study on ecology of the rlce gall midge in thailand · 268 pan rice experiment stat ion, chiengrai...
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16. STUDY ON ECOLOGY OF THE RICE GALL MIDGE IN THAILAND
T. WoNGSIRI*, P. VuNGSILABUTR* and T. HIDAKA**
Annual Fluctuation of Infestation of the Rice Gall Midge
267
The infestation of the rice gall midge in Chiengrai Province during the planting season was surveyed at an interval of 15 km from Payao to l\Iaesai as long as 160 km or more in distance. In 1970, the survey was also extended to Lampang and Chiengmai Provinces for clarifying annual and seasonal flutuation of the damage to rice plants. Percentage of the damaged tiller (Fig. 1) was comparatively low in each place from June to July, but from September to October it prominently increased up to 15 to 65% in 1968. On the other hand, the striking outbreak of the rice gall midge was observed in this Province in 1969, and the percentage of the damaged tiller increased as much as over 85% in each place where the rice yield extremely decreased by 60%. The peak of the infestation was seen in September. It is provided that annual fluctuation of the insect population density has been observed in Chiengrai Province ,vhere they believe that severe damage caused by the insect occurs in every 3 to 5 years.
Distribution of the Rice Gall Midge in Thailand It is interesting that the rice gall midge is distributed in east, northeast, and
north districts in Thailand (Fig. 2.1-2). It was found that an isothermal line of mean temperature of 27°C in July in Thailand is in conformity with distribution pattern of the insect, and the mean temperature zone of 27°C in September, when the highest population of the insect occurs, occupied the area where the rice gall midge is distributed.
Effect of the Climatic Condition on Seasonal Prevalence of the Insect
A study on effect of climatic condition on seasonal prevalence of the rice gall midge adults was conducted (Fig. 3.1-5). (1) The optimum mean temperature at which the rice gall midge emerged and laid her eggs in the paddy field ranged from 23 to 27°C. The mean temperature was over 25 to 27°C while the highest populatioin of the insect was seen in September at Pan, Chiengrai Province. (2) Before the planting season, the rice gall midge began to appear in May, 1969 and .at the end of March, 1970. This is suggesting that the appearance of the insect is closely related to the rainfall or water supply which is needed by the growth of the larvae on the alternate host plants. During the dry season before rain comes, the larvae on the alternate host plants were the first to second instar larvae so far as the writers examined plants grown in the dried place. On the other hand, a small
* Technical Division, Rice Department, Bangkhen, Bangkok, Thailand. ** The Pan Rice Experiment Station, Chiengrai, Thailand (The present project has also been carried
out under the cooperative programme of agricultural research work between Thailand and Japan since 1968.)
268
Pan Rice Experiment
Stat ion, Chiengrai
ii fl I,,
1968 \
1969
1970 I
I l-.lulv .:\ugust ~eptemher October
l.~pland rice- at
.:\laechan. ChiPngrai
Floating 11c P dt
1968 I
70 -
""''"· Chi,,,:~ 1968~1/CO n __ L_o_n n j l }lh n h _ril, ,---
j .JunP July August SeptemhPr October Xo,-emher
Fig. 1. Infestation of the rice gall midge in Chiengrai Province from 1968 to 1970.
98 100 102 104 106'
Nakhon
• Ubol
~ -----~ B k I
~
'rachin Buri ang o (
•
July (1937--1960)
1 /8, 000, 000
20'
18
16
14
12
10
8
-6
Fig. 2.1. Relation between distribution of the rice grll midge in Thailand and isothermal line of mean temperature.
269
270
98
l
100
$Chiengrai
Chiengmai'-1 9 Nan
/ Lampang (
102 104 106°
:,akon Nakhon
1 re P\hra0~ ...
\ ~c<chohca 6 KL,m K:eo
~ Cbol
~~khon Ratehasima @
Prach in
""'''"'~
September !J937-l 960)
l / 8,000, 000
20'
18
16
14
12
10
8
6
Fig. 2. 2. Relation between distribution of the rice gall midge in Thailand and isothermal line of mean temperature.
~\ir tt·rnpt·ratut·t:'.
