Forster, B.; Knizek, M.; Grodzki, W. (eds.) 1999: Methodology of Forest Insect and Disease Survey in Central Europe.
Proceedings of the Second Workshop of the IUFRO WP 7.03.10, April20-23, 1999, Sion-Chiiteauneuf, Switzerland.
Birmensdorf, Swiss Federal Institute for Forest, Snow and Landscape Research (WSL) 261-263.
ON THE SURVEY OF NUN MOTH (LYMANTRIA MONACHA L)
1. Introduction
Algimantas Ziogas,
Lithuanian University of Agriculture
Nun moth outbreaks in Lithuania are registered since the 18th century. Over recent 30 years the largest areas were damaged in 1979 (2.1 thou. ha) and in 1993 ( 11 .3 thou. ha). The outbreaks area usually observed too late in their eruptive (Ill) or even critical (IV) stage. This is related to the fact, that in Lithuania during the last invasions nun moth injured exceptionally pine stands where eggs survey is very difficult. Besides, all instructions and standards of that time were general for the whole Soviet Union and failed to comply with local conditions.
In Lithuania forest pathologists follow abundance changes of nun moth in pine stands and calculate its pupae and moths, however, they are faced by difficulties, as far as neither pupal nor imago stages have been investigated more thoroughly. Preparing injury forecasts, it is also necessary to know peculiarities of pupae and imago location on tree stems as well as on separate parts of a tree. Knowing this, it is possible to calculate the number of sampling trees.
The aim of this work - to improve nun moth appraisal and forecasting of future injuries.
2. Study method
L. monacha observation and appraisal was conducted in pine stand of southern
Lithuania in 1992 - 1995. The number of pupae on separate parts of pine trees was ascertained by felling down 26 pine trees of prevailing thickness and height in stands of VII - VIII age classes. The number of females on pine stems in respect to geographical points was found in 1993 - 1994 by calculating over 800 moths on 115 pine trees. Range limits were calculated under 0.95 probability.
Female on individual pine trees were calculated in 1993 in pine stands of IV- X age classes. A total of 1722 pine trees were closely inspected and all females on their stems were counted. The main biometrics indices were calculated. The relationship between stand age and the number of nun moths on separate tree stems was checked by placing ungrouped data into a correlative field. The number of sampling pines, required to find out nun moth abundance at a certain precision on a site, also was calculated (JlaKH.Ii 1980).
Data enabling to forecast defoliation degree in all possible ways were collected and processed as well.
3. Peculiarities of nun moth survey and forecast
Seeking to have a reliable forecast of L. monacha invasions, to know the dynamics of its population abundance, an accurate survey and observation are necessary. The main principle - not a single stand should be injured above its resistance limit.
The threat of L. monacha may be defined in any stage of its development: eggs, larvae, pupae, imago.
3.1. Survey of eggs. Survey of eggs usually is done in autumn. In spring (March- April) it is necessary to check their viability. Pine stems are inspected up to 1.5 m height. In spruce stands model trees are felled.
According to the number of eggs defoliation hazard is estimated.
, .. .. .. ..
.... .. ... .
l ..
.. ? •• ....(.}Q ... ) ... ... ).}Q ... ... J .. ?..Q ... .J ..
?..Q ...L_!Q ... ... ... l.JQQ ... )
i Number of eggs i 200 i 400 i 550 i 750 i 1000 i 1250 i 1500 i 2000 i 2500 i 3000 i
•...••••••... .... ... .. • • ..•.• . .... ... . . ... . . . : . . ... : .... ... ... ! ... ...•.... : ... . ... . : . ... . . .... ... ... .. : . .•....••••••.• ••. : ... .. : ••• ••••••••.•••••. . • .. ... ...
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On the whole, survey of eggs due to great labour consumption is not perspective.
3.2. Survey of larvae. Larvae are counted: a) under trap belts (suitable on pine trees);
b) calculating "mirrors" of hatched larvae; c) in the canopy, by felling control trees down on sheets; d) taking off model branches; e) after chemical knock - down; f) according to the amount of excreta. According to the number of larvae on a tree defoliation degree may be foreseen (CnpaBoqHHK no ...
It is suggested to estimate defoliation degree by the number of I instar larvae per tree (HJihHHCKHH, 1965, BopoHQO,B1991 ). However, it requires to know the quantity of green needle mass (Table 2).
Table 2. Pine defoliation dependence on the number ofl instar larvae (HJihHHCKHlJ 1965, .. .. ... y . .. . . .. .. .. . . , . . . , . .. . . .. . . y . . . , . . . .. . . .. . . ,
i Defoliation deoree 'X i 10 i 20 i 30 i 40 i 50 i 60 i 70 i 80 i 90 i 100 i
; ... &:/ ••••••.. ? ... ... ; •..•...•...•... .f. ... ( ...•... ; ..•••...•. ; •... .(. ...• i ... ;. ... ( ... J.
ofl instar larvae 1.4 2.8 4.2 5.6 7.0 l 8.4 l9.8 l11.2 l12.1 l13.9 l
i \.oo P.er 1 00 P needles i i i i i i i i i i i
Nevertheless, the stage ofl instar larvae is quite short. Besides, they hatch not all at once and before the onset feeding population abundance changes considerably. Thus, more accurate data are needed. They are needed, having observed injured trees (new outbreaks) for the first time, to specify foreseen control measures as well as to predict new ones. For this purpose 0.5- 1 m long 3 model branches (or model trees) are cut and needles as well as larvae (by instars) on them are counted. Knowing, that 100% defoliation is possible under a certain number oflarvae (Table 3). It is possible to know the degree of defoliation in future (Ziogas,
1994).
