To save content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about saving content to .
To save content items to your Kindle, first ensure email@example.com
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about saving to your Kindle.
Note you can select to save to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
Starch levels, used as a measure of plant stress, were not consistently reduced in root or crown tissue of purple loosestrife plants after 2 yr of severe Galerucella calmariensis or Galerucella pusilla (Coleoptera: Chrysomelidae) defoliation. Early in the season, defoliation from Galerucella spp. approached 100%, but the majority of Lythrum salicaria plants regrew by the end of August, resulting in an average reduction of 81% of the aboveground biomass compared to the control. The stress imposed by Galerucella spp. defoliation was less than that achieved from more severe stress imposed by mechanical shoot clipping at 2- or 4-wk intervals from June to October. Both shoot-clipping treatments killed the majority of plants after one growing season. Galerucella spp. feeding reduced plant stature, which may reduce competitiveness. However, considering the extensive carbohydrate reserves present in the large woody crowns of Lythrum salicaria, it will require in excess of 2 yr of consistent, severe leaf defoliation to cause plant mortality. A combination of stresses, such as winter crown injury, or other biological control agents in addition to Galerucella leaf defoliation may be required for plant mortality.
The effect of shoot feeding by the biocontrol agents, Galerucella calmariensis and Galerucella pusilla (Coleoptera: Chrysomelidae) on purple loosestrife (Lythrum salicaria) seed production and seed germination was quantified in two Minnesota wetlands. In a wet meadow where Galerucella spp. were present on isolated plants, feeding by adults and larvae during shoot elongation resulted in stunting and malformation of shoot tips. There was a subsequent reduction in purple loosestrife inflorescence length and number of flower buds and seed capsules. As Galerucella spp. larvae preferentially fed on shoot meristems, even low levels of feeding on a whole-plant basis (approximately 10% defoliation) reduced seed production. In a sedge meadow wetland with severe feeding damage (a minimum of 70% leaf defoliation), few to no flower buds formed on plants, and subsequently, few to no seed capsules were produced on purple loosestrife plants. Of the few capsules that were produced, number of seeds per capsule and percent germination of seeds did not differ from control plants. In both wetlands, feeding on a main shoot of purple loosestrife did not result in a compensatory increase in the number of axillary inflorescences. Feeding by Galerucella spp. and the subsequent reduction in number of seeds produced on purple loosestrife plants will decrease the number of seeds available for dissemination to new sites. Fewer seeds will enter the seedbank, and over time, feeding by Galerucella spp. will decrease the number of seeds available for seedling recruitment. The benefit of leaf defoliation on purple loosestrife plants caused by Galerucella spp. feeding has been reported. In this study, we have quantified the additional benefits of reduced seed production from Galerucella spp. feeding on purple loosestrife in North America.
Previous studies have characterized the development of the biological control insects, Galerucella calmariensis and Galerucella pusilla on purple loosestrife and on nontarget Lythraceae species, including two species native to Minnesota, winged loosestrife, and swamp loosestrife. The impact of Galerucella spp. on these plants, when grown in outdoor mesocosms that more closely mimics ecological host range, has not been reported. The first objective of this study was to compare the growth and seed capsule production of purple loosestrife, winged loosestrife, and swamp loosestrife, with and without exposure to Galerucella spp. With purple loosestrife, larval feeding on apical and lateral shoot buds resulted in fewer seed capsules, and reduced aboveground biomass and plant height compared to control plants. No measured plant growth or reproductive parameters were reduced as a result of beetle feeding on swamp loosestrife. Presence of Galerucella spp. on winged loosestrife resulted in a reduction of seed capsules in one of 2 yr of study. A second objective of our study was to compare the phenology of the three Lythraceae species in relation to that of Galerucella spp. In the northern United States, flowering and seed development in swamp loosestrife occurred a month later than in purple or winged loosestrife. The delayed flowering of swamp loosestrife resulted in avoidance of shoot meristem feeding damage caused by the first generation of beetles. Laboratory studies might have overestimated the host range of Galerucella spp. on swamp loosestrife with the finding of asynchronous flowering times of purple and swamp loosestrife. Our mesocosm studies confirm that previous laboratory host range testing did accurately predict the ecological host range of winged loosestrife.
Potato is South America's greatest gift to world agriculture and human nutrition (Graves, 2001). A dietary staple of indigenous Andean peoples for eight millennia, potato was unknown to the rest of the world before the mid sixteenth century. Today, potato is the world's fourth most important food crop, after maize, wheat and rice, and is grown on a significant scale in more than 130 countries on six continents with annual tuber production exceeding 320 million tonnes (Food and Agriculture Organization, 2007). In recognition of potato's potential to provide food security and eradicate poverty, 2008 has been proclaimed International Year of the Potato.
In most production systems, potato is clonally propagated from “seed” tubers. Clonal propagation offers agronomic and genetic advantages, e.g. vigorous early growth, higher yields and consistent expression of desirable traits. More than 10% of world potato production is used to provide “seed tubers” for planting the next production season. Seed potato tubers can be infected with a wide range of pests and pathogens which may affect growth of the crop and health of progeny tubers. Thus, access to high-quality, disease-free seed potatoes has been described as “the single most important integrated pest management practice available to potato growers” (Gutbrod & Mosley, 2001). Seed potato lots can be downgraded or rejected for recertification for myriad causes from “varietal mix” to herbicide injury. However, aphid-transmitted, tuber-borne potato viruses far exceed all others.
Email your librarian or administrator to recommend adding this to your organisation's collection.