30 ~-~~····
](I
'/
:;oo~-200-7-
l 00 .
Tl/ /
.July
0174 8
Precipitation [ mm)
TL 7 PR-HT / lfS /
\To. of adults
3
6
- --1·-- ----~--.,·-- - r-----··-,\ugust September Octol,er
-- ·- ·-1---------:-: ore rn h Pr
Pan Hice Experiment Station, Chiengrai. Thailand ]96~
Fig. 3. I. Seasonal prevalence of number of the rice gall midge adults collected by the light trap at Pan Rice Experiment Station, Chiengrai, from 1968 to 1970. HS; heading stage, PR-BT; primordium to booting stage, TL; tillering stage, TR; transplanting.
271
272
10
100
50
Air temperature
Precipitation (mm)
L/ __ ~R=N_' __ 7 HR
No, of adu Its
I~
December January February March April l\lay .June
1968 Pan Rice Experiment 'Station, Chiengrai, Thailand 1969
Fig. 3. 2. Seasonal prevalence of number of the rice gall midge adults collected by the light trap at Pan Rice Experiment Station, Chiengrai, from 1968 to 1970. HR; harvesting, RN; rice nursery.
20
14,000 +--------------------------10 4
Precipitation (mm)
5
10,000-
No. of adults
500
3
6
1000+---T_R_~----+-----~-.--.---+~-H_S~
500 200
July
7(?)
August September October November
Pan Rice Experiment Station, Chiengrai, Thailand 1969
-100
-50
Fig. 3. 3. Seasonal prevalence of number of the rice gall midge adults collected by the light trap at Pan Rice Experiment Station, Chiengrai, from 1968 to 1970. HS; heading stage, PR-BT; primordium to booting stage, TL; tillering stage, TR; transplanting.
273
274
1001
50
Air temperature
Pr(•cipitation '~min;
'' 'I
V HE / ,_/ __ --'-'l{'-'-,\'---7
/ Tl{/ / I{,'\ __ ,_/
/ HI( /
200 ~
100 i 50::l 15~-10J
! ,\o, of adults
3
11\,/\ I \
L.~----- - --LI \_----.
Decemlwr January
1969
Fig. 3.4. Seasonal prevalence of number of the rice gall midge adults collected by the light trap at Pan Rice Experiment Station, Chiengrai, from 1968 to 1970. HR; harvesting, RN; rice nursery, TR; transplanting.
30
20
100°
July
, LJ l JI I I L~
Xo. i..if adult.:-,
A ugusi September
JL,
October
l-'an Rice Experiment Station, Chicngrai, Thailand 1970
Fig. 3. 5. Seasonal prevalence of number of the rice gall midge adults collected by the light trap at Pan Rice Experiment Station, Chiengrai, from 1968 to 1970. HS; heading stage, PR-BT; primordium to booting stage, TL; tillering stage, TR; transplanting.
275
276
~ 200 .:
L,,---'~
DecemlH:,r
\\
1969 1970
)itation \ mm>
~--February April
Fig. 4. Comparision of gall occurrence between water supplied and dried places during dry season at Pan, Chiengrai, 1969 to 1970. The mark arrow re• presents the peak of each generation.
number of galls appeared from the plants which were supplied with water throughout the dry season (Fig. 4).
During the planting season, much precipitation was observed in the middle of August. The rainfall continued everyday for almost two weeks around the middle of August. On those days, the peak of the second generation of the insect appeared, and then, adults of the second generation were under the optimum climatic conditions for laying her eggs and increasing percentage of hatched eggs. Moreover, the larvae of the third generation propagated more in number than those of the second generation. The insect adults also emerged abundantly in their numbers. (3) While the rice gall midge population increased, cloud cover was more than 80 percent at the Pan Rice Experiment Station in August and September. On the other hand, sunlight hours per day of both months were less than 5 hours on the average, but the sunlight had not been seen at Pan for two weeks around the middle of August. It is presumed that the cloud cover gives apparently the important influence on the activity of laying her eggs, adult longevity, and percentage of hatched eggs which are also under the influence of the sunlight hour. ( 4) The relative humidity during the rice gall midge occurrence in the paddy field was 75 percent on the average and the minimum relative humidity, while the insect disappeared, was 46 percent in December, 35 percent in January, 27 percent in February, and 23 percent in March. If adults of the rice midge emerge during the dry season from December to April, the adults will die of lower humidity under natural their longevity ·will be shortened because of sunlight hours especially in March and April, and theiir survival rate will also decrease in the day tiime during these months ( cf. cultural practice--planting dates).
