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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Characterizing bee communities and pollen limitation in Indiana specialty crops

Eleanor Louise Stroh (20329425) 10 January 2025 (has links)
<p dir="ltr">Lack of adequate pollination limits yield in many specialty crops, and this pollen limitation is determined by crop pollination requirements and pollinator community dynamics. Bee communities and degree of pollen limitation is variable between crops and regions, necessitating a crop-specific, regional approach to describing pollination services. Despite primarily producing agronomic crops, Indiana produces a wide variety of specialty crops, including apples, blueberries, watermelons, and tomatoes (grown for processing in open fields and fresh market in high tunnels). Each crop has variable bloom phenology, pollination requirements, and associated management practices (e.g., thinning in apples and protective cover in high tunnels), with potential implications for their pollinator communities and pollination services. This thesis aims to 1) use flower observations and pan traps to compare pollinator communities between crops, including the contributions of managed and wild bees, community diversity, and composition and 2) assess pollen limitation in each crop using pollination experiments. The study took place on commercial farms throughout Indiana over the course of three summers (2022-2024). We found that distinct pollinator communities persisted in each crop system, with spring-blooming apples and blueberries dominated by honey bees (<i>Apis mellifera</i>) and summer-blooming tomatoes and watermelons dominated by wild bees, particularly <i>Bombus</i> spp. in tomatoes and <i>Lasioglossum</i> spp. in watermelon. We also found evidence of pollen limitation with respect to fruit set in all crop systems except for apples (measured at harvest, after apple thinning occurred). Evidence of pollen limitation with respect to fruit weight was detected only in field tomatoes and apples, but not other crops. Meanwhile, insect pollination increased fruit set and weight in almost every crop, except for high tunnel tomatoes, implying reduced pollination services in this semi-protected system. Our results highlight the importance of protecting wild pollinator communities in Indiana, particularly in watermelons and tomatoes, and identify yield gaps in multiple crops, especially tomatoes, which could be addressed by increasing pollination services. This crop-specific information is a valuable first step in encouraging growers to adopt pollinator friendly management decisions and protecting pollination services in Indiana.</p>
2

Developing Selective Lures to Optimize Striped Cucumber Beetle (<i>Acalymma vittatum</i>) Management by Combining Pheromone and Plant Volatiles

Rachel A Youngblood (18432096), Ian Kaplan (10232781), Donald C. Weber (3178635), Matthew Ginzel (8771376) 30 April 2024 (has links)
<p dir="ltr">The striped cucumber beetle (<i>Acalymma vittatum</i>) is a leading pest across a variety of cucurbit crops in eastern North America. These beetles can rapidly infest and damage a field, leading to frequent insecticide applications to manage them. Chemical control is effective at reducing beetle populations, but it also causes detrimental non-target effects on pollinators, which are essential for cucurbit yield. Developing a holistic IPM (integrated pest management) approach is necessary to manage pests while avoiding non-target effects in cucurbit production systems. </p><p dir="ltr">A unique and well-characterized behavior of striped cucumber beetles is their olfactory attraction to both plant volatiles and their species-specific aggregation pheromone, vittatalactone. The interacting effects of combining these olfactory stimuli for cucumber beetle attraction have not previously been tested. I expected when presented with plant volatiles and pheromone together, the striped cucumber beetles will show synergistic attraction, resulting in enhanced attraction stronger than the sums of the separate effects. Along with targeting striped cucumber beetles, I expected to elicit cross-attraction of related cucurbit pests (e.g., spotted cucumber beetle) to these same signals based on previous findings indicating cross-attraction. The expected cross attraction may be due to the reliance on olfactory cues to inform the related insects on preferrable host plants and nutrition. </p><p dir="ltr">Cucurbit systems are also highly reliant on pollination services for high-quality fruit; thus, the feasibility of these semiochemical tools depends on their influence on pollinator behavior. I expect pollinators to be attracted to floral volatiles but not vittatalactone or individual plant volatiles without the full complement of floral scent (e.g., indole, leaf volatiles). Altogether, this research aims to develop a targeted management tool for striped cucumber beetles and other cucurbit pests, while avoiding pollinator distraction or other detrimental effects.</p><p dir="ltr">To measure the efficacy of using olfactory signals as attractants, clear sticky cards were deployed in the field with combinations of pheromone paired with volatiles (floral and/or leaf), as well as the individual components, to quantify pest responses. Simultaneously, a pan trap sampling method was implemented to measure pollinator responses to the same semiochemical combinations. The results of the study demonstrate that striped cucumber beetles are strongly attracted to volatile lures containing pheromones, floral volatiles, and combinations of the two, although the combined pheromone and floral volatile treatments did not synergize beetle attraction. </p><p dir="ltr">Though combined lures did not synergize attraction, this data demonstrates additive effects on beetle behavior. The findings also highlight the importance of understanding seasonal disparities between the behavior of early and late generations of striped cucumber beetles. Temporal variation in attraction demonstrated by the pests is crucial to understand when to implement lure-based management strategies. Two years of testing floral volatile and herbivory-induced plant volatile (HIPV) lure treatments on key cucurbit pollinators showed varying levels of attraction. There was no attraction of focal cucurbit bees to the striped cucumber beetle pheromone, but there were differences in the response of pollinators to plant volatile components. </p><p dir="ltr">Cucurbits require high pollination activity for successful fruit, though the most important bees in pollinating this system are bees belonging to the genera, <i>Apis</i> and <i>Eucera</i>. Along with these bee groups, other bees such as those belonging to <i>Melissodes</i>, <i>Lasioglossum</i>, and <i>Bombus</i> are also known important pollinators. <i>Lasioglossum</i> bees showed a strong attraction to the full-floral blend, TIC (1,2,4-trimethoxybenzene, indole, (E)-cinnamaldehyde), but no preference for indole or HIPVs. <i>Melissodes</i> bees were most attracted to methyl salicylate and TIC, whereas <i>Eucera</i> bees exhibited strong attraction to ocimene and TIC. These findings suggest that different pollinator taxa have unique preferences for plant volatiles, highlighting the importance of optimizing lure combinations to avoid disrupting pollination activities in cucurbit production.</p><p dir="ltr">Additionally, this study revealed that other key cucurbit pests, such as spotted cucumber beetles and western corn rootworms, also showed strong attraction to the tested volatile components. These findings suggest that the selected volatiles may have broader implications for pest management beyond striped cucumber beetles. Further research is needed to fully understand the efficacy and refine formulations of these volatile lures to implement in IPM.</p>

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