Hyblaea puera , the teak defoliator , is a moth native to south-east Asia. It was first described by Pieter Cramer in The species has also been recently reported to be present in Central America and Africa. The caterpillar feeds on teak and other trees. Recent reports place it in Guadeloupe , and Suriname. Males and females emerge more or less simultaneously and mating takes place within a couple of days.
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The Teak defoliator Hyblaea puera is a pest moth of teak woodlands in India and other tropical regions e. Thailand and is of major economic significance.
This pest is of major concern as it is involved in complete defoliation of trees during the early part of the growing season. Defoliation does not kill teak trees, but it results in huge amount of timber loss. Teak defoliator outbreaks are a regular annual feature in most teak plantations in India and it is extremely difficult to predict the exact time and place of occurrence of these outbreaks.
Evidence from the study of the population dynamics of H. We were therefore interested in investigating the temporal and spatial relationship among various population groups in Nilambur, Kerala India and address the cause of outbreak at the landscape level.
The populations were classified into 'endemic', 'epicenter' and 'epidemic' populations based on the time of occurrence and size of infestation. We have used this method extensively to evaluate the species specificity, reproducibility and to discriminate among the three different characterised populations of teak defoliator.
This method also allowed us to comment with some certainty that the endemic teak defoliator, H. With respect to the hypotheses put forward regarding the origin of outbreaks of the moth, this study confirms the role of migration in outbreak causation, while negating the belief that endemic populations aggregate to cause an epidemic. Teak Tectona grandis L. The Teak defoliator is of major concern since it is involved in complete defoliation of trees during the early part of the growing season.
Defoliation does not kill the trees, but does lead to huge timber loss. It has been estimated that in the Nilambur teak plantation during the study period, protected trees increased by an annual increment of 6.
Teak defoliator outbreaks are a regular annual feature in teak plantations in Kerala, India. It is difficult to predict the exact time and place of these outbreaks.
Evidence gathered from the past decade on the population dynamics of H. Earlier studies also indicated that the outbreaks begin as small epicenters during the pre-monsoon season [ 4 ]. Populations were classified as 'endemic', 'epicenter' and 'epidemic', based on their time of occurrence and the density of the population as represented by the area it infests.
Endemics are insects belonging to the low-density population level; epicenters are patchy, medium density outbreaks that occur during the pre-monsoon season, whilst epidemic represents large area, high-density outbreak populations. An understanding of the origin and spread of the epidemic of this pest, which erupt suddenly following the pre-monsoon rain each year, is an important prerequisite for developing appropriate control strategies.
If progenies of the epicenter populations cause the larger epidemics, control of these could prevent major outbreaks. On the other hand, if immigrant moths were involved, it would be difficult to control major outbreaks.
Thus, understanding the cause and effect relationship between initial small outbreaks and large outbreaks that occur later in the year is crucial for the control of the pest.
Such approaches have also been used to study founder events [ 5 ], geographical invasions [ 6 ], small and large scale displacements [ 7 , 8 ], including movement of entire population demes [ 9 ], and even altitudinal movements related to habitat patchiness and persistence [ 10 ]. Molecular data can yield valuable information when integrated with information from ethology, field ecology, comparative morphology, systematics and palaeontology [ 11 ].
Use of direct and indirect methods of tracking insects along with description of the role and utility of various molecular markers — protein and DNA — in monitoring insect dispersal, has been extensively reviewed [ 12 ]. Arbitrarily-primed DNA markers, and involving the polymerase chain reaction PCR , have proved very useful for genetic fingerprinting and for facilitating positional cloning of genes. This class of markers are particularly important for less studied species, for which genome sequence information is generally not known.
In this study, we used a variant of the RAPD approach involving various nuclear and mitochondrial gene specific primers to trace the origin of teak defoliator outbreaks. It is expected that the molecular data would provide the necessary information to elucidate the origin of the epidemic population.
Such information should prove valuable in planning and implementing measures to control these pests. Therefore, the aim of the present study was to identify the relationship among the three apparent populations — endemic, epicenter and epidemic.
