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5 Cultural/Physical/mechanical control and sanitary measures

5 Cultural/Physical/mechanical control and sanitary measures

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624



usually are required to achieve satisfactory suppression, especially when dealing with overlapping generations. Although very few (if any)

insecticides are able to penetrate the waxy covering of mealybugs, those containing ethyl alcohol

(ethanol), such as some oil-based insecticides,

may allow the material to penetrate through the

waxy covering, killing mealybugs. When applying high-volume sprays, thorough coverage is

imperative, especially when using contact insecticides, because mealybugs are commonly

located in areas that are not easily accessible,

such as the base of leaf petioles, leaf sheaths, and

leaf undersides. Adding a spreader-sticker to a

spray solution may be helpful in improving coverage and penetration. For highly susceptible

plants, it may be prudent to routinely spray with

either an insecticidal soap or horticultural oil to

prevent mealybug populations from reaching

outbreak proportions. Also, it is essential to make

multiple applications when crawlers are present,

because eggs will hatch (with the exception of the

long-tailed mealybug) over an extended time

period. Insecticides classified as reduced-risk

include insecticidal soaps, horticultural oils, insect

growth regulators, and systemic insecticides.

Insecticidal soaps are usually solutions of a

synthetic pyrethrin and a plant-safe detergent. As

with oils, the detergent acts as a surfactant and

spreader for dispersing the pyrethrin evenly, and

as a mild caustic against the insects. Pyrethrins

are synthetic analogs of pyrethrum, the natural

extract from certain Asteraceae. Caution should

be urged with the so-called “safe” insecticidal

soaps, as some plants are sensitive, particularly

tender new tissues.

Horticultural oil, neem oil, and mineral oil are

effective for mealybug suppression. Horticultural,

mineral, or neem oil solutions smother the

insects; so, complete coverage of all sprayed

plants is essential. These oils are mixed with

water and usually a plant-safe detergent for

enhancing the spreading and sticking of the oil.

The main caution with these oil solutions is that

they should never be applied to plants on hot

days or in direct sunlight, as to prevent burning of

tissues. Also, to prevent sun-burning, the chemical should be applied and allowed to dry in shade.



K.G. Pillai



Growth Regulators and Chitin Inhibitors are

classes of insecticides that have some potential

for mealybug management. The insect growth

regulator (IGR) buprofezin was not decisive;

however, the IGR pyriproxyfen and the insecticide flonicamid were not directly or indirectly

harmful to the predator C. montrouzieri and parasitoid L. dactylopii, indicating that these insecticides are compatible with both the natural

enemies when used together for the control of

citrus mealybug in greenhouses and conservatories (Cloyd and Dickinson 2006).

Systemic insecticides, those that move

throughout plant parts, may also be used to

protect plants from mealybug infestations.

Applications should be initiated early in the cropping cycle or before introducing the plants into

interiors. Systemic insecticides may be applied as

either a growing medium drench or granule. It is

important to avoid overwatering plants afterward, so that the roots can absorb the active

ingredient. Systemic insecticides, depending on

the type, may be less effective on mealybugs than

on aphids or whiteflies. This may be associated

with mealybugs not ingesting lethal concentrations of the active ingredient, because they feed

within the mesophyll tissues or on plant stems.

The use of insecticides is the most effective

control against the mealybug when applications

are timed to coincide with the crawler stage. In

greenhouse tests, acephate, oxydemeton methyl,

and kinoprene suppressed populations of both

mealybug species and prevented crop damage.

Overall reductions of Rhizoecus floridanus

(Hambleton) by kinoprene and Ro 10–3108 were

comparable to the insecticides acephate and

oxamyl (Hamlen 1977). In greenhouse against

P.solenenopsis on coleus Solenstemon scutellarioides, soil drenching with thiamethoxam, a

neonicotinoid-based insecticide, provided the

highest mealybug control (Willmott 2012).

