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Shamuratova N. G., Ph.D., candidate of Uzbekistan National Research Institute for Plant Protection E-mail: [email protected]
GYPSY MOTH (LYMANTRIA DISPAR L.) POPULATION IN UZBEKISTAN AND PATHOGENICITY OF THE NUCLEAR POLYHEDROSIS VIRUS
Abstract: In the period from 2015 to 2018, the population of the gypsy moth in the Tashkent region was in a state of transition from an active state to a rest state and a decrease in the degree of its damage was observed. Local isolates of the nuclear polyhedrosis of the gypsy moth are pathogenic with respect to the larvae of the host insect. Keywords: gypsy moth, population, pathogenicity, nuclear polyhedrosis virus, Uzbekistan.
Introduction
The area of distribution of the gypsy moth, begins on the south of Scandinavia in Europe and extends through the Asian territory of Russia reaching the Khabarovsk Region and Far Eastern Federal District. Members of this species can also be found in the countries of North Africa, and in many countries of the Asia. Gypsy moth was brougt to North America in the XIX century and at present the area of its distribution includes a vast territory from the Atlantic to the Pacific oceans. A dis-tincitve feature of the gypsy moth is that outbreaks of its mass reproduction occur periodically, once every few years. During the period of mass reproduction, it aggresively devours leaves of trees on several thousand hectares ofareas, which leads to death of the affected plants. This insect damages practically all types of deciduous trees, as well as a number of coniferous species.
Overview
Over recent years, mass reproduction and spread of gypsy moth have also reached Uzbekistan. In 2012-2013, this species inhabited 500 hectares of the Ugam-Chatkal mountain range, causing great damage to various forest and fruit trees. There exists a possibility of its spread in the basin of the Chirchik river and other foothill areas. Despite the measures to combat the gypsy moth, this species continues to spread to other areas.
To stop this threat and save the ecosystem, it is important to develop environmentally friendly measures to stop the gypsy moth. Work has already been carried out to research the pathogenic virus of nuclear polyhedrosis that can be used against it and to develop a microbiological preparation on its basis. This research is based on the entomopathogenic virus Borrelina repriens, belonging to the genus Borrelina Paillot from the family Baculoviridae. Morphofunctional properties of the entomopathogenic virus Borrelina repriens were first studied by Bergold. In his opinion, the virions of this virus have a rod-like shape with size of 300 x 41 m^, a five-sided polyhedral shape measuring 5-6 x 10 ^m. Each size of the polyhedron has 4-8 virions (4-5 on average). The drug Virin-NSh was developed in Russia to combat the gypsy moth. The
basis of this drug is the nuclear polyhedrosis virus, which penetrates into the larvae of the gypsy moth. During 1995-2001, this drug was used on the territory of more than 170 thousand hectares in the Novosibirsk and Tyumen regions of Russia, in the Altai Region, in the Pavlodar and Petropavlovsk regions of Kazakhstan. The disease caused by the virus of the nuclear polyhedrosis of the gypsy moth is well studied by scientists of the USA and European countries.
Research Technique
In Uzbekistan, study of entomopathogenic microorganisms of the gypsy moth have not been conducted. Therefore, samples were collected in the territory of the Bostanliq district of the Tashkent region. In 2015-2018, studies on the distribution of the gypsy moth, its population density and the pathogenic virus were carried out under stationary conditions in the Bostanliq experimental area of the Institute of Pomology, and along the main road Gazalkent-Sidzhak, Gazalkent-Charvak, Gazalkent-Khumsan, Gazalkent-Aktash. Forest and fruit trees affected by gypsy moth were studied. The dynamics of development of the gypsy moth and infection rate in its population by the nuclear polyhedrosis virus are revealed. For three years of the conducted studies, data was collected on the territory of more than 200 square kilometers in selected areas to study the state of the population of the gypsy moth in the zone of the Ugam-Chatkal National Park.
Larvae that have been collected in the field were contained in 1, 2 and 3 liter cans. Leaves of cherry, quince, apricot and apple were used as the food, and the suitability of them to feed the larvae was also studied. The infected and dead samples were studied separately from the main population. The samples turned into pupae were separated by sex and placed in separate cans. Hatched butterflies were transferred in pairs for reproduction.
Guidance materials were used for this study [1]. In laboratory conditions, the pathogenic effect on the larvae of the gypsy moth was studied on the isolates of entomopatho-genic viruses chosen among them. The samples of the larvae
GYPSY MOTH (LYMANTRIA DISPAR L.) POPULATION IN UZBEKISTAN AND PATHOGENICITY OF THE NUCLEAR POLYHEDROSIS VIRUS
required for the experiments were obtained among the population grown under laboratory conditions. Samples were separately placed in double dishes and treated with a suspension of the microorganism studied by spraying in the required titres.
