Title: Response of XL6 to Icon 6.2FS and Karate Z for Control of Rice Water Weevil. Beaumont, TX

Transcription

1 Title: Response of XL6 to Icon 6.2FS and Karate Z for Control of Rice Water Weevil. Beaumont, TX Project Investigator: M.O. Way TAMU Agricultural Research and Extension Center 1509 Aggie Drive Beaumont, TX Ph: 409/ Fax: 409/ moway@aesrg.tamu.edu Introduction The rice water weevil (RWW), Lissorhoptrus oryzophilus, is the most serious insect pest of rice in the U.S. If current insecticidal control methods were not available, according to USDA estimates in 1989, U.S. rice farmers would lose $25-50 million annually. This pest is native to the Southeastern U.S. but recently invaded Asia (Japan, the Korean peninsula, Taiwan and China) where it is or is fast becoming a key pest. In the South, Furadan 3G was the only insecticide registered for control of RWW until the late 1990's when EPA banned the use of this product on rice due to avian toxicity problems. Now three newly registered insecticides are available for RWW control - Icon 6.2FS, Karate 1EC/Z and Dimilin 2L. In 2000 about 40% of Texas rice acreage was treated with Icon 6.2FS. I estimate that another 20% was treated with Karate 1EC. Virtually no acreage was treated with Dimilin 2L due to the relatively high cost of this product. Thus, I estimate about 60% of Texas rice acreage was treated for RWW in This is a significant increase from the past when farmers were not concerned as much about RWW damage. Texas Agricultural Experiment Station research has shown farmers that RWW can cause high yield losses and must be managed properly to maximize profits. The new RWW products (Icon 6.2FS and Karate 1EC/Z) are less expensive than Furadan 3G and are preventive which has contributed to the increased number of treated acres. Because the marginal gains from rice farming are becoming razor thin, farmers, out of necessity, are becoming better managers and are paying more attention to insect problems, including RWW. XL6 is a hybrid rice, that is and will be increasingly grown on significant acreage in the South, but no data exist concerning its response to RWW damage. Thus, the objectives of this experiment were to: 1) investigate the response of XL6 to RWW damage relative to a commonly grown semi-dwarf variety, Jefferson and 2) determine the relative responses of XL6 and Jefferson, at varying seeding rates, to the RWW control products, Icon 6.2FS and Karate Z. 46

2 Materials and Methods The experiment was conducted in 2000 at the Texas A&M University Agricultural Research and Extension Center at Beaumont. The experiment was designed as a split-split plot with variety (XL6 and Jefferson) as main plots; treatment (untreated, Icon 6.2FS and Karate Z) as sub plots; and seeding rate (20, 30, 40, 50 and 80 lb/acre) as sub-sub plots. The experiment consisted of four replications; thus, total number of plots was 120. Blocks I and II were in the same paddy while blocks III and IV were in an adjacent paddy. Plot size was 20 ft x 4 ft; plots to receive Icon 6.2FS - treated rice or Karate Z were surrounded by metal barriers to prevent outof-plot movement of insecticides. Blocks I and II: On 11 Apr, plots in blocks I and II were drill-planted (seven rows in each plot, 6 inches between rows) with a Kincaid planter which performed well at all seeding rates. Selected seed was treated with Icon 6.2FS at 0.05 lb (AI)/cwt using the Le Sak method. After planting, plots were flushed (temporary flood for 24 to 48 hours followed by drain). Rice in all plots emerged through League soil on 19 Apr. On 25 Apr when rice was in the two leaf stage, rice stand counts (number of plants in 6 ft row) were taken. On 26 Apr, urea was applied to all plots planted with Jefferson at a of 170 lb N/acre (56.7 lb N/acre). Plots were flushed after urea was applied. On 8 May (2 days before application of the permanent flood), three rice plants in each plot were measured for height and inspected for number of culms and leaves. On 9 May, plots were sprayed for weeds with Arrosolo 3-3E at 2 pt/acre, Basagran at 1.5 pt/acre, Facet 75DF at 0.5 lb/acre and AgriDex (non-ionic adjuvant) at 1 pt/acre. Herbicides were applied with a CO 2 pressurized, two-person, 20 ft spray rig (11 nozzles) equipped with tips and 50 mesh screens. Final spray volume was about 15 gpa. On the same day, selected plots were treated with Karate Z at 0.03 lb (AI)/acre. The insecticide was applied with a CO 2 pressurized, one person spray rig (3 nozzles) equipped with tips and 50 mesh screens. Final spray volume was 28.8 gpa. Again, on the same day (9 May - 1 day before application of the permanent flood), urea was applied to all plots planted with XL6 at 60 lb N/acre. XL6 did not receive any additional fertilizer, so total N applied to XL6 was 60 lb/acre. Urea was also applied to Jefferson plots at 56.7 lb N/acre. On 10 May (21 days after emergence of rice through soil), plots were permanently flooded. From emergence to the permanent flood, plots were flushed as needed. On 31 May and 11 Jun (21 and 32 days after application of the permanent flood), five, 4 inch diameter x 4 inch deep mud cores (each core contained at least one rice plant) were removed from each plot. Roots of plants were washed and inspected for immature RWW. On 12 Jun, all plots planted with Jefferson received another 56.7 lb N/acre in the form of urea. So, Jefferson plots received a total of 170 lb N/acre for the entire growing season. On 4 Aug (107 days from emergence), Jefferson plots were harvested with a small plot combine. On 10 Aug (113 days from emergence), XL6 plots were harvested. Blocks III and IV: On 18 Apr, plots in blocks III and IV were drill-planted using the same materials and methods for blocks I and II. Plots were flushed 2 days later. On 27 Apr, rice in all plots emerged through League soil. On the same day, Jefferson plots were fertilized with urea at 56.7 lb N/acre. On 8 May, rice stand counts (number of plants in 6 ft of row) in each plot were taken. On 18 May, (2 days before application of the permanent flood), plant characteristics were recorded for each plot as was done in blocks I and II. On 19 May, herbicides and Karate Z were applied using the same materials and methods for blocks I and II. On the same day, plots 47