When using pesticides, nymphs are easier to

control than mature mealybugs. Insecticides used

for mealybug control should be rotated to minimize resistance buildup. Insecticides should be

applied using a sprayer that provides complete

spray coverage of plant. Particularly for mealybugs, it is important to totally wet the entire plant,



68 Glasshouse, Greenhouse and Polyhouse Crops



including the basal portion. All pesticide labels

should always be read and followed.

The following insecticides are registered for

use against mealybugs in greenhouses:

Acephate, Acetamiprid, Azadirachtin, Beauveria

assiana, Bifenthrin, Buprofezin, Chlorpyrifos,

Cyfluthrin,

Dinotefuran,

Fenoxycarb,

Fenpropathrin, Flonicamid, Imidacloprid,

Kinoprene, Paraffinic oil, Petroleum oil,

Potassium salts of fatty acids, Spirotetramat,

Thiamethoxam.



68.7



Biological control



With some of these chemicals facing phase-out,

and with the rising environmental and economic

concerns surrounding chemical control tactics,

biological control presents a promising alternative to chemical control for greenhouse ornamental growers. The waxy covering may be the

reason for the rare occurrence of pathogens and

nematodes as major infesting agents of the

mealybug (Franco et al. 2009). Still, biological

control of greenhouse pests through introduction

of natural enemies offers a viable alternative to

chemical controls. The use of biological control

agents such as parasitoids and predators has been

successful in managing mealybugs, primarily citrus mealybugs, under specific crop production

systems and interiorscapes. Biological control of

mealybug in greenhouse production relies on

augmentative releases of parasitoids and predators. Biological control agents that are available

commercially include a variety of tiny parasitic

wasps, brown lacewings, green lacewings, and

lady beetles. Some of the commercially available

mealybug natural enemies are the parasitoids

Anagyrus pseudococci (Girault), Leptomastidea

abnormis (Girault) and L. dactylopii (Howard)

(all Hymenoptera: Encyrtidae) for P.citri, and the

predator Cryptolaemus montrouzieri (Mulsant)

(Coleoptera: Coccinellidae) for many mealybug

species (Chong and Oetting 2007).

Biological control in greenhouse ornamental

production is characterized by the diversity of

plants and pests. A biological control program

for one pest must be compatible with the produc-



625



tion practices and the management program

against another pest. The nontarget effects of a

biological control agent on other beneficial or

nonpest organisms have to be investigated. The

most suitable host stages may achieve higher

rates of parasitism, survival and development,

and produce a higher number of progeny consisting of mainly female parasitoids. The mean temperature of the greenhouse should be maintained

at 15 to 30 °C for the parasitoids to achieve the

highest developmental rate. Choosing the appropriate release time and environmental conditions

can enhance the establishment and effectiveness

of the parasitoid population. The parasitoids can

be released as an inundative or seasonal inoculative biological control agent when the mealybug

population level is low. When the mealybug population is high, chemical control may be required to

reduce the mealybug population below the damaging level, before the parasitoids can be released.

Insecticides of choice may include insect growth

regulators and other compatible chemicals.



68.7.1 Planococcus citri

Biological control agents currently available for

suppression of citrus mealybug populations

include the predatory ladybird beetle,

Cryptolaemus montrouzieri, commonly referred

to as the “mealybug destroyer,” and the parasitoid, Leptomastix dactylopii. The larval stages of

the mealybug destroyer resemble mealybug

adults. L. dactylopii females only attack the third

instar and young adult female life stages. Both

the natural enemies are effective in suppressing

or regulating citrus mealybug populations, and

they can be used together under certain systems

and situations. Doutt (1952) demonstrated that

the mealybug P. citri could be successfully controlled on gardenias by two encyrtid parasites

(Leptomastix dactytopii and Leptomasiidea

abnormis) and the ladybird Cryptolaemus

montrouzieri Mulsant. One of the difficulties

encountered in the use of a predatory insect as an

agent of pest control is that the near eradication

of the host, in this case mealybugs, is followed

by the disappearance of the predator. This

necessitates reintroduction of the natural enemy.



