Beaumont, TX 2006 Introduction This experiment is a continuation of a multi-year study to investigate the relationship between rice planting date and rice water weevil (RWW) activity. Determining yield response to RWW damage relative to planting date was the main objective of these experiments. Another objective was to evaluate the efficacy of labeled RWW insecticides in changing population densities observed across different planting dates. Five planting dates were conducted at the Beaumont Center. Cultural practices basically were the same for all planting dates (see below). Agronomic and Cultural Information Planting dates: Irrigation: Herbicide: Fertilizer: Drill-seeded Cocodrie @ 90 lb/acre into League soil (ph 5.5, sand 3.2%, silt 32.4%, clay 64.4% and organic matter 3.8-4.8%) Plot size = 7 rows, 7 in. row spacing, 18 ft long with metal barriers around plots Experimental design: randomized complete block with 4 replications Flushed plots after planting (temporary flood for 48 hours, then drain) Note: Plots were flushed as needed from emergence to permanent flood Permanent flood approximately 3 wk after emergence Stam 80EDF @ 2.0 lb, Basagran @ 0.75 lb, Facet 75DF @ 0.25 lb and Ordram @ 2.0 lb (AI)/acre and Agri-Dex @ 1.0 pt/acre applied approximately 10-14 days after emergence for early season weed control Urea was applied by hand according to 2004 Rice Production Guidelines. All dates received 170 lb N/acre plus an additional 40 lb N/acre late season. Treatments: All treatments are foliar sprays applied with a hand-held spray boom (3-800067 nozzles, 50 mesh screens, 25 gpa) See Table 1 for treatment descriptions, timing and rates. Sampling: Harvest: RWW cores (5 cores per plot, each core 4 in. diameter, 4 in. deep, containing at least one rice plant) were collected approximately 3 wk after permanent flood and 10-14 days following. Core samples were stored in a cold-room, later washed through 40 mesh screen buckets and immature RWW counted. Note: Prior to analysis RWW counts transformed using square root (x + 0.5) Entire plot harvested for yield Yields converted to lb/acre adjusted to 12% moisture 13
Discussion In each planting date, all insecticide treatments controlled immature RWW except in the Jun 7 planting (Table 1). The before flood (BF) applications of Karate Z, Silencer and V10170 50WDG in the Jun 7 planting provided significant control of immature RWW. Best yield response to controlling RWW occurred in the earliest plantings (Mar 10 and 28). Yield response in later plantings was less pronounced. Heaviest RWW infestations occurred in the late March planting. Previous research indicates yield potential declines after an optimum planting window. In this experiment, yields declined significantly in the May 12 and Jun 7 plantings despite controlling immature RWW. Table 1. Rice water weevil (RWW) and yield data. Beaumont, TX. 2006 Rate [lb No. immature RWW/5 cores Yield (lb/acre) Description (AI)/acre] Timing 1 st cores 2 nd cores Main Ratoon Total Mar 10 planting date Untreated --- --- 40 a 112 a 7113 b 1905 9018 b Karate Z 0.0300 BF a 0 b 3 d 8212 a 2232 10444 a Karate Z 0.0300 3 DAF b 2 b 2 d 8405 a 2183 10588 a Mustang Max 0.0225 BF 1 b 9 bc 7776 ab 2065 9842 ab Mustang Max 0.0225 3 DAF 0 b 6 bcd 8252 a 2139 10390 a Prolex 0.01625 BF 0 b 3 d 8034 a 2189 10223 a Prolex 0.01625 3 DAF 1 b 4 