Dan H. Meckenstock

Oviposition Preference of Spodoptera latifascia (Lepidoptera: Noctuidae) for Sorghum, Maize and Non-Crop Vegetation

Oviposition preferences of Spodoptera latifascia (Walker) (Lepidoptera: Noctuidae) for sorghum [Sorghum bicolor (L.) Moench (Poaceae)], maize [Zea mays (L.) (Poaceae)], and various non-crop species were examined in field cage experiments. A higher percentage (pooled means) of the total number of eggs per plant were laid on Amaranthus sp. (probably A. hybridus L. or A. viridis L.) (Amaranthaceae) 24%, maize 32%, and Ixophorus unisetus (Presl.) Schlecht (Poaceae) 26%, than on Ipomoea sp. [(probably I. purpurea (L.) Jacq.] (Convolvulacea) 2%, Melampodium divaricatum (Rich. ex pers.) Dc. (Asteraceae) 6%, Portulaca oleracea L. (Portulacaceae) 7%, and sorghum 3%. Only maize had a significantly higher percentage of the total number of eggs laid per plant than the other plant species in one of two experiments. Plant growth stage (seedling vs. older) did not appear to influence oviposition on any of the plant species tested. Moths exhibited a wide host oviposition range in our cage experiments. In contrast, eggs were collected only from Amaranthus sp., I. unisetus, and maize in the field in southern Honduras, suggesting that S. latifascia oviposition response in nature may be somewhat restricted to certain non-crop species and maize. Our data support results from previous investigations revealing the potential benefits of non-crop host plants in reducing damage by S. latifascia to sorghum and maize in intercropped production fields during the early growing season in southern Honduras.

Potential for using maize as a trap crop for the fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae), where sorghum and maize are intercropped on subsistence farms

The effectiveness of a maize trap crop in reducing fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith), larval infestations on sorghum, Sorghum bicolor (L.) Moench. in areas where sorghum and maize, Zea mays L., are grown together in the same field was investigated in small plots at Choluteca, Honduras in 1984 and at Starkville, Mississippi in 1984 and 1985. Infestations of FAW larvae were similar on sorghum treatments with and without the maize trap crop in Honduras and in one test in Mississippi, 1984. Apparently, the area ratio of 2:1 for sorghum : maize plantings in close proximity did not differentially restrict FAW activity on the preferred maize plants. However, significantly higher FAW larval infestations and plant damage were observed on maize than on sorghum in pure stand or when grown together with maize as the trap crop in a second test conducted in 1985 in Mississippi. The results of these studies support reported observations in greenhouse and field cages showing higher oviposition by FAW moths on maize than on sorghum. The higher infestation of FAW on maize further suggests the potential for use of maize as a trap crop for monitoring insect populations and its possible use as a trap crop control tactic for FAW in areas of low rainfall where sorghum is grown as a main crop and this insect is a serious pest.