EVALUATION OF INSECTICIDES FOR ONION THRIPS CONTROL ON DRY ONION, 1996:

 

R. F. L. Mau and L. R. Gusukuma-Minuto
University of Hawaii
Dept. of Entomology
3050 Maile Way, Rm. 310
Honolulu, HI 96822
Phone: (808) 956-7063
 
R. S. Shimabuku
Cooperative Extension Service
310 Kaahumanu Ave., Bldg 214
Kahului, HI 96732

 

ONION: Allium cepa L. ‘Grano 1015Y’

Onion thrips (OT); Thrips tabaci Lindeman

The insecticides were evaluated at the Kula Research Station, Maui Agricultural Park, from June to September. The field was set up in a randomized complete block design with six treatments and four replications (blocks). Each treatment plot consisted of four rows of plants planted at 8 in. between plant spacing. Each row consisted of 45 plants. Seedlings were transplanted into the field on 17 Jun. Treatments were applied using a compressed carbon dioxide sprayer at 60 psi and 100 GPA. Two twin jet nozzles (TJ-6502) were used per two rows. Applications of Warrior @ 0.02 and 0.03 lb. ai/A, Lannate, and Ammo were made at 7-day intervals on 16, 23, 30 July, 6, 13, 20 Aug for a total of six applications. The second treatment of Warrior @ 0.03 lb. ai/A was made when thrips numbers exceeded 3 thrips/plant. Thrips monitoring via in-field monitoring on 10 randomly selected plants in each plot were made. If the thrips average for all four replicates exceeded 3 thrips/plant, a treatment was made on the following day. Treatments were made on 23 July, 6, 20 Aug.

A pre-treatment survey was made on 15 Jul. Subsequent surveys were made on a bi-weekly schedule. In surveying for thrips, ten plants were randomly selected and removed . The bulb and leaves were removed and the whorl of the onion was placed in separate plastic zip lock bags.

Each sample was washed in a detergent solution and the thrips were collected in a 150 mesh sieve. The thrips were transferred into plastic 20 ml vials, preserved with 70% ethyl alcohol, and counted at a later date. Thrips were recorded by developmental stages first instar larvae (LI), second instar larvae (LII), and adults (A).

Weekly Warrior and Ammo treatments were very effective in causing a ten- to 20-fold reduction in thrips numbers. There was no difference in the thrips control produced by either rate of Warrior. Both were equally effective. Treatment with Warrior using a 3-thrips threshold was as effective as weekly calendar sprays of the insecticide. A single application of Warrior using a treatment threshold was ostensibly as effective as the two weekly applications of Warrior. The Lannate LV treatment increased moderately, but not at the same rate as in the untreated check. At the final post-treatment survey, the same order of effectiveness was found. Warrior and Ammo treatments successfully regulated thrips numbers at low levels. Thrips density in the Lannate LV treatment equaled that of the untreated check.

 

                                                                        __________Mean number of thrips/10 plants__________
                                                                        _____________Pre-treatment (15 July)_____________
Treatment     Rate/Acre     LI   LII   A     Total
Warrior II 1 EC     0.03 lb.(AI)     8.85+1.76b   15.88+2.42a   6.63+0.89a     31.35+4.50a
Warrior II 1 EC     0.02 lb. (AI)     8.08+1.24b   17.15+2.54a   6.90+0.92a     32.13+4.12a
Warrior II 1 EC     0.03 lb.(AI)
(3 thrips/plant threshold)
    10.85+1.20ab   16.58+2.13a   4.98+0.53a     32.40+3.19a
Lannate LV     0.45 lb.(AI)     8.85+1.69b   19.25+2.47a   7.65+0.96a     35.75+4.22a
Ammo 2.5 EC     0.08 lb. (AI)     11.28+1.20ab   13.25+1.54a   6.60+0.75a     31.13+2.81a
Untreated check     ---     14.80+1.90a   12.20+2.02a   4.75+0.48a     31.75+3.62a

Means in the same column followed by a different letter are significantly different (P>0.001, SAS for Windows version 6.11). Data was transformed by square root (Y+0.5) prior to analysis. Untransformed means are presented.

 

 

                                                                        __________Mean number of thrips/10 plants__________
                                                                        _______________*6 DAT 2 (29 July)_______________
Treatment     Rate/Acre     LI   LII   A     Total
Warrior II 1 EC     0.03 lb.(AI)     0.13+0.06c   0.15+0.07d   1.08+0.21bc     1.35+0.24d
Warrior II 1 EC     0.02 lb. (AI)     0.30+0.10c   1.25+0.36cd   0.63+0.17cd     2.18+0.50d
Warrior II 1 EC     0.03 lb.(AI)
(3 thrips/plant threshold)
    1.13+0.28bc   1.68+0.29cd   0.23+0.08d     3.03+0.52cd
Lannate LV     0.45 lb.(AI)     12.98+2.12a   12.33+2.19b   1.73+0.25ab     27.03+4.20b
Ammo 2.5 EC     0.08 lb. (AI)     3.05+0.55b   3.73+0.80c   0.83+0.17bcd     7.60+1.23c
Untreated check     ---     12.35+1.30a   26.38+5.18a   2.93+0.60a     41.65+5.89a
Means in the same column followed by a different letter are significantly different (P>0.001, SAS for Windows version 6.11). Data was transformed by square root (Y+0.5) prior to analysis. Untransformed means are presented.
*6 DAT 1 for treatment Warrior II 1 EC @ 0.03 lb. ai/A with 3 thrips/plant threshold

