Study on the economic threshold level of corn leaf aphid, Rhopalosiphum maidis (Fitch) on super sweet corn
1997
Watchara Choonhawong | Auranuj Kongkanjana (Department of Agriculture, Bangkok (Thailand). Entomology and Zoology Div. Rice and Temperate Cereals Entomology Group)
Corn leaf aphid, Rhopalosiphum maidis (Fitch) (Homoptera : Aphididae) is an important insect pest of super sweet corn in Thailand. Adults and nymphs suck the sap of the corn from the vegetative stage to harvesting. Study on the economic threshold level of the corn leaf aphid on super sweet corn, Composit No. 1 DMR, was carried out at Damnornsaduak, Ratchaburi province during December 1994-February 1995. Randomized complete block design with 4 replications was used. Treatments were five different applications included with check (untreated). A three-spray schedule of 0.01 percent imidacloprid at one week interval was conducted at different growth stages of plant. It was found that the highest income of 6577.52 and 6257.53 baht per rai were obtained from the treatment of three-spray schedules at 32, 45 and 52 days after emergence (DAE), and 45, 52 and 59 DAE, respectively. The unsprayed plots gave the lowest of corn can be used as an indication for controlling of this pest. In addition, chemical application should be made either when the number of aphids per plant were 22.08-38.73 or percentage of leaf damage were 5-10. The proper time of apply chemical should be at the late whorl stage (39-45 DAE) or before the pollination, if the chemical were applied after these period it might be caused an economic losses.
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