two experiments were conducted in 2011 and 2012 at the delta research and extension center ( drec ) in stoneville , ms , to determine the impact of delayed flooding and the impact of multiple flushes with water between planting and flood on the efficacy of seed treatments against rice water weevil in rice . the soil type at this location for both years and experiments was sharkey clay ( very fine , smectitic , thermic chromic epiaquerts ) ( www.websoilsurvey.nrcs.usda.gov ) . the rice variety ( linscombe et  al . 2000 ) , seeded at 95  kg / ha , was used for both experiments in both years . seed treatments and their use rates for both studies included thiamethoxam ( cruiser 5fs , syngenta crop protection ) at 248  ml/100  kg of seed , chlorantraniliprole ( dermacor x-100 , e.i . dupont de nemours ) at 130  ml/100  kg of seed , and clothianidin ( nipsit inside , valent agricultural products ) at 124  ml/100  kg of seed . plots in both studies during each year measured 1.73 by 4.57  m and were drill seeded at 95  kg / ha . an experiment was conducted to determine the impact of a delayed flood on the efficacy of insecticidal seed treatments targeting rice water weevil . treatments were in a split - plot arrangement within a randomized complete block design with four replications in 2011 and eight replications in 2012 . the main - plot factor was time to flood and included timings of 6 and 8 wk after planting . the sub - plot factor was seed treatment and included the three seed treatments and rates previously described plus an untreated control . plots were planted 11 may 2011 and 26 april 2012 for the 8-wk timing , and 24 may 2011 and 10 may 2012 for the 6-wk timing . all plots were flooded 30 june 2011 and 22 june 2012 . during the time from planting to flood establishment rainfall events of 2.74 and 2.95  cm occurred on 26 total precipitation was 8.56  cm from time of planting to flood establishment for 2011 . in 2012 , total precipitation was 2.21  cm from 3 may 2012 to 20 may 2012 . from 31 total precipitation from time of planting to flood establishment for 2012 was 21.39  cm . planting dates were varied for different flood timings so that all treatments could be flooded at the same time . rice water weevil adults migrate into fields and begin oviposition upon establishment of the flood ( everett and trahan 1967 , rice et  al . 1999 , 2000 ) , and rice water weevil adult densities can vary greatly from week to week . planting all treatments on the same date and establishing the flood at different dates would likely bias the results because some plots may have been exposed to different levels of rice water weevil densities . planting at different dates and establishing the flood on the same date ensured that all plots were exposed to similar densities of rice water weevil . all plots were mechanically harvested for yield on 6 october 2011 and 20 september 2012 . an experiment was conducted to determine the impact of multiple flushes with water on the efficacy of seed treatments targeting rice water weevil . treatments were in a split - plot arrangement within a randomized complete block design with four replicates in 2011 and eight replicates in 2012 . the sub - plot factor was seed treatment and included the treatments and rates previously described . the first flush was applied on 7 june 2011 and 18 may 2012 . during 2011 , plots received a total of 4.55  cm of rainfall from planting to the first flushing with a major rainfall event occurring on 26 may 2012 , totaling 2.74  cm . in 2012 , plots received a total of 0.48  cm of rainfall from planting to the first flush . the second flush was on 15 june 2011 and 13 june 2012 . in 2011 , a rainfall event occurred on 22 june 2011 of 2.95  cm and the total precipitation from planting to flood establishment of 6.76 cm . in 2012 , plots received 18.92  cm of rainfall between the first and second flush , totaling 19.43  cm from time of planting to flood establishment . the plots receiving only one flush were flushed at the time of the second flush in the two - flush treatments . the last bay ( lowest elevation ) was flushed two times with the middle bay being flushed one time and the first bay only receiving the permanent flood . plots were sampled 4 wk after flood establishment on 1 august 2011 and 19 july 2012 . plots were mechanically harvested on 6 october 2011 and 20 september 2012 . to determine the effectiveness of the seed treatments in both experiments , 2 10  cm in diameter    15.2  cm in depth core samples were collected from each plot 4 wk after establishment of the flood , based on information by thompson et  al . samples included removing upper vegetative growth from plants located in the interior of the plot , then using a modified bulb planter to collect the bottom portion of the plant , its root mass , and the surrounding soil . samples were placed in 3.79-liter ziploc bags and taken to the laboratory to be washed through a series of screens separating larvae from the root mass . the basket was placed in a 10% nacl solution and the number of rice water weevil larvae was determined ( stout et  al . 