Most oviposition by Helicoverpa zea (Boddie) occurs near the top of the canopy in soybean, Glycine max (L.) Merr, and larval abundance is influenced by the growth habit of plants. However, the vertical distribution of larvae within the canopy is not as well known. We evaluated the vertical distribution of H. zea larvae in determinate and indeterminate varieties, hypothesizing that larval distribution in the canopy would vary between these two growth habits and over time. We tested this hypothesis in a naturally infested replicated field experiment and two experimentally manipulated cage experiments. In the field experiment, flowering time was synchronized between the varieties by manipulating planting date, while infestation timing was manipulated in the cage experiments. Larvae were recovered using destructive sampling of individual soybean plants, and their vertical distribution by instar was recorded from three sampling points over time in each experiment. While larval population growth and development varied between the determinate and indeterminate varieties within and among experiments, we found little evidence that larvae have preference for different vertical locations in the canopy. This study lends support to the hypothesis that larval movement and location within soybean canopies do not result entirely from oviposition location and nutritional requirements.

中文翻译：

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玉米夜蛾（鳞翅目：夜蛾科）幼虫在有限和不确定大豆中的垂直和时间分布


大多数产卵者玉米夜蛾（Boddie）出现在大豆树冠顶部附近，大豆(L.) Merr 和幼虫丰度受植物生长习性的影响。然而，幼虫在冠层内的垂直分布尚不清楚。我们评估了垂直分布玉米幼虫有确定的和不确定的品种，假设幼虫在冠层中的分布会因这两种生长习性和时间的推移而变化。我们在自然感染的复制田间实验和两个实验操纵的笼子实验中检验了这一假设。在田间实验中，通过操纵种植日期来同步品种之间的开花时间，而在笼养实验中则操纵侵染时间。通过对单个大豆植株进行破坏性采样来回收幼虫，并在每个实验中随时间从三个采样点记录幼虫的龄期垂直分布。虽然幼虫种群的生长和发育在实验内和实验之间的确定品种和不确定品种之间存在差异，但我们发现几乎没有证据表明幼虫对树冠中不同垂直位置有偏好。这项研究支持了以下假设：大豆冠层内幼虫的运动和位置并不完全由产卵位置和营养需求决定。