To prepare the virus suspension, insect samples infected with the virus were placed in a porcelain foot and diluted with distilled water in the required ratio and filtered. After determining the titer of the suspension obtained this way, it was added to the food of larvae that were kept not fed for some time. Samples of insects were observed until their death, or 5-20 days, after which the dead samples were counted. The dead samples were examined under a microscope.
Table 1. - Development phenology of the gypsy
According to the data received at the Bostanliq district experimental area of the Institute of Pomology, in 2015, fruit trees suffered largest harm from the gypsy moth. The trees had more than 3-5 eggs of gypsy moth. In summer, the number of larvae increased significantly and reached an average of 8-15 larvae on one branch.
During the next two years, the density of the gypsy moth population began to decrease in stationary experimental areas, the rate of eggs in 2016 was 1 egg for every 2-3 trees. Tree lesions of larvae of gypsy moth were not observed. In the beginning of June, larvae of butterflies that came from other territories appeared on branches of some trees. And in the third year of the study, (in 2017) eggs or larvae of gypsy moth were not detected in the experimental area. To determine the population of the gypsy moth, observations were made along the selected routes. Around the Gazalkent-Aktash, Gazalkent-Charvak-Khumsan routes at an altitude of 880-1025 m above sea level, the gypsy moth was not detected in quantities that could endanger the ecosystem. In the mountainous area above the Khumsan village, at an altitude of 950 m above sea level, trees that were affected by these insects have been discovered.
Therefore, it was established that in 2015-2018 in the territory of the Bostanliq district of the Tashkent region the population of the gypsy moth was experiencing a period of transition from an active state to a rest (remission), that is, an
Results
Based on the results of experiments conducted at the experimental area of the Institute of Pomology of Uzbekistan in the Bostanliq district, a developmental phenotype of the development of the gypsy moth in 2015 (Table 1) was completed. According to the collected data, the larvae of the gypsy moth hatch in the third decade of April. The period of development and growth of larvae continues until the first decade ofJune. On 3-6 ofJune the pupae has developed. In the second decade of June they turned into butterflies and began laying eggs starting from 16 ofJune.
moth population in the Bostanliq district in 2015
intensive reduction in the range of distribution and damage from the gypsy moth.
During the study, in 2015-2017, five isolates of the nuclear polyhedrosis virus were distinguished from the specimens of the gypsy moth larva and their pathogenic properties were studied. As a result of studies conducted in May 2015 on the experimental area of the Institute of Pomology in the Bostanliq district, specimens infected by the nuclear polyhedrosis virus were identified and harvested. In the course of the experiments, it was found that 9 specimens (12.5%) from total of 72 were infected with the virus. The discovered virus was named VNP-Ld-11. Also, from samples of later stage larvae of the gypsy moth that were harvested from fruit and forest trees along the road on the first chosen route Gazalkent-Charvak, and on the second route Char-vak-Sidzhak, two isolates of the virus were discovered. In addition, during the study, two more isolates were discovered and were named VNP-Ld-44 and VNP-Ld-55 respectively. The pathogenic properties of isolates of the virus of the nuclear polyhedrosis of the gypsy moth, discovered in 2015-2016, in relation to the larvae of the insect host were studied. As the results showed, the pathogenicity of the isolate at 2.5 x 107 polyhedron/ml titer is 40.0 ± 7.3 and 59.1 ± ± 6.6%. Adjustment of the working titer of the isolate to the value of 1 x 108 polyhedron/ml increases the pathogenicity of VNP-Ld-44 and VNP-Ld-55 isolates and ensures the
Month April May June July
Third II III I II III I II III
E
L L L L L
P
I
I
E
Note: development stages of the insect: E - egg; L - larva; P - pupa; I - imago
larvae mortality rate of 83.3 ± 4.1 and 95.0% respectively. In general, the isolates showed a high pathogenicity relative to the larvae of the gypsy moth. The dead larvae showed signs of disease caused by these viruses.
Conclusion
In 2015-2018, the population of the gypsy moth in the territory of the Tashkent region experienced a period of transi-
tion from an active state to a rest (remission), that is, an intensive reduction in the range of distribution and harmfulness of the gypsy moth.
From the population of the gypsy moth scattered in the Tashkent region, isolates of the nuclear polyhedrosis virus were identified and the pathogenic properties of the virus against larvae of the insect host were researched.
References:
1. Барджес Г. Д., Хасси Н. У Микроорганизмы в борьбе с вредными организмами и клещами. - М.: Колос, 1976.- С. 7-16.