K.G. Pillai



626



The parasitic wasps Leptomastix dactylopii and

Anagyrus pseudococci are commercially available for the control of citrus mealybugs.

Generalist predators, such as green lacewings

Chrysoperla spp., and a mealybug predator

Cryptolaemus montrouzieri are also marketed as

biological control agents of mealybugs.

Cryptolaemus montrouzieri is highly effective in

the control of mealybugs in greenhouses.

Cryptolaemus has also been often used to control

the mealybugs in glasshouses. The temperature

has to be above 20 °C in the glasshouse, and the

mealybug infestation should be great enough to

provide adequate food for the predator (Panis and

Brun 1971). Planococcus citri on gardenias and

Phenacoccus gossypii on chrysanthemum were

controlled effectively by the release of C. montrouzieri. One adult per plant of gardenia and one

for each two chrysanthemum plants were

released. C. montrouzieri was recommended to

compliment L. dactylopii for the control of ornamentals in the glasshouse. Good control of P.

citri on Clivia and crotons, and reasonable control on Pelargonii, Saintpaulia, Cattleya, and

Pilea were observed (Copland et al. 1985). C.

montrouzieri was used to control P. citri on the

crops grown in glasshouses (Lagowska 1995). In

the green net house, Cryptolaemus, when released

at 20 larvae/plant, was found highly effective in

clearing the mealybugs P. citri on the ornamentals red ginger, Heliconia, etc. within 2 months of

its release in India. In Canada, C. montrouzieri

was found in greenhouses on P. citri and P. gossypii (McLeod 1939). P. citri is the major pest of

ornamental citrus plants in greenhouses. A

predator:prey ratio of 1:15, in most cases, resulted

in lower populations of P. citri. When compared

with Nephus reunioni (Fursch), C. montrouzieri

caused a significant reduction in the mealybug

population. In most cases, significant differences

in pest reductions were not detected between C.

montrouzieri and methidathion on potted orange

plants (Hamid and Michelakis 1994; 1997).

In a commercial greenhouse in Leiden,

Netherlands, biological control of the pseudococcid P. citri on Stephanotis plants was carried out

with the coccinellid predators Cryptolaemus

montrouzieri and Nephus reunioni, and with the

encyrtid parasitoids Leptomastix dactylopii and



Leptomastidea abnormis. Successful control was

obtained during summer and autumn, but not in

winter when the temperature was 13-17 °C.

Leptomastix dactylopii was more successful in

summer and Leptomastidea abnormis in autumn.

Aggregation of adults of Leptomastix dactylopii

occurred at the level of sample areas, but no spatial relationship was found between host density

and percentage of parasitism.

Introduction of parasitoids gave improved

biological control of P. citri in a large glasshouse

stocked with a variety of ornamental plants in the

United Kingdom, supplementing that achieved

by the coccinellid predator Cryptolaemus montrouzieri. Following the release of parasitoids

Leptomastix dactylopii and Leptomastidea

abnormis, there was evidence of mealybug population regulation on guava and coffee bushes

with reduced and stabilized mealybug numbers

and stable percentage parasitism. The encyrtid

Leptomastidea abnormis was responsible for

about 90 % of the parasitism observed; the

remainder was by another encyrtid, Leptomastix

dactylopii. The combinations of L. dactylopii and

other parasitoids (e.g., L. abnormis) and predators (e.g., C. montrouzieri) are most effective

against P. citri in greenhouses (Copland et al.

1985; Chong and Oetting 2007). Inoculative

release of five encyrtid parasitoids, Leptomastidea

abnormis, Anagyrus pseudococci, L. dactylopii,

Chrysoplatycerus splendens (Howard), and

Coccidoxinoides perminutus (Timberlake),

resulted in the rapid suppression of citrus mealybug, P. citri, on greenhouse citrus. Several parasites, L. abnormis, A. pseudococci, and L.

dactylopii, persisted for periods >20 weeks and

maintained the host at reduced densities through

delayed density-dependent regulation (Summy

et al. 1986; Van Lenteren and Woets 1988).



