PARAsmSM AND PREDATION OF RICE LEAFFOLDERS, MARASMIA PATNALfS (BRADLEY) AND CNAPHALOCROCfS MEDfNALfS (GUENEE) (LEPIDOPTERA: PYRALIDAE) IN LAGUNA PROVINCE, PHllJPPINES'

G. S. Arida and B. M. Shepard' Department of Entomology, International Rice Research Institut.e

P.O. Box 933, Manila, Philippines

ABSTRACT

There were no significllnt differences in rates of p£lnlsitism and predation 011 eggs of Icuffoldcrs (primarily Marsmia palmi/is IBradleyl and Cllapllll[ocrocis medinalis IGucneeJ) in transplllnlcd and direct seeded ricc. Egg parl.lsil-ism rCllched a peak of about 80% in August ill both trnnsplanled and direct seeded rice hut averaged about 40'1.,. Highest. levels of pnrasitism occurrcd when predation was lowest. 7'ricJlOgramma "'p. was the mosl abundant egg parasiloid. At least t\Ych'c species of parasitoids emerged from Icaffolder larvae. A hypcrpllrl:lsitoid, EUf)1oma bracoTlidis (Ferriel'c). lliso WliS collectcd. Prcdlltion on Icaffoldcl" eggs rcachcd a maximum of about 85%.

Key Words: Rice, leaffoJdcrs, MlJr(lsmia palT/alis. Cllapllalocrosis medina/is. Ilarasitoids, predators, biocontrol. Lepidoptcra, Pyralidac.

J. Agric. Entomol. 7(2): 113-118 (April 1990)

Rice leaffoldel's (LF) were previously considered minor 01' sporadic pests (Capco 1957, Lim 1962). but in recent years their importance has increased (Kalode 1974, Soejardjon and [man 1980). Severe outbreaks were reported in Vietnam in 1981 (Heinrichs, personal communication), in lndia (personal observation) Hnd Southwestel'll Japan (Hirao 1981).

A recent survey of LF species collected from irrigated lowland lields in Laguna province, Philippines revealed that of more than 3,500 larvae collected. over 90% were Marasmia patna/is (Bradley). Cnaphalocrocis metlinalis (Guenee) was next: most abundant. IVI. ruraLis (Walker) and M. exigua (Butler) were found in sparse population densities (Arida and Shepard 1986).

Modern high-yielding rice varieties have no resistance to LF, and chemical insecticides are used frequently for their control. The impact of natural enemies is not considered in farmers' decision-making about whether or not chemical applica­tions are needed. However, it is clear that predators and parasitoids playa major role in maintaining several species of insect pests of rice below economically important levels (Ooi and Shepard in press) and the impact of predators and parasitoids on LF populations is likely to be significant.

Many species of parnsitoids and predators of LF have been identified from different parts of Asia. Rao et al. (l969) reported 32 SI)ccies of larval and pupal parasitoids of C. medina/is in India. In the Philippines, Barrion et 81. (1979) listed nine SI)ecies of parasitoids which attacked LF larvae and pupae but did not report parasitoids of eggs.

Hcceived for publicMtion Hi Novcmber 19BB; accepted 1;\ December 19B9. Currenl uddress: Clclllson Univcnlity Cmlstal Reseorch und EduClltioll Centcr, 28(1:"' Savunnllh HighwllY, Charleston, SC 29407

11:3

114 J. Agric. Entomol. Vol. 7, No.2 (1990)

'The incidence of parasitism and predation was monitored from the yellow stern borer, Scirpophaga incerlulas (Walker), eggs in the Philippines by Shepard and Arida (1986) in transplanted and direct~seeded rice. They found parasitism higher in transplanted than in direct-seeded rice.

LF eggs also are vulnerable to natural enemy attack. Predators were reported to cause 70% mortality while egg parasitism was 20% (Kamal 1981).

The objectives of our study were to identify major parasitoids and predators of LF eggs and parasitoids of LF larvae in rice in Laguna Province, Philippines. Also, the seasonal abundance of major parasitoids of LF was determined.

MATERIALS AND METHODS

This study was conducted on the International Rice Research Institute (IRRI) experimental farm from November 1985 - October 1986. Fields were established each month of the year by direct-seeding or transplanting with rice selection IR1917-3-17. Experimental fields were divided into five 300-m2 plots. Means were compared using the Student's t-test at P < 0.05.

