Identification, distribution, management and quarantine issues of invasive pests
- Part 1 -

AN Shylesha *

The term 'invasive species' is defined as 'non-native species which threatens ecosystems besides habitats or species' by European Environment Agency (2004), which has been widely used to describe the introduced species. The invasive is also termed introduced, non-indigenous, exotic, alien or sometimes invasive. Introduction of invasive species constitute a global change of great magnitude (NRC, 2000).

Most cultivated crops in US, eight of the nine of the most economically importance, originated from outside US (Simberloff 2000). In India several crops which are non-native microorganisms, plants that cause or transmit diseases, displace native species of diminish economic or aesthetic value of a product or the environment (Herber et al., 2002).

Several papers have been published on the status of invasive pests in India, notable among them is the proceedings of the workshops held at Chennai and Dharwad (Ananthakrishnan and Jesudasan, 2009; Goud et al., 2010). In the present article a review was done on the status of classical biological control of the invasive pests and the prospects of the pests which are likely to become invasive pests and the options for management through classical biological control.

INVASIVE SPECIES AND CLIMATE CHANGE

Climate change and invasive species present greatest threats to biodiversity and the provision of valuable ecosystem services. Strong currents, winds and wave action can facilitate the movement of invasive at regional level. There is also a chance for the native species to have increased impact than the invasive species, a phenomenon more common in the aquatic environments.

Invasive species can compromise the ability of the intact systems to sequester carbon which helps off set green house gas emissions. The mountain pine beetle has the potential to increase the tree mortality thereby decreasing the amount of CO2 that can be sequestered (Wood, 2006). Changes in soil composition, flood and drought cycles, fire regimes and glacial extent and warming permafrost may all provide fertile ground for invasive species.

The damage caused by storms will increase the disturbance in habits providing opportunists for the establishment and spread of already extant invasive species. Managing invasive species must be considered as a frontline strategy in adaptation to climate change. A decline in chemical efficacy of herbivorous on invasive plants with rising CO2 was noticed (Ziska, 2005).

There is substantial lack of research investigation on the interactive effects of climate change and invasive species on agriculture, especially of projected rates of change and basic climate date for major agricultural and forested areas. The management of invasive species under the tool for ecosystem-based adaptation under climate change as it can reduce one of the major stresses of ecosystem (Burgiel and Muir, 2010).

CLASSICAL BIOLOGICAL CONTROL

Biological control, ie conservation augmentation and introduction of exotic natural enemies has been accepted as an effective, environmentally non-degrading, technically appropriate, economically viable and socially accepted method of pest management (Singh, 2004).

Classical biological control aims at introducing the exotic natural enemies of inadvertently introduced alien organism (which have become pests in the absence of natural enemies in the new environment) in order to re-establish the balance between the pests and the natural enemies (Singh, 2004).

In India, so far 169 exotic biological control agents have been introduced of which 33 could not be released into the field, 71 recovered after release, 6 providing excellent control, 7 substantial controls and 4 partial control.

1. Prickly pear, Opuntia spp.

Opuntia spp. was deliberatively introduced due to cochineal trade in 1787. Opuntia vulgaris was introduced from Brazil in to South India by traders for production of cochineal dye. Dactylpiusceylonicus was introduced from Brazil in 1795 in the mistaken belief that it was crime dye producing D. coccus.

D. ceylonicus was multiplied on Opuntia ficus and released on O. vulgaris in north and central India, bringing spectacular suppression of O. ulgaris and subsequently spread to southern India during 1836-1838. D. opuntia, a North American species was imported from Sri Lanka which showed spectacular control of O. stricta and O. elatior.

2. Water Fern, Salvinia molesta DS Mitchell

Water fern, a native of south eastern Brazil was first introduced in India though botanical gardens. It was first observed I 1955 in Vole Lake (Kerala) and has assumed pest status since 1964. Biological control agent, Cyrtobagoussalviniae native to Brazil was imported from Australia in 1982 and after screening for more than 75 economically important plants was declared safe for releases.

After the release the population of S robusta was drastically reduced in irrigation canals in Thrissur and Thiruvananthapuram to Shernur canal. A vast area of around 2000 km-2 has already been cleared by this insect resulting in substantial saving.

3. Water hyacinth, Eichhorniacrassipes (Martius)

Water hyacinth, a native of South America was introduced in 1896 in Bengal as an ornamental plants and is presently occupying an area of around 200000 ha of water surface. Three exotic natural enemies, Neochetinabruchi, N. Eichhornia were imported from Argentina and Orthagalumnaterebrantis from South America were imported via USA in 1982.