68.7.2 Pseudococcus viburni syn.

P. affinis and P. obscurus

Good control of Pseudococcus obscurus (Essig)

on cacti and Clivia were achieved by using C.

montrouzieri (Copland et al. 1985). The

Australian ladybird beetle Cryptolaemus montrouzieri is used to control the mealybugs in



68 Glasshouse, Greenhouse and Polyhouse Crops



glasshouses. A minimum temperature of 21 °C

was needed for the predator to feed and lay eggs.

The time between the introduction of adults into

a house and the next generation of adults was 6

weeks during summer. It is suggested that under

greenhouse conditions, predators could maintain

their populations and provide continuous control

of mealybugs for at least 4 months in the year

(Codling 1977).

Biological control of mealybugs on various

kinds of ornamental plants in greenhouses at

Antibes in southern France was attempted by

means of the release of Cryptolaemus montrouzieri and the encyrtid Hungariella pretiosa

(Timb.), either alone or together, and of H. pretiosa with another encyrtid, Pseudaphycus maculipennis (Merc). P. maculipennis gave good

control of Pseudococcus obscurus at temperatures of 20-25 °C, even when the mealybugs

were attended by Iridomyrmex humilis (Mayr).

C. montrouzieri controlled the mealybugs at over

20 °C, but were ineffective at lower temperatures

or in the presence of ant attendants. C. montrouzieri gave good control of Pseudococcus affinis

(Maskell) on Streptocarpus hybridus, citrus,

Passiflora, potato, and coffee in glasshouses

(Copland 1983). C. montrouzieri was used to

control the coccid pests in the glasshouses of the

botanic garden in Lublin, Poland (Golan and

Górska-Drabik 2004). In glasshouses, good control was achieved against the obscure mealybug

P. viburni by C. montrouzieri, irrespective of the

hairiness of the plant species. The plants used

include Citrus limon, Coffeae arabica,

Lycopersicon esculentum, Passiflora caerulea,

Solanum tuberosum, and Streptocarpus sp.

(Heidari 1999).



68.7.3 Phenacoccus madeirensis

Anagyrus loecki (Noyes and Menezes)

(Hymenoptera: Encyrtidae) is a parasitoid of the

Madeira mealybug P.madeirensis in the greenhouse ornamental production in Georgia (Chong

2005). Anagyrus sinope sp. nr is a highly hostspecific parasitoid that develops only in P. madeirensis (Chong and Oetting 2007).



627



68.7.4 Phenacoccus solenopsis

Several parasitoids and predators have been identified that attack P. solenopsis. The incorporation

of parasitoids into the management system provides the opportunity to control pest populations

at low densities. Aenasius bambawalei (Hayat

2009) can be exploited for the control of P. solenopsis infesting plants in the greenhouses.



References

Chong JH (2005) Biology of the Mealybug Parasitoid,

Anagyrus loecki, and its Potential as a Biological

Control Agent of the Madeira Mealybug, Phenacoccus

madeirensis. Ph.D. Dissertation, University of

Georgia, Athens, GA, 186 p

Chong JH, Oetting RD (2007) Specificity of Anagyrus sp.

nov. nr. sinope and Leptomastix dactylopii for six

mealybug species. BioControl 52:289–308

Cloyd RA, Dickinson A (2006) Effect of Insecticides on

Mealybug Destroyer (Coleoptera: Coccinellidae) and

Parasitoid Leptomastix dactylopii (Hymenoptera:

Encyrtidae), Natural Enemies of Citrus Mealybug

(Homoptera: Pseudococcidae). J Econ Entomol

99(5):1596–1604

Codling A (1977) Biological control of mealybug. Nat

Cact Succ J 32(2):36–38

Copland MJW (1983) Temperature constraints in the control of mealybug and scale insects. Bull SROP

6(3):142–145

Copland MJW, Tingle CCD, Saynor M, Panis A (1985)

Biology of glasshouse mealybugs and their predators

and parasitoids. In: Hussey NW, Scopes NEA (eds)

Biological pest control: the glasshouse experience.

