The recent registration of sulfentrazone, a selective, soil-applied, PRE herbicide labeled for control of various weeds in cranberry, expanded the number of modes of action that could be used in the crop. A 2018 preliminary study in Massachusetts showed that high rates of sulfentrazone applied at the cabbage head stage reduced the number of flowering uprights (vertical stems) without impacting the final yield. To clarify the use patterns needed to promote crop safety when using sulfentrazone, six studies were conducted in New Jersey and Massachusetts in 2019 and 2020. Studies compared sulfentrazone applications made at two timings (spring dormant, SD; or cabbage head [CH] stage), two rates (280 and 420 g ai ha−1), and three application volumes simulating either chemigation (3,740 L ha−1) or boom application (190 L ha−1 alone or followed by 0.25 cm water wash-off). Boom application studies in New Jersey in 2018 and 2019 did not show significant long-lasting injury (necrosis or stunting). However, a comprehensive observation of cranberry uprights 8 wk after treatment showed a high rate of terminal bud necrosis, a reduction in the number of reproductive structures, and the development of axillary shoots associated with a high rate of sulfentrazone applied at CH. A mitigation study conducted in 2019 and 2020 confirmed the safety of chemigated sulfentrazone at the high rate with no yield reduction, regardless of crop stage at application. Washing off the herbicide from the cranberry canopy immediately after boom application did prevent the necrosis of terminal bud and the related development of nonproductive secondary shoots. Considering the results of this study, application of sulfentrazone over the top of cranberry vine before scales of the terminal bud start loosening would be prudent practice at this time.

The interactive effects of nitrogen rate (0, 28, 56, and 112 kg/ha), vine density (0, 1.8, 3.6, and 5.4 t/ha of the cultivar ‘Stevens’), and weed management (preemergence herbicide, postemergence control, inoculation with weed seeds, and untreated) were determined on the recolonization of open spaces caused by localized biomass removal in a newly planted commercial cranberry bed. To assess the effect of the 64 treatment combinations on initial colonization, all cranberry and weed biomass was removed from a randomly selected 930-cm2 area in each plot in Year 1. To quantify recolonization of the disturbed area, the same quadrat was resampled and all plant biomass was collected in Year 2. Cranberry biomass production in the disturbed area increased in a quadratic fashion with increasing N rates for all vine densities except zero. Cranberry biomass in the year after disturbance was positively correlated with cranberry biomass present in the previous year. Weed stem biomass in the year after disturbance was positively correlated with weed stem biomass from Year 1 and negatively correlated with percentage cranberry biomass from Year 1 and Year 2. Less than one-third of the treatment combinations recovered enough to produce at least 200 g/m2 1 yr postdisturbance (a reasonable expectation of biomass production). Growers who have low weed pressure and extensive cranberry cover on their farms can expect that disturbed areas will be recolonized by cranberry vines when they utilize adequate, but not excessive, nitrogen regimes.

Sand stockpiles, located near commercial cranberry beds in Massachusetts, New Jersey, Washington, and Wisconsin, were sampled quarterly over a 2-yr period. Samples were collected from the surface and the interior of the piles. Utilizing a simple greenhouse germination bioassay, 74 plant species representing 23 plant families were identified across all locations and samples. Plant density varied by region and by sampling depth; species richness varied by region only. More seedlings germinated from samples taken from the surface of the stockpile compared with interior samples. Almost half of all species detected in either surface or interior samples were represented by only one seedling. Fifty-nine percent of the plant species from Massachusetts and New Jersey samples, and 79% and 96% of the plant species from Wisconsin and Washington, respectively, were considered to be weeds in cranberry production. Only one-third of the identified species had wind-blown seeds; seed dispersal was by other mechanisms in almost half of the species. This survey documented the weed management implications of spreading stockpiled sand on cranberry bogs for horticultural or pest management purposes. To minimize the introduction of additional weed problems, growers and integrated pest management consultants should evaluate the seedbank potential of a stockpile prior to application of the sand to the production area.