Hogg Brian N, Moran Patrick J, Smith Lincoln
USDA-ARS, Exotic and Invasive Weeds Research Unit, 800 Buchanan St., Albany, CA (
Environ Entomol. 2017 Jun 1;46(3):552-558. doi: 10.1093/ee/nvx074.
The impacts of weed biological control agents may vary with plant ontogeny. As plants grow, structural and chemical changes can alter plant resistance, which may reduce herbivory via chemical or structural defenses, and plant tolerance, which may enable plants to maintain fitness despite attack. Resistance and tolerance generally increase as plants grow. Nonetheless, prerelease tests of agent efficacy often overlook plant ontogeny. Here, we assess the performance and impacts of a candidate biocontrol agent, the psyllid Arytinnis hakani (Loginova), in relation to the age of its host plant, the invasive shrub French broom, Genista monspessulana. We also examined whether the psyllid can consistently kill plants when its densities are sufficiently high. Survival of psyllids to adulthood and the timing of adult emergence did not differ between plant sizes, indicating that performance of nymphs was not influenced by plant size. However, adult psyllid survival was reduced on small plants, suggesting that nymphs and adults responded differently to ontogenetic changes in plant quality. Psyllids affected the growth of small and large plants similarly; all measured plant growth parameters were lower in the presence of psyllids regardless of plant size. In a separate experiment, effects on plant survival depended on psyllid density, as higher realized densities of ∼9 psyllids per cm stem length were necessary to consistently kill plants. Thus, results suggest that the psyllid would be equally effective on a range of plant sizes, particularly at high densities, and show the potential of the psyllid to help control French broom in California.
杂草生物防治剂的影响可能会因植物个体发育而有所不同。随着植物生长，结构和化学变化会改变植物的抗性，这可能通过化学或结构防御降低食草动物的侵害，同时也会改变植物的耐受性，使植物即使受到攻击也能保持健康状态。抗性和耐受性通常会随着植物生长而增加。尽管如此，生物防治剂功效的释放前测试往往忽略了植物个体发育。在此，我们评估了一种候选生物防治剂——木虱Arytinnis hakani（Loginova），针对其寄主植物——入侵灌木法国金雀花（Genista monspessulana）的年龄所产生的表现和影响。我们还研究了木虱在密度足够高时是否能持续杀死植物。木虱发育至成虫的存活率以及成虫出现的时间在不同大小的植物之间并无差异，这表明若虫的表现不受植物大小的影响。然而，小型植物上成年木虱的存活率降低，这表明若虫和成虫对植物质量个体发育变化的反应不同。木虱对小型和大型植物生长的影响相似；无论植物大小，在有木虱存在的情况下，所有测量的植物生长参数都较低。在另一个实验中，对植物存活的影响取决于木虱密度，因为每厘米茎长约9只木虱的更高实际密度是持续杀死植物所必需的。因此，结果表明木虱在一系列植物大小上同样有效尤其是在高密度时，并显示出木虱在加利福尼亚帮助控制法国金雀花的潜力。