2001 ) . the 10% nacl changes the specific gravity of the water , allowing the rice water weevil larvae to float . at the end of the season , each plot was mechanically harvested with a plot combine . all data were analyzed with analysis of variance ( proc mixed of sas , littell et  al . 1996 ) . for both experiments , the main - plot factor , the sub - plot factor , and their interactions years were considered environmental or random effects , allowing for inferences to be made over a range of environments ( carmer et  al . replication nested in year and replicate by water treatment nested within year were random terms in the model , and served as the error terms for the main - plot and sub - plot factors , respectively . an experiment was conducted to determine the impact of a delayed flood on the efficacy of insecticidal seed treatments targeting rice water weevil . treatments were in a split - plot arrangement within a randomized complete block design with four replications in 2011 and eight replications in 2012 . the main - plot factor was time to flood and included timings of 6 and 8 wk after planting . the sub - plot factor was seed treatment and included the three seed treatments and rates previously described plus an untreated control . plots were planted 11 may 2011 and 26 april 2012 for the 8-wk timing , and 24 may 2011 and 10 may 2012 for the 6-wk timing . all plots were flooded 30 june 2011 and 22 june 2012 . during the time from planting to flood establishment rainfall events of 2.74 and 2.95  cm occurred on 26 total precipitation was 8.56  cm from time of planting to flood establishment for 2011 . in 2012 , total precipitation was 2.21  cm from 3 may 2012 to 20 may 2012 . from 31 total precipitation from time of planting to flood establishment for 2012 was 21.39  cm . planting dates were varied for different flood timings so that all treatments could be flooded at the same time . rice water weevil adults migrate into fields and begin oviposition upon establishment of the flood ( everett and trahan 1967 , rice et  al . 1999 , 2000 ) , and rice water weevil adult densities can vary greatly from week to week . planting all treatments on the same date and establishing the flood at different dates would likely bias the results because some plots may have been exposed to different levels of rice water weevil densities . planting at different dates and establishing the flood on the same date ensured that all plots were exposed to similar densities of rice water weevil . all plots were mechanically harvested for yield on 6 october 2011 and 20 september 2012 . an experiment was conducted to determine the impact of multiple flushes with water on the efficacy of seed treatments targeting rice water weevil . treatments were in a split - plot arrangement within a randomized complete block design with four replicates in 2011 and eight replicates in 2012 . the sub - plot factor was seed treatment and included the treatments and rates previously described . the first flush was applied on 7 june 2011 and 18 may 2012 . during 2011 , plots received a total of 4.55  cm of rainfall from planting to the first flushing with a major rainfall event occurring on 26 may 2012 , totaling 2.74  cm . in 2012 , plots received a total of 0.48  cm of rainfall from planting to the first flush . the second flush was on 15 june 2011 and 13 june 2012 . in 2011 , a rainfall event occurred on 22 june 2011 of 2.95  cm and the total precipitation from planting to flood establishment of 6.76 cm . in 2012 , plots received 18.92  cm of rainfall between the first and second flush , totaling 19.43  cm from time of planting to flood establishment . the plots receiving only one flush were flushed at the time of the second flush in the two - flush treatments . the last bay ( lowest elevation ) was flushed two times with the middle bay being flushed one time and the first bay only receiving the permanent flood . plots were sampled 4 wk after flood establishment on 1 august 2011 and 19 july 2012 . to determine the effectiveness of the seed