Under the above mentioned climatic conditions, actually six peaks in Hl68 and 9 peaks in 1969 and 1970 were recognized throughout the year. The highest peak was observed during September in the said three years. The adults appeared from May in 1969 and from the end of March in 1970, and disappeared in the middle of November during the
C\o, of tillers
10
;\o. of gro\Ying puint-..;
l'rimo1d1um and
2, stages
20· \' . ,0.
IO .-
>.. o. nf
lU ,-
1
]
July :\uµ:ust Se1Jtem};er Uctoher .\(>Vernber
Fig. 5.1. Relation between growing stages of rice plants and gall occurrence in the different planting dates at Pan Rice Experiment Station, 1969. 5--1; transplanted in July 7, 5--2; trnnsphmted in August 25.
277
278
20
10 -! i L----------- ---,------------7
20 I
4 3 2 l
Primordium initiat:on
Sept:~:mbt·r Octo)_it'r
Primordiu!n heading stage:;
P '.a,t)·t_;as ter idaf'
---·---, ---
December
Fig. 5.2. Relation between growing stages of rice plants and gall occurrence in the different planting dates at Pan Rice Experiment Station, 1969. 5-1; transplanted in July 7, 5-2; transplanted in August 25.
279
three yean,. During the planting season, they had six and seven so far as the writers examined at the Pan Rice Experiment Station. Number of generations in the different planting dates is also given in the Figures 5.1-2.
Control of the Rice GaU Midge A study en control of the rice gall was carried out means
of cultural practice and utilization of resistant varieties.
Effect of the Planting Dates o;:1. the Damage Caused by the Rice Gall Midge
Cultural practice with special reference to the different planting dates of rice plants was investigated at the Pan Rice Experiment Station in Thailand (Fig. 5.2-1 and Fig;. G). Rice plants transplanted in July were severely damaged; in another word, less infestation is obtained in late transplanting in August due to the short period of the vegetative growth when photo-sensitive rice varieties were examined. Rice yield apparently increased in late transplanting of rice plants as well as the number of the panicles and dried straw per hill. Less infestation ,vas also observed in the second crops of rice during the dry season.
J 00
B AB AB AB
C C
D ll
::_:: JO
-·---r--·- ;·------ r--July 7 25 :\ug. 7
PA:,/ 1969
A Tl B
u
2 ;::
'-' '"
10 ~ -- ~ ('C .........
b .,, "Cl
r- -:;; Au~ 25 ~
L..........._\/'______J q PARCAK, CHIE:\'GRAI 1969
Fig. 6. Relation between damage and yield in different planting dates at Pan and Paruak, Chiengrai, 1969. A; damage in per cent, B; yield in ton per hectare, C; No. of panicles per hill, D; dried straw per hill in gramme.
It ,vas clarified that the insect population usually increased in number during vegetative growth of rice plants due to a lot of the growing points formed. The larval population of the fourth generation was more increasing than that of the other generation. The peak of the larva !population of the fourth generation came at the time of the peak of the growing point formation. This is suggested that the insect population increased in proportion to the increase in number of the growing points. The primordium initiation began to increase in number and the peak reached in the middle of October. The larval population usually decreased after the primordium initiation ,vhich is the most important factor to reduce the larval population. In another word, the rice gall midge larvae can not grow on the primordium of rice plants.
280
Relation between Growing Stage of Rice Plants and Infestation of the Rice Gall Midge The writers proved in 1968 that the most susceptible stage of rice plants against
the rice gall midge attack was 30 to 45 days after sowing seeds (Fig. 7). The high
100-
40 T
14 28 42 56 70 34 98
Days after scnving
Fig. 7. Gall occurrence in different growing stages of rice plants at Bangkhen and Pan, 1968.