3 planted with Jefferson received urea at 56.7 lb N/acre and plots planted with XL6 received urea at 60 lb N/acre. XL6 plots did not receive additional fertilizer, so total N applied to XL6 was 60 lb/acre. On 20 May (23 days after emergence of rice through soil), plots were permanently flooded. From emergence to the permanent flood, plots were flushed as needed. On 10 and 23 Jun (21 and 34 days after application of the permanent flood), RWW were sampled as in blocks I and II. On 12 Jun, Jefferson plots received another 56.7 lb N/acre in the form of urea; thus, Jefferson plots received a total of 170 lb N/acre for the entire growing season. On 11 Aug (106 days after emergence), Jefferson plots were harvested with a small plot combine. Five days later XL6 plots were harvested with the same combine. Blocks I - IV: After harvesting, rice from each plot was aspirated, if needed, and weighed. Percent moisture was also determined and yields converted to 12% moisture. A portion of the rice from each plot was air dried to 12% moisture and milled using a Rapsco small sample milling machine. RWW counts were transformed using x and all data analyzed using ANOVA for split-split plot design and means separated by LSD. Results Rice Stand: Across treatments and seeding rates, rice stand was significantly better for XL6 than Jefferson (about 17% better stand) (Tables 1 and 2). However, neither treatment (Icon 6.2FS or Karate Z) affected stand. Thus, Icon 6.2FS or Karate Z did not improve or reduce stand. As expected, seeding rate had a profound influence on stand (the higher the seeding rate, the higher the stand). The only significant interaction was between variety and seeding rate which means rice stand was affected differently by seeding rate, depending on variety. Plant height: As expected, across treatments and seeding rates XL6 was significantly taller than Jefferson about the time of the permanent flood (Tables 1 and 2). However, the mean difference was only about 3 cm. Icon 6.2FS and Karate Z did not affect plant height. Culms per plant: At about the time of the permanent flood, none of the variables significantly affected culm density (Tables 1 and 2). Leaves per plant: Across treatments and seeding rates, XL6 produced more leaves than Jefferson (Tables 1 and 2) as observed 2 days before the permanent flood. Icon 6.2FS and Karate Z did not affect number of leaves. RWW populations: Across treatments and seeding rates, XL6 harbored significantly more RWW than Jefferson (Tables 1 and 2). In fact, on the first sample date, XL6 harbored 4x the number of RWW as Jefferson. This suggests that XL6 may be susceptible to RWW (XL6 may be more attractive to egg-laying females or may be a better larval/pupal host than Jefferson). This is an important finding which justifies further research. Across varieties and seeding rates, Karate Z performed better than Icon 6.2FS (although not significantly better on the first sample date). However, be aware that at the lower seeding rates (20, 30 and 40 lb/acre), Icon 6.2FS was applied at lower than recommended rates. I wanted to find out if Icon 6.2FS was effective at low seeding rates given an application rate of 0.05 lb (AI)/cwt. If so, then the cost of the XL6 seed with Icon 6.2FS would be less and consequently more affordable to the producer. 48

