Project Highlights. Abstract

Transcription

1 POTENTIAL OF NUCLEAR POLYHEDROSIS VIRUS (NPV) AND BACILLUS THURINGIENSIS (BT) FOR SPODOPTERA CONTROL IN YELLOW GRANEX ONIONS (MICROBIAL CONTROL OF SPODOPTERA IN ONIONS) Baltazar, A.M., E.C. Martin, M.C. Casimero, F.V. Barivan, S.R. Obien and S.K. De Datta Weed management in rice-onion systems. Proceedings IPM-CRSP Symposium, May 15-21, 1997, Guatemala City, Guatemala, pp Baltazar, A.M., E.C. Martin, M.C. Casimero, F.V. Barivan, S.R. Obien and S.K. De Datta Mahor weeds in rainfed rice-onion cropping systems in the Asia site in The Philippines. IPM-CRSP Working Paper No.98-1, presented, 3 "' IPM CRSP Symposium, May, 1998, Virginia Tech, Blacksburg, Virginia, 22 pp. Project Highlights Farmers' weed control practices can be reduced by 50% from two herbicides and two hand weeding operations to just one herbicide and one hand weeding, without reducing weed cont r ol efficacy and onion yields, cutting production costs significantly. In San Jose, one glyphosate application and one hand weeding was just as effective as farmer's practice of sequential application of gluphosate and fluazifop and two hand weeding operations in onion fields under straw mulch. Second herbicide application and hand weeding were not necessary or effective against the dominant weeds, because additional weed suppression was provided by the rice straw mulch. Mulching with rice straw suppressed growth of most weeds, but did not suppress growth of dominant broadleaf weeds, especially Cleonie viscosa, which grew through the mulch. In Bongabon, where straw mulching is not a common practice, a single application of fluazifop and one hand weeding were just as effective as sequential applications of oxyfluorfen and fluazifop and two hand weedings for effective weed cont r ol. Dominant weeds in onion fields of both San Jose and Bongabon sites were similar but differed in proportions of broadleaf weeds, sedges, and grasses; broadleaf weeds were dominant in rice straw-covered onion fields of San Jose, while sedges were dominant in exposed onion fields of Bongabon. Potential of Nuclear Polyhedrosis Virus (NPV) and Bacillus thuringiensis (Pt) for Spodoptera Control in Yellow Granex Onions (Microbial Control of Spodoptera in Onions) Investigators: L.E. Padua ', A.C. Lapus ', V.P. Gapud 2, C.V. Pile 2, B.A. Santiago ', N.S. Talekar 3, and E. Rajotte 4 Abstract Field trials in Bongabon, Nueva Ecija have shown that NPV, Bt, and NPV+Bt are more effective against Spodoptera larvae, than Karate insecticide application. Larval counts were significantly lower in the microbial treatments than the control or Karate treatment later in the season. Onion yields in the Bt+NPV- treated and the Karate-treated plots were significantly higher than in the control (no insecticide) plots, although the differences between them were not significant. The lowest yields were observed in control plots. These results show that microbials, alone or in combination, are effective alternatives to insecticide application, confirming their positive potential for Spodoptera management. Onion yields among the treatments in San Jose, Nueva Ecija also had the same trend. Onion yields were significantly higher in NPV+Bt-treated plots than in NPV- and Karate treated plots, respectively. However, the cutworm larval densities were too low to demonstrate the effects of the treatments on them and on onion yields. 1 UPLB (BIOTECH) 2 PhilRice 3 AVRDC 4 Penn State 243

2 Asian Region The degree of onion leaf damage caused by larvae was relatively higher in the Demonstration farm in Bongabon than in the farmer's field in Palestina, San Jose, Nueva Ecija, which could be attributed to late planting. Onion yields from both sites differed considerably owing to rice hull burning, which could have reduced soil-borne diseases and nematodes, the timing of planting, the planting density, and the soil type. Objectives (1) To mass produce NPV-CRSP for field trials in combination with Bt (2) To develop a better formulation for NPV (3) To evaluate the efficacy of NPV-CRSP against S. litura (4) To continue field trials using the most promising Bt and NPV-CRSP as microbial control agents against S. litura IPM Constraints Safe and economical alternatives to chemical control against Spodoptera litura in onions were considered as possible options for pesticide reduction. Research Methods Plans to develop a viable formulation for NPV-CRSP were proposed to replace the NPV crude extract currently used in field experiments, to minimize if not eliminate the pungent odor of the crude suspension. Mass-rearing of Spodoptera was continued using