Browsing by Author "RAMAIAH, M"
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ThesisItem Open Access BIOSYSTEMATICS OF LEAFHOPPERS IN MANGO ORCHARDS AND THEIR MANAGEMENT WITH CERTAIN NEWER INSECTICIDES(ACHARYA N.G. RANGA AGRICULTURAL UNIVERSITY, RAJENDRANAGAR, HYDERABAD, 2010) RAMAIAH, M; RAMA SUBBA RAO, VThe studies on “Bio-systematics of leafhoppers in mango orchards and their management with certain newer insecticides” was undertaken during 2006-08. The taxonomic studies on the leafhopper fauna associated with mango orchards in Andhra Pradesh were carried out in the department of Entomology, S.V. Agricultural College, Tirupati after collection of leafhoppers from different mango orchards of various places in Andhra Pradesh. The field experiments regarding the studies on the influence of abiotic and biotic factors with population buildup of leafhoppers on mango crop, incidence of leafhoppers on different mango varieties and evaluation of different spray schedules of insecticides in the management of leafhoppers were undertaken in xiv the existing mango orchards at Regional Horticultural Research Station, A.P. Horticultural University, Anantarajupet of Kadapa District. Four leafhoppers viz., Amritodus atkinsoni (Lethierry), Amritodus brevistylus (Viraktamath), Idioscopus nagpurensis (Pruthi) and Idioscopus niveosparsus (Lethierry) were identified, described and illustrated male genitalia structures. A key for distinguishing all these species was provided. The leafhopper, Amritodus brevistylus (Viraktamath) is reported for the first time and hence it is a new record on mango from Andhra Pradesh. Among the above four species recorded from Andhra Pradesh, A. atkinsoni was a dominant species (62.80%) followed by I. niveosparsus (31.70%) and the remaining two species I. nagpurensis (5.3%) and A. brivistylus (0.02%) were less abundant. The natural enemies associated with mango leafhoppers recorded were lysomanid spider, Telamonia sikkimensis (Tikader), coccinellid predators, Cheilomenes sexmaculata (Fabricius) and Anegleis cardoni (Weise) and chrysopid, Chrysopa lacciperda Kimmins. The leafhopper population increased gradually from the first week of September and reached to a peak during second to fourth week of February and thereafter the population declined gradually in the first week of May. The correlation between the leafhopper population, minimum temperature and evening relative humidity was negative and significant, whereas correlation with maximum temperature, morning relative humidity and rainfall were also negative but not significant. The relationship between leafhoppers, coccinellid xv predators and spiders was positive and significant. The mango varieties viz., Mulgoa, Neelum, Totapuri, Banganpalli and Rumani were observed to be relatively less by mango leafhoppers. Among all the insecticidal treatments tried, thiamethoxam 25 WG @ 0.005% given in three sprayings gave significantly highest percentage reduction of leafhoppers and highest yield including highest cost-benefit ratio (1: 16). Chlorfenapyr 10 SC @ 0.01% sprayed thrice and the treatment with three sprayings where in first spraying with chlorfenapyr 10 SC @ 0.01%, second spraying with thiamethoxam 25 WG @ 0.005% and third spray with diafenthiuron @ 0.07% were also found good next in the order against mango leafhoppers, but with low cost benefit ratio (1:4.66 to 4.86). The conventional insecticides of monocrotophos 36 SC @ 0.072%, imidacloprid 17.8 SL @ 0.006% and carbaryl 50 WP @ 0.15% given in first, second and third sprayings also recorded comparatively high cost benefit ratio (1:6.80 to 8.87) and hence this spray schedule can also be recommended against mango leafhoppers.ThesisItem Open Access STUDIES ON BIOLOGY AND MORPHOMETRICS OF IMPORTANT SPODOPTERA SPECIES(PROFESSOR JAYASHANKAR TELANGANA STATE AGRICULTURAL UNIVERSITY, 2018) RAMAIAH, M; UMA MAHESWARI, TThe present study entitled “Studies on biology and morphometrics of important Spodoptera species”was carried out at Department of Entomology, College of Agriculture, PJTSAU, Rajendranagar, Hyderabad during 2017 - 2018. During the period of study, biology and morphometrics of important Spodoptera species viz., S. litura, S. mauritia and S. exigua on respective host (S. litura on castor, S. mauritia on rice and S. exigua on chickpea) were documented under laboratory conditions. With regard to S.litura the total life period lasted for 32.13±5.48 days with a fecundity of 890.50±16.26. S.mauritia took 38.37±4.62 days with a fecundity of 1013.10±21.92 eggs and S.exigua 32.38±5.13 days with a fecundity of 308±25.46 eggs indicating the total development period for Spodoptera spp in general ranging from 26.65 to 42. 