Soil polarization is a nonchemical pest management practice that can be used, under some circumstances, as an alternative to chemical fumigation for control of numerous weeds and soil pathogens. The efficacy of polarization is dependent on both biotic and abiotic factors. The uses and limitations of polarization for small fruit production will be discussed. Strategies for future research will be suggested.
Kim D. Patten and John Wang
Kim D. Patten and John Wang
The relationships between canopy density of three perennial weed species (Potentilla pacifica Howell, Aster subspicatus Nees, and Lotus corniculatus L.) and `Mcfarlin' and `Stevens' cranberry (Vaccinium macrocarpon Ait.) yield and fruit quality were evaluated. Yield was more severely affected by weed interferences than fruit size or color. Best-fit regression equations for the effects of weed density on yield, fruit size, and color were linear or quadratic polynomials with a strong linear component. For each bog, the slope of the linear relationship between yield and weed density was more negative as the mean yield of weed-free controls increased. `Stevens' fruit size and yield were more sensitive and fruit color was less sensitive to changes in P. pacifica population density than those of `McFarlin'.
Kim Patten, Gary Nimr, and Elizabeth Neuendorff
Blueberry production is enhanced by the use of an organic mulch. An alternative to off-farm sources of mulch is the production of winter and summer living mulch cover crops grown in the row middles of the blueberry planting. These crops are mowed and then windrowed for use as a mulch. We evaluated living mulch crops for blueberries for the following parameters: adaptation to low soil pH, mulch production, ease and cost of stand establishment, mowing tolerance, allelopathic weed control, and N contributed by mulch. Rye, ryegrass, and crimson clover were the most overall suitable crops for the winter; while for summer, pearl millet was best adapted. Nitrogen was the major limiting factor that affected nonlegume production. Legume yields were limited by deer foraging and low soil pH. Pearl millet had the greatest allelopathic response on weeds of all cover crops tested. Maximum dry matter production for the living mulches ranged from 6000 kg/ha for elbon rye in the winter, to 30,000 kg/ha for pearl millet in the summer. With the appropriate cover crop selection and adequate soil fertility living mulches appear to be a efficacious practice to aid blueberry production in the south.
Richard Novy, Nicholi Vorsa, and Kim Patten
The cranberry cultivar `HcFarlin', selected from a natural bog in Massachusetts in 1874, has become the most widely grown cultivar in the Northwestern U.S.A. Washington state growers have noted variable productivity among `McFarlin' bogs. The determination of whether there is a genetic basis for the variability has been made difficult by a paucity of reliable morphological descriptors in cranberry. A random amplified polymorphic DNA (RAPD) analysis of 45 clones sampled from 12 WA `McFarlin' bogs identified 17 unique RAPD profiles. Cluster analysis identified 7 groups having various numbers of distinct, but related individuals. Eight clones were found to have RAPD profiles identical to the cultivar `Howes' indicating varietal misclassification had occurred in some bogs. One group of clones that originated from bogs classified as “Good” or “True” Mcfarlin' by growers had RAPD profiles similar to those of representatives from WI and MA `Mcfarlin' bogs. RAPD analysis has shown that `McFarlin' is represented by several genotypes, suggesting that the observed variability in production may have a genetic component.
Kim Patten, Rod Macfarlane, and Dan Mayer
The pollination of cranberries and pears by honey bees is often inadequate. The pollination efficacy of feral (Bombus spp.) and/or commercial bumble bees was evaluated for these crops. Preliminary evaluation of commercial B. vosnesenskii and B. occidentalis hives indicated poor forage activity on pears, but good activity on cranberries. Hive stocking densities of B. occidentalis on cranberries required to match feral Bombus populations was 8-10 hive/ha. Hives required 1-2 weeks in the field prior to full bloom to achieve suitable forage density during bloom. Parasitism of commercial hives by wax moth and bumble bee brood fly was common. Commercial colonies did not appear to be cost effective at this time. Only short-tongued feral Bombus species foraged on cranberries. Acceptance of artificial domiciles by these species was poor. Enhancing feral populations required provision of supplemental food sources and improved nesting habitat. Management of alternative food resources for feral bumble bees will be discussed.
Nicholi Vorsa, Richard Novy, and Kim Patten
WA State bogs of the cultivar `McFarlin' exhibit highly variable productivity. Yield and various fruiting characteristics were sampled in 14 WA `McFarlin' bogs, representing two growing areas. Significant differences were found for yield, fruit number/area, percent fruit set, flowers/upright, fruit/upright, fruit weight and seed number/fruit. The variable, flowers/upright, accounted for 69% and 75% of the observed variation for yield and fruit number/area, respectively. A multivariate analysis model accounted for 93% of the variation for yield with 3 variables: flowers/upright (69%), fruit weight (20%), and seed number (4%). Principal component analysis identified three `groups' based on fruiting characteristics. DNA fingerprinting suggests, that variability in yield and fruiting characteristics, has a genetic component.