 

 

                                                                        __________Mean number of thrips/10 plants__________
                                                                        _____________*6 DAT 4 (12 August)______________
Treatment     Rate/Acre     LI   LII   A     Total
Warrior II 1 EC     0.03 lb.(AI)     0.40+0.16c   2.18+0.78c   2.48+0.36b     5.05+1.14c
Warrior II 1 EC     0.02 lb. (AI)     0.43+0.19c   1.35+0.30c   1.18+0.25b     2.95+0.60c
Warrior II 1 EC     0.03 lb.(AI)
(3 thrips/plant threshold)
    2.25+0.50c   4.05+0.68c   1.93+0.33b     8.23+1.28c
Lannate LV     0.45 lb.(AI)     9.68+1.14b   31.75+4.04b   7.38+1.98a     48.80+5.57b
Ammo 2.5 EC     0.08 lb. (AI)     1.35+0.40c   5.18+1.04c   1.98+0.32b     8.50+1.51c
Untreated check     ---     17.20+2.19a   63.05+8.25a   5.53+1.00a     85.78+9.96a
Means in the same column followed by a different letter are significantly different (P>0.001, SAS for Windows version 6.11). Data was transformed by square root (Y+0.5) prior to analysis. Untransformed means are presented.
*6 DAT 2 for treatment Warrior II 1 EC @ 0.03 lb. ai/A with 3 thrips/plant threshold


                                                                        __________Mean number of thrips/10 plants__________
                                                                        _____________*6 DAT 6 (26 August)______________
Treatment     Rate/Acre     LI   LII   A     Total
Warrior II 1 EC     0.03 lb.(AI)     0.33+0.12b   1.58+0.40b   0.80+0.21c     2.70+0.53b
Warrior II 1 EC     0.02 lb. (AI)     0.65+0.24b   1.63+0.30b   1.43+0.23bc     3.70+0.61b
Warrior II 1 EC     0.03 lb.(AI)
(3 thrips/plant threshold)
    1.15+0.30b   2.10+0.35b   0.83+0.16c     4.08+0.58b
Lannate LV     0.45 lb.(AI)     8.90+1.35a   25.33+3.38a   4.10+0.80a     38.33+4.68a
Ammo 2.5 EC     0.08 lb. (AI)     0.83+0.18b   3.53+0.40b   0.98+0.18bc     5.33+0.53b
Untreated check     ---     8.45+1.37a   28.48+3.78a   2.08+0.37b     39.00+5.11a
Means in the same column followed by a different letter are significantly different (P>0.001, SAS for Windows version 6.11). Data was transformed by square root (Y+0.5) prior to analysis. Untransformed means are presented.
*6 DAT 3 for treatment Warrior II 1 EC @ 0.03 lb. ai/A with 3 thrips/plant threshold

 

 

                                                                        ______Seasonal Means (Number of thrips/10 plants______  
Treatment     Rate/Acre     LI   LII   A     Total
Warrior II 1 EC     0.03 lb.(AI)     2.43+0.53e   4.94+0.81c   2.74+0.31b     10.11+1.52c
Warrior II 1 EC     0.02 lb. (AI)     2.36+0.41de   5.34+0.84c   2.53+0.31b     10.24+1.45c
Warrior II 1 EC     0.03 lb.(AI)
(3 thrips/plant threshold)
    3.84+0.47cd   6.10+0.74c   1.99+0.22b     11.93+1.29c
Lannate LV     0.45 lb.(AI)     10.10+0.81b   22.16+1.64b   5.21+0.62a     37.48+2.41b
Ammo 2.5 EC     0.08 lb. (AI)     4.13+0.48c   6.42+0.60c   2.59+0.28b     13.14+1.19c
Untreated check     ---     13.20+0.89a   32.53+3.02a   3.82+0.34a     49.53+3.67a

Means in the same column followed by a different letter are significantly different (P>0.001, SAS for Windows version 6.11). Data was transformed by square root (Y+0.5) prior to analysis. Untransformed means are presented.

 

 

Trade Composition\Common name     Formulation         name     Source
Ammo     EC         cypermethrin     FMC Corp.
                       
Lannate     EC         methomyl     DuPont
                       
Warrior     EC         lambdacyhalothrin     Zeneca.