 2001). The natural enemies of the major pests in greenhouse
crops are given in Table 1.
Effective biological control of diseases is a more difficult goal to achieve and to
date few were successful. However, studies using the fungi, Trichoderma and other
microbial natural enemies to manage some of the diseases hopefully will be available in
the near future.
Chemical
Pesticides are important tools in the control of pests and diseases in crops. There
are a wide range of pesticides available for this purpose (Heng et al., 1994). Pesticides are
popular amongst farmers because they are effective, easy to use and available easily in the
market. The disadvantages of pesticides are that they pollute the food produce, the
environment, kill non-target organisms and sometimes result in secondary pest outbreaks.
The unilateral approach of pesticide dependency has also led to the development of
pesticide resistance in many pests. Pesticides should be used when necessary in
combination with other control tactics available (Syed, 1990).
Integrated Pest Management (IPM)
IPM involves the integration of cultural, physical, biological and chemical
practices to produce crops with minimal use of pesticides (Greer and Davis, 1999). The
primary goal of IPM is to optimize pest control in an economically and ecologically
sound way. IPM will utilize monitoring, sampling and record keeping to determine when
control options are needed to keep pest populations below the economic injury level. A
good example would be the development and implementation of IPM for the
diamondback moth, Plutella xylostella in Cameron Highlands, Malaysia (Syed et al.,
1996).
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 Tables
Table 1. Major pests of crops cultivated in greenhouses and protective structures.

Pest Common species Crops Pesticides Biological control agents

Mites Two spotted spider mites Vegetables, Cinnamaldehyde, methiocarb, Predatory mite, Phytoseiulus persimilis,
(Tetranychus urticae) ornamentals, hexythiazox, bifenazate, Amblyseius spp.;
strawberries abamectin, neem oil, dicofol, Metaseiulus spp.;
fenbutinexide, bifenthrin, Neoseiulus spp.;
fluvalinate, pyridaben, lacewings, Chrysoperla spp.;
chlorfenapyr, insecticidal potash predatory cecidomyiid, Feltiella spp.
soap
Thrips Western flower thrips Vegetables, Cinnamaldehyde, pyrethrin, Fungus, Beauveria bassiana;
(Frankliniella occidentalis); ornamentals methiocarb, azadirachtin, predatory mites, Neoseiulus degenerans,
Greenhouse thrips abamectin, imidacloprid, neem N. cucumeris, Hypoaspis miles, H. aculeifer;
(Helicothrips haemorrhoidalis); oil, endosulfan, acephate, predatory bugs, Orius insidiosis, Orius spp.
Onion thrips chlorpyrifos, insecticidal potash
(Thrips tabaci) soap, spinosad
Whiteflies Greenhouse whitefly, Vegetables, Pyrethrin, azadirachtin, Fungus, Beauveria bassiana &
(Trialeurodes vaporariorum); ornamentals novaluron, pyriproxyfen, Verticillium lecanii;
Silverleaf whitefly, abamectin, imidacloprid, neem parasitic wasp, Encarsia formosa &
(Bemisia argentifolii); oil, endosulfan, acephate, Eretmocerus californicus;
Tobacco whitefly, malathion, whitefly destroyer, Delphatus pusillus;
(Bemisia tabaci) chloropyrifos/cyfluthrin, green lacewing, Chrysoperla carnea
bifenthrin, cyfluthrin, fluvaline,
permethrin
Leafminers Serpentine leafminer, Vegetables, Azadirachtin, cyromazine, Parasitoid wasp, Chrysocharis paksi,
(Liriomyza trifolii); ornamentals novaluron, pyriproxyfen, C. pentheus, Opius pallipes, Hemitarsenus
Pea leafminer, abamectin, imidacloprid, varicornis, Diglyphus begini, Diglyphus isaea,
(L. huidobrensis); acephate, chlorpyrifos, Dacnusa sibirica
vegetable leafminer, permethrin, chlorfenapyr,
(L. sativae); spinosad
garden pea leafminer,
(Chromatomyia horticola)

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 Table 1 (continued). Major pests of crops cultivated in greenhouses and protective structures.