Tliaibnd
\'@j--- -------
'---~-®------~-- ___ @. _ __ ®)
(.,OOG',C": l'C C...C
N 0l C<l
:L :L :L :L ;.:_; ~ ~ ,-,
""' ~ ·2 ~ ;:::; ....c: ..c:
µ..i OU
' '; '-0 ,r-..,. t-...... 10 .---! ,......;
-- z. ~--00 --.._.- 00
~~es xxx £-1 i:,.; b 1-40 ~
-----®--
@ VT
Rice nriety, Pan Rice Experiment Station, 1969
@ ®'
~.,., :.L
" ':.L :<J
" " -"'"" ~ .-:
Fig. 8. Screening test of resistant varieties from Thailand, India, and Japan at Pan Rice Experiment Station, 1969.
281
mortality of the insect was seen from primordium to the heading stage of rice plants. It is also considered that the susceptible stage against the rice gall midge is suggesting the timing of insecticidal application.
Varietal Reaction against the Rice Gall Midge 155 rice varieties including 16 Japanese and 5 Indian varieties were tested in order
to list up the resistant varieties (Fig. 8). Two lines of EK from India were so highly resistant that these could be used as a parent of hybrid for improvement of rice varieties in Thailand. Infestation of 16 Japanese varieties showed 15 to 35 percent of the damaged tillers. All of Thailand recommended varieties used in the present study were also susceptible.
Leaf blade : Surfoccl !
V
1-.~---:i~~ . -~ EK ,1263
t ' Leaf blade L,·af sheath , hcn,,ath 1 1
1-~-~--i --L ~ m;/s2\1
[ I DA\,!K ~!ALI 3
, --~-----~ , J __ -~ 100 50 0 50 100,
No. of eggs laid Penetration of larvae
Fig. 9. Preference of egg laying and penetration of newly hatched larvae into growing points of 3 rice varieties at Pan, 1969.
0
EK 1263
Days after hatched egg
1
Di\WK \IALl 3 \
~--
Fig. 10. Cornparision of larval development between a susceptible (Dawk Mali 3) and a resistant (EK 1263) varieties at Pan, Chiengrai, 1970. Ll-3; Larval instar, PP; prepupa, P; pupa, A; adult.
282
Resistant Mechanism on Rice Plants against the Rice Gall Midge
Factors of resistance against the insect between susceptible and n·sistant varieties were comparatively studied from the vie,vpoint of the number of egg laying, penetration of larvae to growing points, and the larval development of the rice gall midge on rice plants (Figs. 9 and 10). It was clarified that any difference of the number of egg laying and penetration of the larvae could not be found between susceptible and resistant varieties. However, the larvae on a highly resistant na-iety, EK 1263, could not grow to the advanced development stage and they were almost the first instar larvae. On the other hand, the larvae which penetrated into a susceptible variety, Dawk Mali 3, were seen to normally develop up to the adult stage. It is considered that the larval development is prominently inhibited by some kindR of substance in the resistant variety or that a nutritional substance, which is necessary for the larval development, will be deficient.
Bionomics of the Rice Gall Midge Bionomics of the rice gall midge has been studied in the following facts. The average longevity of adults ,vas 2.28 days (Fig. 11), the average number of
lnnge\·ity of adult at'ti\ it:,; of egc; laying
3 Days after emergence
Fig. 11. Relation between longevity of adult female and activity of egg laying at Pan Rice Experiment Station, 1968.
J 00
r~·-; ·---7----T ~-T-~--r-· N c'? ~ N C"l C'l ,._. C',J C,") -tj-< LO '-.0 t-
' I I I I I I I I I ,.......C>.lC'":7.,._.,NM~Li:)(.,D C"--1 C'-J <:'-1 N
TinH: of odposition
Fig. 13. Time of egg laying by the rice gall midge at Pan, Chiengrai, 1968.
o--o dcpn::-,iU-'d eg;4,c:,
e---o o\·arian (•gg~ afkr oripo;-;ition_
---T·-------- - !
100 200 300 Xo. of eggs
Fig. 12. No. of ovarian and laid eggs per female at Pan, 1968.
