Planococcus citri (citrus mealybug)

Keeping fruit trees pruned so that they do not touch each other may help slow spread of P. citri, and cleaning farm equipment and other objects immediately after use in the field can help prevent its transport between trees and orchards. 

In the highlands of Java, Indonesia, the shade tree Leucaena glauca is the main food plant of P. citri at altitudes above 600 m. Measures that proved successful for the control of P. citri were mainly directed against infestation of this tree and consisted of removing the flower clusters or, when necessary, pruning all foliage and flowers. It is also claimed that P. citri can be controlled by increasing the shade in plantations and that this was undesirable for Robusta coffee but suitable for Arabica at high altitudes (Le Pelley, 1968). Good results were obtained by providing three covers, one above the other, of Leucaena, Erythrina and Albizia, or with Leucaena and Albizia only. It is further suggested that because the insect infests mainly the flowers and pods of L. glauca, other shade trees that seldom flower, such as L. pulverulenta [L. leucocephala], or a sterile hybrid of L. glauca and L. glabrosa should be planted (De Fluiter, 1939).

In Texas, USA, P. citri infestation on Citrus was controlled indirectly by controlling the milk vine Cynanchum unifarium [Cynanchum racemosum var. unifarium] (milk vine), a climbing plant that grows within the citrus tree canopy (French and Reeve, 1978).

Biological Control

P. citri is often attended by ants for the sugary honeydew it excretes. Ants from multiple genera are involved, including species of Crematogaster, Pheidole, Camponotus and Wasmanniaauropunctata, with different species active in different countries and conditions, on various crops (Way and Khoo, 1991). Ants defend the mealybugs from predators and parasitoids, and can render biological control agents ineffective. Ant control is therefore an essential component in the biological control of P. citri.

P. citri has natural enemies in 22 genera belonging to 7 families (García et al., 2016). Several natural enemies, both parasitoids and predators, have been studied and evaluated for the biological control of P. citri (Viggiani, 1974; Berlinger et al., 1979, 1985; Barbier and Raimbault, 1985; Mani and Krishnamoorthy, 1990a,b,c; Reddy et al., 1991, 1992, 1997, Reyd et al., 1991; Islam and Jahan, 1992, 1993; Kanika-Kiamfu et al., 1993; Khandakar and Jahan, 1993; Su & Li, 1993, Vos et al., 1993; van Baaren et al., 1994; Yigit et al., 1994; Blumberg et al., 1995; Mani, 1995). The food plants of the pest may affect the activity of natural enemies (Copland et al., 1993). Natural enemies that have been successfully used include the parasitoids Leptomastix dactylopii, of South American origin, and Anagyrus pseudococci; and the predators Cryptolaemus montrouzieri and Exochomus flavipes (Panis and Brun, 1971; Panis, 1977; Narasimham, 1987; Pillai, 1987; Smith et al., 1988; Viggiani, 1988; Nagarkatti et al., 1992; Reddy et al., 1992, Barbagallo et al., 1993; Reddy and Bhat, 1993a; Mani, 1994).

P. citri was successfully controlled with the introduced predator C. montrouzieri and the parasitoid L. dactylopii in Italy (Panis, 1977), Sicily (Liotta et al., 1976), France (Panis and Brun, 1971), India (Pillai, 1987; Reddy et al., 1992; Reddy and Bhat, 1993b; Mani, 1994), former USSR (Kurdyukov and Alan, 1973), Queensland in Australia (Smith et al., 1988), Italy (Fronteddu et al., 1996) and Morocco (Abdelkhalek et al., 1998).

In Peru, the encyrtid parasitoid Pauridia peregrina [Coccidoexnoides peregrinus], which was introduced accidentally from Texas (USA) and first discovered in Peru in 1963, gave remarkably good control of P. citri on Citrus (Salazar, 1972).

On Citrus in the former Soviet Union (Niyazov, 1969), P. citri was kept under control by the indigenous parasitoid Anagyrus pseudococci, which destroyed up to 75% of the mealybug population in areas that were not treated with insecticides. In Turkmenistan and Georgia, however, the effects of Leptomastix abnormis [Leptomastidea abnormis] and Leptomastix dactylopii introduced from the USA in 1960 were much reduced by the presence of hyperparasitoids such as Chartocerus subaeneus, which was also responsible for 18-20% parasitism of another parasitoid, Allotropa mecrida, which in turn was responsible for up to 20% parasitism of P. citri. The larvae of predatory Leucopis alticeps and Crysopa carnea [Chrysoperla carnea] are reported as virtually destroying all stages of P. citri in the former USSR, and introduction of Clausenia josefi from the Mediterranean was discussed (Niyazov, 1969).

