Resource Information

     
Efficacy of Hot-Water Immersion Against the Taro Root Aphid, Hawaii, 1995  
     

By: A. H. Hara, R.F.L. Mau, T. Y. Hata and B.K.S. Hu

Beaumont Agri. Res. Center University of Hawaii-Manoa 461 W. Lanikaula Street Hilo, Hawaii 96720, Phone (808) 935-2885

HOST: CHINESE TARO: Colocasia esculenta
TARGETED PEST: 'Chinese' Taro root aphid: Patchiella reaumuri (Kaltenbach)


EXPERIMENTAL PROCEDURE
Efficacy trials were conducted from 21 Apr through 24 Apr 95. Taro hulis (0.5 inch cut stem with petiole attached) were harvested from a infested field in Kaiwiki, Hi, (1,500 ft elev.) placed in bags (three hulis per bag) made from Reemay crop cover material, and transported in a cooler to the University of Hawaii at Manoa Waiakea Experiment Station in Hilo, Hi. Roots and soil were left on the hulis to maintain a sufficient test population. Taro hulis (ca. 15 inches long x 2 5 inch base diameter) and Reemay bags were immersed in 49 C water from 0 to 5.5-min at 30 sec intervals. The bags were used to catch aphids which fall off during treatment. Immediately following treatment, hulis were cooled in a water bath at ambient temperature (26 C) for a time equal to the heating time then held in a dark room until evaluation. The control was dipped in water at ambient temperature for 30 sec. Three days after treatment, hulis were dissected and the number of live and dead aphids counted.

RESULTS
Hot-water treatment at 49 C for 5.0 and 5.5 min resulted in 100 % mortality of aphids on the taro petiole and roots, respectively. Survivors were mobile and were usually found in pockets between the dense roots. In actual commercial production. hulis do not contain roots and soil.

Table 1 . Percent mortality of taro root aphids after hot-water treatment at 49 C.

Treatment Root Petiole Total
No Treatment 5.8 (931)a 9.8 (92) 6.2 (1023)
Water Dip (Ambient) 20.3 (989) 9.7 (226) 18.4 (1215)
0.5 min 0 4 (767) 2.9 (173) 0.9 (940)
1.0 min 35 3 (485) 55.1 (89) 38.3 (574)
1.5 min 73.0 (241) 75.0 (80) 73.5 (321)
2.0 min 89.0 (374) 90.6 (32) 89.2 (406)
2.5 min 64.7 (966) 62.4 (311) 64.1 (1277)
3.0 min 87.5 (376) 77.8 (54) 86.3(430)
3.5 min 94.7 (636) 96.8 (63) 94.8 (699)
4.0 min 99.8 (1112) 100.0 (272) 99.9 (1384)
4.5 min 95.8 (288) 99.2 (131) 96.9 (419)
5.0 min 99.2 (1705) 100.0 (156) 99.2 (1861)
5.5 min 100.0 (1511) 100.0 (244) 100.0 (1755)

aNumber of aphids recovered.


PRECAUTIONARY STATEMENT
Use pesticides safely. Follow the pesticide label. Consult with the Cooperative Extension Service or the Hawai'i State Department of Agriculture for authorized special local need registrations or additional information. The user is responsible for the proper use, application, storage, and disposal of pesticides.

DISCLAIMER
Reference to a company or product name does not imply approval or recommendation of the product by the College of Tropical Agriculture and Human Resources, Cooperative Extension Service University of Hawaii, or the United State Department of Agriculture and does not imply its approval to the exclusion of other products that may be suitable. All materials should be used in accordance with label instructions or manufacturer's directions.