Kansas State University, Agricultural Research Center - Hays, Hays, KS 67601, USA.
J Insect Sci. 2007;7:21. doi: 10.1673/031.007.2101.
Foliar and soil-drench insecticide treatments were used in attempts to manipulate infestation of cultivated sunflower plants, Helianthus annuus LeConte (Asterales: Asteraceae) by Dectes texanus LeConte, (Coleoptera: Cerambycidae) a serious pest of sunflowers in the High Plains of the USA. Seed yields were assessed on a per-plant basis for both oilseed and confection type sunflower hybrids in two years. Both insecticide treatments (foliar ë-cyhalothrin and soil-drench carbofuran) improved yield of oilseed sunflowers in 2004, but not in 2005. Yield of confection hybrids was improved by a systemic fungicide (thiophanate methyl) in 2005, but insecticides did not improve yield in either year. Both insecticide treatments gave good control of various stalk-boring insects such as Cylindrocopturus adspersus (Coleoptera: Curculionidae), Mordellistena sp. (Coleoptera: Mordellidae), and Pelochrista womanana (Lepidoptera: Tortricidae), but neither gave better than 50% control of D. texanus. Plants were sorted according to the presence or absence of D. texanus larvae and no reduction was found in total seed weight, seed size, or oil content as a result of infestation. However, mature larvae of D. texanus girdle stalks at the base in preparation for overwintering, a behavior that reduced stalk breakage force by 34-40%, leading to yield losses through lodging. At harvest in 2005, there were differences between cultivars and among treatments in the proportions of D. texanus larvae that had girdled their plants at harvest. It was concluded that further research aimed at reducing crop losses to D. texanus should focus on means of delaying stalk desiccation and/or deterioration, factors that appear to trigger girdling behavior.
叶面和土壤灌根杀虫剂处理被用于尝试操纵美国高平原地区 Helianthus annuus LeConte（Asterales：Asteraceae）被 Dectes texanus LeConte（鞘翅目：天牛科）严重侵害的栽培向日葵植株的侵染。在两年中，以每株为基础评估了油用型和食用型向日葵杂交种的种子产量。两种杀虫剂处理（叶面氯氟氰菊酯和土壤灌根涕灭威）均提高了 2004 年油用型向日葵的产量，但在 2005 年没有提高。2005 年，一种内吸性杀菌剂（甲基硫菌灵）提高了食用型杂交种的产量，但在这两年中，杀虫剂都没有提高产量。两种杀虫剂处理都很好地控制了各种蛀干昆虫，如 Cylindrocopturus adspersus（鞘翅目：象甲科）、Mordellistena sp.（鞘翅目：叶甲科）和 Pelochrista womanana（鳞翅目：卷蛾科），但没有一种能达到 50%以上的 D. texanus 防治效果。根据 D. texanus 幼虫的存在与否对植株进行分类，发现感染并没有导致总种子重量、种子大小或油含量降低。然而，D. texanus 成熟幼虫会在茎基部环绕茎干，为越冬做准备，这种行为会使茎干断裂力降低 34-40%，导致植株倒伏，从而造成产量损失。在 2005 年收获时，不同品种和处理之间，在已环绕植株的 D. texanus 幼虫比例方面存在差异。研究得出结论，进一步研究旨在减少 D. texanus 对作物的损失，应集中于延迟茎干干燥和/或恶化的方法，这些因素似乎会触发环绕行为。
