Story Jim M, Corn Janelle G, White Linda J
Montana Agricultural Experiment Station, Western Agricultural Research Center, Corvallis, MT 59828, USA.
Environ Entomol. 2010 Feb;39(1):164-8. doi: 10.1603/EN09123.
Field studies were conducted at two sites in western Montana during 2006 and 2008 to assess the compatibility of mowing with five seed head insect species introduced for biological control of spotted knapweed, Centaurea stoebe Lamarck subsp. micranthos. In 2006, mowing of spotted knapweed plants at the bolting and flower bud stages resulted in the development of new seed heads that contained significantly more seeds and significantly fewer larvae of each insect species than in seed heads in unmowed controls. No seed heads were produced in the plots mowed at the flowering stage. Seed numbers per seed head in 2008 were also significantly higher in plots mowed at the bolting stage than in unmowed controls, but between-treatment differences in insect numbers were more variable. The seed head insects Larinus spp. and Urophora affinis Frauenfeld were the primary cause of the reduced knapweed seed numbers per seed head in 2006. Spotted knapweed should not be mowed at the bolting and flower bud stages if large populations of seed head insects are present because mowing can result in the formation of new seed heads that are free from the insects' attack, thus allowing greater seed production. Mowing of spotted knapweed at the flowering stage and later can be conducted without a subsequent increase in seed production, but the mowing may cause mortality of the insect larvae.
2006年和2008年期间，在蒙大拿州西部的两个地点开展了田间研究，以评估割草与为生物防治斑点矢车菊（Centaurea stoebe Lamarck subsp. micranthos）而引入的5种种子头昆虫的兼容性。2006年，在抽薹期和花芽期对斑点矢车菊植株进行割草，结果新形成的种子头所含种子显著增多，且每种昆虫的幼虫数量显著少于未割草对照中的种子头。在开花期割草的地块未产生种子头。2008年，抽薹期割草地块的每个种子头的种子数量也显著高于未割草对照，但不同处理间昆虫数量差异更具变异性。种子头昆虫拉瑞象属（Larinus spp.）和亲缘斑翅实蝇（Urophora affinis Frauenfeld）是2006年每个种子头矢车菊种子数量减少的主要原因。如果存在大量种子头昆虫，斑点矢车菊在抽薹期和花芽期不应割草，因为割草会导致形成不受昆虫侵害的新种子头，从而使种子产量更高。在开花期及之后对斑点矢车菊进行割草不会导致后续种子产量增加，但割草可能会导致昆虫幼虫死亡。