treatments in both experiments , 2 10  cm in diameter    15.2  cm in depth core samples were collected from each plot 4 wk after establishment of the flood , based on information by thompson et  al . samples included removing upper vegetative growth from plants located in the interior of the plot , then using a modified bulb planter to collect the bottom portion of the plant , its root mass , and the surrounding soil . samples were placed in 3.79-liter ziploc bags and taken to the laboratory to be washed through a series of screens separating larvae from the root mass . the basket was placed in a 10% nacl solution and the number of rice water weevil larvae was determined ( stout et  al . the 10% nacl changes the specific gravity of the water , allowing the rice water weevil larvae to float . at the end of the season , each plot was mechanically harvested with a plot combine . all data were analyzed with analysis of variance ( proc mixed of sas , littell et  al . 1996 ) . for both experiments , the main - plot factor , the sub - plot factor , and their interactions were considered fixed effects in the model . years were considered environmental or random effects , allowing for inferences to be made over a range of environments ( carmer et  al . replication nested in year and replicate by water treatment nested within year were random terms in the model , and served as the error terms for the main - plot and sub - plot factors , respectively . a significant interaction between flood timing and seed treatments was observed for rice water weevil densities ( f  =  3.87 ; df  =  3 , 66 ; p  =  0.01 ; table 1 ) . this interaction resulted from differences in larval densities observed between the untreated control for the 6-wk flood timing and the untreated control for the 8-wk flood timing . there were no significant differences in larval densities between the treated plots and the untreated plots for the 6-wk flood timing . larval densities in the untreated plots for the 8-wk flood timing were significantly higher than all other seed treatment  flood timing combinations ( table 1 ) . when the permanent flood was established at 6 wk after planting , densities of rice water weevil larvae ranged from 14.00 to 16.25 in the treated plots and 20.67 in the untreated plots . for the 8-wk flood treatment , densities of rice water weevil larvae ranged from 14.67 to 15.17 in the treated plots compared with 42.42 for the untreated plots . table 1.impact of flood timing and insecticide seed treatment on mean ( sem ) numbers of rice water weevil larvae per core for 20112012treatmentmean  +  se no . larvae per core6 wk8 wkseed treatment meanthiamethoxam16.25    3.03b14.83    2.90b15.42    2.06chlorantraniliprole14.00    1.20b14.67    2.34b14.33    1.29clothianidin14.00    2.51b15.17    2.98b14.58    1.91untreated control20.67    4.56b42.42    11.65a31.54    6.52mean16.23    1.5421.71    3.51means followed by the same letter are not significantly different (   =  0.05).untransformed data presented , but statistics are based on square root - transformed data . impact of flood timing and insecticide seed treatment on mean ( sem ) numbers of rice water weevil larvae per core for 20112012 means followed by the same letter are not significantly different (   =  0.05 ) . untransformed data presented , but statistics are based on square root - transformed data . there was no significant interaction between flood timing and seed treatments for yield ( f  =  0.58 ; df  =  3 , 66 ; p  =  0.63 ; table 2 ) . however , flood timing ( f  =  9.16 ; df  =  1 , 11 ; p  =  0.01 ) and seed treatment ( f  =  9.07 ; df  =  3 , 66 ; p  < plots flooded at 8 wk after planting yielded significantly higher than plots flooded at 6 wk after planting . plots flooded at 8 wk yielded 7,723  kg / ha rough rice yield compared with 7,330  kg / ha rough rice yield in plots flooded at 6 wk . across flood timings , all seed treatments resulted in significantly higher yields than the untreated control ( table 2 ) . yields ranged from 7,610 to 7,845  kg / ha rough rice yield for the treated plots compared to 6,960  kg / ha rough rice yield for the untreated plots . table 2.impact of flood timing and insecticide seed treatment on mean ( sem ) rough rice yields in 20112012treatmentmean  +  se yield ( kg / ha)6 wk8 wkseed treatment meanthiamethoxam7,464    1857,919    2297692    151achlorantraniliprole7,727    1557,964    1637846    113aclothianidin7,288    1827,932    2977610    183auntreated control6,844 2007,077    1196960    116bmean7,330    100b7,723    116ameans followed by the same letter