Spatial dynamics of teak defoliator (Hyblaea puera Cramer) - Cochin ...

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oads, streams, etc. on copies of plantation maps prepared earlier. The area was estimated using Geographic Information System (GIS) as described in Chapter 4. 3.5. OBSERVATIONS IN THE ENTIRE NILAMBUR TEAK PLANTATIONS The study area at Nilambur was divided into 149 grids and 20 observers were employed to report defoliator incidence. The area under supervision ofeach ofthe observers was visited at least once every week to verify their observation. Whenever outbreak was reported, the date of egg laying at the site and the area under outbreak was determined as described above. 14
CHAPTER IV STUDIES ON THE SPATIAL DISTRIBUTION OF OUTBREAKS IN KARIEM MURIEM TEAK PLANTATIONS AT NILAMBUR 4.1. INTRODUCTION The teak defoliator outbreaks are characteristic in their sudden occurrence over large plantations. It has been observed that outbreaks are prevalent only during some part ofthe year (Beeson, 1941). Light-trap collections ofdefoliator moths at Jabalpur, Madhya Pradesh (Vaishampayan et al., 1983) showed that a large number of moths were collected all of a sudden in July, preceded by a period of nearly 6 months when no moths were collected. This suggested that the insect is not breeding locally. Either migration or diapause was thought to be influencing the population level. A later study in Kerala (Nair and Sudheendrakumar, 1986) showed that the insect is active continuously in the teak plantations eventhough the population density fluctuated over the period - large scale outbreaks occurred during April-July and a very low population comprising overlapping generations ofthe insect was present during the rest ofthe year. In a three year study based on sample plots (Mohanadas, 1995), it was inferred that several distinct phases were recognized in the population trend of teak defoliator. The first phase during February to April is characterized by small patch infestations. This is followed by heavy and widespread infestations. It was observed that in a given large area, a second outbreak might occur before the moths of the existing generation has emerged. In the third phase, the population density declines and infestations become erratic. Following a lull period, erratic infestations occur again in August, September, or October and subside. Following this, it was observed that until the first phase begins again next year, the population remains very low, almost undetectable. However, very little is known on the distribution of defoliator outbreaks in space. Maps of plantations showing defoliation prepared by Beeson (1928)
Page 1 and 2: SPATIAL DYNAMICS OF TEAK DEFOLIATOR
Page 3 and 4: CERTIFICATE This is to certify that
Page 5 and 6: Mr. Rajan James, Mr. A. Moosa, Mr.
Page 7 and 8: 4.3.5. Correlation between outbreak
Page 9 and 10: CHAPTER I INTRODUCTION Insects are
Page 12 and 13: covering the entire plantations of
Page 14 and 15: Burma and recommended that providin
Page 16 and 17: In a two-year light trap study at J
Page 18 and 19: during 1983-94 and 1987-89 recorded
Page 21: area of 50 ha. A group of ten grids
Page 25 and 26: within these various spatially refe
Page 27 and 28: 4.2.3. Correlation between outbreak
Page 30: 4.3. 2. Outbreak pattern, 1993 The
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Page 35 and 36: _ 0 _ 1 0 2 _ 3 _ 4 _ 5
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Page 39 and 40: Table 4.7. The relationship between
Page 41 and 42: Fig. 8. Location of first outbreak
Page 43 and 44: Table 4.9. Elevation and aspect oft
Page 45 and 46: aspect and outbreak frequency. The
Page 47 and 48: map. The methodology adopted for da
Page 49 and 50: The sixth outbreak occurred on 26 M
Page 51 and 52: explained as caused by progenies of
Page 55 and 56: Fig.5.3. Map ofNilambur teak planta
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Page 67 and 68: Fig.5 .15. Map ofNilambur teak plan
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Fig.5 .21. Map ofNilambur teak plan
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6.2. METHODS In this study, post em
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was observed at around 06.15 h on t
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Two moths (one male and one female)
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Aggregations of the moths were pred
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CHAPTER VII DEVELOPMENT OF OUTBREAK
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-.-.-._ --- _--. Black light tube -
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Table 7.1. Correspondence between l
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foliage. If folds are detected, obs
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study has considerable bearing on t
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maximum of 13 ha (see Section 5.2,
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c) Variation in plant quality I ava
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away places. These populations seld
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Berryman, A. A. (1987) The theory a
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Nair, K. S. S., Mohanadas, K and Su
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APPENDIX A ALGORITHM: FOR COMPUTATI
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Date *No. of Incidence Local Date *
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Date "No. of Incidence local Date "
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