Key message: More frequent gradation period and decrease of latency
Assessment: Insect gypsy moth (Lymantria dispar L.) is the largest pest of the deciduous forests in Serbia, and also is a significant pest in fruit growing. Its overpopulation (gradation) often has the character of a natural disaster requiring significant engagement of labour and financial resources for the purpose of suppression. In the forests, defoliation caused by gypsy moth leads to a decrease in the growth and weakening of the vitality of trees, and if this damage is in a chain reaction, it can also lead to the occurrence of drying of forests. Overpopulation of gypsy moth usually lasts from 3 to 6 years. In the period since 1862, the time when it has been monitored in the territory of our country, to date 18 gradations have been registered, and the new (19th) gradation of the gypsy moth is underway in 2017, with the increased presence of gypsy moth nests on relatively small surfaces, so that the gypsy moth came out of the latency and entered the first phase of gradation – progradation. During 2018, there is a trend of increasing the number, and expanding territory under attack, which is mainly of low intensity.
Science has not yet established the reason for the occurrence of gradations, however, the analysis of the appearance of gypsy moth in Serbia in the period from 1862-2019 clearly shows the trend of increasing the frequency of gradations during the past 20 years. It is clearly visible that the duration of the latency period is reduced, which is only two years after the last three gradations. There are some scientific researches that presuppose that the frequency of occurrence of gradations can be dramatically increased by the increase in temperature, change of precipitation regime and climate change.
Literature: Predviđanje prenamnoženja gubara (Limantria dispar L.) u svetlu klimatskih promena – Dejan Stojanović, Milena Kresoja, Milan Drekić, Leopold Poljaković-Pajnik, Nataša Krklec-Jerinkić, Nataša Krejić, Saša Orlović https://scindeks-clanci.ceon.rs/data/pdf/0563-9034/2016/0563-90341698015S.pdf
Indicator Name: Monitoring and gradation of gipsy moth (Limantria dispar) in the forests of Serbia
Institution/Author: Public Enterprise Srbijasume/Dejan Miletić
Use and interpretation:
Key question(s) which indicator helps to answer: The indicator helps to answer on question on what is the status of gypsy moth population in Serbian forests.
Use of indicator: This indicator monitors the frequency of occurrence increase gypsy moth population (Lymantria dispar L.), i.e. the occurrence of outbreak – gradation and normal population numbers, i.e. hibernation – latency. The gypsy moth belongs to gradogenic pest insects. The main characteristic of the species is the occurrence of cyclic increase population number – gradation, with a high and very high population level. Increasing population numbers means the beginning of gradation. The decrease a population number is known as a latency, i.e. an inaction of gypsy moth population when the gypsy moth population number is at constant low level.
Scale of appropriate use: The indicator is monitored by regular monitoring of the health status of forests by forest users on the surveyed areas as an obligation in accordance with the Forest Law.
Potential for aggregation:
Meaning of upward or downward trends (“good or bad”): Period of gradation usually lasts from 3 to 6 years. In the period since 1862, when monitoring is active in our country, there have been 18 registered gradations until today, with the new (19) gradation, when in 2017 is recorded increase presence of gypsy moth on relatively small area, so gypsy moth is coming out of latency and entered the first phase of gradation – progradation. During 2018, the trend of increasing population number is continued and gypsy moth are spread of larger territory, with still on low intensity. There is recorded, in past three decades, more appearance of gradation and shorted period of latency faze of gypsy moth.
Possible reasons for upward or downward trends: Science has not yet determined the reason for gradation. There are assumptions that with the frequency of the occurrence of gradations, temperature rise and change of precipitation regime, due to climate change, can drastically increase (source: PREDICTION OF GYPSY MOTH (LYMANTRIA DISPAR) OUTBREAKS UNDER CLIMATE CHANGE Dejan Stojanović1 , Milena Kresoja2 , Milan Drekić1 , Leopold Poljaković-Pajnik1 , Nataša Krklec-Jerinkić2 , Nataša Krejić2 , Saša Orlović ) https://scindeks-clanci.ceon.rs/data/pdf/0563-9034/2016/0563-90341698015S.pdf
An important role in reducing the population of the gypsy moth is pathogen fungi, Entomophaga maimaiga, introduced in Bulgaria in 1999 and later recorded in Serbia (source: (Tabaković -Tosic et al., 2012).
Implications for biodiversity management of change in the indicator: Forest users are obliged to monitor the forest health conditions and the occurrence of gypsy moth egg sacs and the data are delivered to the Forestry Institute (Central Serbia) and the Institute for Lowland Forestry and Environment (Vojvodina), which make an annual report.
Units in which it is expressed: duration of gradation and latency, years
Description of source data: Annual Report on Diagnosis of pest organisms.
Calculation procedure: The users of the forest based on the monitoring at established permanent surface areas and the application itinerary method, provide data on the number of gipsy moth egg sacs per unit of area, and by measuring the number and vitality of the eggshell samples, the Forestry Institute gives recommendations and assesses the intensity of the attack.
Most effective forms of presentation: Graph
Limits to usefulness and accuracy: None
Updating the indicator: Yearly
Closely related indicators: None
Additional information and comments: Gypsy moth (Lymantria dispar L.) is the most economically significant and abundant pest in deciduous forests in Serbia. It is also very important pest in fruit orchards. His outbreak often has the character of a natural disaster that requires a significant commitment of manpower and financial resources in order to suppress it. Defoliation caused by gypsy leads to reduction of tree increment and weakening of vitality of trees, that could lead to the appearance of forest dieback.
Period of gradation usually lasts from 3 to 6 years. In the period since 1862, when monitoring is active in our country, there have been 18 registered gradations until today, with the new (19) gradation, when in 2017 is recorded increase presence of gypsy moth on relatively small area, so gypsy moth is coming out of latency and entered the first phase of gradation – progradation. During 2018, the trend of increasing population number is continued and gypsy moth are spread of larger territory, with still on low intensity.
Science has not yet determined the reason for gradation, but analysing period from 1862-2019, obviously is recorded, in past two decades, more appearance of gradation and shorted period of latency faze of gypsy moth.
There are assumptions that with the frequency of the occurrence of gradations, temperature rise and change of precipitation regime, due to climate change, can drastically increase (source: PREDICTION OF GYPSY MOTH (LYMANTRIA DISPAR) OUTBREAKS UNDER CLIMATE CHANGE Dejan Stojanović, Milena Kresoja, Milan Drekić, Leopold Poljaković-Pajnik, Nataša Krklec-Jerinkić, Nataša Krejić, Saša Orlović) https://scindeks-clanci.ceon.rs/data/pdf/0563-9034/2016/0563-90341698015S.pdf
Table: Monitoring and gradation of gypsy moth
Serbia