Infestation of Quadrastichus erythrinae Kim (Eulopidae: Hymenoptera) an invasive pest on Erythrina spp, a popular standard for black pepper ( Piper nigrum ) in Idukki district in Kerala, India

: Black pepper is an important spice crop grown in Kerala state. Idukki and Wayanad districts contribute major share in production of this spice crop. More than 80 percent of pepper vines grown in this area are trailed on Erythrina spp. A survey has been conducted to ascertain the severity of gall wasp infestation in Erythrina spp. The total number of locations and black pepper gardens covered during the survey include 6 blocks and 37 panchyats in Idukki district of Kerala state. E. variegata (dense thorn) could be rated as moderately resistant (Scale 2-25% infestation and less) and E. variegata (white thorn) as less susceptible (Scale 3 – 25 to 50 % infestation). The reaction of different types/species of Erythrina to EWG has revealed that the infestation was higher in black thorn type of E. variegata where in the infestation was 75 to 100 percent. Chakkupallam, Erattayar, Kanchiyar of Kattappana panchayats recorded maximum infestation since the pepper growers used black thorned type of E. variegata as standards.


INTRODUCTION
Black pepper is an important spice crop grown in Kerala state.Idukki and Wayanad districts contribute major share in production of this spice crop.More than 80 percent of pepper vines grown in this area are trailed on Erythrina spp.The tree is commonly known as coral tree, tiger's -claw, Japanese coral tree is noted for its seasonal showy red flowers.It is generally propagated through cuttings.The tree is commonly preferred as standards for trailing pepper on account of its faster growth, supplementation of nutrients, less competition and presence of thorns which helps in easy trailing by pepper plants.Erythrina spp were found affected by various pests and diseases.The most devastating one recorded was Erythrina Gall Wasp (EGW) Quadrastichus erythrinae Kim. (Eulopidae: Hymenoptera).Severe incidence of Quadrastichus erythrinae has been reported from plains of Thiruvananthapuram on E. stricta.(Faizal et al. 2006) Outbreak of this pest on Erythrina spp was recorded all over Idukki district and the problem has actually felt by farmers of Chellarkovil, Kungiripetty and Myladumpara villages of Chakkupallam panchyat, parts of Udumbanchola and Kattapana block panchyat.(Rajkumar et al. 2007).He also reported that black thorned type of Erythrina variegate was most susceptible compared to other species.Jacob and Devasahayam (2010) reported incidence of EGW in major black pepper areas of Kerala and Karnataka.The survey indicated that EGW was present in all the districts and taluks surveyed in Kerala and Karnataka.
The incidence and severity of damage caused by EGW significantly varied on various Erythrina spp and also on various types of E. variegata.Narayana and Dhanya (2011) reported that there was a reduction in the incidence of the pest since the farmers used alternative standards for trailing pepper.An extensive survey in all panchyats of Idukki district for this invasive pest was lacking and hence the survey has been undertaken.The results revealed that the EGW was present in all six blocks and thirty seven panchyats of Idukki district in Kerala.The percentage of trees infested by EGW was higher in Kattapana block (25.4 %) followed by Nedumkandam (23 %) which were in turn on par with Idukki (21.9),Thodupuzha (15.0 %) and Adimali blocks (14.9 %).The thorn less or less thorn type of.E. subumbrans was found to be free of infestation by EGW.

MATERIALS AND METHODS
A survey has been conducted during 2010-11 to ascertain the severity of gall wasp infestation in Erythrina spp.The total number of locations and black pepper gardens covered during the survey include 6 blocks and 37 panchyats in Idukki district of Kerala state.The black pepper gardens in various panchyats were selected from prominent growers of black pepper who use Erythrina spp. as standards for trailing black pepper.From each garden, 15 trees were selected at random and the number of trees with symptoms of damage was recorded and the total number of twigs available and number infested was also recorded to calculate the percentage of trees/twigs infested in each garden.The percentage of trees/ twigs infested was also calculated for each panchyat and each block of Idukki district.
A scale has been developed to measure the infestation of gallwasp.Three species of Erythrina namely E. variegata, E. subumbrans ( Thorn less or less thorned) and E. stricta were generally used as standards and further three distinct types of E. variegata namely, black-thorn type, white-thorn type and white dense-thorn type were also found to occur in different panchayats of Idukki District Kerala India.The reaction of different species/type of Erythrina was also studied by developing a scale based on the percent infestation of the twigs by EGW.The rating is as follows.R. Narayana and M.K. Dhanya

RESULTS AND DISCUSSION
The results revealed that the EGW, Quadrastichus erythrinae Kim. was present in all six blocks and thirty seven panchyats of Idukki district in Kerala.The percentage of trees infested by EGW was higher in Kattapana block (25.4 %) followed by Nedumkandam (23 %) which were in turn on par with Idukki (21.9),Thodupuzha (15.0 %) and Adimali blocks (14.9 %).The  4).Rajkumar et al.(2007) reported an outbreak of pest on Erythrina spp all over Idukki district and severe in Chellarkovil, Kungiripetty and Myladumpara villages of Chakkupallam panchyat, parts of Udumbanchola and Kattapana block panchyat.Jacob and Devasahayam (2010) reported incidence of EGW in major black pepper areas of Kerala and Karnataka.The survey indicated that EGW was present in all the districts and taluks surveyed in Kerala and Karnataka.

Scale
The reaction of different types/species of Erythrina to EWG has revealed that the infestation was higher in black thorn type of E. variegata where in the infestation was 75 to 100 percent.This was in accordance with the findings of Rajkumar et al. (2007).The pest infestation was less than 25 per cent in dense thorn type of E. variegata.The infestation was 25 to 50 percent in the white thorn type of E. variegata.The thorn less or less thorn type of.E. subumbrans was found to be free of infestation by EGW.Jacob and Devasahayam (2010) reported the incidence and severity of damage caused by EGW significantly varied on various Erythrina spp and also on various types of E variegata.
The rating of resistance / susceptibility of various species/ types of Erythrina to EGW based on the percentage of damaged twigs indicating that E. subumbrans thorn less type could be

Table . 4 Incidence of EGW, Quadrastichus erythrinae on Erythrina spp in major black pepper growing panchyats
Means followed by the same letter are not significantly different in Duncans test P = 0.01 classified as resistant (Scale 1-No infestation) and E. variegata (black thorn type) highly susceptible (Scale 5-Highly susceptible) 75-100 % infestation.E. variegata (dense thorn) could be rated as moderately Resistant (Scale 2-25% infestation and less) and E. variegata (white thorn) as less susceptible (Scale 3 -25 to 50 % infestation).
Infestation of Quadrastichus erythrinae Kim on Erythrina