In Athens (Greece), introduced C. montrouzieri failed to establish on Citrus, whereas in Antibes (France) it was found to be effective at temperatures above 20°C but proved ineffective at lower temperatures or in the presence of attendant ants (Panis and Brun, 1971). In Israel, laboratory and field experiments showed that the efficacy of predators was reduced when P. citri fed on the alkaloid-containing legumes Erythrina corallodendrum and Spartium junceum, compared to non-toxic plants (Mendel et al., 1992).

Studies conducted in Italy on hypersensitivity and allergic responses in a group of workers employed in breeding insects for biological pest control showed a lesser degree of allergy to P. citri than to other insects (Cipolla et al., 1997).

Laboratory experiments conducted at Purdue University, West Lafayette, USA, on Coleus, showed that plant size, variegation and other parameters including plant height, leaf number and leaf area had no significant effect on attack rates, searching strategy and selected life history characteristics of C. montrouzieri (Garcia and O'Neil, 2000). On the other hand, increasing prey density on plants significantly increased the rate of attack, which reached a plateau of approximately 3.5-4.0 prey attacked on plants containing 16 prey individuals. There was an inverse relationship between prey density and the estimated area searched. Moreover, C. montrouzieri development was slower, and survival and fourth-instar and adult body weight was lower when provided with fewer prey. However, the sex ratio was unaffected.

Laboratory experiments on the reproduction of C. montrouzieri showed that whilst the ladybirds did not reproduce or lay eggs after consuming Orthezia tillandsiae, a small amount of a feed mixture consisting of the ensign scales O. tillandsiae and P. citri at a ratio of 3:1 was enough to stimulate the ladybirds to lay eggs. A further experiment with the same feed-mixture showed that C. montrouzieri pupated and continued to develop (Voigt, 2000). In India the biology and predation of C. montrouzieri on P. citri and Dactylopius tomentosus was studied in the laboratory at 29.4-32.1°C and 65-71% RH (Baskaran et al., 1999). C. montrouzieri completed its growth successfully with both prey species, but preferred P. citri to D. tomentosus.

See also Waterhouse (1998).

On coffee in Kenya, P. citri is controlled indirectly by spraying chemicals or applying baits against attendant ants, to encourage natural enemies that would otherwise be killed by them (Le Pelley, 1968). Chlorpyrifos, deltamethrin, ethion and hydramethylnon were used to control ants on coffee in Kenya.

Phosalone, trichlormetafos-3, malathion and dimethoate were effective against P. citri in Peru and the former USSR (Khalilov, 1972; Kurdyukov and Alan, 1973). The most suitable periods for insecticide application on grapevines in the former USSR were during the transition phase and during the emergence of third-instar larvae; spraying could be replaced by the release of the predator Cryptolaemus montrouzieri. ULV application of malathion (Limon de la Oliva and Blasco Pascual, 1973) has also been used.

On grapefruits and oranges in Spain (province of Castellou), spot treatments with fenitrothion, fenitrothion + dimethoate or dimethoate were effective but expensive (Limon de la Oliva et al., 1972).

In Italy, 40 insecticides effective against P. citri were assessed for their effect on the natural enemies, Leptomastidea abnormis and Scymnus includens (Viggiani et al., 1972). Twenty-one of these, including a preparation of Bacillus thuringiensis, a mixed spray of chlorfensulphide [superseded], chlorfenethol [superseded], demeton [superseded], dicofol, liquid mineral oil and pyrethrum, were found to be least harmful to natural enemies.

Other chemicals used elsewhere include fenthion in Italy (Cabitza et al., 1994), dimethoate in Australia (Murray, 1978a) and, indirectly, chlorpyrifos, deltamethrin, ethion, hydramethylnon inacide and used to control attendant ants on coffee in Kenya to encourage survival of parasitoids and predators that would be killed by the ants (Anon., 1990). On persimmon fruits, the application of chlorpyrifos and diazinon around the trunk gave excellent results against mealybug attendant ants and greatly reduced the population of mealybugs (Izhar, 1999).

In Citrus orchards in Israel, the application of chlorpyrifos in early April (before flowering) prevented cork scars on fruits, whereas application in early summer (mid-June) only reduced damage (Gross et al., 1999).