are not significantly different (   =  0.05 ) . impact of flood timing and insecticide seed treatment on mean ( sem ) rough rice yields in 20112012 means followed by the same letter are not significantly different (   =  0.05 ) . there was no interaction between number of flushes and seed treatments observed for densities of rice water weevil larvae ( f  =  0.99 ; df  =  6 , 90 ; p  =  0.44 ) . however , the main effects of flush number ( f  =  8.65 ; df  =  2 , 20 ; p  <  0.01 ) and seed treatment ( f  =  17.48 ; df  =  3 , 90 ; p  < flushing one or more times resulted in significantly lower densities of rice water weevil larvae compared with no flushes . across all flush treatments , all seed treatments significantly reduced larval densities compared with the untreated control ( table 3 ) . the average numbers of rice water weevil larvae ranged from 14.16 to 14.86 in seed treatment plots compared with 25.03 in the untreated control ( table 3 ) . table 3.impact of flush number and seed treatment on the mean ( sem ) number of rice water weevil larvae per soil core 20112012seed treatmentmean  +  se no . larvae per core0 flush1 flush2 flushesmeanthiamethoxam19.25    2.7412.92    2.3211.33    1.4314.50 1.38bchlorantraniliprole17.00    2.1212.83    2.8012.64    2.0214.53    1.33bclothianidin16.92    2.4613.83    3.2413.83    1.7114.86    1.45buntreated control32.58    9.7122.67    5.7119.76    1.8924.42 3.86amean21.44    2.73a15.56    1.92b14.39    0.97bmeans followed by the same letter are not significantly different (   =  0.05)untransformed data presented , but statistics are based on square root - transformed data . impact of flush number and seed treatment on the mean ( sem ) number of rice water weevil larvae per soil core 20112012 means followed by the same letter are not significantly different (   =  0.05 ) untransformed data presented , but statistics are based on square root - transformed data . a significant interaction between number of flushes and seed treatments was observed for yield ( f  =  8.14 ; df  =  6 , 90 ; p  <  0.01 ; table 4 ) . all of the treated plots that received zero or one flush yielded significantly more compared with the untreated control that received zero or one flush . plots treated with chlorantraniliprole that received two flushes produced significantly more rough rice yield than plots treated with thiamethoxam , clothianidin , or the untreated plots that received two flushes . yields ranged from 7,957 to 8,127  kg / ha of rough rice for the treated plots that did not receive a flush compared with 6,837  kg / ha of rough rice for the untreated control that did not receive a flush . the application of one flush did not negatively impact yield for treated plots . yields ranged from 7,650 to 8,064  kg / ha of rough rice for the treated plots that received one flush compared with 6,994  kg / ha of rough rice for the untreated control that received one flush . as flush number increased from 0 and 1 to 2 , thiamethoxam and clothianidin were negatively impacted based on rough rice yield , producing 7,326 and 7,402  kg / ha , respectively . when two flushes were applied thiamethoxam and clothianidin were not significantly different from the untreated control . plots treated with chlorantraniliprole that received two flushes were not negatively impacted and yielded 8,242  kg / ha of rough rice compared with 7,465  kg / ha of rough rice for the untreated control that received two flushes . additionally , no differences were observed among chlorantraniliprole treatments across flush treatments . table 4.impact of flush number and seed treatment on the mean ( sem ) rough rice yields 20112012seed treatmentmean  +  se yield ( kg / ha)0 flush1 flush2 flushesmeanthiamethoxam8,083    299ab7,836    372ab7,326    171c7,749    173chlorantraniliprole8,127 258ab8,064    342a8,242    140ab8,147    146clothianidin7,957    330ab7,650    385b7,402    135c7,669    174untreated control6,837 246c6,994    276c7,465    83c7,094    131mean7,751    1587,636    1787,608    85means followed by the same letter are not significantly different (   =  0.05 ) . impact of flush number and seed treatment on the mean ( sem ) rough rice yields 20112012 means followed by the same letter are not significantly different (   =  0.05 ) . a significant interaction between flood timing and seed treatments was observed for rice water weevil densities ( f  =  3.87 ; df  =  3 , 66 ; p  =  0.01 ; table 1 ) . this interaction resulted from differences in larval densities observed between the untreated control for the 6-wk flood timing and the untreated