Search Results

You are looking at 1 - 10 of 24 items for :

  • Author or Editor: Ian A. Merwin x
  • HortScience x
Clear All Modify Search
Authors: and

Temporal and spatial combinations of tree-row weed suppression treatments were evaluated during 5 years in a New York apple (Malus domestica Borkh. cv. Imperial Gala on Malling 26 rootstocks) orchard planted in Apr. 1991, and provided with trickle irrigation. Twenty-eight factorial treatment combinations [0, 2, 4, and 6 m2 weed-free areas (WFAs); and May, June, July, August, May + June, June + July, May + June + July, and June + July + August weed-free times (WFTs)] were maintained from 1991 to 1995 by postemergence paraquat herbicide applications in tree-row strips. Trunk cross-sectional area (TCA) growth and yield were monitored annually, and few differences were observed as WFA increased from 2 to 4 to 6 m2 per tree. However, WFT substantially influenced TCA, fruit production, and yield efficiency. Early summer WFTs increased TCA during the first two growing seasons, compared with late summer treatments. When trees came into production in 1993-94, yields increased as the duration of WFT increased, but where similar periods of WFT had been established later during the growing season, annual yield, cumulative yield efficiency, and the ratio of crop value to weed-control costs were all reduced. Groundcover species distribution was evaluated each year in September, and graminaceous weeds were more prevalent in the early and midsummer WFTs, while herbaceous broadleaf weeds dominated in the August treatments. A quadratic model regressing cumulative yield efficiency on WFTs grouped into 30-, 60-, and 90-day categories showed that efficiency peaked between 60 and 90 days of WFT. It appeared that timing of weed suppression may be as important as the area of suppression beneath trees in comparable apple orchards, that early summer weed control was especially important for newly planted trees, and that drip irrigation allowed reductions in the area and amount of tree-row herbicide applications, without significant losses in apple tree growth or crop value.

Free access

We planted grafted and seedling chestnuts of six cultivars in Lansing, N.Y., in April 1995 to evaluate performance of the different cultivars in our region and to compare grafted and seedling trees. We used the following cultivars: the Chinese chestnut cultivar Mossbarger (Castanea mollissima) and five interspecific hybrid cultivars [Douglas 1A (C. mollissima × C. dentata), Eaton [C. mollissima × (C. crenata × C. dentata)[, Skioka (C. mollissima × C. sativa), Layeroka (open-pollinated daughter of `Skioka'), and Grimo 142Q (an open pollinated daughter of `Layeroka')]. Growth was not significantly different between cultivars. There were no notable correlations between trunk cross-sectional area at planting and any measurement after the first year. Significant differences between cultivars were found for mortality, yield, and yield efficiency. `Eaton' had the lowest mortality rate (2%) of all cultivars. `Grimo 142Q' and `Layeroka' had the highest dry weight yields and the greatest yield efficiencies, although `Grimo 142Q' had significantly larger nuts than `Layeroka'. In 1998, the largest nuts (5.2 g) were harvested from `Mossbarger' and `Eaton trees'. `Skioka' had the highest mortality (48%), lowest yield, lowest yield efficiency, and smallest nut size. In the first 2 years, most grafted trees showed significantly higher yields and greater yield efficiency than seedling trees. By the third year, differences in yield between grafted and seedling trees were no longer significant for most cultivars. Over the 3 years most grafted trees revealed higher mortality and slower growth than seedlings of the same cultivar. Seedlings did not show more variability in measurements than grafted trees of the same cultivar.

Free access

One-year-old potted `Mutsu' apple (Malus domestica) trees on MM.111 and M.9 rootstocks were grown outdoors from May to Nov. 1997, under three levels of soil-water availability (–20, –80, and –200 kPa), to evaluate the effects of water stress on soil/root respiration and root morphology. At weekly intervals, we measured soil/root respiration using a portable infrared gas analyzer and rootsystem size or functional activity using an electric capacitance meter. These observations were tested as nondestructive methods to estimate relative differences in root size and morphology in situ compared with final dry weight and form of excavated apple rootstocks. Root size-class distributions were estimated by digital imaging and analysis of harvested root systems. Root growth was substantially reduced by water stress; the magnitude of reduction was similar for both rootstocks, but the percentage of shoot growth reduction was higher for MM.111. Root: shoot ratios were higher and average specific respiration rates over the growing season were lower for M.9 root systems. Water stress increased the root: shoot ratio, specific root length, and carbon costs of root maintenance as indicated by specific respiration rates. Soil/root respiration was more closely correlated than root electric capacitance with actual root system size. The observed r 2 values between root capacitance and root dry weight were as high as 0.73, but root capacitance was also confounded by other factors, limiting its usefulness for nondestructive estimation of root size or activity. Rootstock genotype significantly affected root capacitance, which provided better estimates of root dry weight for M.9 than for MM.111.