The nuclear and mitochondrial gene specific primers chosen did not produce any amplification product when used in combination with the corresponding primers as described in the UBC primer set kit [ 17 ].
RAGEP markers were first tested for polymorphisms, species-specificity and repeatability. The bands scored for each nuclear RAGEP used in the present study were of a size range bp to bp.
In each marker, the average number of bands scored varied from 7— The maximum number of bands was detected using primer cytC-B-3', while the maximum number of monomorphic bands were detected using primer EFS M depicts variability in Lepidopteran species. Subsequently similarity matrixes of all experimental patterns were combined to generate a UPGMA Unweighted pair-group mathematical average tree. Similarly in the second major cluster, the remaining populations from the epicenter and entire epidemic insect populations were likewise seen to fall into two distinct sub-clusters.
Using the mitochondrial RAGEP markers, the average numbers of bands scored for each primer ranged from 6— All bands scored were of size range bp to kb. The maximum numbers of bands detected was found using primer SR-J, the minimum numbers using marker N4-N Among mitochondrial markers, an average of 1—2 monomorphic bands were observed. The maximum number of monomorphic bands was observed using marker CB-N One of these clusters comprised the majority of the endemic samples with a few samples from epicenter insects, whilst the other cluster was comparatively larger and had the two major sub clusters.
From this dendrogram, it may be deduced that all the seven epidemic population samples tested in the study shared the same gene pool with sets of epicenter populations. In contrast, the endemic populations are genetically distant from the epicenter populations. Preliminary information on the life history of H. It was then suspected that population build-up in the early outbreak epicenters might account for the subsequent widespread epidemic. However, a study using the time lapse developmental time between two epidemics to determine whether an earlier epidemic was responsible for causing the subsequent outbreak showed that all subsequent outbreaks could not be attributed to previous outbreaks, thereby indicating the possibility of migrant populations being involved [ 19 ].
Several technical advancements on the DNA fingerprinting methodologies have been established to resolve the taxonomic uncertainties and address the issue on species variability and migration [ 13 - 16 , 20 , 21 ]. Longer mitochondrial 19—26 nucleotide gene encoding primers are likely to increase the reproducibility and specificity when compared to RAPD technique. This method was found to be efficient, simple and highly reproducible. Here it has been effectively used to discriminate the various population groups of H.
It can also be used to discriminate taxonomically various closely — related moths to the species level. Mitochondrial DNA sequences are frequently transferred to the nucleus-giving rise to NUMTs, which are considered to be common in eukaryotes [ 22 ]. Very high rate of horizontal transfer between organellar and nuclear genomes has been reported in the brown mountain grasshopper, Podisma pedestris L. Age groups, sexes, life history variants, etc.
While studying the differentiation process of grain aphid, Sitobion avenae F. Highly diagnostic banding patterns in individuals of S. Monophyly and a strong biogeographic pattern of each biotype have been reported in whitefly, Bemisia tabaci Gennadius populations studied throughout the world [ 27 ].
While evaluating the genetic structure in introduced population of the fire ant, Solenopsis invicta Buren using different classes of markers, it was confirmed that both mitochondrial and nuclear markers display the same hierarchical structure [ 28 ].
Distinct mitochondrial and nuclear DNA sequence divergence patterns for phylogenetic inference has been established among nymphalid butterflies [ 29 ]. The present study using RAGEP-PCR provides a tool for a logical continuation of the earlier work to trace the relationship of endemic, epicenter and epidemic populations of the teak defoliator. The dendrogram produced from nuclear RAGEP clearly indicates that the endemic insects are not involved in causing the epidemic; however, they are apparently involved in the localized spread by building up small epicenter populations.
Similarly, while evaluating the observation based on mitochondrial RAGEP's, it is further apparent that endemic populations were not involved in causing the epidemic. This suggests that all the epidemic insects, which are spatially distinct, but temporally co-occurring, share the same gene pool.
Randomness of genome amplification methods have been efficiently used in constructing the phylogenetic history in the weevil, Aubeonymus mariafranciscae Roudier , which had diverged recently [ 5 ], whilst the origin of the Argentine stem weevil, Listronotus bonariensis Kuschel in New Zealand, was traced to the eastern coast of South America [ 30 ].
