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Insect pestsand their natural enemiesin ratoon riceC. G. dela Cruz and J.A. LitsingerDepartment of Entomology, International Rice ResearchInstitute, P.O. Box 933, Manila, PhilippinesABSTRACTA ratoon crop is potentially at risk from insect pests because it extends the time rice isavailable as a host. With its shortened vegetative stage, a ratoon crop is unsuitable toearly season insects — whorl maggot Hydrellia philippina and caseworm Nymphuladepunctalis. Stem borer numbers are severely reduced at main crop harvest, but somesurvive to attack the ratoon crop. Leaffolder infestation is higher at the vegetative stageon a ratoon crop than on a sown main crop. The lack of land preparation in establishinga ratoon crop allows a high carryover of natural rice pest enemies, particularly of thepredators which prevent significant buildups of brown planthopper, whitebackedplanthopper, and green leafhopper. Virus diseases on the main crop pose the mostserious insect-related problem in ratoon rice.As with any system that intensifies production, double rice cropping involving aratoon crop may create a higher risk of pest buildup. Intensified cropping thatextends the time rice is available allows more insect generations per year. Insectpopulations increase exponentially with time. In theory, ratoon rice should sustainhigher insect populations than a single or a double rice crop separated by a fallow orrotation with a nonrice crop (20).During a rice-free period, specializing pests must either subsist on suboptimalhosts, on which their rate of increase is low or negative; enter a quiescent or dormantstage, during which they are often subject to severe mortality; or undertake highlyrisky, long distance dispersal. The potential increase of a pest population over theannual cycle depends on the length of time rice is available.Loevinsohn et al (21) indicate that increasing the cropping intensity within acontiguous area greater than 1 km 2 (314 ha) can encourage insects that are ricespecialists. Brown planthopper (BPH) is an exception, it has a dispersal range of 2km. Using a composite index of spatio-temporal intensity/number of “hectaredays,” Loevinsohn et al showed exponential increases in populations of five riceinsect pests.The effect of a ratoon crop on pest populations could be positive, negative, orneutral. Insect groups that prefer the vegetative stage should decrease, because thevegetative stage is radically shorter in a ratoon crop. Insect groups that have noparticular preference for a crop growth stage or that prefer the reproductive orripening stages should stay the same, or increase.
196 RICE RATOONINGExcept for rice whorl maggot (RWM) Hydrellia philippina (12), ratoon cropshave been reported to harbor rice insect pests that primarily attack late vegetativeand reproductive stage crops. Examples are gall midge (GM) Orseoli oryzae (10, 18,28, 35), tarsonemid mite Steneotarsonemus spinki (11), stem borers (SB) Scirpophagaincertulas and Chilo suppressalis (6, 8, 14, 17), and leaffolder (LF)Cnaphalocrocis medinalis (5). Vectors and the related virus diseases also show up:BPH Nilaparvata lugens and grassy stunt (15, 23, 26), whitebacked planthopper(WBPH) Sogatella furcifera (22) and green leafhopper (GLH) Nephotettix virescensand tungro virus (24, 29, 33). Yellow dwarf virus vectored by Nephotettix spp. andRecilia dorsalis is known as the ratooning disease, because it most often shows up ona ratoon crop (19).Work at CRRI (3) compared the suitability of ratoon and direct-seeded cropsas hosts to pink stem borer (PSB), striped stem borers (SSB), and GM but found nodifferences.The stability of GLH and BPH resistence in a ratoon was studied by Wildeand Apostol (34). They found a slightly lower level of resistance in an older ratooncrop than in a direct-seeded crop.On the other hand, a ratoon crop may also be a favorable environment fornatural enemies of rice pests. Agronomic preparation does not involve habitatdisturbingland preparation. Higher rates of GM parasitization were observed in aratoon crop because parasite numbers increase toward the end of the wetseason (18).In areas where irrigation and drainage are well developed and where laborcosts are high, farmers increasingly are direct seeding pregerminated rice (wetseeding)rather than transplanting. It is not known whether crop establishmentmethod alters insect pest or natural enemy populations in the succeeding ratooncrop.Standing water in a rice paddy attracts aquatic insect pests such as RWM andcaseworm (CW) as well as aquatic natural enemies such as the ripple bug. Ratooncrops may or may not get standing water.We designed a study to1. compare the population buildup of insect pests and their natural enemies ina ratoon crop and a seeded second crop;2. determine if water management and crop establishment method affectarthropod abundance; and,3. assess the suitability of a ratoon crop as host to rice insect pests.MATERIALS AND METHODSIn the 1983 wet season, a field trial at IRRI compared the population buildup ofinsect pests and natural enemies in a ratoon and in a seeded second crop andexamined the effects of crop establishment methods and water regimes on arthropodpopulations. In the same year, the suitability of a ratoon crop as host to nine riceinsect pests was studied in the greenhouse.