control for the 8-wk flood timing . there were no significant differences in larval densities between the treated plots and the untreated plots for the 6-wk flood timing . larval densities in the untreated plots for the 8-wk flood timing were significantly higher than all other seed treatment  flood timing combinations ( table 1 ) . when the permanent flood was established at 6 wk after planting , densities of rice water weevil larvae ranged from 14.00 to 16.25 in the treated plots and 20.67 in the untreated plots . for the 8-wk flood treatment , densities of rice water weevil larvae ranged from 14.67 to 15.17 in the treated plots compared with 42.42 for the untreated plots . table 1.impact of flood timing and insecticide seed treatment on mean ( sem ) numbers of rice water weevil larvae per core for 20112012treatmentmean  +  se no . larvae per core6 wk8 wkseed treatment meanthiamethoxam16.25    3.03b14.83    2.90b15.42    2.06chlorantraniliprole14.00    1.20b14.67    2.34b14.33    1.29clothianidin14.00    2.51b15.17    2.98b14.58    1.91untreated control20.67    4.56b42.42    11.65a31.54    6.52mean16.23    1.5421.71    3.51means followed by the same letter are not significantly different (   =  0.05).untransformed data presented , but statistics are based on square root - transformed data . impact of flood timing and insecticide seed treatment on mean ( sem ) numbers of rice water weevil larvae per core for 20112012 means followed by the same letter are not significantly different (   =  0.05 ) . untransformed data presented , but statistics are based on square root - transformed data . there was no significant interaction between flood timing and seed treatments for yield ( f  =  0.58 ; df  =  3 , 66 ; p  =  0.63 ; table 2 ) . however , flood timing ( f  =  9.16 ; df  =  1 , 11 ; p  =  0.01 ) and seed treatment ( f  =  9.07 ; df  =  3 , 66 ; p  < plots flooded at 8 wk after planting yielded significantly higher than plots flooded at 6 wk after planting . plots flooded at 8 wk yielded 7,723  kg / ha rough rice yield compared with 7,330  kg / ha rough rice yield in plots flooded at 6 wk . across flood timings , all seed treatments resulted in significantly higher yields than the untreated control ( table 2 ) . yields ranged from 7,610 to 7,845  kg / ha rough rice yield for the treated plots compared to 6,960  kg / ha rough rice yield for the untreated plots . table 2.impact of flood timing and insecticide seed treatment on mean ( sem ) rough rice yields in 20112012treatmentmean  +  se yield ( kg / ha)6 wk8 wkseed treatment meanthiamethoxam7,464    1857,919    2297692    151achlorantraniliprole7,727    1557,964    1637846    113aclothianidin7,288    1827,932    2977610    183auntreated control6,844 2007,077    1196960    116bmean7,330    100b7,723    116ameans followed by the same letter are not significantly different (   =  0.05 ) . impact of flood timing and insecticide seed treatment on mean ( sem ) rough rice yields in 20112012 means followed by the same letter are not significantly different (   =  0.05 ) . there was no interaction between number of flushes and seed treatments observed for densities of rice water weevil larvae ( f  =  0.99 ; df  =  6 , 90 ; p  =  0.44 ) . however , the main effects of flush number ( f  =  8.65 ; df  =  2 , 20 ; p  <  0.01 ) and seed treatment ( f  =  17.48 ; df  =  3 , 90 ; p  < flushing one or more times resulted in significantly lower densities of rice water weevil larvae compared with no flushes . across all flush treatments , all seed treatments significantly reduced larval densities compared with the untreated control ( table 3 ) . the average numbers of rice water weevil larvae ranged from 14.16 to 14.86 in seed treatment plots compared with 25.03 in the untreated control ( table 3 ) . table 3.impact of flush number and seed treatment on the mean ( sem ) number of rice water weevil larvae per soil core 20112012seed treatmentmean  +  se no . larvae per core0 flush1 flush2 flushesmeanthiamethoxam19.25    2.7412.92    2.3211.33    1.4314.50    1.38bchlorantraniliprole17.00 2.1212.83    2.8012.64    2.0214.53    1.33bclothianidin16.92    2.4613.83    3.2413.83    1.7114.86    1.45buntreated control32.58 9.7122.67    5.7119.76    1.8924.42    3.86amean21.44    2.73a15.56    1.92b14.39    0.97bmeans followed by the same letter are not significantly different (   =  0.05)untransformed data presented , but statistics are based on square root - transformed data . impact of flush number and seed treatment on the mean ( sem ) number of rice water weevil larvae per soil core 20112012 means followed