cd 8250 a 2149 10400 a Dimilin 2L 0.1875 3 DAF 0 b 10 b 7856 a 2121 9978 a Mar 28 planting date Untreated --- --- 116 a 119 a 8832 1905 b 10737 Karate Z 0.0300 BF 2 bc 2 bc 9332 2696 a 12027 Karate Z 0.0300 3 DAF 2 bc 1 c 9413 2787 a 12200 Mustang Max 0.0225 BF 2 bc 4 b 9220 2673 a 11892 Mustang Max 0.0225 3 DAF 3 b 1 c 9406 2451 a 11857 Prolex 0.01625 BF 0 c 1 c 9370 2676 a 12045 Prolex 0.01625 3 DAF 2 bc 1 c 9605 2647 a 12251 Dimilin 2L 0.1875 3 DAF 5 b 2 bc 9098 2597 a 11695 a BF = immediately before permanent flood b DAF = days after flood Means in a column followed by the same or no letter are not significantly different () at the 5% level (ANOVA, LSD). Table 1 continued below 14
Table 1. Rice water weevil (RWW) and yield data (continued). Beaumont, TX. 2006 Rate No. immature RWW/5 cores Yield (lb/acre) Description [lb (AI)/acre] Timing 1 st cores 2 nd cores Main Ratoon Total Apr 14 planting date Untreated --- --- 61 a 83 a 9062 2675 11737 Karate Z 0.0300 BF a 1 cd 5 d 8866 2582 11448 Karate Z 0.0300 3 DAF b 2 bc 9 cd 9352 2558 11909 Mustang Max 0.0225 BF 0 d 19 bc 8645 2333 10978 Mustang Max 0.0225 3 DAF 1 cd 23 b 8575 2440 11015 Prolex 0.01625 BF 0 d 9 cd 9179 2702 11880 Prolex 0.01625 3 DAF 5 b 8 cd 8793 2324 11117 Dimilin 2L 0.1875 3 DAF 5 b 3 d 9184 2452 11635 May 12 planting date Untreated --- --- 59 a 34 a 7540 NA NA Karate Z 0.0300 BF 3 d 1 e 7716 NA NA Karate Z 0.0300 3 DAF 15 c 7 bcd 7542 NA NA Mustang Max 0.0225 BF 4 d 5 cd 7334 NA NA Mustang Max 0.0225 3 DAF 18 bc 11 bc 7567 NA NA Prolex 0.01625 BF 4 d 3 de 7599 NA NA Prolex 0.01625 3 DAF 19 bc 8 bc 7673 NA NA Dimilin 2L 0.1875 3 DAF 26 b 13 b 7810 NA NA Jun 7 planting date Untreated --- --- 75 a 37 a 5484 NA NA Karate Z 0.0300 BF 16 fg 9 b 5654 NA NA Karate Z 0.0300 3 DAF 50 bc 12 b 5523 NA NA Mustang Max 0.0225 BF 23 ef 17 b 5450 NA NA Mustang Max 0.0225 3 DAF 40 cd 15 b 5507 NA NA Prolex 0.01625 BF 28 de 16 b 5822 NA NA Prolex 0.01625 3 DAF 61 ab 16 b 5264 NA NA Dimilin 2L 0.1875 3 DAF 77 a 36 a 5497 NA NA Silencer 0.03 BF 13 fg 8 b 5911 NA NA V-10170 50WDG 1.5oz prod./acre BF 8 g 14 b 5909 NA NA V-10170 50WDG 1.5oz prod./acre 11 DAF 43 bcd 15 b 5725 NA NA a BF = immediately before permanent flood DAF = days after flood Means in a column followed by the same or no letter are not significantly different () at the 5% level (ANOVA, LSD). 15
Discussion (continued) Table 2 shows comparisons between untreated plots and the average of all insecticide treatments for each planting date. Previous research suggests controlling RWW in the main crop can contribute to ratoon yield. This is most evident in the Mar 28 planting where main crop treated rice ratooned over 700 lb/acre more than untreated rice. Table 3 examines the means of all treatments (including the untreated) within each planting date. Immature RWW data are less instructive in this analysis. However, yield data confirm earliest planting dates have the greatest yield potential. Early March plantings avoided heavier RWW infestations but suffered from colder temperatures at planting and emergence. Heaviest RWW pressure tended to coincide with optimum planting date (mid March to mid April), suggesting treatment for this pest continue to be an integral part of rice management. Table 2. Comparison of treated and untreated plots for each planting date. Bmt., TX. 2006 No. immature RWW/5 