黄地老虎幼虫为害棉花植株根茎部的模拟研究体系
A system for simulating the infestation of cotton plants by Agrotis segetum larvae in the laboratory
张倩，耿亭，陆宴辉
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DOI：10.7679/j.issn.2095-1353.2022.147
作者单位：中国农业科学院植物保护研究所，植物病虫害生物学国家重点实验室，北京 100193
中文关键词：黄地老虎；幼虫；棉花植株；根茎部；为害级别
英文关键词：Agrotis segetum; larvae; cotton plant; root and stem; damage degree
中文摘要：【目的】 黄地老虎Agrotis segetum Schiff是新疆棉田的一种重要地下害虫，主要取食为害棉花植株的根茎部。本研究拟在室内条件下，构建黄地老虎幼虫对棉花植株根茎部的为害模拟研究体系，为黄地老虎为害对地上害虫及天敌种群发生影响研究奠定基础。【方法】 将黄地老虎各龄幼虫1、2、3和4头分别接种到3叶期和5叶期棉花植株上，限制幼虫在植株根茎部取食3 d。根据棉花植株的受害程度，提出幼虫为害分级标准，并筛选出适合接种的幼虫龄期和数量。【结果】 依据黄地老虎幼虫取食棉花根茎的受害状及被取食高度将为害级别划分6级，根茎部无明显受害状为0级，根茎韧皮部被取食高度≤3 cm为1级，3 cm˂根茎韧皮部被取食高度≤5 cm为2级，5 cm˂根茎韧皮部被取食高度≤7 cm为3级，根茎韧皮部被取食高度>7 cm为4级，根茎部折断为5级。将4头2龄黄地老虎幼虫接种到1株3叶期和5叶期棉花上取食3 d后形成的为害级别小（0-2级），2头5龄和2头6龄幼虫取食后棉花茎秆易折断（5级），2头3龄幼虫对3叶期棉花植株和2头4龄幼虫对5叶期植株的为害程度中等（3-4级）。【结论】 黄地老虎幼虫对棉花植株根茎部为害模拟研究体系的构建，主要在3叶期棉花植株接种2头3龄幼虫、5叶期棉花植株接种2头4龄幼虫，连续取食3 d。这样既能形成较为严重的取食为害，又可保证棉花植株的继续生长。该研究体系的构建为棉花植株地下部和地上部昆虫的相互作用研究奠定了基础。
英文摘要：[Objectives] Agrotis
segetum Schiff is an important underground pest of cotton in Xinjiang,
mainly feeding on the roots and stem. To facilitate research on
the effects of A. segetum infestation
on aboveground pests and natural enemies, we set up a system to simulate the
infestation of cotton plants by A.
segetum larvae in a laboratory. [Methods] Different numbers of different instars of A. segetum larvae were introduced to cotton plants with either 3 or 5 true leaves, and confined to the root and stem of each plant. The
optimal larval instar and density per
plant was then determined based on the degree of plant damage. [Results]
Agrotis
segetum larvae feed mainly on the phloem tissue of the roots and stems of cotton plant in spiral
paths. The amount of damage to
cotton plants was categorized into six levels; level 0, no evident damage; levels 1-4, in which the height of phloem damaged by larvae was classified as
either ≤3 cm, between 3 cm and 5 cm, between 5 cm and
7 cm or ＞7 cm, respectively, and level 5 in which the plant was
broken. The degree of damage to cotton plants infested
with four, 2nd instar
larvae was minor 3 days after infestation,
(level 0-2). Plants infested with two, 5th instar larvae, or two, 6th instar larvae, sustained level 5 damage. Cotton plants
with 3 true leaves infested
with two, 3rd instar larvae, or plants with 5 true leaves infested with
two 4th instar larvae sustained moderate damage (level 3-4). [Conclusion] A system for simulating the infestation of cotton
plants by A. segetum larvae was developed in a laboratory by infesting plants
with 3 true leaves with two,
3rd instar larvae and plants with 5
true leaves with two, 4th instar larvae and allowing larvae to feed on the root and stem of each plant for 3 days. Although severely infested with A. segetum larvae, all plants in our
study survived long enough to complete the experiment.