Michael A. Norman, Kim D. Patten, and Sarangamat Gurusiddaiah
Three indicator species [rye (Secale cereale L.), radish (Raphanus sativus L.), and alfalfa (Medicago sativa L.)] and nonrooted cuttings of `Stevens' cranberry (Vaccinium macrocarpon Ait.) vines were grown in pots to establish the dose response levels for a sand-applied phytotoxin(s) from a crude extract of Pseudomonas syringae (strain 3366) culture. At 114 ppm [milligrams phytotoxin(s)/kilograms sand], the material was noninhibitory, whereas 1140 ppm reduced root and shoot growth significantly in all four species. In subsequent experiments, a 10-ppm dose controlled corn spurry (Spergula arvensis L.) and fireweed (Epilobium angustifolium L.) seedlings, while 103 ppm reduced root or shoot growth of cuttings of the perennial weeds birdsfoot trefoil (Lotus corniculatus L.) and silverleaf (Potentilla pacifica Howell). Root and shoot growth of partially rooted `McFarlin' cranberry vines was reduced at 103 and 563 ppm, respectively. The phytotoxin(s) could potentially control germinating annual weeds in newly established `Stevens' cranberry bogs.
Glenn C. Wright, Kim D. Patten, and Malcolm C. Drew
`Tifblue' and `Brightwell' rabbiteye blueberry (Vaccinium ashei Reade) and `Sharpblue' southern highbush blueberry (primarily V. corymbosum) were treated with 0, 25, and 100 mm Na+ as Na2SO4 or NaCl, and 0, 1, 3, and 10 mm supplemental Ca2+ in sand culture in the greenhouse. For rabbiteye plants salinized with Na2SO4, leaf Na+ concentrations increased 54-fold and the percentage of total plant Na+ found in the leaves increased from 9% to 63% with increasing external Na+. Calcium supplementation reduced the Na+ concentrations in leaves by up to 20%. Leaf Ca2+ concentrations increased with Ca2+ supplementation, but accounted for a decreasing percentage of the total Ca2+ found in the plant, since root Ca2+ concentrations were much higher. Root Na+ concentrations increased with increasing Na+ treatments to a smaller extent than in the leaves and were also reduced by Ca2+ supplements. Potassium concentrations in leaves and roots decreased with increasing Na+ treatment levels, particularly in roots, where K+ concentration was about half at 100 mm Na+ (as Na2SO4.) Leaf Na+ concentrations were up to two times greater when Na was supplied as NaCl compared to Na2SO4. For plants salinized with NaCl, leaf Na+ levels increased to 1.1% and did not decrease when supplemental Ca2+ was applied. Leaf Cl- concentrations also increased greatly with NaCl, reaching >1.0% (dry weight basis.). Root Cl- concentrations also increased with increasing salinity and were not affected by Ca2+ supplements. Ca2+ supplementation led only to a greater Ca2+ concentration in leaves and roots, but this did not alter Na+ concentrations. Nutrient concentrations in `Sharpblue' leaves, stems, and roots were greater than those of the rabbiteye cultivars, but were influenced by salinity and Ca2+ in essentially the same way. Excess Na+, Cl-, or both, together with lowered K+, were likely the cause of extensive leaf necrosis and may be indicative of a lack of a mechanism to control Na+ influx into blueberry leaves.
Glenn C. Wright, Kim D. Patten, and Malcolm C. Drew
`Tifblue' rabbiteye blueberry (Vaccinium ashei Reade) and `Sharpblue' southern highbush blueberry (primarily V. corymbosum) were treated with 0, 25, or 100 Mm Na+ as Na2SO4 or NaC1, and 0, 1, 3, or 10 Mm supplemental Ca2+ in sand culture in the greenhouse. Greatest stomatal conductance (gs) and net assimilation (A) occurred in unsalinized `Tifblue' plants not given additional Ca2+. Stomatal conductance, A, transpiration (E), and xylem water potential(Ψ)of `Tifblue' and `Sharpblue' plants were all lowered as salinity increased, and these effects were more pronounced with NaCl than with Na2SO4. After 63 days, for plants given 100 Mm Na+ as NaCl, gs and net assimilation rate were reduced to only 10% of the unsalinized controls, while for plants salinized with 100 mm Na+ as Na2SO4, gs and A were 35% and 43%, respectively, of unsalinized controls. Leaf necrosis was more extensive on `Sharpblue' plants given NaCl than on `Tifblue' plants. Neither Ca2+ nor Na+ treatments led to severe chlorosis; reductions in leaf chlorophyll content were mainly due to necrosis. The Na+- induced reduction in gas exchange was associated with negative Ψw Ca2+ deficiency, or a combination of these factors. Additional factors leading to inhibition of gas exchange in NaCl- stressed plants include Cl- toxicity and leaf necrosis. Calcium supplements were unable to ameliorate NaCl damage in `Tifblue' or `Sharpblue' plants, possibly because of the inability of Ca2+ to counter Cl- entry and toxicity. In contrast, additional Ca2+ improved gs, A, Ψw, and leaf chlorophyll content of `Tifblue' plants that received Na2SO4. For plants treated with 25 mm Na+ as Na2SO4 and 1 mm Ca2+, gs was 1.5 to 2.5 times higher than in plants without added Ca2+. Low (1 mm) concentrations of Ca2+ were more effective in ameliorating the effects of 100 mm Na+ as Na2SO4. than were 3 or 10 mm Ca2+ supplements, possibly because higher Ca2+ concentrations damaged the metabolism of the calcifuge blueberry.