Egg parasitism and predation: C. medinalis were allowed to oviposit on plants by caging field-collected moths

overnight in the laboratory on potted plants of the same age and variety as those in the field. Five pots, each bearing 25 LF eggs, were placed in transplanted and direct-seeded fields 55 d after seeding. Missing eggs were recorded after 48 hand plants were brought to the labol'atory where remaining eggs were held individually in test tubes until LF hatched or parasitoids emerged. Parasitoids were counted and identified.

Larval parasitism: An average of 100 LF larvae were collected every 2 w from December 1984 to

November 1985 from the same fields from which egg parasitism was determined and from private fields. Larvae were reared individually in glass tubes (16 by 150 em) on cut rice leaves which were changed as needed until parasitoids 01' LF emerged. LF larvae were not identified to species because of high mortality caused by unfolding the leaves to examine larvae. Parasitoids were identified by the Commonwealth Institute of Entomology (erE), London, England.

RESULTS AND DISCUSSION

Egg parasitism and predation: Thchogramma sp. and Copidosomopsis nacoleiae (Eady) were the only parasitoids

which emerged from LF eggs. Their seasonal incidence, as detected by the prey enrichment method, is shown in Fig. L More than 95% of the parasitized eggs were attacked by Trichogramma sp. Parasitism reached two smaller peaks (about 20 - 40%) in January and March and began increasing in June, reached the highest peak of about 80% in August and declined to near undetectable levels by October (Fig. 1). The seasonal mean parasitism levels were the same (P < 0.05) irrespective of whether the crop was transplanted or direct-seeded (Figs. 1, 2A).

ARIDA and SHEPARD: Parasitim and Predation of Leaffolders U5

EGG PARASmSII '")

Tran8pJantad

• -. Trichoqramma.!2.-'

0- 0 CoDldoeomopsle nocoleIge

•

NOlI Doc Jan Feb liar ~r lIay Jun Jul Aug Sop Oel

MOmH OF SAMPUNG

Fig.!. Parasitism of rice leaffolders, Cnaphalocrocis medinalis eggs by Tricho­gramma sp. and Copidosomopsis nacoleiae in transplanted and direct seeded rice. IRRI Farm. Los Banos, Philippines.

The seasonal incidence of predation on LF eggs is shown in Fig. 28. Egg predation was highest in October-November and in February-April. As with parasitism, no significant differences in mean levels of predation could be detected between the two crop establishment methods (transplanted vs. direct-seeded). In general, when egg predation was high, parasitism was low and vice versa (Fig. 2).

Density of eggs on sentinel plants may have influenced our estimates of parasitism and predation. These "resource patches" of egg· laden plants in the field could have altered parasitoid and predator behavior, thereby increasing attacks by these natural enemies over that which may ordinarily occur without artificial manipulation of host numbers. Also, removal of parasitized eggs by predators could bias estimates of parasitism.

100

90

80

70

60

50

~

30

20

10

a

100

90

80

70

60

50

~

30

20

10

a

Direct seeded

• -. Trichoqrammo..!2.

0-0 Copldosomoosle nacoletae

116 J. Ap;ric. Ent.omol. Vol. I, No.2 (1990)

PARAS!T1Slot (K)

100

90 B 80

70

80

50

40

JO

20

10 OL---'-_--'-_-'-----'_--'-_--'-_'----'-_--'-_-'-----''------'-_--'

Nov Doc Jan Feb Nar Apr Nay Jun Jul Aug Sep Oct

MONTH OF SAMPUNG

Fig. 2. Percent parasitism (A) and predation (B) of eggs of rice leaffolders in transplanted and direct seeded rice. IRRI Farm, Philippines, 1985-86.

Larual parasitism: The seasonal activity of larval parasitoids from the IRRI farm and from

farmers' fields is shown in Figure 3. In general, parasitism rates were highest in Apl'il, May, November and December. Parasitism reached peak of ovel' 65% in private fields in April, but overall mean larval parasitism was 301)-;;' Twelve species of larval parasitoids emerged from LF larvae. In addition, one egg-larval parasitoid, C. nacoleiae was round (Table 1). Five species collected on larvae made up 83% of t.he total numbel' of species from IRRJ farm and 72% from private fields. Gonio2us triangulifer Kieffer was one of the most common parnsitoids found in both locations but it was not abundant during the months of May and June at the IRRI fal111. Other abundant parasitoid groups included Cardiochiles philippinen-s/:<; Ashmead, Macrocentnts nr. trimaculatus (Cameron) Trichoma, sp. and 7'emelucha sp.