4 Across varieties and treatments, RWW populations were higher at lower seeding rates. A significant interaction was detected for variety by treatment which means control of RWW by Karate Z or Icon 6.2FS depended on variety. This is not surprising given higher RWW populations associated with XL6. In short, Karate Z performed well when applied to XL6 planted at any seeding rate. Icon 6.2FS also performed well but was not as effective as Karate Z at the lower seeding rates (20, 30 and 40 lb/acre) which was probably due to lower than recommended application rates of Icon 6.2FS at these lower seeding rates. Yield: Jefferson matured a few days earlier than XL6. Across treatments and seeding rates, XL6 outyielded Jefferson by almost 1600 lb/acre which is equal to about a 20% increase in yield over Jefferson (Tables 1 and 2; Figs. 1 and 2). Across varieties and seeding rates, Icon 6.2FS and Karate Z resulted in about the same yield response (about 980 lb/acre more than the untreated). If rice sold for $5/cwt, the value of the treatments would be about $50/acre minus the cost of the treatments. The cost of the treatments is about $15/acre, so net profit in this situation is about $35/acre - a very nice return on RWW control. For XL6 treated with Icon 6.2FS or Karate Z, highest yields were achieved at RiceTec s recommended seeding rate of 40 lb/acre (Tables 1 and 2; Fig. 3). For Jefferson treated with Icon 6.2FS or Karate Z, highest yields were achieved at the highest seeding rate - 80 lb/acre (Tables 1 and 2; Fig. 4). These results are due in part to the higher stand density of XL6 at all seeding rates compared to Jefferson (Tables 1 and 2). Across varieties and treatments, highest and lowest yields were achieved at the highest and lowest seeding rates, respectively (Table 2). However, yields at 80 lb/acre were not significantly higher than at 40 lb/acre. A significant interaction between variety and seeding rate was due to higher yields of XL6 which peaked at 40 lb seed/acre versus Jefferson yields which peaked at 80 lb seed/acre. Milling: In general, milling was poor for both Jefferson and XL6 (Tables 3 and 4). Due to untimely rains, we were unable to harvest at the optimum grain moisture. We harvested XL6 and Jefferson at about 12-15% moisture, so milling data from the experiment are not very meaningful. However, across varieties and seeding rates, milling quality was unaffected by the treatments (Icon 6.2FS or Karate Z) (Table 4). Conclusions Based on this experiment, XL6 appears to be more susceptible to RWW (in terms of densities) than Jefferson. Both Icon 6.2FS and Karate Z provided good control of RWW, but Karate Z was more effective at the lower seeding rates (20, 30 and 40 lb/acre). The Icon 6.2FS rate of 0.05 lb (AI)/cwt seed resulted in lower than label rates at these lower seeding rates. However, yields of Icon 6.2FS and Karate Z-treated plots were not significantly different and outyielded the untreated by almost 1000 lb/acre. In addition, XL6 outyielded Jefferson by almost 1600 lb/acre - a 20% yield increase over Jefferson. At this point, farmers who grow XL6 should consider controlling RWW due to XL6's significant yield response to RWW protection. However, I emphasize that these conclusions are based on a single year of data collected at a single location in Texas. 49

5 Future Research Efforts In 2001, I recommend the following entomological research on XL6 (or hybrid varieties/lines with improvements over XL6): 1) Repeat RWW experiment conducted in 2000 with the following modifications: a) Cocodrie vs XL6 b) treatments = Karate Z at same rate as 2000, Icon 6.2FS at and lb (AI) per acre (not per cwt) and untreated c) seeding rates = 20, 40, 60 and 80 lb/acre Data from b) and c) will quantify effectiveness of Icon 6.2FS at mid and lowest label rates 2) Include XL6 in our RWW host plant resistance experiment where we screen selected varieties in paired untreated and RWW-treated plots 3) Include XL6 in our stem borer host plant resistance experiment in Ganado where we screen selected varieties in stem borer - untreated plots. 4) We are now investigating storability of Icon 6.2FS on XL6 seed treated this winter or next spring followed by planting next spring. These data will be available next summer. Appendix The appendix includes plot plans of the research and summaries of cultural information pertinent to the experiment described in this report. 50