by the same letter are not significantly different (   =  0.05 ) untransformed data presented , but statistics are based on square root - transformed data . a significant interaction between number of flushes and seed treatments was observed for yield ( f  =  8.14 ; df  =  6 , 90 ; p  <  0.01 ; table 4 ) . all of the treated plots that received zero or one flush yielded significantly more compared with the untreated control that received zero or one flush . plots treated with chlorantraniliprole that received two flushes produced significantly more rough rice yield than plots treated with thiamethoxam , clothianidin , or the untreated plots that received two flushes . yields ranged from 7,957 to 8,127  kg / ha of rough rice for the treated plots that did not receive a flush compared with 6,837  kg / ha of rough rice for the untreated control that did not receive a flush . the application of one flush did not negatively impact yield for treated plots . yields ranged from 7,650 to 8,064  kg / ha of rough rice for the treated plots that received one flush compared with 6,994  kg / ha of rough rice for the untreated control that received one flush . as flush number increased from 0 and 1 to 2 , thiamethoxam and clothianidin were negatively impacted based on rough rice yield , producing 7,326 and 7,402  kg / ha , respectively . when two flushes were applied thiamethoxam and clothianidin were not significantly different from the untreated control . plots treated with chlorantraniliprole that received two flushes were not negatively impacted and yielded 8,242  kg / ha of rough rice compared with 7,465  kg / ha of rough rice for the untreated control that received two flushes . additionally , no differences were observed among chlorantraniliprole treatments across flush treatments . table 4.impact of flush number and seed treatment on the mean ( sem ) rough rice yields 20112012seed treatmentmean  +  se yield ( kg / ha)0 flush1 flush2 flushesmeanthiamethoxam8,083    299ab7,836    372ab7,326    171c7,749    173chlorantraniliprole8,127    258ab8,064    342a8,242    140ab8,147    146clothianidin7,957    330ab7,650    385b7,402    135c7,669    174untreated control6,837 246c6,994    276c7,465    83c7,094    131mean7,751    1587,636    1787,608    85means followed by the same letter are not significantly different (   =  0.05 ) . impact of flush number and seed treatment on the mean ( sem ) rough rice yields 20112012 means followed by the same letter are not significantly different (   =  0.05 ) . in mississippi , the flood is generally established between 4 and 6 wk after planting . flood establishment at 8 wk is not a common agronomic practice in mississippi except in instances where rice development is delayed . with the commercialization of clearfield rice in 2002 , the need for early flood establishment for red rice control was reduced ( roel et  al . 1999 , bond and walker 2011 ) . delaying the flood by 24 wk allows rice plants to accumulate more biomass and become more tolerant to injury before rice water weevil infestations occur ( rice et  al . 1999 , stout et  al . water management practices have a strong influence on the relationship between rice and rice water weevil ( hesler et  al . 1992 ) , but little information exists about the impact of water management on current seed treatments . in a study by stout et  al . ( 2001 ) , the efficacy of fipronil ( icon , basf corporation , research triangle park , nc ) was lower in delayed flooded plots ( 34 days after planting ) than in early flooded plots ( 20 days after planting ) . it was proposed that the efficacy of fipronil had deteriorated before larval densities were determined . in the current experiment , rice water weevil densities in the untreated plots were higher for the 8-wk flood timing compared with the 6-wk flood timing . ( 1999 ) , who observed that delaying the flood resulted in lower densities of rice water weevil larvae infesting rice plants . all seed treatment were efficacious at the 8-wk flood timing and larval densities in the treated plots were lower than those observed in the untreated plots . larval densities in the untreated control were higher at the 8-wk flood timing compared with the 6-wk flood timing for the untreated plots ; however , the untreated plots with the 8-wk flood timing yielded higher than untreated plots with the 6-wk flood timing . rice tolerance to rice water weevil injury increases with plant age ( stout et  al . 