99 days. Observations on morphological variations in different stages of three species of Spodoptera revealed a clear difference where eggs of S.litura were spherical in shape, yellowish creamy in color covered with yellowish brown hairs, S. mauritia has spherical shaped eggs that were green in color covered with greyish hairs and S.exigua had typically white colored eggs covered with white scales giving a fuzzy or cottony appearance. In the case of active feeding larval instar i.e., 3 rd and 4th instars which cause much crop damage in the field, variation in the morphology was observed as, body color being dark green dosally with large black spot on 1st and 8th abdominal segments and pale greenish yellow ventrally in S.litura. The third instar larva has three yellowish bands which were not clear but later in the fourth instar these bands became distinct with a central band being bright orange and the lateral ones yellow in colour. In the case of S.mauritia, the third instar was pale green in color with lateral reddish lines and fourth instar had three dull white longitudinal lines with black intermittent dots on each segment arranged dorsally along the length of the body where as fifth instar larvae became greenish black with prominent black triangular markings. In the case of S.exigua, third and fourth instars were pale green in color with stripes on dorsal and lateral surface of the body. Fifth instar larvae of S.exigua typically showed colour polymorphism recording about 34 morphs ranging in colors from green, black, pink to yellow in combination. Being different from S.litura and S.exigua, S.mauritia had sixth instar which was grayish black in color having prominent wide and dark triangular markings dorso laterally With regard to larval behavior while rearing in the laboratory during the period of study, cannibalism was observed in S.exigua where the fifth instar larvae were observed feeding on both the larvae and pupae of their own species. In the present study, the arrangement of crochets on the planta of prolegs of three species of Spodoptera was found to be uniordinal homoideous mesoseries. However, their arrangement in a single row differed by being half circular with a deep curve in the inner line crochet arrangement in S.litura, complete half circle in S.mauritia and half circle with slight deepness in the lower line of crochets in S.exigua Reddish brown to dark brown pupae were observed commonly both in S.litura and S.maurita though the pupae were light brown in colour in S.exigua. Adult female of S. litura was brown with crisscross cream colored streaks and male had white prominent band on forewings. Where as in S. maurita, female had grayish brown forewings with dark spot in the middle and male has bright grayish forewings. Typically male of S.mauritia showed tuft of hairs on forelegs differing from S.litura and S.exigua. In the case of S.exigua, forewings were mottled gray and brown in color with an irregular banding pattern and light colored bean-shaped spot where females were brightly colored than males. The morphometrics data showed that among the three species of Spodoptera, diameter of the egg ranged from 0.41 to 0.56 mm being bigger in S.exigua as 0.56 and smaller in S.litura as 0.41 where as S. mauritia have 0.43. The body length and width from first instar to fifth instar was 1.49 ± 0.09 mm and 0.23 ± 0.03 mm, 4.44±0.82 mm and 0.51±0.07 mm, 11.92±1.48 mm and 1.49±0.06 mm, 23.15±0.55 mm and 3.44±0.87 mm and 37.72±0.45 mm and 5.94±1.47 mm, respectively in S.litura. In the case of S.mauritia, first to sixth instar, body length and width was 1.30 ± 0.14 mm and 0.38 ± 0.07 mm, 2.64±0.28 mm and 0.51±0.02 mm, 5.56±0.22 mm and 1.23±0.16 mm, 16.50±0.23 mm and 2.30±0.12 mm, 27.00±0.10 mm and 3.49±0.28 mm and 36.50±0.08 mm and 5.60±0.45mm, respectively. In the case of S.exigua, body length and width from first to fifth instar was 1.23 ± 0.16 mm and 0.27 ± 0.03 mm, 4.51±0.25 mm and 0.84±0.05 mm, 9.13±0.68 mm and 1.55±0.15 mm, 13.63±0.76 mm and 2.25±0.20 mm and 22.00±1.47 mm and 3.37±0.41 mm, respectively. Pupae were small being 12.00 mm in S.exigua and big in S.mauritia being 16.40 mm in size where S.litura had medium size of 14.05 mm. Adults of S exigua was having less body length and wing span ranging from 11.00 to 13.00mm and 25.00 to 26.00mm respectively. However, S.mauritia was mediam in size having a body length of 16.00 to 18.00 mm and wing span ranging from 30.00 to 34.00 mm. S.litura has a body length ranging from 15.50 to 17.50 mm and wing span of 37.00 mm. With regard to growth ratio of Spodoptera species, S.litura has the growth ratio between 1 st and 2nd instar as 1.44, 2nd and 3rd as 1.38, 3rd and 4th as 1.40, 4th and 5th as 1.59. The average ratio of increase in head capsule width in each instar was calculated as 1.45. Revealing consecutive larval instars followed a more or less regular geometrical progression of 1.45. In the case of S.mauritia, growth ratio between 1st and 2nd instar was 1.68, 2nd and 3rd was 1.52, 3rd and 4 th was 1.46, 4th and 5th was 1.98, 5th and 6th was 1.45 showing an average ratio of 1.62 for all the consecutive larval instars. In case of S.exigua, growth ratio between 1st and 2nd instar was 1.41, 2 nd and 3rd was 2.61, 3rd and 4th was 1.05, 4th and 5th was 1.64 with an average of 1.68 which was observed as slightly deviating from dyar’s law. In specific, it was 2.61 between 2nd and 3rd instar deviating from the geometrical linear growth.