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Bumble bees are commonly used to provide pollination services within crop fields and greenhouses, with Bombus impatiens Cresson; Hymenoptera: Apidae, a bee native to the eastern United States, being the only managed bumble bee available commercially in the United States. Although many researchers have explored managed bumble bees' ability to pollinate various crops and the potential spread of pathogens by managed bumble bees, scant research is available on how managed bumble bee colony health is affected after foraging within crop fields. We measured 10 B. impatiens colony health parameters: 1) colony weight; number of 2) honey/pollen pots, 3) workers, 4) queens, 5) drones, 6) immatures, 7) eggs; and weight of 8) workers, 9) drones, and 10) queens from colonies that foraged within blueberry or watermelon fields, and compared them to control colonies that were purchased and immediately frozen upon receipt. Bees that foraged within blueberry increased in colony weight and in the number of immatures and eggs during the bloom period compared to control colonies. In contrast, bee colonies placed within watermelon decreased in colony weight, number of workers and immature bees, and individual bee weight compared to control colonies. Blueberry appeared to provide bees with sufficient nectar and pollen, whereas watermelon may not have provided adequate resources for the bees. Bees foraging within watermelon were probably forced to search for other sources of pollen and nectar, resulting in colony health parameter declines. Our data suggest that some crops (e.g. blueberry) can support managed B. impatiens , potentially adding to localized bumble bee populations, while others (e.g. watermelon) cannot. [ABSTRACT FROM AUTHOR]

Impatiens downy mildew is caused by Plasmopara obducens, a pathogen known in the United States for over a hundred years, but newly attacking ornamental Impatiens walleriana in production and in the landscape. Little is known about the life cycle of P. obducens; thus, in this study an attempt was made to determine whether the pathogen is homothallic or heterothallic. Fourteen single-sporangium isolates and three single-zoospore isolates were used in single and dual inoculations of stem tissue to see whether the pathogen was homothallic or heterothallic; all isolates tested were able to produce oospores when inoculated singly, suggesting homothally. Cold treatment at 0 C for at least 1 mo induced oospores to germinate and produce primary sporangia. Inoculation of plant tissue with germinating oospores resulted in infection. Other incubation temperatures (−10, 10, and 20 C) did not induce germination, but fluctuating temperatures (between −10 and 0 C, or 0 and 10 C) induced some germination. Spores incubated at −10 C had significantly thicker walls than spores incubated at other temperatures. Evidence suggests that oospores can serve as an overwintering stage. [ABSTRACT FROM AUTHOR]

Impatiens downy mildew (IDM) caused by Plasmopara destructor is currently the primary constraint on the production and use of impatiens ( Impatiens walleriana ) as bedding plants worldwide. Downy mildew has been documented since the 1880s from wild-grown Impatiens spp. but epidemic outbreaks of the disease affecting the commercially grown, ornamental I. walleriana were only reported for the first time in 2003 in the United Kingdom and in 2004 in the United States. Here, we assess the genetic diversity, level of differentiation, and population structure from 623 samples associated with current and preepidemic IDM outbreaks, by genotyping the samples with simple sequence repeat markers. P. destructor population structure following the emergence of IDM in the United States is subdivided into four genetic lineages characterized by high genetic diversity, mixed reproduction mode, inbreeding, and an excess of heterozygosity. P. destructor genotypes are significantly differentiated from preepidemic IDM samples from hosts other than I. walleriana but no geographical or temporal subdivision is evident. P. destructor samples from different Impatiens spp. show significant but very low levels of differentiation in the analysis of molecular variance test that did not hold in discriminant analysis of principal components analyses. The same was observed between samples of P. destructor and P. velutina recovered from I. walleriana . The finding of shared genotypes in samples from different countries and lack of differentiation among U.S. and Costa Rican samples indicate the occurrence of international movement of the pathogen. Our study provides the first high-resolution analysis of the diversity of P. destructor populations and the IDM epidemic that may be instrumental for disease management and breeding efforts., Competing Interests: The author(s) declare no conflict of interest.

The twospotted spider mite, Tetranychui urticae Koch, is an important pest of impatiens, a floricultural crop of increasing economic importance in the United States. The large amount of foliage on individual impatiens plants, the small size of mites, and their ability to quickly build high populations make a reliable sampling method essential when developing a pest management program. In our study, we were particularly interested in using spider mite counts as a basis for releasing biological control agents. The within-plant distribution of mites was established in greenhouse experiments and these data were used to identify the sampling unit. Leaves were divided into three zones according to location on the plant: inner, intermediate, and other. On average, 40,33, and 27% of the leaves belonged to the inner, intermediate, and other leaf zones, respectively. However, because 60% of the mites consistently were found on the intermediate leaves, intermediate leaves were chosen as the sampling unit. These results lead to the development of a presence-absence sampling method for T. urticae by using Taylor coefficients generic for this pest. The accuracy of this method was verified against an independent data set. By determining numerical or binomial sample sizes for consistently estimating twospotted spider mite populations, growers will now be able to determine the number of predatory mites that should be released to control twospotted spider mites on impatiens. [ABSTRACT FROM AUTHOR]

Investigates the role of plant density on mixed mating systems and reproduction of Impatiens capensis in Dane County, Wisconsin. Effect of mating system on plant reproduction; Derivation of plant outcrossing rate and biparental inbreeding; Relationship among mating systems parameters and inbreeding coefficients.

Investigates the growth, death and size distribution change in a natural self-thinning population of impatiens pallida in Pennsylvania. Survivorship, lodging and herbivory of the species; Effects of biomechanical constraints on self-thinning relationships and patterns of size structure change in herbaceous plant populations; Importance of field studies in understanding the behavior of suppressed plants.

Describes an experimental study of neighbor interactions in `Impatiens capensis' through the manipulation of the plant phenotypes their neighbors by removing the apical tip from selected plants. Neighbor interaction and the measurement of selection; Kin selection in `Impatiens'; Phenotypic plasticity and the measurement of kin selection.

Discusses a study of yellow nutsedge or Cyperus esculentus and purple nutsedge or Cyperus rotundus in Georgia which are naturally infected with Impatiens necrotic spot virus. Usual emergence of the virus in ornamentals under greenhouse production; Detection of the virus in peanut in Georgia and Texas and in tobacco in the southeastern United States.