6 Table 1. Comparative response of XL6 to rice water weevil as a function of seeding rate. Beaumont, TX Variety Treatment Seeding rate (lb/ac) 0 no. rice plants/6' row 0 plant height (cm) 0 no. culms/plant 0 no. leaves/plant 0 no. immature RWW/5cores (1 st sample) 0 no. immature RWW/5 cores (2 nd sample) 0 yield (lb/ac) Jefferson Icon Karate Untreated XL6 Icon Karate Untreated

7 Table 2. Statistical analysis of data in Table 1. Avg. a Avg. a Avg. a Avg. no. plant no. no. Avg. Avg. Avg. rice plants/ height culms/ leaves/ no. RWW/5 cores no. RWW/5 cores yield Treatment effects 6' row (cm) plant plant (1st sample) (2nd sample) (lb/ac) Main plot effects Jefferson 51.6b 19.3b b 7.9b 5.7b 8093b XL a 22.4a a 31.7a 12.4a 9685a NS P= P = P = P = P = P = LSD (0.05) = 4.03 LSD (0.05) = 0.69 LSD (0.05) = 0.68 LSD (0.05) = 19.5 LSD (0.05) = 5.8 LSD (0.05) = 1014 Split plot Icon b b 6.9b 9100a Karate c b 0.7c 9331a Untreated a 19.4a 8236b NS NS NS NS P = P = P = LSD (0.05) = 12.5 LSD (0.05) = 5.8 LSD (0.05) = 241 Split-split plot d e 21.4a a 24.4ab 12.2a 8600c d 21.0ab abc 24.6a 10.4ab 8800bc c 20.4b c 19.1abc 8.5b 8985ab b 21.2a ab 16.6bc 9.2ab 8904b a 20.4b bc 14.1c 4.8c 9155a NS P = P = P = P = P = P = LSD (0.05) = 3.51 LSD (0.05) = 0.71 LSD (0.05) = 0.51 LSD (0.05) = 8.0 LSD (0.05) = 3.3 LSD (0.05) = 205 Interaction V x T NS NS NS P = P = P = NS V x SR P = P = NS NS NS NS P = T x SR NS NS NS NS NS P = NS V x T x SR NS NS NS NS NS NS NS a Plant characteristics taken 2 days before permanent flood Icon = Icon 0.05 lb (AI)/cwt Seeding rate (lb/acre) lb(ai) fipronil/acre c Karate = Karate 0.03 lb (AI)/acre d Split-split plot = seeding rates of 20, 30, 40, 50 and 80 lb/acre

8 Table 3. Comparative milling response of XL6 to rice water weevil as a function of seeding rate. Beaumont, TX Variety Treatment Seeding rate (lb/ac) 0 % whole grains 0 % whole and broken grains Jefferson Icon Karate Untreated XL6 Icon Karate Untreated

9 Table 4. Statistical analysis of data in Table 3. Treatment effects 0. % whole grains 0 % whole and broken gains Main plot effects Jefferson 41.2 a 69.2 a XL b 66.7 b P = P = LSD (0.05) = 7.60 LSD (0.05) = 0.86 Split plot Icon a Karate b Untreated NS NS Split-plot plot c P = P = LSD (0.05) = 1.59 LSD (0.05) = 0.54 Interaction V x T NS NS V x SR NS P = T x SR NS NS V x T x SR P = NS a Icon = Icon 0.05 lb (AI)/cwt b Karate = Karate 0.03 lb (AI)/acre c Split-split plot = seeding rates of 20, 30, 40, 50 and 80 lb/acre 54

10 Yield (lb/acre) Response of XL6 to Icon 6.2FS and Karate Z for control of rice water weevil Fig. 1. Yield as a function of varieties and treatments across seeding rates. Beaumont, TX Jefferson XL Untreated Icon 6.2FS Karate Z 55

11 Yield (lb/acre) Response of XL6 to Icon 6.2FS and Karate Z for control of rice water weevil Fig. 2. Yield as a function of seeding rate across treatments. Beaumont, TX XL-6 Jefferson Seeding rate (lb/acre)

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