Cheruiyot Duncan, Chiriboga Morales Xavier, Chidawanyika Frank, Bruce Toby J A, Khan Zeyaur R
International Centre of Insect Physiology and Ecology (icipe) PO Box Nairobi 30772-00100 Kenya.
Department of Zoology and Entomology University of the Free State PO Box 339 Bloemfontein 9300 South Africa.
Entomol Exp Appl. 2021 Oct;169(10):966-974. doi: 10.1111/eea.13083. Epub 2021 Jul 22.
Production of maize, L. (Poaceae), in sub-Saharan Africa is threatened by a new invasive pest, fall armyworm (FAW), (JE Smith) (Lepidoptera: Noctuidae). To mitigate this threat, push-pull companion cropping, a system originally developed for management of lepidopteran stemborers, may be used to control FAW. The original system involved trap crops that functioned as a 'pull' component to attract moths away from the main crop. How grass species can be used as trap crops in a push-pull system to control FAW is a question that remains to be answered, because maize is already a highly preferred host plant. Therefore, we tested oviposition preference of FAW female moths in no-choice and two-choice experiments and larval performance on six selected grasses (Poaceae) to assess their roles as trap crop 'pull' plants in the system. In no-choice tests, numbers of eggs deposited on (Hochst. ex A. Rich.) R. Webster cv. 'Piata', cv. 'Mulato II', and cv. 'Xaraes', and Napier grass ( K. Schumach) cv. 'South Africa' were not statistically different from those deposited on maize. In two-choice tests between grasses and maize, there were no significant differences in number of eggs laid when the plants were of the same size. However, in two-choice tests with maize plants half of the size of the grasses, significantly more eggs were laid on cv. Xaraes and cv. South Africa than on maize, suggesting that crop phenology could make a difference. Numbers of larvae arrested on grass leaf cuts were considerably lower than those on maize leaf cuts after 48 h. In two-choice tests with maize, molasses grass ( P. Beauv.) was the only grass that was significantly preferred to maize for larval settlement after 24 h. After 48 h in the two-choice test, it was the only grass that retained larvae, although the larval count was significantly lower than on maize. Our data show that none of the grasses tested were strongly preferred to maize, but the results indicate plants attractive to FAW adults and larvae that could be utilized in a multiple trap crop approach to target various stages of the pest. Furthermore, results indicate the importance of planting these companion plants earlier than maize.
撒哈拉以南非洲地区的玉米（L.，禾本科）生产受到一种新的入侵害虫——草地贪夜蛾（FAW）（JE·史密斯）（鳞翅目：夜蛾科）的威胁。为减轻这一威胁，推-拉式间作套种这种最初为防治鳞翅目蛀茎害虫而开发的系统，可用于控制草地贪夜蛾。最初的系统包括诱集作物，其作为“拉”的组成部分，将蛾子从主要作物吸引开。在推-拉式系统中，草种如何用作诱集作物来控制草地贪夜蛾仍是一个有待回答的问题，因为玉米已经是其高度偏爱的寄主植物。因此，我们在无选择和二选一试验中测试了草地贪夜蛾雌蛾的产卵偏好，并在六种选定的禾本科草种上测试了幼虫生长情况，以评估它们在该系统中作为诱集作物“拉”植物的作用。在无选择试验中，产于（霍赫斯特 ex A. 里奇）R. 韦伯斯特品种“皮亚塔”、“穆拉托二号”和“哈拉伊斯”以及象草（K. 舒马赫）品种“南非”上的卵数与产于玉米上的卵数在统计学上无显著差异。在草种和玉米之间的二选一试验中，当植株大小相同时，产卵数无显著差异。然而，在玉米植株大小为草种一半的二选一试验中，产于“哈拉伊斯”品种和“南非”品种上的卵显著多于产于玉米上的卵，这表明作物物候可能会产生影响。48小时后，附着在草叶切口上的幼虫数量远低于附着在玉米叶切口上的幼虫数量。在与玉米的二选一试验中，糖蜜草（P. 博韦）是24小时后幼虫定居时唯一显著比玉米更受偏爱的草种。在二选一试验48小时后，它是唯一留住幼虫的草种，尽管幼虫数量显著低于玉米上的幼虫数量。我们的数据表明，所测试的草种中没有一种比玉米更受强烈偏爱，但结果表明了对草地贪夜蛾成虫和幼虫有吸引力的植物，可用于采用多种诱集作物方法来针对害虫的不同阶段。此外，结果表明了比玉米更早种植这些伴生植物的重要性。