cores Yield (lb/acre) Planting Date Treatment a 1 st cores 2 nd cores Main Ratoon Total Mar 10 T 1 5 8112 2154 10266 U 40 112 7113 1905 9018 Mar 28 T 2 2 9349 2647 11996 U 116 119 8832 1905 10737 Apr 14 T 2 11 8942 2484 11426 U 61 83 9062 2675 11737 May 12 T 13 7 7606 NA 7606 U 59 34 7540 NA 7540 Jun 7 T b 42 17 5531 NA 5531 U 75 37 5484 NA 5484 a T = treated for RWW, U = untreated b treated plots from Jun 7 planting date do not include Silencer and V-10170 50WDG treatments Table 3. Comparison of mean data for all treatments a within each planting date. Bmt., TX. 2006 No. immature RWW/5 cores Yield (lb/acre) Planting Date 1 st cores 2 nd cores Main Ratoon Total March 10 5 18 7987 2123 10110 March 28 16 16 9284 2554 11838 April 14 9 20 8957 2508 11465 May 12 18 10 7597 NA 7597 June 7 46 20 5525 NA 5525 a Mean data include untreated plots and does not include Silencer and V-10170 50WDG treatments from June 7 planting date See economic analysis below. 16
Discussion (continued) Treating for RWW (especially on the Mar 10 and 28 plantings) provided a significant yield advantage (Table 4). Also, the economic advantage in $/acre was highest in these earliest planting dates (Table 5). Economic data are calculated using the following parameters concerning insecticide costs, aerial application charges and cwt price of rice: $6.90/cwt price of rice (ca. loan rate, does not include hauling and drying costs) Karate Z applied BF: $412.25/gal (no aerial charge if tank-mixed with pre-flood herbicides) Karate Z applied 3 DAF: $412.25/gal + $7.50/acre aerial charge Mustang Max applied BF: $227.76/gal (no aerial charge if tank-mixed with pre-flood herbicides) Mustang Max applied 3 DAF: $227.76/gal + $7.50/acre aerial charge Prolex applied BF: $395.00/gal (no aerial charge if tank-mixed with pre-flood herbicides) Prolex applied 3 DAF: $395.00/gal + $7.50/acre aerial charge Dimilin 2L applied 3 DAF: $186.75/gal + $7.50/acre aerial charge Table 4. Yield advantage of RWW treatments across five planting dates. Beaumont, TX. 2006 Yield advantage [Treated Untreated (lb/acre)] Mean a Treatment Timing Mar 10 Mar 28 Apr 14 May 12 Jun 7 (lb/acre) Karate Z BF 1426 1290-289 176 170 555 Karate Z 3 DAF 1570 1463 172 2 39 649 Mustang Max BF 824 1155-759 -206-34 196 Mustang Max 3 DAF 1372 1120-722 27 23 364 Prolex BF 1205 1308 143 59 338 611 Prolex 3 DAF 1382 1514-620 133-220 438 Dimilin 2L 3 DAF 960 958-102 270 13 420 Mean b advantage (lb/acre) 1248 1258-311 66 47 a Mean yield advantage for each individual treatment across five planting dates b Mean yield advantage for each individual planting date across all treatments Table 5. Economic advantage of RWW treatments across five planting dates. Bmt., TX. 2006 Net return ($/acre) Mean a Treatment Timing Mar 10 Mar 28 Apr 14 May 12 Jun 7 ($/acre) Karate Z BF 92.41 83.03-25.92 6.16 5.75 32.29 Karate Z 3 DAF 94.85 87.47-1.61-13.34-10.79 31.31 Mustang Max BF 50.45 73.72-58.35-20.19-8.33 7.46 Mustang Max 3 DAF 88.69 71.30-55.80-4.12-4.39 19.14 Prolex BF 78.02 85.12 4.74-1.06 18.19 37.00 Prolex 3 DAF 82.73 91.84-55.41-3.45-27.81 17.58 Dimilin 2L 3 DAF 41.07 40.93-32.21-6.54-24.27 3.80 Mean b advantage ($/acre) 75.46 76.20-32.08-6.08-7.38 a Mean $/acre advantage for each individual treatment across five planting dates b Mean $/acre advantage for each individual planting date across all treatments 17