Branford Press, Poole, pp 82–86

Doutt RL (1952) Biological control of Planococcus citri

on commercial greenhouse -stephanotis. J Econ

Entomol 45(2):343–344

Franco JC, Zada A, Mendel Z (2009) Novel approaches

for the management of mealybug pests. In: I. Ishaaya

and A.R. Horowitz (eds) Biorational control of arthropod pests. Springer, Dordrecht, pp 233–278

Golan K, Górska-Drabik E (2004) The scale insects of

some tropical fruit plants in greenhouses of Botanical

Garden in Lublin (Poland). Latvian J Agron 7:39–42

Hamid HA, Michelakis S (1994) The importance of

Cryptolaemus

montrouzieri

Mulsant

(Col.,

Coccinellidae) in the control of the citrus mealybug

Planococcus citri (Homoptera: Coccoidea) under specific conditions. J Appl Entomol 118:17–22

Hamid HA, Michelakis SE (1997) The use of

Cryptolaemus montrouzieri (Mulsant) for the control

of Planococcus citri (Risso) in Crete – Greece. Bull

OILB/SROP 20:7–12



628

Hamlen RA (1977) Laboratory and greenhouse evaluations of insecticides and insect growth regulators for

control of foliar and root infesting mealybugs. J Econ

Entomol 70(2):211–214

Hayat M (2009) Description of a new species of Aenasius

Walker (Hymenoptera: Encyrtidae), parasitoid of the

mealybug, Phenacoccus solenopsis Tinsley Homoptera:

Pseudococcidae ) in India. Biosystematica 3:21–26

Heidari M (1999) Influence of host-plant physical defenses

on the searching behaviour and efficacy of two coccinellid predators of the obscure mealybug, Pseudococcus

vibruni (Signoret). Entomologica 33:397–402

Laflin HM, Parrella MP (2004) Mealybug species

(Hemiptera: Pseudococcidae) found on ornamental

crops in California nursery production. Proc Entomol

Soc Wash 106:475–477

Lagowska B (1995) The biological control perspective of

scale insects (Homoptera, Coccinea) on ornamental

plants in glasshouses. Wiadomosci Entomologiczne

14:5–10

McLeod JH (1939) Biological control of greenhouse

insect pests. Rep Entomol Soc Ont 70:62–68



K.G. Pillai

Panis A, Brun J (1971) Trial of biological control against

three species of Pseudococcidae (Homoptera,

Coccoidea) in greenhouses of ornamental plants.

Revue de Zool Agricole 70:42–47

Summy KR, French JV, Hart WG (1986) Citrus mealybug

(Homoptera: Pseudococcidae) on greenhouse citrus:

density-dependent regulation by an encyrtid parasite

complex. J Econ Entomol 79(4):891–985

Van Lenteren JC, Woets JV (1988) Biological and integrated pest control in greenhouses. Annu Rev Entomol

33(1):239–269

Waterworth RA, Redak RA, Millar JG (2011) Pheromonebaited traps for assessment of seasonal activity and

population densities of mealybug species (Hemiptera:

Pseudococcidae) in nurseries producing ornamental

plants. J Econ Entomol 104(2):555–565

Willmott AL (2012) Efficacy of systemic insecticides

against the citrus mealybug, Planococcus citri, and

pesticide mixtures against the western flower thrips,

Frankliniella occidentalis, in protected environments. Master’s thesis. Kansas State University,

Manhattan, KS



69



Root Mealybugs

Maicykutty Mathew and M. Mani



Root mealybugs are several small species of

mealybugs found below the soil surface, and

feed on root and root hairs in numerous plants.

They are also called soil mealybugs and subterranean mealybugs. Infestations frequently are

not detected as the pests occur in the soil, and

populations are quite slow to develop, with

3–6 months occurring before infestations are

easily visible. Careful examination of infested

roots will reveal white, cotton-like masses.