, .. .. ..
.. .... ... ,
i Instar i I i 11 i Ill i IV i V i VI i
In general, the number of larvae allows to define very quickly and precisely the degree of possible defoliation, it enables to specify current forecast and control measures. However, such surveys are very time and labour consuming occupations.
3.3. Survey of pupae. Carrying out the survey of pupae it is necessary to know their location on a tree. Literature sources point out, that pupae are found between needles and bark cracks (HnhHHCKHH, 1965; CnpaBoqHHK no .. l,988). Our study data show, that pupae are found on all parts of pine trees, however, their location depends on the total number of pupae on a tree (Table 4).
, .. .. ..
.. .. .. ... .. .. ... ,Number of .. .. ... J
[ .. .. ...
j .. .. .. ... ... l .. ... l .. .. ... j ... ... j
i 5-9 i 52.2 i 46.2 i 1.6 i - i - i
i 28-32 i 39.4 i 31.8 i 17.5 i 7.8 i 3.6 i
... .. . . .. ... .. . . .. . .. .. .. ... . . . . .. . . .. . .. . . , •• • •• • •••••••••••••• • • • •••••••• •• ••• , . . . .. .. ... . ... . ... . . . . .. .. . ... . . . .. . . .. ... ... 1
The stage of pupae lasts for about two weeks. Survey of pupae is purposeful during 11 - Ill outbreak stages. Data on the location of pupae on stems make the survey shorter and east er.
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3.4. Survey of imago. Adult moths fly at the end of July - in August, though massively only 8 - 9 days. The onset of flying in related to the degree of stand defoliation. Application of light and pheromone traps in burdened by the necessity of pheromone and electricity supply.
Therefore, it is suggested to carry out the survey of females by choosing certain routes and inspecting trees on one side only. Distribution of egg lying females opines in 1993, 1994 was:
north side of stem- 66.2±4.8%; east- 8.4±2.7%; south- 7.9±2.4%; west- 27.5±4.4%. Later, according to the given ratio the data are recalculated for the whole tree, slite or stand. Number of trees in the survey is inversely dependent on the population abundance and is ascertained by a table 5.
, .. .. ... , ... , ... , ... , ... , ... , ... ., ... ,
.. ..
.. .?... ... 1 ... ... ) ... ?. ... .. ... . .?. ... .. ... ... ... ) . .9.:.?. ... 1
... ... ... ... ... .L..P?. ... ... l
4. Conclusion
1. The outbreaks area usually observed too late in their eruptive (Ill) or even critical (IV) stage.
2. Survey of eggs (classical) in pine stands due to great labour consumption is not perspective.
3. Survey of larvae enables to ascertain comparatively quickly and sufficiently precisely the degree of possible defoliation. Nevertheless, this survey also requires much time and labour input.
4. Survey of pupae is purposeful during 11-Ill outbreak stages. Data on the location ofpupae on stems make the survey shorter and easier.
5. The onset of flying aldult moths is related to the degree of stand defoliation. Application of light and pheromone traps in burdened by the necessity of pheromone and electricity supply.
Therefore, it is suggested to carry out the survey of females by choosing certain routes and inspecting trees on one side only. Number of trees in the survey is inversely dependent on the population abundance.
5. References
1. Mastauskis S. Verpikas vienuolis Lietuvoje. Kaunas, 1931, 1-16 p.
2 . Svarbesnieji miskq kenkejai. Spaudos fondas, 1931. - 28-31 p.
3. Ziogas A Pusq spygliq nugrauzimo prognozavimas. "Miskininkyste", LMI darbai, Kaunas, 1994, 34: 218-227 p.
4. A.H., M03orreBcKa51 E.r., CoKorroBa 3.C. TexHorrorM51 3ai..QMThi rreca. M., 1991,- 304.
5. MrrhMHCKMH A.H. Ha,r:pop, y1.1eT M rrporH03 MaccOBhiX pa3MHO)I{eHMH xBoe - M JIMCTorpM3YI..QMX HaceKOMhiX. M., 1965.- 365.
6. JlaKMH r.<I>. EMoMeTpM51. M. 1990. - 294.
7. CrrpaBOl.fHMK no 3ai..QMTe rreca OT Bpe,n;MTerreU: M 6orre3HeH I r.A. TMMl.feHKO, H.,LJ;.
ABpaMeHKO, H.M. 3aBa.n;a M ,n;p. K.: Ypo)l{aif, 1988, 224 c.
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