Scope of Pentatomidae as bio-control agents in India

S Salini / KJ David *

Pentatomidae, commonly known as stink bugs, are a diverse assemblage of insects, yet often under estimated for their economic importance either as pest or predators. There are four sub-families viz., Asopinae, Pentatominae, Podopinae and Phylloce-phalinae known from India (Salini and Viraktamath, 2015). Of these Asopinae are exclusively predators whereas more than 80% of species of Pentatomidae belongs to a single subfamily Penta-tominae.

Pantatominae comprises pests of agricultural crops (Nezaraviridula, Bagradahilaris, Eurydema spp., Cappaeataprobanensis, Rhynchocorishumeralis, Dolyocoris indicus, Ago-noscelisnubilis, Udonga- montana, Menida versicolor etc.), ebible species (Udongamontana), invasive pests of quarantine importance (Halyomorphahalys), vectors of phytoplasma (Halyomorphahalys) and species causing public nuisance (Udongamontana, Catcanthus incarnatus, Agonoscelisnubilis).

A major pest rice black bugs is a Pentatomid pest belonging to Podopinae, involves an array of species with diverse distribution. Phyllo-cephalinae are major grass root feeders, a very underexploited group.

Pentatomidae are known for their cyptic and warming colouration. Some are known to merge with their surroundings, especially those groups of genera, which are specialized to inhabit tee trunks. This can be considered as an evolutionary adaptation for these bugs to compartmentalize the resources as well as to re-route natural enemy. This is particularly evident in their ability to camouflage with the bark colouration.

Majority of these genera were also found to be nocturnal and are confined to concealed habitat like trunk holes or any cracks or crevices of bark during day time.

ASOPINAE AS BIOCONTROL AGENTS

Asopinae, commonly known as predatory stinkbugs or soldier bugs possessing a predaceous feeding habit for both nymphs (with the exception of first instars) and adults. First instars of Asopinae are not predaceous and take up only water or plant juices (De Clercq, 2000). They are characterised by having a crassate rostrum. The first segment is markedly thickened and free, only the base being embedded between the bucculae.

This enables a fully forward extension of the rostrum and thus facilitates feeding prey. The stylets are inserted at any soft area of the prey body and inject salivary toxin into the prey body by which they can quickly immobilize the prey. While feeding the prey, the only contact between predator and prey is by the labium and stylets (De Clercq, 2000).

The feed on a variety of insects such as Coleoptera, Lepidoptera, Hymenoptera especially at larval stages, and other small and soft bodied arthropods (Lefroy and Howlett, 1909; Fletcher, 1914; Kalshoven, 1981). However, they also feed on other insect orders or developmental stages.

Members are often observed to feed on plants, that provides them with moisture and perhaps some supplemental nutrients at critical time, though the damage inflicted to plants by sucking o plant sap is negligible (De Clercq, 2000). Though they feed on plants at times, in contrast to other predatory heteropterans (e.g. Geocoris, Dicyphus, Marcolophus), plant feeding asopines have not been reported to injure crops.

Many Asopines are known for their brilliant and aposematic colouration like AmyoteaEllenreider, ZicronaAmyot& Servile etc. A few of them like CaziraAmyot&Serville, are well equipped with various armature and have a bizarre appearance. Approximately 303 species of Asopinae are known from worldwide (Rider et al., 2018), of which only 10% have been studied in more or less detail.

Certain species however, received much attention across the world regarding their potential to manage the agricultural pests. There are about 30 species of Asopinae are known to occur in India but the knowledge of their prey or feeding potentials of majority of these Asopines remain poorly understood.

Only a small proportion of the species belonging to this subfamily have been studied so far. Future studies on their biology of this group of bugs are essential for exploring them for their biocontrol potential.

Majority of Asopines are generalist predators attacking a wide range of prey in a diverse habitat whereas a few f them appears to be ore closely associated with a limited number of insect pest species occur in a few habitats (D Clercq, 2000).

For example, the spined soldier bug, Podisusmaculiventris (Say), which is being commercialized in North America and Europe mainly for biological control of the Colorado potato beetle in potatoes and of noctuid caterpillars in vegetables, shows a particular preference for Lepidop- teran larva. P. maculiventris was found feeding on more than 90 insect species from eight orders, including Coleo-ptera, Diptera, Ephemeroptera, Hetroptera, Homoptera, Hymenoptera, Lepidoptera, and Orthoptera (De Clercq, 2000).

Another popular predatory bug, the two spotted stink bug, Perillusbioculatus (Fabricius) a native of North America, is recorded as a predator of grubs of Zygogrammabicolorate by Prasad and Pal (2015) and Kaur et al. (2012) and is restricted to northern parts of India. Eocantheconafurcellata (Wolff.) a predominant species, is found throughout India and has been studied increasingly as a biocontrol agent of agricultural insect pests in southeastern Asia and India.

It is documented as a predator, mostly lepidopteran pests of agricultural crops and forest plantations in the Indian subcontinent (De Clercq, 2000). Shophiya and Sahayaraj (2014) tested the biocontrol potential of E. furcellata against Pericalliaricini (Fab.) larva. Lenin and Rajan (2016) found Corcyra cepahlonica as a suitable host for rearing E. furcellata. Srikumar et al. (2018) recorded Eocantheconaconcinna to manage Bistonsuppressaria, which is one of the major defoliating pests of tea.

They also recorded E. concinna as a potential predator of various Lepidopteran pests in tea plantations and a promising candidate for biological control of looper pests. Aspopinae are distributed all over the world and are represented by nearly 30 species in 17 genera from India. Commonly occurring predatory species are dealt with below:

Amyoteamalabarica (Fabr.)