natural host plants to provide for the mass production of NPV-CRSP needed for the experiments. The best Bt and NPV-CRSP strains continued to be tested in the field together with Karate, a common insecticide used by farmers for Spodoptera larval control. A farmer's field in Palestina, San Jose and a field in the Demonstration (Demo) farm in Bongabon, Nueva Ecija were used to compare the effects of Bt alone, NPV alone, NPV + Bt, and Karate application (fanner practice) on cutworm larval densities and onion yields. Each treatment was set up in RCBD using four replicated plots measuring 4m x 5m each. Treatments were applied for six weeks at biweekly intervals. The degree of onion leaf damage caused by larval feeding among the treatments was measured by taking the percent of leaves damaged per plant, using 10 plants for each treatment and replication, every two weeks starting 4 weeks after transplanting. Research Results A wettable powder formulation for NPV-CRSP was developed in August 1998 at the Insect Pathology Laboratory, Department of Entomology, U.P. Los Banos. This formulated product will replace the NPV crude extract being used in field experiments for Spodoptera control. The characteristic pungent odor of the crude suspension has been greatly minimized in the wettable powder for better handling and preparation of the spray solution. The Insect Pathology laboratory has produced five (5) kilograms of NPV-CRSP wettable powder with x 10 8 PIBs per gram. They are maintained in the freezer for future use. Mass production of NPV-CRSP is a continuing activity of the project. The comparative effects of Bt product, NPV-CRSP crude extract and Karate on Spodoptera litura and Helicoverpa larval populations and onion yields from farmer's field in NOGROCOMA Demonstration Farm, Bongabon, Nueva Ecija are shown in Table 1. Cutworm larval densities were observed to be relatively low during the season in Bongabon, especially 2 weeks after transplanting (WAT) up to 10 WAT, after which the number per plant increased slightly. However, larval densities differed significantly among treatments 12 WAT. Lowest mean larval density was observed in NPV-treated plots, followed by plots treated with Bt alone, NPV + Bt, and control, in increasing levels. Karate-treated plots had the highest larval densities. Onion yields were highest in NPV+Bt-treated and Karate-treated plots, although the differences between them were not significant. Yields in NPV-treated and Bt-treated plots were not significantly different than in the untreated control. Table 1. Effect of B. thuringiensis product (Bt), NPV-CRSP crude extract and Karate on larval populations and onion yields in Demo Farm, Bongabon, Nueva Ecija, DS Mean number o4'. litura and Helicoverpa larvae (4 Replications) n=10 plants Treatment 2 WAT T 5 WAT 8 WAT 11 WAT 14 WAT Yield S.1/tom Helico. S.litura Helico. S.litura Helico. S.lihtra Helico. S.litaa a Helico. (ton/ha) Tl-Bt 0.90a ' a a 0.18a 0.35b 0.23ab 0.53b 0.38a 16.63ab T2-NPV 0.20a a a 0.25a 0.25b 0.18b 0.50b 2.73a 16.12ab T3-NPV+Bt 0.20a a a 0.23a 0.30b 0.53a 0.83ab 0.15a 19.06a T4-Karate 1.67a a a 0.03a 1.33a 0.33ab 1.33a 0.58a 18.85a T5-Control 1.03a a a 0.58a 0.77ab j 0.28ab 1.18ab 0.10a 14.15b 2Means in a column with the same letter are not significantly different at 5% level of significance using DUNCAN'S MULTIPLE RANGE TEST. Whether the yields were affected by other factors, e.g., soil- species, Helicoverpa arrnigera,could have affected the borne diseases, nematodes, or other insects, remains cutworm densities owing to the territorial and solitary uncertain. It is also likely that the presence of another larval behavior of H. arnzigera larvae, exhibiting control of onion 244

3 POTENTIAL OF NUCLEAR POLYHEDROSIS VIRUS (NPV) AND BACILLUS THURINGIENSIS (BT) FOR SP0D0PTERA CONTROL IN YELLOW GRANEX ONIONS (MICROBIAL CONTROL OF SPODOPTERA IN ONIONS) leaves over cutworm larvae. Likewise, the timing of sampling could have affected the observed cutworm larval densities., The shift to night sampling in the next year's activity may reflect a different picture of larval populations. In San Jose, Nueva Ecija, where the farmer planted early (November, 1997), cutworm larval densities were low and did not differ among treatments, which in effect were not adequate to reflect the adavantage of microbiais over insecticide applications (Table 2). Likewise, onion yields were very high and did not differ significantly among treatments. The very high yields (four times as high as in the Demo Farm) in San Jose could be attributed to early planting, higher plant density per unit area (no furrows between rows and