100

90

80

70

60

50

40

JO

20

10

o

0-0 Transplanted A• -. Direct seeded

PREOATlON (K)

117 ARIDA and SHEPARD: Parasitim and Predation of Leaffolders

LARVAl PARASmSM (ll:)

100 ,---..,r----,--.....,...--,--..,.--..-----,---,----,---r---,--,..----,

90 0-0 IRRI FARM • - • FARMERS' FlElD

80

70

80

50

40

3D

20

10

O'--"-----''------'---'-----L---'----'---'----'---''---'---'-----' Dec Jan Feb Mar Apr May Jun Jul Aug Sap Oct NaY

MONTH OF SAMPUNG

Fig. 3. Seasonal incidence of leuffoldel' larval parasitoids from IRRI Farm and nearby Carmel'S' fields. Los Banos, Philippines.

Table 1. Parasitoids from rice leaffolders, Marasmia pal!lalis and Cnaphalocrocis medirwlis. Laguna Province, Philippines. 1985-86.

Family Species Stage parasitized

Bethylidae Braconidae

Goniows trianguli[er Kieffer Apanteles allguslibasis Cahan A. schoenobii Wilkinson

Larva Lmva Lalva

Cardiochiles phiLippinensis Ashmead Macrocenlru.s or. trimaculatus

Larva

Ceraphonidae Elasmidae

Encyrtidae Trichograrnrnatidae Pteromalidae Ichneumonidae

Eulophidae Eurytomidae

(Cameron) Aphnogmus fijiensis (Ferriere) Elasmus claripennis Cameron Elasmus sp. Copidosomopsis naco/ciue (Eady) Tn"cllOgramma sp. Trichomalopsis nr. shirahii Crawford Trichoma sp. Temelucha sp. Trat.ala sp. 'letrasliclws ayyari Rohwer Ewytoma brachonidis Ferriere

Lalva Larva Larva Larva Egg-larva Egg Larva Larva L8Iva Larva Pupa hyperparasite

It is clear from these results that parasites and predators are an important source of LF mortality. Efforts to consclve these indigenous natural enemies should include development of workable aClion lhresholds. a practical monitoring program and selective chemical or microbial insecticides applied only when LF population density reaches threshold levels.

liB J. Agric. Entomol. Vol. 7, No.2 (I990)

REFERENCES CITED

Alida, G. S., and B. M. Shepard. 1986. Seasonal abundance of the rice lcaffolder complex in Laguna Province, Philippines. J. of Agri. Entomol. 3: 382-383.

Barrion, A. T., J. P. Bandong, M. D. Lumahan, P. C. Pantus, R. A. Apostol, and .J. A. Litsinger. L979. Natural enemies of the rice learrolder. Cnaphalocrocis medinalis in the Philippines. International Rice Research Newsletlcr 4(2): 18.

Capeo, S. R. 1957. A list of plant pests of the Philippines with special reference to field crops, fruit trees and vegetables. Philippine Journal of Agriculture 22: 3-80.

Himo, J. 1981. Widespread outbreaks of immigrating lcofColders and whitebackcd pJanthoppcrs in Southwestern Japan. International Rice Research Newsletter 6(5): 18.

Kalodc, M. B. 1974. Recent changes in the relative pests status of rice insects us influenced by cultural, ecological und genetic factors. Puper presented at the International Rice Research Conference, International Rice Research Institute, Los Banos, Philippines. Mimeo, 22 pp.

Kamal, Q_ N. 1981. Suppression of whitebacked planthopper Sogatefla (urci(era (Horvath) and rice leaffolder, Cnaphalocrocis medinalis (Cuenee), populations by natural enemies. Ph.D. dissertation. Gregorio Araneta University Foundation, Metro Manila, Philippines.

Lim, L. L. 1962. Biology of the rice leaffolder, Cnaphalocrocis medinalis (Guenee). B. S. thesis. University of the Philippines, Los Banos. 30 PI'. Ooi, P. A. C., and B. l\'f. Shepard. In press. Predators and parasitoids of rice insect pests. In:

E. A. Heinrichs. Management of rice insects. Wiley· Eastern. Rao, V. P., M. J. Chako, V. R. Phalak. and H. Dinesh Rao. 1969. Leaffeeding caterpillars of

paddy and their natural enemies in India. Journal of Bombay National History Society 66: 455-477.

Shepard, B. M., and G. S. Arida. 19M. Parasitism and predation of yellow stem borer, Scirpopllaga irrcertulas (Walker) (Lepidoptera: Pyralidae) eggs in transplanted and direct seeded rice. J. Enlomol. Sci. 21: 26-32.

Soehardjan, M., and M. [man. 1980. The role of integrated pest management in the green revolution in Indonesia. Paper presented at the XVI International Congress of Entomology, Kyoto, Japan, Aug. 3-9, 1980. Mimeo, 27 pp.