Free access

Apple replant disease (ARD) is a common problem typified by stunted growth and reduced yields in successive plantings of apple (Malus ×domestica Borkh.) in old orchard sites. ARD is attributed to biotic and abiotic factors; it is highly variable by sites, making it difficult to diagnose and overcome. In this experiment, we tested several methods of controlling ARD in a site previously planted to apple for >80 years. Our objective was to evaluate practical methods for ARD management. We compared three different experimental factors: four preplant soil treatments (PPSTs) (compost amendments, fumigation with Telone C-17, compost plus fumigation, and untreated soil); two replanting positions (in the old tree rows vs. old grass lanes); and five clonal rootstocks (`M.26', `M.7', `G.16', `CG.6210', and `G.30') during 4 years after replanting. The PPSTs had little effect on tree growth or yields during 4 years. Tree growth was affected by planting position, with trees planted in old grass lanes performing better than those in the old tree rows. Rootstocks were the most important factor in overcoming ARD; trees on `CG.6210' and `CG.30' grew better and yielded more than those on other rootstocks. Rootstock selection and row repositioning were more beneficial than soil fumigation or compost amendments in controlling ARD at this orchard.

Free access

We tested 40 seedling lots and 17 clonal accessions—representing 941 genotypes and 19 species or interspecific hybrids of Malus—for their resistance or tolerance to apple replant disease (ARD) in a mixture of five New York soils with known replant problems. Total plant biomass, root necrosis, root-infesting fungi, and root-lesion nematode (RLN; Pratylenchus penetrans Cobb) or dagger nematode (DN; Xiphinema americanum Cobb) populations were evaluated in apple seedlings and clones grown for ≈60 days in the composite soil. In addition to phytophagous nematodes, various Pythium, Cylindrocarpon, Fusarium, Rhizoctonia and Phytophthora species were isolated from roots grown in the test soil. Plant growth response was categorized by a relative biomass index (RBI), calculated as total plant dry weight in the pasteurized field soil (PS) minus that in an unpasteurized field soil (FS), divided by PS. Nematode reproduction on each genotype was defined by a relative reproduction index (RRI), calculated as final nematode populations in roots and soil (Pf) minus initial soil populations (Pi), divided by Pi. The RBI, RRI, and other responses of accessions to ARD soil were used to rate their resistance, tolerance, or susceptibility to apple replant disease. None of the accessions was completely resistant to ARD pathogens in our test soil. Seedling accessions of M. sieversii Roem. and M. kirghisorum Ponom. appeared to have some tolerance to ARD, based upon their low RRIs and RBIs. Three clonal rootstock accessions (G.65, CG.6210, and G.30), and four other clones (M. baccata Borkh.—1883.h, M. xanthocarpa Langenf.—Xan, M. spectabilis Borkh.— PI589404, and M. mandshurica Schneid.—364.s) were categorized as tolerant to ARD. The disease response of other accessions was rated as susceptible or too variable to classify. We concluded that sources of genetic tolerance to ARD exist in Malus germplasm collections and could be used in breeding and selecting clonal rootstocks for improved control of orchard replant pathogens.

Free access

Growth, nutrient uptake, and yield of peach (Prunus persica) trees was evaluated in various groundcover management systems (GMSs) for three years, with and without preplant soil additions of Zn, B, and Cu. In July 1990, micronutrients (none, or 135kg Zn·ha-1+100kg Cu·ha-1+1.1kg B·ha-1) were incorporated into the upper 20 cm of a silty clay-loam soil (pH 6.7, 4% organic matter), and a fine-leaf fescue (Festuca ovina) turf was established. Trees were planted Apr. 1991, and four GMS treatments (wood-chip mulch, pre-emergence herbicide, post-emergence herbicide, and mowed turf) were superimposed upon the “+/-” micro-nutrient preplant treatments. Extractable Zn, Cu and B concentrations were greatly increased in soil of plots which had received preplant amendments. Peach leaf content of Zn, Cu and B was also greater in preplant fertilized plots in the year of planting. However, in subsequent years only leaf B (in 1992) and leaf Zn (in 1993) continued to respond positively to preplant soil treatments. No significant interactions were observed between GMS and micronutrient availability or uptake. Peach growth and yield were not affected by preplant treatments, but were substantially greater in mulch and pre-emergence herbicide plots compared with the mowed fescue turfgrass.

Free access

Meadow vole (Microtus pennsylvanicus Ord) populations, feeding activity and damage to young apple (Malus ×domestica Borkh.) trees were monitored for several years in a New York orchard by direct observation, trap counts, and a feeding activity index in various groundcover management systems (GMSs). Meadow vole population density differed among GMSs, with consistently higher densities and more trees damaged in crown vetch (Coronilla varia L.), hay-straw mulch, and red fescue (Festuca rubra L.) turfgrass tree-row strips. Vole densities were high in autumn and low in spring each year. Anticoagulant rodenticides and natural predation did not adequately control voles in GMSs providing favorable habitat. Groundcover biomass per m2 was weakly correlated with vole densities in 2 of 3 years, while the percentage of soil surface covered by vegetation was not significantly correlated with vole populations. Applications of thiram fungicide in white latex paint were better than no protection, but less effective than 40-cm-high plastic-mesh guards for preventing vole damage to tree trunks. A combination of late-autumn trapping, close and consistent mowing of the orchard floor, trunk protection with mesh guards, contiguous habitat for vole predators, and herbicide applications within the tree rows provided effective control of meadow-vole damage to trees at this orchard during 3 years without applications of rodenticide baits. Chemical names used: Tetramethylthiuram disulfide (thiram)

