Industrial hemp, Cannabis sativa L., production has been negatively impacted by larvae of corn earworm, Helicoverpa zea (Boddie), which feed on developing inflorescences. Adult H. zea oviposit on hemp once flowers develop, and late-instar larvae can cause serious loss to both quality and yield. A 2-year study to assess the influence of hemp variety and fertilization practices on damage caused by H. zea was conducted. Differences in damage ratings among varieties were observed in both years; however, the rate of nitrogen applied did not influence biomass yield or damage rating. These results indicate that increasing nitrogen fertility may not be an effective means of cultural control for mitigating damage from H. zea. Floral maturity was very influential on damage caused by H. zea as late-maturing varieties had much less floral injury than those which matured early in outdoor field trials. Some cannabinoids were also correlated to damage rating, but this relationship was due to late-maturing plants with immature flowers low in cannabinoid concentrations receiving less floral injury. Based on these results, the selection of high-yielding varieties that flower when ovipositional activity of H. zea is expected to decline should be the first step in an integrated pest management program for hemp production. This research expanded our knowledge of the role of fertility rate, varietal characteristics, cannabinoid profile, and floral maturity on damage caused by H. zea to hemp. Findings from this research will allow growers to make more informed agronomic decisions before planting to improve hemp production.

中文翻译：

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大麻、大麻品种（Rosales：大麻科）和施肥率对玉米穗虫、Helicoverpa zea（鳞翅目：夜蛾科）造成损害的影响

工业大麻 Cannabis sativa L. 的生产受到以正在发育的花序为食的玉米穗虫 Helicoverpa zea (Boddie) 幼虫的负面影响。一旦花朵发育，成虫H. zea就会在大麻上产卵，晚龄幼虫会导致质量和产量的严重损失。进行了一项为期两年的研究，以评估大麻品种和施肥实践对玉米须造成的损害的影响。两年间观察到品种间受损程度存在差异；然而，施氮量并不影响生物量产量或损害等级。这些结果表明，增加氮肥力可能不是减轻玉蜀黍危害的有效栽培控制手段。花的成熟度对 H. 造成的损害影响很大。在户外田间试验中，作为晚熟品种的玉米比早熟品种的花损伤要少得多。一些大麻素也与损害等级相关，但这种关系是由于晚熟植物的未成熟花大麻素浓度较低，受到的花损伤较少。基于这些结果，选择在玉米产卵活性预计下降时开花的高产品种应该是大麻生产害虫综合防治计划的第一步。这项研究扩展了我们对生育率、品种特征、大麻素特征和花成熟度对玉米对大麻造成的损害的作用的认识。这项研究的结果将使种植者在种植前做出更明智的农艺决策，以提高大麻产量。