The weevils were first released in 1983 in Karnataka resulting in spectacular decrease in the population of water hyacinth. The mite O. Terebrantis was release. In areas where the weevils were not effective, the mites were effective in bringing the population of water hyacinth (Singh, 2004).

4. Cotton cushion scale, Icerya purchase Maskell

Cottony cushion scale, a native of Australiawas introduced on imported orchard stock of flower plants from Sri Lanka and has spreader to cultivated wattles, rose bushes and citrus. It was first reported in 1928 in Nilgiris on cultivated wattle, Acacia spp.

The pest is prevalent almost in the southern Peninsual and Maharrastra. Rodalia cardinalis (Origin: Australia) was introduced in India in 1926 vial USA and released in Nilgiris. The predator has substantially reduced the populations of I. purchase on citrus and Casuarina.

RECENTLY INTRODUCED INVASIVE AND THEIR BIOCONTROL

The Madeira mealybug, Phenacoccusmadeirensis Green

The Madeira mealybug is of Neotropical origin and is widespread in tropical South America, but was originally described from Madeira. It is continuing to expand its geographical range; Williams (2004) recorded it from Pakistan in 1997, Philippines in 1999, Vietnam in 1997 and Taiwan in 2006.

Madeira mealybug is highly polyphagous, feeding on members of 44 plant families, including many herbaceous crops, fruit trees, and ornamentals (Ben Dov, 2010) with potential to spread further in Southeast Asia infesting cassava (Manihot esculenta), brinjal, oats, cotton, Coleus, Hibiscus, potato, Capsicum and many other crops including Citrus spp. It has a wide geographical distribution in Europe, Africa, North and South America, Mexico, USA, and Central America including the Caribbean islands. Anagyrusloecki is a parasitoid of the Madeira mealybug.

A loechi is an arrhenotokous parasitoid with an average lifetime fecundity of 78 progeny. The survival rate of the parasitoid larvae was above 94%. These host stages were able to support the development of a higher number of progeny, a female-biased sex ratio, the shortest developmental time and the highest survival rate.

A. loecki exhibited a type II functional response, meaning that the parasitism rate decreased exponentially with increase in P. madeirensis density. A. loecki has the potential to be an effective biological control agent of P. madeirensis in green house ornamental production (Chong, 2005).

Tomato leafminer, Tutaabsoluta (Meyrick, 1917)

Tutaabsoluta, synonym Gnoromoschemaabsoluta (Clarke, 1962), Scro-bipalpulaabsoluta (Povolny, 1964) is a native of Latin America and has established in Europe, middle east and North Africa. Its primary host is tomato, although potato, aubergine, tomato, capsicum, tobacco, Datura, Lycium spp., Malva spp. common bean, physalis and various wild solanceous plants are also suitable hosts. Tutaabsoluta is a devastating pest of Tomato. Recently, Tutaabsoluta considered to be a serious threat to tomato production in Mediterranean region.

Effectiveness of chemical control is limited due to insect's nature of damage as well as its rapid capability of development of insecticide resistant strains. The use of biological factors are still largely under development and not ready to combat this pest effectively and in a cost effective way. Using sex pheromone traps as an early detection tool, mass trapping and lure and kill application of phe-romone has been found to be effective to control T. absoluta.

The following bio-agents have been reported on T. absolutaa.e., Tricho-gram-mapertiosum, Tricho- grammaachaeae, Macrolo- phuspygmaeus, Nesidio- coris tenuis, Nabi-spseudoferus, Necre-mnus, Pseudo-apanteles and Podisus. The egg parasitoid, Trichogrammaachaeae has been identified as a ccandidate for biological control, in greenhouse conditions a high efficacy, 91.74% of damage reduction was obtained when releasing 30 adults plant-1 (= 75 adults in m-2 every 3-4 days on August and September of 2008 in the southeast of Spain (Cabello et al., 2009).

Bacillus thuringiensis var. kurstaki have exhibitedsatisfactory efficacy against T. absoluta larval infestations in Spanish outbreaks. Delayed application of Bacillus thuringiensis may cause higher insect mortality if the insects become more susceptible to the pathogen after a longer period of feeding on the resistant crop.

It is reported that in a combine application of mass release of Trichoderma pertiosum and Bacillus thuringiensis resulted fruit damage of only 2% in South America (Medeiros et al., 2006). Entomopathogenic fungus, Metarhi-ziumanisopliae cause morta- lity up to 37.14%. Laboratory studies indicated Beauveria bassiana could cause 68% larval mortality.

to be continued .....