JO()
0-0 -
----r----.---------i-·--r--i ~--r-~--. ::J',Q,......iC'-]{V)~ ,-1 N N C'-1 N C"l ,--, N er, -tj< L0
c'.:.QO~~M...;,~~M..,~ ,,...~~--INl"'lNC'JC'-l
1';r.,e of flight lo the light trap
Fig. 14. No. of adults collected by the lignt trap at Pan, 1968.
283
ovarian eggs per female ,vas 276.12 and the average number of eggs deposited was 221.26 (Fig. 12). The peak of egg laying was at midnight (Fig. 13). Most adults were caught at 21 :00 o'clock in the light trap (Fig. 14) and the incubation period was 3.22 days on the average (Fig. 15). The peak of hatching occured at 3:00 a.m. (Fig. Hatchiability was higher than 80 in percentage when the humidity was more than 60 percent (Fig. 17). As usual, the eggs were commonly deposited on beneath of the leaf blade of rice plants and the eggs were mainly laid on the fourth leaf of rice seedlings (Fig. 18). The larva had three instars, requiring four for the first instar, six days for the second instar, and four days for the third ins tar, respectively (Fig. 19). The first instar larvae commonly penetrate dO\vn along the inside of the leaf sheaths until they reach the growing point of the tillers. After the penetration is over, the oval chamber is formed within two days. The period of the prepupae was three days and the pupae three days on the average. Pupation occurs around the growing point. Pupae just before emergence climbed up along the inside of the gall and reached to the spongy part of the gall, then, the pupal body was kept half way out. It was proved that the growth of the gall was in proportion to the developmental stage of the rice gall midge (Fig. 19), and especially that the gall had rapidly grown from prepupal to pupal stage. Usually the adults emerged at 22:00 o'clock (Fig. 20), beginning to
,'J,
;t 1 co ~
Days aftf't' egg laying
Fig. 15. Incubation period at Pan, 1968.
100-
20 40 60 80 100
11:,n::iciity )
Fig. 17. Effect of humidity on hatchiability of the rice gall midge at Pan, 1969.
] lOO " " .c
0
·"'
1J L.----, -.-, --.--r,-·-·,-,--·---.-
N c---:i -..,ti C'-J C'--1 ':'-l ,....., N C'0 ~ 10 ,..0 t-- CO
I I I I ! I I I' I I I ,-...,,:,;:c,J"'i'.....-!NM~L!')<'.Dt'N N N C'sl
Time
Fig. 16. Time of egg hatching at Pan, 1968.
50-
0 z
~ benea th I. leaf blade D surface J • leaf sheath
1 2 3 4 leaf age
5 6 7
Fig. 18. Preference of egg laying on riee seedlings at Pan, 1968.
284
C
"
Days after egg laying
30
20
10
6
" er.
"' oD
0
-:5 en
" .;;;
Fig. 19. Dtvelopmentai stl'g,s of the rice gdl midge and growth of gall i:t Pan, 1968.
~ 7 ~ ~ f:'i ~ :-~ ~ ::~ ~ t- C0 C; C) .,, --::·; -·, ·--• ,...... N r-1 ,-. ,....... c,,J C'-.1 C-·-J <.:'-. '--~
Fig. 20. Time of adult emergence at Pan, 1968.
lay the eggs one day after emergence (Fig. 11). Number of days required for one generation was twenty five days in general, but
sometimes the period was remarkably shortened as short as twenty days from October to November because of nutritional effect of rice plants after the primordium initiation period.
How to Distinguish between Healthy and Damaged Seedlings
During rice seedlings, the presence of the gall cannot be observed from outside of rice plants until the causal larva grows up around the prepupal stage. Sometimes it is very difficult to distinguish between healthy and damaged seedlings. The writers proved that the damaged seedling was significantly shorter than the healthy seedling. The details are given in the Table 1.
Preference of Larval Attack by the Rice Gall Midge on Rice Tillering It is interesting that the larva of the rice gall midge prefers to attack mainly the
primary tiller in which the insect developmental stages were the highest in the total number (Fig. 21). The population desity of the insect found in the growing points tends to be higher in the order of the primary, secondary, tertiary, fourth, and fifth tillerings. In the primary tillering, all of the developmental stages are found, but some of the stages could not be found in the secondary, tertiary, fourth, and fifth tillerings. In another word, it was seen that the older stage of the insect was always.