closer spacing), and the sandy loam type of soil. Moreover, the Field was subjected to rice hull burning which has been shown to reduce soil-borne disease incidence, weeds, and nematodes. In contrast, onion fields in the Bongabon Demo farm were planted late (December- January), had lower plant density (plants were arranged in distinct rows with furrows between rows), and the clay loam type of soil. Rice hull burning is not a common practice in Bongabon farms as it is among San Jose farmers. Considering all these factors, which could have influenced onion yields in both sites, the effects of NPV and Bt still remain inconclusive. Perhaps, the real potential of Bt and NPV may be realized at higher concentrations, which should be considered in next year's experiments. Table 2. Effect of B. thuringiensis product, NPV-CRSP crude extract and Karate on S. litura populations and onion yields in farmer's field in Palestina, San Jose, Nueva Ecija, DS Number of larvae per plant (4 replications) ' Yield TREATMENT 2 WAT 5 WAT 8 WAT 11 WAT 14 WAT (dha) Tl, Bt alone 0.03a 0.03a 0.68a 0.67a Oa 51.83a T2, NPV alone 0.03a 0.03a 0.43a 2.00a Oa 58.27a T3, NPV+Bt Oa Oa 1.38a 2.57a 0.03a 60.48a T4, Karate Oa Oa 2.00a 1.33a Oa 53.44a T5, Control Oa Oa 1.00a 1.50a 0.05a 50.13a 'Means in a column with the same letter are not significantly different at 5% level of significance using DUNCAN'S MULTIPLE RANGE TEST. The extent of onion leaf damage owing to larval feeding is 4 WAT to as high as 41.75% at 12 WAT in Karate-treated shown in Tables 3-4 and Figures 1-2. In the Bongabon site, plots, implying that Karate did not effectively suppress overall leaf damage did not differ significantly among cutworm larval populations. Overall, the NPV-treated plots treatments. Percent damage ranged from as low as 11.5% at had the lowest leaf damage (Figure 1). Table 3. Extent of leaf damage caused by Spodoptera litura larvae on Yellow Granex onion using Bt, NPV-CRSP, and Karate, Demo Farm, Bongabon, San Jose, DS Percent (%) Leaf Damage (n = 10 plants) ' Treatment 4 WAT 1 6 WAT 8 WAT 10 WAT 12 WAT Overall T1, Bt alone 20.50a 15.00a 20.75a 19.50a 30.50ab T2, NPV alone 13.50a 17.25a 18.00a 17.00a 27.00b T3, NPV+Bt 13.50a 18.25a 21.00a 21.50a 26.25b Karate 11.50a 18.00a 22.25a 25.25a 41.75b Control 20.75a 18.75a 25.75a 25.75a 34.50ab 'Means in a column followed by the same letter are not different at 5% level of significance using DUNCAN'S MULTIPLE RANGE TEST 45, m o* m a WAT 6 WAT 8 WAT 10 WAT 12 WAT Weeks After Transplanting Bt -E. - NPV Bt + NPV Karate Control Figure 1. Effects of treatment with Bt, NPV, and Karate on leaf damage caused by cutworm larvae in onion field, Demo farm, Bongabon, Nueva Ecija, DS

4 Asian Region In San Jose, the control plots showed the highest leaf damage 4 weeks after transplanting, but there were no significant differences between treatments. No significant differences were observed between treatments or the control for the remainder of the experiment (Table 4, Figure 2). As mentioned earlier, the much lower larval densities in the site may only reflect a negligible level of leaf damage, which ranged from as low as 0 at 4 WAT to as high as 21.75% at 10 WAT in NPV+Bt-treated plots. The higher level of leaf' damage in onion plots observed in the Bongabon Demo site could have been due to the late planting, with the vegetative stage of the crop coinciding with higher cutworm larval populations in the site. Table 4. Extent of leaf' damage caused by Spodoptera litura on Yellow Granex onion treated with Bt, NPV-CRSP, and Karate, Palestina, San Jose, Nueva Ecija, DS Percent ( %) Leaf Damage (n = 10 plants) _ Treatment 4 WAT 6 WAT 8 WAT 10 WAT 12 WAT Overall Ti, Bt alone 2.00b 10.25a 15.75a 13.75a 3.25a 9.00a T2, NPV alone 2.50b 6.00a 13.00a 13.25a 3.25a 7.60a T3, NPV+Bt Ob 5.00a 20.25a 21.75a 3.00a 10.00a T4, Karate 2.50b 7.25a 18.50a 19.25a 3.25a 10.15a T5, Control 6.25a 10.75a 18.75a 16.25a 5.25a 11.45a Weans in a column with the same letter are not significantly different at 5% level using DUNCAN'S MULTIPLE RANGE TEST. 4 WAT 6 WAT 8 WAT 10 WAT 12 WAT Weeks After Transplanting Figure 2. Effects of treatment with Bt, NPV, and Karate on leaf damage caused by cutworm larvae in onion fields, Palestina, San Jose, Nueva Ecija, DS In the Bongabon site, while the experiment was being conducted, nearby plots were heavily invaded by armyworms (Spodoptera exigua). Surprisingly, however, they were not observed in the field where the microbial experiment was conducted. It may indicate that microbials are effective against armyworms. Impact on host country The use of Bt and NPV as alternatives to insecticide