100
Pest Common species Crops Pesticides Biological control agents
Aphids Melon aphid, Vegetables, Cinnamaldehyde, pyrethrin, Fungus, Beauveria bassiana &
(Aphis gossypii); ornamentals methiocarb, azadirachtin, Verticillum lecanii;
Green peach aphid, pyriproxyfen, imidacloprid, predator lacewing, Chrysoperla spp.;
(Myzus persicae); neem oil, horticultural oil, gall-midge, Aphidoletes aphidimyza;
Potato aphid, endosulfan, acephate, hymenopterous parasitoids, Aphidius spp.,
(Macrosiphum euphorbiae) chlorpyrifos, bifenthrin, Lysiphlebus testaceipes, Diaerectiella rapae,
delthmethrin, fenpropathrin, Aphelinus abdomenalis
lambda-cyhalothrin,
pymetozine, insecticidal potash
soap
Lepidoptera Diamondback moth Vegetables, Pyrethrin, azadirachtin, Bacteria, Bacillus thuringiensis kurstaki,
(Plutella xylostella); ornamentals diflubensuron, novaluron, B. thuringiensis aizawai;
beet armyworm, tebufenozide, acephate, egg parasitoids, Trichogramma spp.;
(Spodoptera exigua); chlorpyrifos, bifenthrin, parasitoid wasp, Cotesia spp.,
loopers, cyfluthrin, deltamethrin, Diadegma spp., Microplitis spp.;
(Trichoplusia ni), fluvalinate, permethrin, insect viruses, Nucleapolyhedrosis viruses
(Chrysodeixis chalcites); spinosad, abamectin, neem oil, (NPV), Granulosis viruses (GV)
fruit borers, indoxacarb
(Heliothis armegera)
(Maruca testulalis)
Slugs and Common garden snail, Vegetables, Snail and slug metaldehyde baits Nematodes, Phasmarhabditis hermaphrodita
Snails (Helix aspera); ornamentals,
white garden snail strawberries
(Theba pisana);
gray garden slug
(Agriolimax reticulates);
field slug,
(Deroceras reticulatum)

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 Table 2. Major diseases of crops cultivated in greenhouses and protective structures.

Diseases Pathogen/causal agent Crops Pesticides Other control methods

Powdery mildew Erysiphe spp; Vegetables, myclobutanil, sanitation,
Sphaerotheca spp.; ornamentals azoxystrobin, ventilation
Oidium neolycopersici fenarimol,
triadimefon,
thiophanate-
methyl,
propiconazole,
potassium
bicarbonate,
sulfur
Downy mildew Peronospora spp.; Vegetables, mancozeb, sanitation,
Plasmopara spp. ornamentals copper 50%, ventilation
fosetyl-al
Damping-off/ Rhizoctonia solani; Vegetables, mefenoxam, seed treatment with
Root rot/ Pythium spp. ornamentals prodione, PCNB, Streptomyces
Soil pathogens triophanate- griseoviridis,
methyl, Trichoderma spp.,
trifumizole soil solarization,
soil heating,
soil fumigation
Late blight disease Phytophthora infestans Solanaceous azoxystrobin, resistant cultivars,
crops chlorothalonil, sanitation
pyraclostrobin,
maneb

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Table 2 (continued). Major diseases of crops cultivated in greenhouses and protective structures.

Disease Pathogen/causal agent Crops Pesticides Other control methods

Gray mold Botrytis cinerea Vegetables, fenhexamid, sanitation,
ornamentals, azoxystrobin, ventilation,
strawberries iprodione reduce humidity
(drench),
thiophanate-
methyl (drench),
chlorothalonil,
mancozeb
Sclerotinia stem rot Sclerotinia sclerotiorum Vegetables botran, sanitation,
chlorothalonil soil fumigation
Viral diseases Impatiens ecrotic spot virus; Vegetables, vector control sanitation,
(spread by vectors, Cucumber mosaic virus; ornamentals with pesticides, clean seed and stock,
aphids, mites, whiteflies, thrips). Tobacco mosaic virus; weed control resistant varieties
Some virus also spread mechanically. Tomato ringspot virus; with herbicides
Tomato spotted wilt virus;
Tobacco ringspot virus
Bacterial diseases Xanthomonas campestris Vegetables, copper sanitation,
(several subspp.); ornamentals compound clean planting materials,
Pseudomonas solanacearum; seed treatment,
P. maculicola; ventilation,
P. syringae; resistant varieties
Erwinia (several) spp.

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