In Maryland, USA, micronized dusts of chlorpyritos dispersed in a greenhouse by release of carbon dioxide proved highly effective against nymphs of P. citri (Smith and Boswell, 1972). In Tokat province (Italy), diazinon gave effective control in two applications made 5 weeks apart in June and July (Aykac and Erguder, 1972). These three insecticides were also found to be effective in Turkey. In Bulgaria, phenthoate was most effective, but was phytotoxic to ferns. Dimethoate also afforded some control (Tsalev, 1970).

In a study of the influence of six selective pesticides on adult longevity, progeny production and prey consumption by the predator Cryptolaemus montrouzieri, no detrimental effects were observed on progeny production of the beetle on plants treated with chlorpyrifos, neem seed kernel extract, dicofol and copper oxychloride. Diflubenzuron had a pronounced effect on the adult females, yielding only 278 progeny compared to 419 by untreated females (Mani et al., 1997). It was suggested that these selective pesticides, with the exception of diflubenzuron, could be considered in integrated pest management programmes.

Pirimiphos-methyl effectively controlled P. citri, scales and beetles on yam tubers in storage and as a result significantly reduced associated fungal infections caused by Fusarium spp., Penicillium spp., Aspergillus spp., Curvularia spp., Epicoccum spp. and Helminthosporium spp. (Morse et al., 2000).

In Cyprus, the development of resistance by P. citri to some insecticides was reported (Cyprus Agricultural Research Institute, 1981).

In quarantine, suspected host plants or plant parts may be dipped in insecticidal solutions such as an insecticidal soap composed of potassium salts of fatty acids with fluvalinate (Hansen et al., 1992a). Alternatively, plants may be subjected to vapour heat treatment as described by Hansen et al. (1992b). Anthurium andreanum, Leucospermum sp. and the flowers and foliage of orchids were, however, very sensitive to the vapour heat treatment.

In Australia, a greater reduction in fruit infected with P. citri in the calyx was achieved with low volume pesticide spraying than with a conventional high volume pesticide sprayer (Cunningham and Harden, 1999). The reduction in insecticide dose rate using lower spray volumes resulted in the pests not being controlled in some of the lower volume treatments.

Tests on insect growth regulators showed that kinoprene and epotenonane (R010-3108) gave effective control of P. citri comparable to that achieved with conventional insecticides such as dimethoate and methiodathion (French and Reeve, 1979).

The synthetic juvenile hormone analogues kinoprene (ZR-777) and hydroprene (ZR-512) prolonged the duration of the total life cycle and reduced female fecundity (Gaaboub et al., 1979), but female emergence was much less affected. In Switzerland, Vogel et al. (1977) showed that nymphs of P. citri treated with the juvenile hormone epofenonane moulted several times into intermediate forms between nymph and adult, the number of anal pores being reduced during each supernumerary moult.

In California, the insect growth regulators, ZR-619, ZR-512, ZR-520 and ZR-777 all reduced the number of progeny due to adult mortality as well as sterility induced in the survivors (Staal et al., 1973). In Ohio, insect growth regulators (kinoprene), Safer's soap and Murphy's Oil soap (a non-insecticide preparation) reduced the number of citrus mealybugs (presumably including P. citri) on foliage plants (Lindquist, 1981). The moulting inhibitor buprofenzin inhibited development of first-instar nymphs of P. citri and also (at lower concentrations) resulted in a marked decrease in the egg production of surviving females in laboratory studies in Hungary (Darvas and Szabo, 1987). Vogel et al. (1976) showed that applications of epofenonane could be as effective for the control of P. citri on grapefruits as dimethoate.

The insect growth regulator buprofezin was effective at three different application rates against P. citri on celery plants 26 days after treatment, when large numbers of dead early-instar larvae were observed on buprofezin-treated plants (Bedford et al., 1996). There was an indication that effects on mealybugs were greater, the higher the rate of buprofezin applied. However, low numbers of surviving mealybugs, within even the highest rate, indicated that a repeat application may be required for complete or continued control. No phytotoxic damage or response was observed on any of the celery plants within any of the treatments.

Pheromones

Several synthetic analogues of the sex pheromone dextro-cis-planococcyl acetate have been developed in the former USSR, Sweden, Israel, Japan and Italy (Rotundo and Tremblay, 1974, 1975, 1976a, 1980a, b; Dunkelblum et al., 1986). One analogue has been effectively used to monitor P. citri populations (Panis, 1979); its use for control purposes is quite promising (Rotundo and Tremblay, 1975) because it has proved highly attractive to males under field conditions.