use would greatly benefit onion farmers who depend heavily on insecticides for cutworm control. Direct effects are reduced pesticide use, better health of farmers, and sustainable Spodoptera management. In addition, farm-produced NPV will reduce the cost of crop protection by farmers. As a result, the market quality of their onion produce will be greatly enhanced by their low insecticide residue levels, thereby meeting the export requirements of foreign markets. Networking Activities Workshops participated in: Third IPM CRSP Symposium, Planning Workshop, and Technical Committee Meeting, Virginia Tech, Blacksburg, Virginia, May 15-18, 1998 Research Investigator Exchanges As Scientist exchange (L. Padua) at Penn State University to conduct research on Nuclear Polyhedrosis Virus (NPV) with U.S. counterparts, August November, 1998 Research information and product exchange Prepared training booklet on mass production of NPV for adoption by onion farmers. 246

5 EFFECTS OF RICE HULL BURNING ON SOIL-BORNE DISEASES, WEED SURVIVAL AND GROWTH, AND THE RICE ROOT-KNOT NEMATODE, MELOIDOGYNE GRAMINICOLA IN A RICE-ONION CROPPING SYSTEM Distributed NPV materials for use by Bongabon farmers. Publications and Presentations L.E. Padua, V.P. Gapud, R.C. Suiza, E.C. Martin, C.V. Pile, B. Santiago, N.S. Talekar, E. Rajotte, and V. Recta Management tactics for Spodoptera control, Working Paper, presented, Third IPM CRSP Symposium, May 1998,. Virginia Tech, IPM-CRSP, 12 pp. Training Output Trained 20 Bongabon farmers in the production of NPV at farmer level. Project Highlights e A wettable formulation of NPV-CRSP developed at UPLB (BIOTECII) with mass production capability; 5 kg of wettable NPV-CRSP have been produced. The presence of larvae of Helicoverpa ar-nzigera upset the cutworm larval populations in Demo farm, Bongabon, Nueva Ecija. Lowest cutworm larval densities occurred in NPVtreated plots in Demo farm, Bongabon, Nueva Ecija. Differences in cutworm larval densities, level of onion leaf damage, and onion yields between San Jose and Bongabon are attributed to timing of planting, planting density, soil type, and the presence of other lepidopterous larvae, e.g., Helicoverpa armigera. The use of NPV+Bt and NPV alone is a promising alternative to the use of insecticides for managing Spodoptera litura and Helicoverpa in onions. Effects of Rice Hull Burning on Soil-Borne Diseases, Weed Survival and Growth, and the Rice Root-Knot Nematode, Meloidogyne graminicola in a Rice-Onion Cropping System Investigators: E. B. Gergon ', R. T. Alberto ', M. C. Casimero ', E.C. Martin ', M. V. Judal ', M.V. Duca l, S.E. Santiago ', F. Bajo ', S.R. Obien ', A.M. Baltazar 2, F.V. Barivan 2, S.K. De Datta 3, A.M. Mortimer`', and S. Miller 5 Abstract The continuing study on the effects of rice hull burning on soil-borne diseases in San Jose and Bongabon showed that fungal populations were much lower in burned plots than in unburned plots. In San Jose, fungal colonies were slightly higher in burned plots treated with compost than in those without compost, implying that compost could be favorable for fungal growth. Onion yields, however, were the same in both treatments. In unburned fields, a similar trend was observed but at lower levels, and with similarly low yields. It would appear that yields were more influenced by rice hull burning than by compost. Plots exposed to rice hull burning produced twice as much yield as those not exposed. In the Bongabon Demo farm, pink root (Phoma terrestris) incidence and severity were slightly higher in burned fields with compost than in burned fields without compost. In unburned fields, the same trend for pink root was observed. The corresponding onion yields, however, were adversely affected by the armyworm Spodoptera exigua infestation associated with the El Nino phenomenon which affected many parts of the country, especially Central Luzon. Rice hull burning reduced the density and fresh weight of Cyperus rotundus, the major weed in Palestina, San Jose, Nueva Ecija, by 88% and 79%, respectively, over unburned plots. Yields in burned plots were increased by 58% over unburned plots. Experiments in San Jose showed that the heat caused by rice hull burning was effective in suppressing nematode populations up to a soil depth of 20 cm. Under field conditions, rice hull burning effectively reduced nematode populations with or without compost, resulting in larger and heavier onion bulbs. The experiment in Bongabon Demo farm showed a similar trend, but onion yields were greatly reduced by the armyworm infestation, which PhilRice 2 UPLB 3 Virginia Tech 4 IRRI 5 Ohio State 24 7