2002a ) . the plants in the untreated plots with the 8-wk flood timing were older than those in the plots that received the 6-wk flood timing and should have accumulated more root mass , making them more tolerant to rice water weevil injury . these data suggest that with an economical weed management strategy , growers can delay the permanent flood and reduce injury from rice water weevil feeding . during the time from planting to flood , flushing is often required for herbicide activation to facilitate emergence of seedlings and to irrigate water stressed seedlings ( roel et  al . 1999 , webster and levy 2009 ) . in hot dry conditions , such as those observed in 2011 and 2012 , flushing two or more times prior to establishing the flood is not uncommon . in this experiment , there was no significant interaction between seed treatment and number of flushes for rice water weevil densities . plots that received one flush or two flushes had significantly fewer larvae than plots that did not receive a flush . in both years , plots that did not receive a flush showed severe signs of drought stress . plots that received one or two flushes were visibly larger and healthier than those that did not receive a flush . the advanced growth stage of these plants could have been mistaken as older less desirable plants for oviposition ( stout et  al . seed treatments performed similarly and all reduced rice water weevil densities below the level in the untreated control . although no differences were observed in rice water weevil densities among seed treatments , the application of the second flush had a negative impact on yield in the thiamethoxam- and clothianidin - treated plots . the water solubility of thiamethoxam ( 4100  mg liter ) and clothianidin ( 340  mg liter ) ( pesticide properties database [ ppdb ] 2013 ) may be the reason for the yield losses observed in this study . yields for plots treated with chlorantraniliprole that received two flushes were not significantly different compared with the chlorantraniliprole - treated plots that received zero or one flush , suggesting that chlorantraniliprole provided better protection when multiple flushes were applied . this could be contributed to the water solubility of chlorantraniliprole ( 0.88  mg liter ) ( ppdb 2013 ) being much lower than the neonicotinoids . during a flush , the entire field the additional water may have moved thiamethoxam and clothianidin out of the root zone preventing or reducing uptake by the plants resulting in yield loss . these data suggest that currently labeled seed treatments reduce overall rice water weevil densities in conditions that require multiple flushes with water prior to flooding . however , when multiple flushes were applied in plots treated with thiamethoxam or clothianidin significant yield losses were observed . when using thiamethoxam or clothianidin in hot and dry conditions that require multiple flushes with water , supplemental applications with a foliar insecticide may be needed to protect rice yields .
two experiments were conducted at the delta research and extension center in stoneville , ms , during 2011 and 2012 to determine the impact of water management practices on the efficacy of insecticidal seed treatments targeting rice water weevil , lissorhoptrus oryzophilus kuschel . 
 larval densities and yield were compared for plots treated with labeled rates of thiamethoxam , chlorantraniliprole , and clothianidin and an untreated control . in the first experiment , 
 plots were subjected to flood initiated at 6 and 8 wk after planting . 
 seed treatments significantly reduced larval densities with the 8-wk flood timing , but not the 6-wk flood timing . 
 overall , the treated plots yielded higher than the control plots . in the second experiment , 
 the impact of multiple flushes on the efficacy of insecticidal seed treatments was evaluated . 
 plots were subjected to zero , one , or two flushes with water . 
 all seed treatments reduced larval densities compared with the untreated control . 
 significantly fewer larvae were observed in plots that received one or two flushes compared with plots that did not receive a flush . 
 all seed treatments resulted in higher yields compared to the untreated control in the zero and one flush treatments . 
 when two flushes were applied , yield from the thiamethoxam and clothianidin treated plots was not significantly different from those of the control plots , while the chlorantraniliprole treated plots yielded significantly higher than the control . 
 these data suggest that time from planting to flood did not impact the efficacy of seed treatments , but multiple flushes reduced the efficacy of thiamethoxam and clothianidin .