Seasonal incidence

Seasonal incidence and host plant preference:

Among the different larval parasitoids on H.armigera, C.chloridae and C.illota were most active on seasonal crops and also during most seasons. Achan et al., (1968), Anonymous (1974), Bhatnagr et al., (1983) and Pawar et al., (1985) Manjunath et al., (1989) have provided information on the influence of seasons and host plants on parasitism of H.armigera various species. Hymenopterans were predominant on sorghum and chickpea and dipterans on pigeonpea. Parasitism by dipterans on sorghum, pigeonpea and chickpea was up to 2.1%, 22% and 3%, respectively and by hymenopterans on sorghum, pigeonpea and chickpea was 4.9%, 5% and 17.2%, respectively (Bhatnagar et al., 1982; 1983). G.halli was most important factor for H.armigera on cotton. Palexorista spp. was recorded from the cotton and pigeonpea, in Maharashtra (Bilapate, 1981a).

C.illota and Exorista xanthaspis provided about 24.54% parasitism on sunflower (Patel and Talathi, 1987) in Gujarat. In same state C.illota caused pupal mortality of H. armigera on groundnut (Koshiya and Patel, 1987). In Orissa, Campoletis chloridae and C.illota played a key role in suppressing the larval population during the podding stage of chickpea (Patnaik et al., 1991). In Orissa, C.chloridae, C.illota and Apanteles sp. were important parasitoids on cotton, chickpea and pigeonpea. These were active in the cooler months of December and January (Mishra et al., 1992). In Maharashtra, C. chloridae and G.halli were the most important parasitoids causing mortality of H.armigera on cotton and chickpea (Billapate, 1989). On pigeon pea C.chloridae, C.illota and G.halli caused 1.38%, 1.95-2.89% and 3.5-7.88% parasitism, respectively. C.illota and G.halli were reared from H.armigera infesting sorghum, cotton, tomatoes and other crops. Field studies on cotton and sorghum by Bilapate 1981 reported 20% and 52% parasitism by G.halli and C.illota, respectively. The caterpillars collected from Lucerne and chickpea for rearing of these parasitoids indicated that C.illota was dominant in October – November and G.halli in January on chickpea in Andhra Pradesh.  

H.armigera on sorghum pigeonpea intercrops in the Indian subcontinent reveals that the pest was heavily parasitised by hymenopteran parasitoids on sorghum than pigeonpea. They build up in high populations on sorghum; they give little advantage to the companion pigeonpea. They do not move and parasitize Helicoverpa on the pigeonpea. It is true with tachnidae. Their activity is very low on sorghum, but they are major parasitoids of H.armigera on pigeonpea (Manjunath et al., 1985).  Indicates that the tachinids are only key parasitoids of H.armigera on pigeonpea but 52% parasitoid record of the tachinids on H.armigera on sorghum by Bilapate (1983) cannot be ignored. Chaudhari (1996,2000,2001a, 2002) recorded 52 % parasitism of H.armigera on pigeonpea by C.illota. There is considerable crop influence on the activity of parasitoids. In general, the hymenopteran larval parasitoids are more active in cereal crops and the dipterans are more prevalent in legumes, particularly pigeonpea. This might be because nectar food source provided by pigeonpea crop to dipteran parasitoids and sugary sweet food source provided to hymenopteran parasitoids by cereals.

The seasonal incidence of H.armigera by S.illota on pigeon pea and chickpea reported maximum 52,43.24 and 45.45 per cent parasitism in second   and first fortnight of November 1993,1994 and December 1995, respectively. The average percent parasitism was 13.053 of three season’s 1993-94,1994-95 and 1995-1996. The maximum percent parasitism were 28, 36 and 42.6 in the months of November 1993, 1994 and December 1995, respectively.  The minimum percent parasitism was 0.8, 1.67 and 4.2 in the months of March and January, respectively during the year 1993-94, 1994-95, and 1995-96.  The percent parasitism observed was low i.e. 10.503 during 1994-95. The average monthly activity for three season indicated that it was higher in November and then goes on decreasing.  No incidence of parasitism was recorded during first and second fortnight of February and March 1994, respectively. Similarly it has not been observed during the first, second and first fortnight of December and February 1995, respectively particularly on chickpea (Chaudhari.2000, 2001a, 2002). The reasons for this erratic behaviour could not be ascertained.

