The sweetpotato whitefly (SPWF), Bemisia tabaci Gennadius, is a serious cotton pest in the and southwest and other parts of the U.S. cotton belt. Control measures are difficult because immatures develop on leaf undersides where it is difficult to effectively deliver control agents to the underside of leaves. Two trials with candidates for chemical control of SPWF on cotton were conducted at a site in Maricopa, Arizona. In the first of two trials with small plots (5 plots = 0.052 ac), agents tested included: two pyrethroids, bifenthrin (Capture(TM)) and fenpropathrin (Danitol(TM)) with and without the organic phosphate acephate (Orthene(TM)) as a possible synergist; two formulations of the insect growth regulator (IGR), Azadirachtin (Margosan-O(TM) and AD1000(TM)); the IGR buprofezin (Applaud(TM)); two non-phosphate compounds, amitraz (Ovasyn(TM)) and imidaeloprid (Confidor(TM) [Bay NTN 338931]), and a Cyclo-compound, endosulfan (Thiodan(TM)). Data for mean egg numbers per cm² of leaf for the last four of 7 applications showed significant control (P < 0.01) as percent reduction from a block of untreated plots as: pyrethroids with or without acephate -- 94.-to 96.%, amitraz -- 84%, azadirachtin -- 82%, endosulfan-- 82%, buprofezin --81%, and acephate 73.3%. Data for large immatures per cm2 of leaf for the last four of 7 applications showed significant control (P < 0.05) as percent reduction from a block of untreated plots as: pyrethroids with or without acephate -- 97-98%, buprofezin -- 99%, amitraz -- 98%, imidacloprid -- 97%, azadirachtin as AD1000 -- 96%, and endosulfan-- 96% For the first 3 applications, the overall mean adult population per plot per cm² of sticky card was 13.47 ± 0.51 SE and ranged from 10.92 to 16.65 with no significant differences between treatments and controls. For the second 4 applications, the mean adult population per plot per cm² of sticky card was 22.17 ± 0.83 SE and ranged from 14.34 to 26.32 with no significant differences between treatments and controls by ANOVA. The large increase in the mean adult population present in the 2nd half of the test compared to the 1st half of the test (22.17 versus 13.47) was highly significant at P < 0.001.

In the 2nd trial with large cotton plots (each group of 5 plots comprised a treatment block of 1.12 ac), agents tested included buprofezin (Applaud(TM)) and amitraz (Ovasyn(TM)) with and without endosulfan (Thiodae(TM)), the latter was also tested alone. For the last two of 5 applications, mean numbers of eggs were reduced by 69.9 to 92.3 % from control plots at P < 0.01 for all agents and combinations tested with the two most effective treatments being buprofezin/endosulphan and amitraz/endosulfan. For the last two of 5 applications mean numbers of large immatures per cm² of leaf showed significant control (P < 0.01) as percent reduction from adjacent control plots as: buprofezin, with or without endosulfan 99%; endosulfan -- 94%; amitraz with endosulfan -- 93%; and amitraz alone 67%. For the first 3 applications and the last two of the 5 application, means of adult populations were significantly reduced, by 4 of the 5 treatments (exception was amitraz), by 46.2 to 65.1 % from those in control plots at P < 0.01 and P < 0.05 for the first 3 and last 2 applications respectively. The large increase in the mean adult population per control plots per cm² present in the 2nd half of the test compared to the 1st half of the test (29.3 versus 13,95) was highly significant at P < 0.01.