Table 1. Distinguishable characters between health!y and infested rice seedlings.
Items
L 2. Leaf age
3. Tillering
24. 21 cm
4.95 1-5
32. 74 cm
6.12 1~3
285
The 5th leaf of main stem is districtly The 6th is prominently visible extended to 4th leaf auricle, distance be-tween 4 and 5th auricles is about 2-3 cm 1 in an average, the 6th leaf invible. The 4 and 5th leaf sheathes are clearly apart if 6th leaf occured.
4. Colour dull green green
5. General status basal part of stem rather hard and cylindered in shape
basal part of stem flattened softly
'fl
;, ] 5 U)
0
c;
p
pp
L3
L2
LJ
'"· '-
" E ·;: ;:,.,
c;
LI
C' " " C: 0 C,
'" Cf)
p p + L3
+-PP
L2 .J}'P <-L3
L1 L1 £ 1
:>. ii g h h "' :, µ.. 0
h Q
µ.. f-,
Fig. 21. Relation uetween larval development of the rice gall midge and growth of tillering of rice plants at Pan. Ll-3; larval instar, PP; prepupa, P; pupa, G: gall.
in the primary tillering and the younger stage was in the secondary and tertiary tillerings. It is suggested that the larval development among these tillerings is closely related with the growth rate of the growing points of rice plants.
Alternate Host Plants of the Rice Gall Midge Several kinds of the alternate host plants found in northern Thailand are as follows.
1. Oryza offici'nulis (wild rice), 2. Ischaenum aristatum, 3. Echinoclora colonum, 4. Paspalurn sp., and 5. Leersin sp., which is belonging to the Family Graminanceae. Adults reared on lschaenuni aristatum is comparatively small in size and slightly darker in body colour than the adult which emerged from rice plants. The gall on Jschaenum aristaturn is extremely shorter than that of rice plants. Adults from wild rice had the same body size and colour as those from rice plants. Adults reared on wild rice could attack rice plants and the larvae normally developed on rice plants. Larvae survived on Leersia sp. and Echinoclora colonum were extremely lower than those of wild rice and Paspalum sp. It is considered that the larval development may be inhibited
286
during the dry season because of shortage of water supply. Anyway, the wild rice ,vould be the most suitable plants for sustaining the insect geneartion to generation and the plant will be occurrence o:ources of the insect before the planting.
N ahrral Enemies of the Rice Gall Midge Ar:: far a,; the v.'riten,' investigntion on natural enemies of the rice g,1]] midge,
..:\ug
Fig. 22.1-A.
50
10
0----0 para~ite .:rnd predator
~ tliP ric<:' gall 1nidgc
LJ damaged tiller
~~---·11T·········~--n..,. . 1].T. September October November
Fluctuation of parasitism against the rice gall midge at Pan in Chiengrai Province, wet season, 1970.
Eupelmi<l sp.
\
7\/\ /'-, I - \
September October November
Fig. 22.1-B. Fluctuation of parasitism against the rice gall midge at Pan in Chiengrai Province, wet season, 1970.
287
three species of Hymenopterous parasites of the Families Platygasteridae, Pteromalidae and Eupelmidae were collected, besides one species of predator belonging to the Family Carabidae was also found in the paddy field. The parasitic and predacious activities the Pan Rice Experiment Station in 1970 are given in the Figures 22.1 A and B. lt is observed that the Platygasterid parasite was dominant among the natural enemie,, the rice gall midge and that her to increase from Sep-tember which to larval occurrence of the fourth generation. On the other hand, in began to appear from the beginning of September and could not appear in the first to third generation of the rice gall midge in and August (Fig. Parasitism of the Platygasterid parasite reached at least 15 percent in
50 --------
Aug S eptembe:r
Yan=oi. Lampanr; J.070
O.,,-o parasit<::~ and predator
~ the rice gall m
LJ cLma.;;ed tiller
j',/-~/
October 2\Jovember
Fig. 22. 2 A. Fluctuatim1 of parasJ.tism 11gainst the rice gall midge at Yan-oi in Lampang Province, wet sell.son, 1970.