           Of the Tachinids recorded by Achan et al., (1968) during the survey, Drino imberbis Wiedemann C.illota, and Goniopthalmus halli Mesnil appear to be promising species, the maximum parasitism being 18, 16 and 20 per cent, respectively during March 1962 to February 1967.  In the present study with S.illota is slight higher (17.07%) for October 1995 to March 1996.  Field study on sorghum during 1978-80 by Bilapate (1981) recorded 52% parasitism by S. illota on H. armigera in December. It supports 52% parasitism observed during second fortnight for November 1993.  It was found to be 42.6% on pigeon pea in December 1995. It is less and quite comparable, but promising. The percent parasitism recorded in the month of November every year is considerable & suggests that this parasitoid is active in the month of November than January (Chaudhari.2000, 2001a, 2002) (Table5, 6,7).   

Table 5. Extent of larval parasitism by S.illota on H. armigera during 1993-1996.

Months	Years 1993-94a               1994-95b                   1995-96c
October	11.69	13.88	08.66
November	28.00	36.00	31.28
December	09.6	07.08	42.6
January	15.19	01.67	4.2
February	03.5	02.00	9.143
March	0.8	02.39	6.57
Overall	11.5816	10.503	17.0755

Average of 3 years 13.053

For 3 years P<0.05

a = r = - 0.4212                        b = r = -0.33029                       c = r = - 0.1369

Table 6. Extent of larval parasitism by S.illota on H. armigera around Rahuri taluka during during fortnight.

Years	1993-94		1994-95	1995-96
Fortnight	I          II               Avg.		I          II         Avg.	I          II         Avg.
Months
October	11.30     11.71       11.69	12.83    19.64     13.88		6.25    12.76     08.66
November	20.00     52.00       28.00	43.24    28.57     36.00		26.78    40.58    31.28
December	10.76       7.6           09.6	-           12.95     07.08		45.45    37.28      42.6
January	10.00     24.00       15.19	2.52         -          01.67		6.76       3.7         4.2
February	-             7.89        03.51	17.14      02.00		14.24      4.58    9.143
March	1.3            -             0.8	2.19     1.95       02.39		6.46      7.14      6.57
Overall Average	11.5816	10.503		17.0755

Table: 7. Natural Control based on host plant preference by S.illota on H. armigera.

Collection period	Host plant	Percent parasitism
December 7, 1993 to January 15,1994	Pigeonpea Chickpea	9.60 15.95
December 7, 1994 to January 21,1995	Pigeonpea Chickpea	7.20 2.73
December 1, 1995 to January 21,1996	Pigeonpea Chickpea	35.37 4.55

The incidence of parasitism recorded in the month of   November every year and three season’s average (31.76 %) data was higher than January (7.02%) (Chaudhari and Nikam, 1999). The activity of the parasite was then goes on decreasing in succeeding months. It indicate its less incidence in chickpea season than pigeonpea highlights that S. illota cannot afford the acidic secretions produced by the chickpea plant, whereas C. chloridae can afford with gram (Yadav et al., 1982). Due to acidic exudates on chickpea & pigeonpea plants, parasitism by trichogramma was either nil or extremely low (Yadav, 1980; Yadav and Patel, 1981; Bhatnagar et al., 1982; Reddy and Manjunath, 1999). The activity of C. illota was dominant during the month of November every year is considerable. It was supported by the work of Sithanantham et al., (1983) where S. illota was found to be dominant during October - November, G. halli was dominant during January 1982.

The parasitism by S. illota   was consistent and appreciable on H. armigera for pigeon pea season and it varies from region to region.  Its collective use with other parasites like C. chloridae can effectively check pest population even on chickpea. The incidence of parasitism varied from 0.8 to 52% on pigeon pea and chickpea (Table5, 6,7). Its natural population can be supplemented by inundative releases of laboratory-reared parasitoids during early season or introduction of additional parasitoids will check the population of H. armigera under sub economic levels. S. illota can be used as a key candidate in control of H.armigera.

Table no.8. Percent parasitoid record of some tachinid species of Helicoverpa spp in INDIA.

Name of tachinid species	Percent parasitism	Host crop	Reference
Carcelia (Senometopia) illota Eucelatoria spp. Eucelatoria bryani C. illota andExorista xanthaspis Goniopthalmus halli Palexorista  laxa General dipterans	4-16 52 52 4.55-15.95 15 5 to 20 24.54 20 18-20 51 12-18 22	Tomato, Pigeonpea, lablab Sorghum Pigeonpea Chickpea Pigeonpea Tomato Sunflower Cotton Tomato, Pigeonpea, lablab Cotton Tomato, Pigeonpea, lablab Pigeonpea	1 2 3 4 7 8 6 2 1 5 1 2

References: 1.Achan et al., 1968; 2.Bilapate, 1983; 3.Chaudhari, 1996,2000,2001a, 2002;

4.Chaudhari & Nikam, 1999; 5.Jackson et al., 1976; 6.Patel and Talathi, 1987; 7.Sithanantham, 1981; 8.Sivaprakasam et al., 1986a