Free access

We are testing control tactics for apple replant disease (ARD) complex, a worldwide problem for fruit growers that is attributed to various biotic and abiotic soil factors. In Nov. 2001, “Empire” apple trees on five rootstocks (M.26, M.7, G.16, CG.6210, and G.30) were planted into four preplant soil treatments—commercial compost at 492 kg/ha soil-incorporated and 492 kg·ha-1 surface-applied), soil fumigation with Telone C-17 (400 L·ha-1 of 1,3-dichloropropene + chloropicrin injected at 30 cm depth five weeks prior to replanting), compost plus fumigant combination, and untreated controls—at an old orchard site in Ithaca, N.Y. Trees were replanted in rows perpendicular to, and either in or out of, previous orchard rows. Irrigation was applied as needed, and N-P-K fertilizer was applied in 2001 to all non-compost treatments to compensate for nutrients in the compost treatment. After two growing seasons, the rootstock factor has contributed most to tree-growth differences. CG.6210 rootstock supported greater growth in trunk diameter, central leader height, and lateral shoot growth (P < 0.05), regardless of preplant soil treatments and replant position. Trees on M.26 grew least over a two year period. Replant growth was greater in old grass lanes than in old tree rows, despite higher root-lesion nematode populations in previous grass lanes. Growth responses to preplant soil fumigation were negligible. Preplant compost did not increase tree growth during year one, but did increase lateral branch growth in year two. Results thus far suggest that replanting apple trees out of the old tree-row locations, and using ARD tolerant rootstocks such as CG.6210, may be more effective than soil fumigation for control of ARD in some old orchard sites.

Free access

Orchard replant disorder (ORD) is a widespread soilborne disease complex that causes stunting and poor establishment of replanted fruit trees. Chemical and cultural control of ORD provide effective, but short-term, control. More-sustainable strategies would involve ORD-resistant rootstocks not yet identified in apple. We tested `Bemali', G11, G13, G30, G65, G189, G210, and G707 clones from the apple rootstock breeding program at Geneva, N.Y., for their response to ORD in a composite soil collected from New York orchards with known replant problems. Clones were tested in the greenhouse in steam-pasteurized (PS), or naturally infested field soils (FS) with about 900 Pratylenchus penetrans and 150 Xiphinema americanum per pot. Plant dry mass, height, root necrosis, and nematode populations were determined after 60 days under optimal growing conditions. Stunting, reduced plant dry mass, and root necrosis were more severe in FS than in PS for most of the clones (P ≤ 5%), but G30 and G210 were substantially more tolerant to replant disorder than smaller ones, but this toleratnce might not be sustained in fields with greater or more prolonged nematode infestations. There is sufficient variation in apple rootstock resistance or tolerance to ORD to suggest that genetic resistance may be identified and developed for better management of orchard replant problems.

Free access

Root observations in situ with a rhizotron camera enabled us to compare the performance of apple (Malus ×domestica Borkh.) trees on 3 rootstock clones planted in a New York orchard with a history of apple replant disease. Visual observations were conducted in situ at monthly intervals during 2 growing seasons through minirhizotron tubes for trees grafted onto 3 rootstocks: M.7 (M.7), Geneva 30 (G.30), and Cornell-Geneva 6210 (CG.6210). There were 3 preplant soil treatments (fumigation, compost amendment, and untreated checks) and 2 tree planting positions (within the old tree rows or in the old grass lanes of the previous orchard at this site). Preplant soil treatments and old-row versus grass-lane tree planting positions had no apparent influence on root systems, whereas rootstock clones substantially influenced root growth and demography. New root emergence was suppressed during the first fruit-bearing year (2004) on all 3 rootstock clones compared with the previous nonbearing year (2003). A root-growth peak in early July accounted for more than 50% of all new roots in 2003, but there was no midsummer root-growth peak in 2004. The median lifespan for roots of CG.6210 was twice that of G.30 and M.7 in 2004. Also, CG.6210 had more roots below 30 cm depth, whereas M.7 had more roots from 11 to 20 cm depth. Trees on CG.6210 were bigger, yielded more fruit, and had the highest yield efficiency in the third year after planting compared with trees on G.30 and M.7 rootstocks. Crop load appeared to inhibit new root development and changed root-growth dynamics during the first bearing year, with a resurgence in new root growth after fruit was harvested in October 2004. Rootstock genotype was the dominant influence on root lifespan and distribution in this study, whereas preplant soil fumigation, compost amendments, and replanting positions had little apparent impact on root characteristics despite their influence on above-ground tree growth and yield.

Free access