50 Platygac;u•riJ
/~
sp. I 7 P<ernmaliJ s, .
. - ------L_-------./ +===~~==:-,,,.-=='-----------~------
Aug September :October :--lovember
Fig. 22. 2-B. Fluctuation of parasitism against the rice gall midge at Yan-oi in Lampang Province, wet season, 1970.
288
1969 and 65 percent in 1970. Parasitism of the Eulopid and Pteromalid parasites was lower than 7 percent in 1969 and 29 percent in 1970. In 1969, lower parasitic activity of the said parasites against the rice gall midge was observed at Pan which suffered from the severe damage caused by the insect occurred. The Parasitic activity at YanDi in Lampang Province (Figs. 22-2 A and B) wa~ so extremely high that severe
,. I 1 oo~
I
S2.np1thong Rice Experiment Station, 1970 0----0 parasite> and prcda or
&----e the rict' gall midge
LJ damaged lil ler
ln_,r=_ _t:='.'1 _ ___ _e::1_
(_)ctoher July August September >;,i\"(•mhPr
Fig. 22. :!-A. Fluctuation of parasitism against the rice gall midge at Sanpatlwng ln Chiengmai Province, wet season, 1970.
A I\
\ July August September 0 ctobcr November
Fig. 22. 3-B. Fluctuation of parasitism against the rice gall midge at Sanpathong in Chiengmai Province, wet season, 1970.
289
damage to rice plants had not been seen in recent years. It is considered that the rice gall midge is well controlled by the Platygasterid parasite. The parasitism reached 75 percent. The parasitism of Petromalid and Eulopid parasites reached 98 percent at the time of rice seedlings at the Sanpathong Rice Experiment Statio nin July, 1969. In 1970, the both parasites attacked the insect and the parasitism was 60 percent in July (Figs. 22-3 A and B), and then in the following months, August, September and October the rice gall midge maintained prominently lower population in the paddy field than in rice nursery because of the severe attack of these parasites.
Discussion Soenardi, Indonesia: The gall midge is found on Jrnperatci cylindrica, lalang grass
in Indonesia. How about in your country? Answer: There are a lot of these grasses in Thailand, too, but so far we have
not yet found I. cylindrica on these grasses in our country. Dyck, the Philippines: Have you found gall midge infestation on the alternate host
plant? Answer: Yes, I have, but the percentage we obtained vvas different from that
which was got in the Philippines. Pathak, IRRI : Have you noticed any increase in the area in Thailand attacked by
the gall midge in recent years? Answer: Yes, in 1970 we found that the east, north and northeast parts of
Thailand were very seriously attacked, but we haven't got any report or any evidence in the south part at all.
Kimura, Japan: Do you have any idea of the control by chemical application such as the power sprayer?
Answer: We did a lot of chemical control in the field in the past. Kimura, Japan: What part of the rice plant is attacked by the gall midge? Answer: The eggs are laid mostly underneath the leaf blade, and then the larvae
go down to the growing point.
References 1. Buranapawang, S., T. Hidaka & P. Vungsilabutr. (1970): Stuc:y en different planting
dates to determine gall midge infestation. Res. No. VI-2 .. ,1, Rice Department, Ministry of Agriculture, Bangkok, Thailand.
2. Hidaka, T. & T. Lekakul (1968) : Study on the susceptibility of different stages of growth of rice plants to the attacks of rice gall midge. Res. No. VI-2-3, Rice Department, Ministry of Agriculture, Bangkok, Thailand.
3. Hidaka, T. & P. Vungsilabutr (1969): Study on environmental factors affecting seasonal fluctuation of population density of the rice gall midge. Res. No. Vl-2-6, Rice Department, Ministry of AgTiculture, Bangkok, Thailand.
4. Hidaka, T. & P. Vungsilabutr (1970). Study on environmental factors affecting seasonal fiuctuation of population density of the rice gali midge. Res. No. VI-2-6, Rice Department, Ministry of Agriculture, Bangkok, Thailand.
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