Biological, microbiological and physical control of Spodoptera frugiperda (Lepidoptera: Noctuidae) in corn and other crops in Colombia

Abstract

The fall armyworm Spodoptera frugiperda (J:E:Smith) is the major economic pest in corn, with early infestations during the dry season which obligate farmers to treat two or three times the corn crop with insecticides in order to reduce the damage caused by the high populations of larvae. Chemical control in addition to increasing the yield costs and to affect human security in the country, eliminates the wide and abundant beneficial fauna which is found on natural conditions. This research study was conducted · to develop <;111 integrated pest management program on S. frugiperda as a corn crop pest. developing an assessing biological options such as parasites of insect eggs and microbiólogical options to increase the larvae mortality, without affecting the natural fauna in the corn crops ecosystems. Egg parasitoids mass breeding techniques were developed under laboratory conditions at 25ºC and 70% relative humidity, in the Corpoica, Research Center in Palmira, Colombia. Telenomus pos. remus, Trichogramma atopovirilia Oatman & Platner, and Trichogramma exiguum Pinto & Platner were bred on laboratory conditions. Parasitic efficacy of these insects was assessed under field conditions, releasing between 33.000 to 100.000 adults/ ha of Telenomüs sp. and 250 inches/ ha of each Trichogramma species, releasing all the three species together, or releasing Telenomus sp. and Trichograrnrne app. separately, dividing up the doss in five or six releasing periods, during the first two or three weeks of the crop development. This biological control of S. frugiperda caused 80-90% parasitism on eggs, with damage of Spodoptera under economic levels. Telenomus sp. showed a higher parasitic capacity. Fungus Nomuraea rileyi and bacteria Bacillus thuringiensis under commercial products, Nomuraea and Xentari respectively (LO Kg/ha) were applied on liquid and bait forms, causing more than 90% mortality of larvae, showing no damage on beneficial fauna and also showing persistence on the crop In addition to the biological and microbiological techniques, the physical effect of the rain was also assessed, since rain causes mortality on small larvae of S. frugiperda. Other natural biological agents that come to the corn crop since the early stages were studied.