Use of RAPDs to examine, for example, population subdivision of the saw toothed grain beetle, Oryzaephilus surinamensis L. Earlier reports involving molecular DNA markers mention the use of these markers in the detection of sibling species of black flies, Simulium spp. With the Teak defoliator, earlier studies based on temporal and spatial distribution of the larvae indicated that the epicenters were not constant over the years and did not represent highly favourable local environments [ 3 ].
The present study found little evidence to show that the aggregation of moths belonging to the endemic populations cause the epicenter populations. On the other hand, the findings do suggest the alternate hypothesis, i. This suggests that under a single demographic structure, two phenotypic classes of H.
The degree of variability observed for RAGEPs also argues that this technique could be useful for a variety of questions, including individual identification, strain identification and phylogenetic analysis.
The present results appear to validate the hypothesis, that control of H. Therefore, appropriate strategies should be adopted to control the epicenter populations, which occurs in a smaller area. This appears to be a more practical and economical approach for teak defoliator management when compared with management of the pest in the total plantation area covering thousands of hectares. Thus the molecular markers detected using RAGEP-PCR can enhance the understanding of insect population dynamics and aid in tracing the spread and cause of epidemics.
Based on the spatial pattern of infestation in the past, the area was divided into convenient observation units of approximately 50 ha, based on natural boundaries of streams, roads and footpaths.
The canopy of teak is continuous within in the observation area. Each area was monitored every 15 days, which was precisely based on the life cycle of H. Larval samples were collected from the infestation sites.
If only lower stages were available, i. Ten 5th instar larvae were preserved for DNA isolation from each sample site, whilst the remaining larvae were reared into the next generation. Using the duration of each instar egg — one day; 1 st and 2 nd instars — two days each, 3 rd to 5 th instars — three days each; pre-pupa — one day and pupa — four days , the temporal data on outbreaks were examined to see whether each subsequent epidemic could be explained on the basis of a previous outbreak.
Landscape of Nilambur teak plantation showing distribution of the endemic, epicenter and epidemic populations of Hyblaea puera. Five endemic populations, twenty six epicenter populations and seven epidemic populations for the year were included in the study. Earlier studies had indicated that outbreak begin as small epicenters in February during the pre-monsoon season and end by June.
Endemic samples were collected throughout that year based on their stray occurrences in various life stages, whilst epicenter samples from each aggregated patch were collected only from the insects that attained the same stage of its life cycle at the time of collection in that patch.
Similarly the epidemic samples were also collected from insects representing the same life stages at the time of collection from each aggressive patch. The temporal relationship between the endemic population and the epicenter populations and that of the epicenter populations with the large-scale epidemics were first worked out.
The larval samples that were geographically close and had a difference of one complete life cycle stage between the population groups were subjected to molecular studies to evaluate their relatedness.
DNA extraction was performed with a minor modification of isolation and purification protocol as described earlier [ 37 ] being extracted from whole larvae and quantified spectrophotometrically using a spectrophotometer at nm Shimadzu.
Each reaction consisted of 1x Taq buffer with 1. Primers were initially screened for polymorphism and repeatability.
List of symptoms / signs
Hyblaea puera Cramer Lepidoptera: Hyblaeidae. Hyblaea puera is a common defoliator of teak Tectona grandis that can be found between the West Indies and Fiji. Apart from teak there is a large number of alternative host plants for these polyphagous caterpillars. The eggs are laid singly on the leaves of the foodplant.
The Teak defoliator Hyblaea puera is a pest moth of teak woodlands in India and other tropical regions e. Thailand and is of major economic significance. This pest is of major concern as it is involved in complete defoliation of trees during the early part of the growing season. Defoliation does not kill teak trees, but it results in huge amount of timber loss. Teak defoliator outbreaks are a regular annual feature in most teak plantations in India and it is extremely difficult to predict the exact time and place of occurrence of these outbreaks. Evidence from the study of the population dynamics of H. We were therefore interested in investigating the temporal and spatial relationship among various population groups in Nilambur, Kerala India and address the cause of outbreak at the landscape level.