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RICERATOONING1988INTERNATIONAL RICE
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ContentsForewordWelcome 1OverviewRi
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Genetics and varietal improvementIn
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2 RICE RATOONINGthe main crop. Harv
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4 RICE RATOONINGTable 1. Area, prod
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6 RICE RATOONINGTable 2. Rice varie
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8 RICE RATOONING1. Effect of spacin
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10 RICE RATOONINGHowever, no signif
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12 RICE RATOONINGrelating to seed v
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14 RICE RATOONING5. Cultivars that
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Economic perspectivesof rice ratoon
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ECONOMIC PERSPECTIVES OF RICE RATOO
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32 RICE RATOONINGla) Developmental
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34 RICE RATOONINGCutting heightStub
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36 RICE RATOONINGEarly flooding enc
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38 RICE RATOONING2. Factors affecti
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40 RICE RATOONING27. Nair, N.R., an
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42 RICE RATOONING1. Changes in till
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44 RICE RATOONINGTable 2. Character
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46 RICE RATOONING9. International R
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48 RICE RATOONINGplot size is 6 row
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50 RICE RATOONINGimproved ratooning
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52 RICE RATOONINGTable 6. Simple co
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Utilization of rice ratooningby far
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RICE RATOONING IN RIO DE JANEIRO 57
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RICE RATOONING IN RIO DE JANEIRO 59
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Rice ratooningin the Dominican Repu
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RICE RATOONING IN THE DOMINICAN REP
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89111306514772Special points Refere
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72 RICE RATOONINGANDHRA PRADESHBasu
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74 RICE RATOONINGrice observed at t
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76 RICE RATOONINGTAMIL NADUBalasubr
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78 RICE RATOONING19. Reddy, T.G., M
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80 RICE RATOONING1. Rice-growing re
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82 RICE RATOONING2. High cutting he
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84 RICE RATOONINGTable 3. Yield tri
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Rice ratoon crop managementin the h
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RICE RATOON CROP MANAGEMENT IN KARN
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23123722821721922222421423122421722
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98 RICE RATOONING1. The Tungabhadra
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100 RICE RATOONINGthe results of po
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102 RICE RATOONINGTable 4. Effect o
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Ratoon rice researchin Karnataka, I
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RATOON RICE RESEARCH IN KARNATAKA 1
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RATOON RICE RESEARCH IN KARNATAKA 1
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112 RICE RATOONINGTable 1. Area and
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114 RICE RATOONINGonly 7.5-49.7% of
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116 RICE RATOONINGTable 5. Relation
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Scope for rice ratoon croppingin th
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RATOON CROPPING IN NORTHEASTERN IND
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Scope for rice ratoon croppingin th
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RATOON CROPPING IN CENTRAL AND NORT
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RATOON CROPPING IN CENTRAL AND NORT
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Potential of rice ratooningin Madag
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RICE RATOONING IN MADAGASCAR 131a.
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RICE RATOONING IN MADAGASCAR 133Tab
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Potential for rice ratooningin east
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RICE RATOONING IN EASTERN INDIA 137
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Ratooning in Bangladesh:prospects a
Page 152 and 153: RATOONING IN BANGLADESH 145RATOON C
Page 154 and 155: RATOONING IN BANGLADESH 147Table 4.
Page 156: RATOONING IN BANGLADESH 149OTHER FA
Page 159 and 160: 152 RICE RATOONINGTable 1. Hybrid s
Page 161 and 162: 154 RICE RATOONINGThe studies sugge
Page 163 and 164: 156 RICE RATOONINGVARIETIES AND CUL
Page 165 and 166: 158 RICE RATOONINGspikelet primordi
Page 167 and 168: 160 RICE RATOONINGTable 5. Effect o
Page 170 and 171: Agronomic principles and practiceso
Page 172 and 173: AGRONOMIC PRINCIPLES AND PRACTICES
Page 184 and 185: Rice ratooning: breeding,agronomic
Page 186 and 187: BREEDING, AGRONOMIC PRACTICES, AND
Page 192: BREEDING, AGRONOMIC PRACTICES, AND
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Page 197 and 198: 190 RICE RATOONINGRESULTSMain crop
Page 199 and 200: 192 RICE RATOONINGRatoon tiller reg
Page 201: 194 RICE RATOONING9. Rister, M. E.,
Page 205 and 206: 198 RICE RATOONINGInsect survivorsh
Page 207 and 208: 200 RICE RATOONING1. Stem borer occ
Page 209 and 210: 202 RICE RATOONING3. Population dyn
Page 211 and 212: 204 RICE RATOONING2, 3). Microvelia
Page 213 and 214: 206 RICE RATOONINGplant chemicals a
Page 215 and 216: 208 RICE RATOONING17. Krishnamurthy
Page 217 and 218: 210 RICE RATOONING1. Yellow dwarf c
Page 219 and 220: 212 RICE RATOONING3. The effect of
Page 221 and 222: 214 RICE RATOONINGAlthough the inte
Page 223 and 224: 216 RICE RATOONINGTable 6. Sheath b
Page 226 and 227: Yellow dwarf disease in ratoon rice
Page 228 and 229: YELLOW DWARF DISEASE IN RATOON RICE
Page 230 and 231: YELLOW DWARF DISEASE IN RATOON RICE
Page 232: YELLOW DWARF DISEASE IN RATOON RICE
Page 235 and 236: 228 RICE RATOONINGTable 1. Estimate
Page 237 and 238: Main crop a Ratoon crop b53.956.155
Page 240 and 241: Disease and insect pestsand their c
Page 242 and 243: DISEASE AND INSECT PESTS IN RICE RA
Page 244 and 245: DISEASE AND INSECT PESTS IN RICE RA
Page 246 and 247: Inheritance of ratooning abilityin
Page 248 and 249: INHERITANCE OF RATOONING ABILITY IN
Page 250 and 251: INHERITANCE OF RATOONING ABILITY IN
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INHERITANCE OF RATOONING ABILITY IN
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248 RICE RATOONINGShould the season
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250 RICE RATOONINGYield and yield-c
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252 RICE RATOONINGMain-crop photosy
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254 RICE RATOONINGShort-termGiven t
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Commercial ratoon rice productionin
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COMMERCIAL RATOON RICE PRODUCTION I
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0.180.200.490.250.160.270.390.350.3
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268 RICE RATOONING1. Path analysis
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270 RICE RATOONINGRecommendationsVa
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ParticipantsT. AhmedRice Experiment
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Varietal indexA200, 221Achra 108/1,
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VARIETAL INDEX 277IR2061-465-1, 12I
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VARIETAL INDEX 279RU7502006, 49, 51
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