This mealybug species has the ability to increase rapidly in population size and spread to cover vast areas where host plants occur, in a relatively short period of time. It has been reported from over 200 hosts. Sinc...
Phenacoccus solenopsis (cotton mealybug); live adult female has pale yellow body. Dorsum with a dark bar, spots on intersegmental areas of thorax and abdomen, with 18 pairs of lateral wax filament.
Phenacoccus solenopsis (cotton mealybug); live adult female has pale yellow body. Dorsum with a dark bar, spots on intersegmental areas of thorax and abdomen, with 18 pairs of lateral wax filament.
This mealybug species has the ability to increase rapidly in population size and spread to cover vast areas where host plants occur, in a relatively short period of time. It has been reported from over 200 hosts. Since the original description of P. solenopsis from Atriplex canescens in New Mexico, USA in 1898, no reports on its presence were reported until 1967 (McKenzie, 1967; McDaniel, 1975). Later, Fuchs et al. (1991) reported small, sporadic populations on cotton in Runnels County, Texas, USA in 1988 that spread 75 to 200 miles from the original site with contiguous populations by 1990. With the increase in international trade over the last few decades, this invasive pest has been collected and identified on host material at international ports and in greenhouses outside its native range (Jansen, 2004). As such, P. solenopsis has become established in the Afrotropical, Australasian, Nearctic, Neotropical, and Oriental regions.
P. solenopsis was initially described by Tinsley (1898a) from specimens infesting the roots and stems of Boerhavia spicata and Kallstroemia californica within the nests of ants, Solenopsis geminata, in New Mexico, USA. Later, Tinsley (1898b) provided a brief description of the adult female collected on the roots of Atriplex canescens. Cockerell (1902) described the species Phenacoccus cevalliae from specimens on the host plant Cevallia sinuata obtained at Roswell, New Mexico, USA. This species name was listed by Fernald (1903), but later synonymized with P. solenopsis by Ferris (1950). The taxonomy of this species was documented by Ben-Dov (1994). The adult female has since been redescribed by Ferris (1950), McKenzie (1967), Kosztarab (1996), Williams and Granara de Willink (1992), Granara de Willink et al. (2007), and Hodgson et al. (2008).
Recently, specimens on cotton [Gossypium spp.] in India with morphological traits that differed from P. solenopsis were referenced as a new species, Phenacoccus gossypiphilous (Ghulam Abbas et al., 2005; Ghulam Abbas et al., 2008; 2009). Earlier, Miller and Kosztarab (1979) recognized the morphological variations within P. solenopsis, inferring that it may consist of two sexual species. The presence of morphological variations among specimens of P. solenopsis in different regions of India often led to misidentification of the mealybug species (Asha and Ramamurthy, 2008). However, because no type specimens were named, Hodgson et al. (2008) considered the name to be a nomen nudum. Also, Hodgson et al. (2008) concluded from a comprehensive morphological study that there were no significant differences in specimens from the Indian subcontinent compared to those from the Neotropics; and thus, considered the name P. gossypiphilous to be a synonym of P. solenopsis.
P. solenopsis is a bisexual species with multiple generations annually. Like other mealybugs, this species is distinguished by the morphology of the adult female. Adult females are covered with a powdery, waxy secretion with six pairs of transverse, dark bands that are located across the pro- to meta-thoracic segments. A series of waxy filaments extend from around the margin of the body with the pair of terminal filaments longest. The ovisac is composed of fluffy, loose-textured wax strands (McKenzie, 1967; Kosztarab, 1996). Adult females range from 2 to 5 mm long and 2 to 4 mm wide.
Slide-mounted females are distinguished ventrally by the presence of nine-segmented antennae, five-segmented legs with translucent pores on meta-femur and meta-tibia, each claw with a minute tooth, two sizes of oral collar tubular ducts, absence of quinquelocular pores, a large circulus, and a series of multilocular pores concentrated around the vulva and submarginal areas of abdominal segments (McKenzie, 1961; 1967; Kosztarab, 1996; Hodgson et al., 2008). On the dorsum, 18 pairs of cerarii, each with two spinose setae, are located around the marginal area, with evenly distributed trilocular pores, and minute circular pores. Also, oral rim ducts, oral collar tubular ducts, and multilocular pores are absent on the dorsum. Upon hatching, female development consists of first (crawler), second, and third instars and the adult, whereas males undergo first, second, prepupa, pupa and adult stages of development. Hodgson et al. (2008) provided comprehensive descriptions and illustrations for the immature stages of the solenopsis mealybug. First instars are separated from the other stages by possessing six-segmented antennae, lack of circulus, and quinquelocular pores on the head, thorax and abdomen. Second-instar nymphs are distinguished by having 18 pairs of distinct cerarii around the margin of the body, the lack of quinquelocular pores on the body and the claw with a distinct denticle. The third instar nymph differs by having seven-segmented antennae and a circulus.
Females of this bisexual species are capable of producing 150-600 pale-yellow eggs in a white, waxy ovisac. The first instar nymphs (crawlers) disperse to settle primarily on the leaves as well as the stems, leaf petioles, and bracts of fruiting cotton (Ben-Dov, 2010). Development from crawler to adult ranges from 25 to 30 days, depending upon the temperature. This mealybug has been reported to be capable of surviving temperatures ranging from 0-45°C, throughout the year (Sharma, 2007). The location on the plant appears to be influenced by humidity as Hodgson et al. (2008) concluded that P. solenopsis occurred more commonly on the roots, stems and foliage close to the soil line in dry climates compared to settling on the upper foliage of the plant in more humid areas. All stages of development were documented to occur on the stems of three Ambrosia spp. in the arid San Ysidro region in southern California, USA (Goeden and Ricker, 1976). The mealybugs damage the plant by extracting sap, which stresses the plant, resulting in leaves becoming chlorotic and shedding over time, as well as fruit bodies being aborted. Flowers or fruit not shed often take on an abnormal shape, reducing yield. Infested leaves of sunflowers were reported to become curled, crinkled and acquiring a rosette pattern with the plant appearing bushy and stunted (Jagadish et al., 2009a). In addition, the high numbers of developing mealybugs produce large amounts of honeydew that fall onto the lower leaves producing a substrate for the development of sooty mould, which inhibits photosynthesis within the plant. The honeydew attracts ants that collect the material rich in carbohydrate, sugars, amino acids and minerals to feed to their brood. The foraging ants enter into a mutualistic association with the mealybugs by collecting the honeydew and keeping the area clean of the excess waste product, while protecting the mealybugs from potential natural enemies. The production of honeydew and its occurrence on the lint can also interfere with the processing of the cotton by making the ginning process more difficult.
The occurrence of P. solenopsis is widespread with the species damaging plants in a variety of habitats ranging from dry arid areas to tropical regions. Dhawan et al. (2009b) reported that the population density of this invasive pest varied on cotton [Gossypium spp.] in surveyed regions in Pakistan.
The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.
P. solenopsis was discovered in 1898 by Tinsley (1898a) in New Mexico, USA. This mealybug was later reported to have spread to Arizona, California, Colorado, Mississippi, Washington D.C., and Texas, USA (McKenzie, 1967). It was reported in Texas on two non-cultivated hosts by 1975 (McDaniel, 1975). Fuchs et al. (1991) discovered from their survey that the species had spread throughout the several cotton- [Gossypium spp.] growing areas of Texas by 1988 and also recorded the mealybug from 29 additional plant hosts. The mealybug was recorded from infestations in 18 USA states. In 2005, P. solenopsis was reported to be seriously infesting cotton plants in the Punjab and Sindh regions of Pakistan (Arif et al., 2007). By 2006, it had spread to a large number of cotton-growing districts where the mealybug not only had a dramatic impact on the plant, but also reduced the value of the cotton. In India, Deshpande (2009) inferred that the invasion by P. solenopsis resulted from growers buying infested Bt. cotton bolls from the USA. Once established, populations of the pest increase due to the waxy tests that protect it from natural enemies and pesticides, the high reproductive rate, its small size that contributes to its ability to hide in cracks and crevices of stems, and its ability to survive on multiple host plants. The pest also has the ability to spread rapidly to uninfested areas by natural carriers such as the wind, rain and water-ways, on farm equipment, and by clinging to clothing and animals. International trade plays a major role in the spread of this pest to new regions of the world. It was discovered to be infesting ornamentals in Nigeria (Akintola and Ande, 2009). Hodgson et al. (2008) inferred that the infestation in Nigeria may have originated from South America.
Based on the range of climates and high number of hosts available on which the solenopsis mealybug can survive and the damage inflicted on the host plants, this species poses the serious threat of expanding its range. The hydrophobic waxy test, cryptic small size, feeding on all parts of the plant, multiple overlapping generations and high reproductive rates, allow P. solenopsis the opportunity to disperse over extended areas. Its cryptic colouration and small size mean that it can be overlooked in infested vegetables and fruits, along with other crops, allowing transport into other regions of the country. As an introduced species, P. solenopsis has the capability to cause direct economic and ecological damage to native fauna and flora with heavy infestations reducing plant vigour and causing plant death. Once the species has established on a host plant within a region, it has the capability of rapid growth resulting in significant damage to the crop. Sharma (2007) documented a seasonal outbreak of P. solenopsis on okra [Abelmoschus esculentus] in 2007, which developed into a heavy infestation on the crop by the end of the season and resulted in a 90% loss of seeds. Wang et al. (2009) recorded 17 provinces and 11 regions in China where this invasive species could spread and cause significant economic and environmental damage. Based on the international pest risk analysis for P. solenopsis, Wang et al. (2009) classified this mealybug as a high risk invasive species to China with risk value 0.856.
This species has been documented infesting 202 plant species representing 55 families with a distribution in Africa, Asia, North America and South America and Oceanic regions including the Caribbean nations. Specimens from the various regions exhibit similar morphological characteristics (Hodgson et al., 2008). Hodgson et al. (2008) noted a significant difference in the ecology of P. solenopsis from the hot, dry climate of southwestern USA. Here the mealybug occurs primarily on the roots and underside of the foliage and stems, compared to the higher humid regions of India and Pakistan, where it is found almost entirely on the upper portions of the foliage, well above the soil line.
The solenopsis mealybug has been recorded on 202 host plant species that include field crops, ornamentals, trees and vegetables. In Pakistan, P. solenopsis obtained the status of a serious pest on a wide host range. In a field survey, Arif et al. (2009) identified the mealybug from 154 plant species, the majority of which belong to the families Malvaceae, Solanaceae, Asteraceae, Euphorbiaceae, Amaranthaceae and Cucurbitaceae. Significant economic damage was determined to occur on cotton [Gossypium spp.], brinjal [Solanum melongena], okra [Abelmoschus esculentus], tomato [Solanum lycopersicum], sesame [Sesamum indicum], sunflower [Helianthus annuus] and China rose [Hibiscus rosa-sinensis] (Sharma, 2007; Arif et al., 2009; Jagadish et al., 2009b). Several cultivated plants, as well as weeds, have been used as trap crops to suppress the population numbers in an area. In surveys of the insect fauna in the southwestern USA, this pseudococcid was recorded on several plant hosts ranging from silver nightshade [Solanum elaeagnifolium] (Goeden, 1971) to jojoba [Simmondsia chinensis] (Pinto and Frommer, 1980).
The extraction of sap by the mealybug results in the leaves of the plant turning yellow and becoming crinkled or malformed, which leads to loss of plant vigour, foliage and fruit-drop, and potential death of the plant, if not treated. Phloem feeding affects the growing regions of the plant often resulting in bunched and stunted growth (Dhawan et al., 2009b; Jagadish et al., 2009a), with plants producing smaller fruit or flowers, which ultimately leads to a reduction in seed or fruit yields.
Females of this ovoviviparous, bisexual species have been reported as capable of producing from 150 to 600 eggs, protected within a waxy ovisac (Lu et al., 2008). Upon hatching, females undergo three immature stages prior to reaching adulthood, whereas males undergo first, second, prepupa and pupa stages prior to adulthood. The period of development from crawler to adult stage is approximately 25-30 days, depending upon the weather and temperature. This species is capable of producing multiple generations annually.
Nutrition
The mealybugs feed on the plant by extracting sap from cells in the leaves or stems. The sap contains soluble sugars, phenols, proteins and other potential nutrients. Mealybug-infested leaves produce high quantities of sugars and proteins compared to the amounts produced in uninfested leaves (Jagadish et al., 2009a). Conversely, Jagadish et al. (2009a) reported a decline in the phenol content in infested sunflower plants.
Environmental Requirements
From studies on the influence of weather on population growth, Suresh and Kavitha (2008b) concluded that maximum temperature and sunshine hours had a positive influence, whereas relative humidity and rainfall had a negative influence on the mealybug.
The solenopsis mealybug possesses a number of defence capabilities to protect themselves from their natural enemies. The development of waxy secretions that cover the body often protects them from some parasitoids and predators. This waxy covering may be the reason for the rare occurrence by pathogens and nematodes as major infesting agents of the mealybug (Franco et al., 2009). Also, species of ants are often associated with the mealybugs, where they obtain honeydew and in return, often protect the mealybug from natural enemies. The solenopsis mealybug was initially discovered in the nests of Solenopsis geminata (Tinsley, 1898a). However, P. solenopsis has more recently been recorded to be found in the nests of the southern fire ant (Taber, 2000) and associated with several species of ants including Myrmicaria brunnea, Oecopylla smaragdina, Solenopsis invicta, and Tapinoma melanocephalum (Helms and Vinson, 2002; Jagadish et al., 2008, 2009b; Zhou et al., 2012). The ants often tend and protect the mealybugs from their natural enemies and they collect honeydew exuded from the mealybugs. Several ant species (i.e. O. smaragdina) have been observed to tend the mealybug population by moving specimens to other locations on the plant to feed (Jagadish et al., 2009b).
However, several parasitoids and predators have been documented to attack P. solenopsis. Three parasitic wasps (Chalcaspis arizonensis, Cheiloneurus sp., and Aprostocetus minutus) were discovered attacking the solenopsis mealybug on cotton [Gossypium spp.] (Fuchs et al., 1991) in Texas, USA. In India, an unidentified species of the solitary endoparasitoid, Aenasius sp., was reported to attack P. solenopsis (Sharma, 2007; Tanwar et al., 2008). Hayat (2009) described a new species of parasitoid, Aenasius bambawalei, associated with P. solenopsis, which has been documented as a very effective candidate for biological control. This parasitoid was found parasitizing cotton mealybugs on several plants (Muniappan, 2009) and reported to parasitize up to 72% of the P. solenopsis populations infesting cotton plants grown in some districts in India (Muniappan, 2009; Pala Ram et al., 2009). Parasitism of this invasive mealybug on okra [Abelmoschus esculentus] increased within one season from its absence at germination to 89% parasitism rate at harvest (Sharma, 2007). However, a hyperparasitoid, Promuscidea unfasciativentris, was found to attack A. bambawalei, which potentially may reduce the efficiency of this parasitoid. Parasitized specimens of the cotton mealybug cease feeding and their exoskeletons turn into reddish-brown mummies (Pala Ram et al., 2009).
The parasitoid, Aenasius sp., was documented to infest 10-45% of the mealybugs on cotton and 5-65% of those were on alternate hosts. Paranathrix tachikawai was recorded parasitizing 30-39% of the mealybugs on cotton in India. Also, the parasitoid Promuscidea unfasciati, produced 30-80% parasitism rate in nature and is a potential candidate to incorporate into a management strategy for the mealybug pest (Bambawale, 2008).
Several species of predators are associated with P. solenopsis. Most predators require high populations of prey to complete their development. The predator, Cryptolaemus montrouzieri, has been used several times to control several mealybug pest species. In India, two coccinellids (Brumoides suturalis and Hyperaspis maindroni) were identified to be associated with P. solenopsis (Patel et al., 2009). Most predators feed on the eggs or crawlers within the mealybug’s ovisac and reduce the number of mealybugs available to extract sap and weaken the plant. Other potential predators, such as the larvae of the lacewing, Chrysoperla carnea, were found to consume 30 mealybug eggs daily in developmental laboratory tests (Rabinder Kaur et al., 2008).
From morphological and taxonomical studies, it may be determined that the solenopsis mealybug is native to the southwestern USA and material from Central or South America is similar to specimens collected and examined from West Africa (Hodgson et al., 2008), whereas specimens from Thailand, Taiwan and New Caledonia appear more similar morphologically to specimens from India and Pakistan. Hodgson et al. (2008) inferred that material from all infested regions of Asia may have originated from international commerce. The species may be dispersed internationally over vast areas by transporting infested plants into new areas by air or sea cargo. Local and regional movement is primarily by wind, irrigation water and by attachment to other insects and birds. The solenopsis mealybug is an important invasive pest that has seriously damaged cotton [Gossypium spp.] in India and Pakistan and poses a severe threat to cotton production in China.
Natural Dispersal (Non-Biotic)
The first instars or crawlers are the main dispersal stage of the solenopsis mealybug. The waxy strands covering the body serve a variety of functions including allowing the specimens to be transported by wind or water to new locations. The crawlers are commonly dispersed by wind for distances ranging from a few metres to several kilometres.
Vector Transmission (Biotic)
Infested host material that is transported from one area to another is an important source of distribution for the mealybug. The waxy test covering the body can adhere to passing animals or the clothes of people, allowing individuals specimens to be transported extended distances from the original infestation site before becoming dislodged in new, previously uninfested sites.
Accidental Introduction
Commercial trade involving infested plants may often be the cause for spread of the invasive species over vast distances. Movement of equipment from an infested area to a non-infested area may also be involved in the accidental spread of the mealybugs.
The solenopsis mealybug is an important plant pest worldwide (Williams and Granara de Willink, 1992; Hodgson et al., 2008). Mealybug feeding may cause the leaves to turn yellow and results in defoliation, reduced plant growth or plant death. The presence of the solenopsis mealybug has the potential to inflict significant damage to field crops (i.e. cotton [Gossypium spp.] and tobacco [Nicotiana spp.]) in all growing regions. This mealybug caused serious damage to cotton in Pakistan in 2005 (Saeed et al., 2007; Dhawan et al., 2009a,b) and India (Jhala et al., 2008; Bhosle et al., 2009). Also, it is a pest of commercial crops including a variety of vegetables, grapes [Vitis vinifera], jute [Corchorus spp.], mesta [Hibiscus cannabinus] and tobacco.
The economy of Pakistan is heavily dependent on the production of cotton. Cotton production is reported to account for 8.2% of the value added in agriculture and 2% of the GDP of Pakistan. The significant damage to cotton caused by P. solenopsis can have significant impact on the economy of the nation. Economic crop losses of an estimated 14% occurred in Pakistan in 2005 and in Punjab, India in 2005-2006 and 2006-2007 (Anon., 2005; Hodgson et al., 2008; Dhawan et al., 2009a). In the 2005 growing season, this invasive pest was responsible for a 44% reduction in seed-cotton yields in Pakistan (Dhawan et al., 2009b). The intense attack by the mealybug on Bt cotton resulted in significant economic losses to growers in the Punjab region (Dutt, 2007). In 2007, the number of hectares committed to growing cotton increased over the previous year, but cotton production had a significant decline over the previous year (Dutt, 2007). Previous field crop losses in cotton have ranged from 30-80% in some regions of India (Nalwar et al., 2009). However, the grower is required to implement chemical applications to save the crop, resulting in increased expenses in production as well as the potential of chemical contamination of soil and water.
As a result of P. solenopsis dispersal, reproductive and survival capacity, this invasive pest has the potential to damage or kill native plant species that could result in their displacement by other more aggressive species. Wang et al. (2009) projected that P. solenopsis could infest regions within 17 provinces of China and posed a pest risk analysis value of 0.856 to the area. Dhawan et al. (2009a) inferred that meteorological parameters influenced the presence and population size of the mealybug, with humidity and rainfall producing a negative effect.
The widespread infestation of the mealybug throughout the cotton [Gossypium spp.] growing regions often requires expensive and numerous applications of insecticides to produce and protect the crop. Because of the crop losses and damaged cotton bringing lower prices, many farmers in some areas are reported to be interested in cultivating other crops. As a result, the additional pest control requirements often lead to a reduced profit margin that affects the standard of living of producers and homeowners. P. solenopsis attacks and damages numerous ornamental plants, therefore it has the potential to affect the aesthetic appearance of the infested areas, reducing tourism trade to the region.
Monitor the stems, leaves and flowers for immature and adult mealybugs. Also, inspect the base of the plant as the mealybugs can survive several millimetres below the soil surface. Observations should be directed to all plant tissue for the white waxy specimens. Distinguishing characteristics on the dorsum of adult females are the series of dark marks on the head and six transverse marks across the pro- and meta-thorax and each abdominal segment. Margins of the body are distinguished by minute dark dash-like marks on the thorax and abdomen. Both the immatures and adult females possess waxy filaments surrounding their bodies. The presence of honeydew on the leaves may also infer an infestation by this mealybug. Initiating field surveys to detect potential infestations early to implement spot or targeted treatments (either handpicking or chemical) is effective to limit damage to commercial crops. Sticky-traps set out in the fields and their borders can be used to detect the presence of the mealybug.
Morphologically, adult females are closely related to Phenacoccus solani based on the presence of nine-segmented antennae, a circulus larger than on most mealybugs, multilocular pores more numerous around the vulva, and with more numerous trilocular pores associated with the anal lobe cerarii and over the dorsum. However, P. solenopsis is distinguished from the adult females of P. solani that are smaller in size, with eight-segmented antennae, smaller circulus, and fewer trilocular pores on the dorsum. P. solenopsis have multilocular pores located medially on abdominal segments VI-IX compared to multilocular pores being located on abdominal segments VI and VII on P. solani.
P. solenopsis also appears to be closely related to Phenacoccusdefectus. The solenopsis mealybug differs from P. defectus by possessing more multilocular pores around the vulva and more pores on the posterior seventh abdominal segment, and the absence of quinquelocular pores.
Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.
Prevention
SPS measures
Several countries have incorporated measures to inspect plant material from locations where the mealybug pest is known to occur. China has initiated a notice of inspection and quarantine for P. solenopsis (Ministry of Agriculture, 2009).
Early warning systems
Use of sticky traps placed throughout the field is an effective means to survey for the presence and population density of the pest.
Control
Cultural control and sanitary measures
It is important to prune or cut infested stems or branches from plants and destroy the infested plant material. Also stalks and crop residue in infested field sites should be removed and destroyed as such residue left in the field can harbour mealybugs, which can survive to invade the new crop. Attention should be given to the field borders for plants that can serve as an alternate host for the mealybug. Such plants should be removed to prevent the mealybugs from overwintering and infesting crops in the future. Trap plants may be planted that initially attract the mealybugs and can be targeted for control treatments to protect the primary crop.
Physical/mechanical control
Small populations of P. solenopsis can be controlled by inspection of plants, removing loose bark where they might be difficult to observe and handpicking the specimens from newly-infested plants. Soap applications are often effective against targeted, small populations of the mealybug.
Movement control
It is necessary to sanitize equipment and check clothing items to prevent the transfer of the pest into new locations.
Biological control
The use of biological control agents represents an effective means of suppressing exotic pest populations of mealybugs providing a non-toxic, self-perpetuating control tactic. 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. Established parasitoids have been recorded to parasitize over 70% of the cotton mealybug populations (Pala Ram et al., 2009). Tactics suggested to suppress populations of the invasive mealybug on crops include allowing the parasitoid to build-up in population numbers prior to applying chemical insecticides; to attach plant parts with parasitoid-infested mealybugs (mummies) on the host plant to be protected; mass releasing parasitoids into mealybug-infested areas; or using a combination of natural enemies to control the exotic pest (Pala Ram et al., 2009). The use of beneficial predators provides the opportunity to control P. solenopsis on cotton [Gossypium spp.] in several countries. The predator, Cryptolaemus montrouzieri, has been imported in India and released in cotton-infested fields as a means of controlling P. solenopsis.
To provide a higher probability of success by implementing natural control agents, several species of ants that are often associated with honeydew-producing mealybugs and protect the population from natural enemies would need to be eradicated (Helms and Vinson, 2002; Tanwar et al., 2007).
Chemical control
The solenopsis mealybug was considered to be a secondary pest of cotton in Pakistan and India, maintained at low population levels by chemical applications to control the primary pest, Helicoverpa armigera. With the emergence of transgenic cotton and the reduced need for chemical applications, the mealybug has emerged as a major pest requiring chemical applications to manage it. The use of insecticides is the most effective control against the mealybug when applications are timed to coincide with the crawler stage. The toxicity of a variety of insecticides (Dhawan et al., 2008; 2009a) was evaluated for efficacy against P. solenopsis.
IPM
A management strategy to control P.solenopsis in India that incorporates cultural, mechanical, biological and chemical control factors has recently been developed (Tanwar et al., 2007). They recommend a survey for the mealybug prior to planting, targeting and chemically treating small populations, removal of alternate host plants and ant colonies, using recommended insecticides for optimal effectiveness on the plants and around their root system, providing an attractive habitat for native and exotic natural enemies, and using a variety of sanitation methods to prevent spread of the pest to new fields.
Monitoring and Surveillance
The placing of sticky traps in the fields and around the borders is useful in early detection of the mealybugs into the area. Observations of the plant stems, leaves and flowers aid in detecting the white, waxy masses produced by P. solenopsis.
Several areas in reference to the biology, development and control of P. solenopsis need to be completed to determine those biotic and abiotic factors that may influence their development and survival. Because this species is associated with a varied host range, studies on their preferred hosts could aid in developing and implementing effective control methods for this mealybug. Comprehensive studies need to be conducted on the parasitoid and predators associated with P. solenopsis, including their life histories, and a determination of the combinations of natural enemies that would be most effective in suppressing the pest populations. For example, it is important that information is obtained and distributed regarding those risk factors that may be necessary to implement a successful programme. Such evaluations on the impact of crop damage or loss in reference to the use of chemical applications, compared to the time needed to obtain established natural enemies to suppress a target pest species, need further study.