Reddish coloured bugs with black markings, distributed all over India. Color polymorphism is known in this species. This species was found to prey upon larvae of soft bodied insects like Lepidoptera (Salini, 2016). Pati and Mathur (2020) found that A. malabarica feeds on the satyrid, Melanitisledaismene, the hesperids, Parnaramathias and P. naso, the noctuidsSpodoptera spp., Sesamiainferens, Mythinmaloreyi and M. venalba, the pyralidsChilo spp. and Scirpophagaincertulas and the lymantriids, Psalispennatula, Laelia fasciata and Euproctis xanthorrhoea. They found a single predator is able to feed upon 73 individual larvae.

Andrallusspinidens (Fabr.)

These bugs are brownish, a white longitudinal stripe on entire lateral margins of hemelytra. This is another remarkable predatory Pentatomid and has been reported as potential biocontrol agents in rice fields in India, Malaysia and Iran (Nageshware Rao, 1965). Both nymhas ad aduts can prey on several caterpillars (eg: Narangaaenescens Moore, Helicoverpaarmigera (Hubner) and Chilosuppressalis (walker), presented in different crops in North Iran (Mohaghegh and AnirMaafi, 2007).

They are aso found feeding on larvae of fall armyworm, Spodopterafrugiperda recently in maize fields of Bangalore (Lalitha, Pers. Comm.). In spite of its wide range of distribution, less attention has been paid to its bionomics, mass rearing and potential to use it as a Biocontrol agent.

Genus CaziraAmyot & Serville

This genus is represented by four species from India namely C. frivaldskyi Horvath, C. similis Distant, C. vegeta Kirkaldy and C. verrucose (Westwood). Of the different species reported, C. verrucosa is the commonly occurring species, found throughout India. They are very bizarre looking insects with dilated fore tibiae, scutellum with wart-like tubercles, humeri usually possessing spines, femora usually armed with spines. They are known to prey upon caterpillars and leaf beetle larvae.

Cecyrinaplatyrhinoides Walk

This species resembles weevils in its external appearance and is rarely seen in its natural habitat. Members of this species are mostly black or castaneous with elongate heads and dilated foretibiae. Even though they are known as predators, the information on its prey and predation potential are largely unknown. This species was known to occur in high altitude areas (Paiva, 1919). They are known from Cachar, Naga hills and in some parts of north eastern India like Assam.

Eocantheconafurcellata (Wolff.)

E. cantheona is an important predator of several crop pests. These are dull brown bugs with scatteed yellowish or ocharaceous patches all over the body. Fore tibiae moderately dilated, with sharp and stout spine on foretibiae. They are feeds on larvae of Hyblaeapuera and Antheraeamylitta (Kirkaldy, 1909).

It is a polyphagous predator and has been reported to feed on a variety of Lepidopterus insects including Noctuidae, Arctiidae, Pyralidae, Hesperidae, Pieridae, Lsiocampidae, Limacodidae,,Saturnidae, Thaumetopoeidae and grubs of oleoptera including chrysomelidae (De Clercq, 2000). The biology of this species was studied under laboratory conditions and the total life cycle was found to be 30 days.

Zicronacaerulea (Linn.)

They are steel blue coloured beetles with rounded humeri and are predatory on several coleopteran larvae. They are distributed in various North Eastern states like Assam, Nagaland etc. These are not much exploited for their predatory potential. A few of them are potential predators though are not native to India.

Perillusbioculatus (Fabr.)

Perillusbioculatus, the two-spotted stink bug or double-eyed soldier bug, is a species of insect in the family Pentatomidae native to North America. Both the larval and adult stages are specialized predators of eggs and larvae of the Colorado potato beetle.

Arma custos (fabr.)

This species is distributed throughout Europe, China and Japan (Thomas, 1994) and is found mainly in arboreal habits (De Clercq, 2000). So far this species is not reported from India. Recent reports from China says that this species is suitable for managing Fall army worms.

Podisusmaculiventris (Say)

This is a most common asopine species of North America; its natural distribution ranges from Mexico, parts of West Indie into Canada. It is associated with a variety of natural habitats such as woods and shrubs and also in orchard and field crops, It is reported to feed on more than 90 insect species from eight orders Ephemeroptera, Orthoptera, Hemiptera, Coleoptera, Lepidoptera, Diptera, Hymenoptera etc.

But it was found that P. maculiventris has a particular preference for the Lepidopteran larvae (De Clercq, 2000). This species was evaluated against several pest species in North America and was found suitable against suppression of population of several major insect pests. It can be reared on several natural and unnatural hosts especially Galleria mellonella L.

CONCLUSION

A small proportion of species of Asopinae have been studied to any extent, it is obvious that an enormous potential remains to be investigated. Several studies on the bionomics and predatory potential of predatory stink bugs in regulating the populations of economically important insect pests need to be undertaken in the present scenario, where various adverse effects of pesticides are increasing.

Climatic conditions may be one of the major factors need to take care to avoid the failure of classical biological control. Hence, a search for the suitable predatory species adapted to the prevalent climatic conditions of India, may help us to include them in the existing IPM modules. A practical problem for the augmentative releases of the predatory Pentatomids is their multiplication. The future of the better use of indigenous predatory pentatomids lies in the challenges of successful mass multiplication.

Though many developed nations like USA, Europe etc are far ahead in multiplying and utilising them in suppressing several major pests, in India, the research and development on predatory Pentatomids and their successful utilization in the agricultural fields, is still in infancy.


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