These white masses contain both mature

females and eggs. Infected plants become

wilted and stunted with foliar yellowing or

chlorosis. They are oval shaped (1/16 to 3/16

of an inch long) that look like they have been

covered by flour. Because they are white or

light grey in colour, they often resemble small

grains of rice. These mealybugs have a thin,

uniform waxy coating and lack the terminal

wax filaments typical of their foliar-feeding

relatives. Root mealybugs are slow moving,

sac-like mealybugs with pronounced crosswise

grooves. They do not have filaments surrounding their body like many of the foliar feeding

mealybugs. Root mealybugs pose serious problem to potted and greenhouse plants and also



field crops. The species belonging to genera

Geococcus,

Rhizoecus,

Xenococcus,

Chorizococcus, Spilococcus, Spinococcus and

Chnaurococcus are known to roots of the

plants (Table 69.1).



69.1



Important Root Mealybug

Species



69.1.1 Gonococcus coffeae

Geococcus coffeae Green can be easily be distinguished by the pair of stout dorsal spines situated

on the head (Green 1933). Geococcus coffeae

was known to infest sweet potato Ipomoea batatas in Tamil Nadu, India (Williams 1985) and

also several other plants such as Theobroma

cacao, Coffea spp., ornamentals, pine apple, and

palms (Ben-Dov 1994).



69.1.2 Geococcus citrinus

Geococcus citrinus is a ground mealybug that

lives in the soil and damages the root of citrus in



M. Mathew (*)

Kerala Agricultural University, Trichur, India

e-mail: maycypm@yahoo.co.in

M. Mani

Indian Institute of Horticultural Research,

Bangalore 560089, India

© Springer India 2016

M. Mani, C. Shivaraju (eds.), Mealybugs and their Management in Agricultural

and Horticultural crops, DOI 10.1007/978-81-322-2677-2_69



629



M. Mathew and M. Mani



630

Table 69.1 List of other root mealybugs on different host plants in different countries

Mealybug species

Dysmicoccus brevipes (Cockerell)

Dysmicoccus texensis (Tinsley)

Dysmicoccus vaccinii sp. n.

Ferrisia virgata (Ckll.)

Geococcus johorensis Williams

Geococcus lawrencei Williams

Geococcus oryzae Kuwana

Phenacoccus salviacus Moghaddam

Phenacoccus hordei (Lindeman)

Planococcoides robustus Ezzat &

McConnell

Planococcus citri (Risso)

Planococcus cryptus Hempel

Planococcus ficus Signoret

Planococcus fungicola sp. nov.

Pseudococcus eriocerei Williams

Pseudococcus viburni (Signoret)

Pseudococcus cryptus Hempel

Polystomophora arakensis

Moghaddam

Rhizoecus maasbachi Jansen



Rhizoecus amorphophalli Betrem



Rhizoecus theae sp.n.



Plants

Pigeon pea & groundnut

Pineapple

Coffee

Cassava

Blueberries

Parthenium hysterophorus

Oil palm

Asplenium nidus

Oryza sativa

Salvia bracteata

Grasses, alfalfa, barley, clover, rye &

wheat

Mango



Country

South India

Many countries

Espirito Santo

Paraguay, Bolivia & Brazil

USA

India

Johore & Malaya

Solomon Islands

Japan & Ceylon

Iran

European countries



Coffee

Citrus

Coffee

Grapevine

Coffee

Cacti

Plum

Coffee

Atraphaxis sp.



Kenya/East Africa

Crete

Brazil

South Africa

Kenya

Argentina

Chile

Espirito Santo

Iran



Segeretia theezans

Michelis sp.

Segeretia sp.

Amorphophallus variabilis

Amorphophallus sp.

Gingiber officinale

Diosorea elephantipes

Curcuma domestica

Amorphophallus variabilis

Colocasia esculenta, Curcuma longa

and Kaempferia galangal

Tea



Netherlands

China

England

Java

India



India



Caroline Islands

Philippines

Japan

(continued)



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