Plant Extracts/Botanical Insecticides

Other unconventional chemical control agents include Citrus oil mixed with azinphos methyl which gave 96% mortality of P. citri in Texas (USA). In Florida, combinations of a hexane extract of the seed of neem (Azadirachta indica) and several of its chromatographic fractions significantly deterred feeding by P. citri and other insects (Jacobson et al., 1978).

In Alexandria (Egypt), application of emulsion sprays containing 3% petroleum distillate and various emulsifiers, all locally produced, gave good control on guavas for up to 5 weeks after treatment in September (El-Sebae and El-Akkawi, 1971).

In a field trial in Karnataka, India, neem oil and Pongamia [?pinnata] oil (both at 4%) were recommended for the control of P. citri on guava, causing 93.2 and 89.4% mortality of the pest, respectively, 10 days after the second spray (applied 10 days after the first) (Hussain et al., 1996).

Simmonds et al. (2000) demonstrated that a crude neem seed extract; a formulation of azadirachtin, a pyrethrum extract, and one of two naphthoquinones isolated from Calceolaria andina (BTG 504 and BTG 505) all influenced the foraging behaviour of C. montrouzieri exposed to leaves and P. citri. Larval and adult foraging behaviour was influenced most by BTG 504 and neem also affected larval behaviour; the predators contacted fewer treated leaves and spent less time on treated than on untreated leaves. The larvae also consumed fewer mealybugs treated with BTG 504 and BTG 505 than untreated mealybugs.

Integrated Pest Management (IPM)

In Florida, USA, a combination of selected chemicals, natural enemies and cultural practices was used to maintain populations of P. citri on Citrus below economic levels (Knapp, 1981).

In greenhouse experiments aimed at developing integrated control methods for P. citri and Nephus reunioni on potted orange trees, the predator C. montrouzieri effectively reduced populations of P. citri at a predator:prey ratio of 1:15 (Hamid et al., 1997). In most cases, no significant differences in pest reductions were detected between C. montrouzieri and insecticide.

On coffee in Kenya, P. citri was controlled indirectly by spraying chemicals such as chlorpyrifos or deltamethrin or applying hydramethylnon as baits against attendant ants in an attempt to encourage natural enemies that would otherwise be killed by the ants (Anon., 1990).

In Crete (Greece) no significant differences were detected between control of P. citri with C. montrouzieri alone and integrated control with C. montrouzieri and chemical treatment (Hamid and Michelakis, 1994). In Italy, however, Viggiani and Tranfaglia (1978) showed in laboratory experiments that the insecticides temephos, methomyl [now banned] and deltamethrin were harmful to L. dactylopii whereas fenbutatin oxide was harmless.

Arthur and Wiendl (1996) showed that irradiation had adverse effects on the development of P. citri. After 50 days of irradiation at different dosages, there were 2087.25 ± 301.34 individuals for the control, and 1348.25 ± 349.77, 288.25 ± 129.62, and 54.25 ± 61.98 individuals for doses of 10, 20 and 30 Gy, respectively. Insects treated with 40 Gy or higher dosages produced no offspring.

Katsoyannos (1996) reviewed progress on integrated pest management, especially biological control, for the main insect pests of citrus including P. citri, in northern Mediterranean countries.

In a field study of an integrated strategy for the control of P. citri, aphids and scale insects on Citrus in eastern Sicily (Italy) involving the control of attendant ants, chlorpyrifos gave the best control and was the least costly (Tumminelli et al., 1997). Insecticidal gum applied to the trunk gave better results than pyrethrum, but had phytotoxic effect on trees less than 10 years old and was also costly to apply. It was concluded that in integrated control programmes, the best time to treat ants and to release beneficial insects was between April and September.

A study in Italy on the biology, damage caused and control of the most important pests of table grapes, including P. citri and P. ficus, produced criteria for reducing the number of pesticide treatments in vineyards and a scheme for the biological control of pests and diseases on grapes (Guario and Laccone, 1996). Also in In Italy, Viggiani (1975a) observed that an infestation level of about 5% was regarded as the threshold for chemical control.

Due to the variable regulations around (de-)registration of pesticides, we are for the moment not including any specific chemical control recommendations. For further information, we recommend you visit the following resources: