Below-ground carbon allocation represents a substantial fraction of net photosynthesis in plants, yet timing of below-ground allocation and endogenous and exogenous factors controlling it are poorly understood.Minirhizotron techniques were used to examine root populations of Vitis labruscana Bailey cv. Concord under two levels of dormant-season canopy removal and irrigation. Root production, pigmentation, death and disappearance to a depth of 110 cm were determined over two wet and two dry years (1997-2000).There was continual root production and senescence, with peak root production rates occurring by midseason. Later in the season, when reproductive demands for carbon were highest and physical conditions limiting, few roots were produced, especially in dry years in nonirrigated vines. Root production under minimal canopy pruning was generally greater and occurred several weeks earlier than root production under heavy pruning, corresponding to earlier canopy development. Initial root production occurred in shallow soils, likely due to temperatures at shallow depths being warmer early in the season.Our study showed intricate relationships between internal carbon demands and environmental conditions regulating root allocation.

Three-year-old field-grown 'Concord' ( Vitis labruscana Bailey) grapevines were destructively harvested at eight growth stages during 1998 to quantify growth, carbohydrate distribution, and nutrient concentrations of different organs. The roots were the major storage organ for carbohydrates and nutrients, accounting for 84% of the starch and 75% of nitrogen stored in the vines at the beginning of the season. About 78% of the reserve starch in the vine was used for prebloom root and shoot growth. Early-season fine-root growth was a sink for stored vine nitrogen; however, the fine roots quickly became a nitrogen uptake source, providing at least 84% of the spring growth nitrogen. Total root biomass increased from bloom to leaf fall, but reserve carbohydrates and nutrients lost in the prebloom period did not begin to recover in roots until the end of rapid shoot development in late July. Crop removal at harvest, and a late-season root flush, further increased vegetative carbohydrate and nutrient reserves in the short postharvest period.

The current study investigated the seasonal phenology, spatial distribution, feeding damage and economic impact of two plant bugs, Lygocoris inconspicuous Knight and Taedia scrupeus Say, in commercial vineyards. For both plant bugs, densities of nymphs were higher on vines located near the edge of woodlots rather than in the interior of vineyards, which may be attributed to the presence of wild vines and other alternate host-plants in wooded areas. Nymphs of both species fed on apical leaves and developing fruit clusters of vine shoots, initiating development after swelling of buds in the spring and reaching the adult stage when vines were in bloom. Confining high densities of L. inconspicuous (10 nymphs) on individual shoots early in the season resulted in significant reduction of the number of fruit clusters per shoot, even when feeding was restricted to short (7 d) duration; the average weight of fruit clusters, in contrast, was not affected to a large extent by feeding activity of nymphs. An experiment evaluating the impact of low density of L. inconspicuous (0-0.3 nymphs per shoot) indicated a marginally significant negative relationship between density of nymphs and average weight of fruit clusters. Control measures may be economically justified when population density exceeds a combined threshold of one nymph of either L. inconspicuous or T. scrupeus per 10 shoots of vines.

One- and 2-year-old 'Concord' (Vitis labruscana L.) grapevines were used to study the effect of soil pH on vegetative growth and nutrition. Ninety-eight, own-rooted, 'Concord' grapevines were planted in 94.6-L pots containing vineyard soil adjusted to seven soil pH levels ranging from 3.5 to 7.5. After the first growing season, seven vines from each soil pH treatment were randomly selected, destructively harvested, and measured for root and shoot growth. The remaining 49 vines over-wintered in the pots, were defruited in year two, and were destructively harvested at the end of the second growing season. There was a reduction in root biomass below soil pH of 4.5 and a greater reduction in shoot biomass leading to a higher root : shoot ratio. There were no significant differences in vegetative growth of young'Concord' vines from a soil pH of 5.0-7.5. However, there was a trend toward lower shoot biomass and higher root: shoot ratio at the highest soil pH level. Phylloxera nodosities on roots were present in equal densities at all soil pH values. However, the negative impact of phylloxera on vine dry mass was greater on vines under nutrient stress at the highest and lowest pH treatments than on those with adequate nutrition at the mid-range soil pH values.

Concord roots are moderately resistant to phylloxera, which form nodosities on the fine roots and weaken the root system. Rootstocks and vineyard floor management both have the potential to eliminate or reduce the effect of phylloxera in New York Concord vineyards. Young, container-grown Concord grapevines were used to evaluate the interaction between rootstock (own-rooted, Couderc 3309), irrigation, and phylloxera infection on vine growth. Phylloxera inoculation alone caused a 21 % decrease in vine dry mass and lack of irrigation (mid-day stem water potential: -0.9 to -1.0 M Pa) alone caused a 34 % decrease in vine dry mass. The combination of phylloxera stress and water stress was additive and caused a 54 % decrease in vine dry mass. Because C3309 rootstock is resistant to phylloxera, the grafted vines showed a response to irrigation but not phylloxera inoculation. This container study shows the potential benefits of irrigating own-rooted Concord grapevines or the use of rootstocks without irrigation to withstand phylloxera infection.

Historically, Concord (Vitis labruscana) native-American fresh juice grapes have not been irrigated when grown with standard heavy pruning in the cool, humid climate and soils of New York. The advent of minimal pruning of vines has: led ro more rapid canopy development and heavier crops that may need more water than conventionally-pruned vines. An experiment was established with minimal versus conventional pruning with and without supplemental drip irrigation. Differences in light interception were documented showing a much more rapid light interception by the minimally-pruned vines although by mid-season differences were small. In a very dry warm year comparisons were made of vine growth and leaf gas exchange responses over the season. The primary difference in response to drought was that the minimally-pruned vines used more soil water early in the season due to the higher early light interception and therefore depleted the soil water supply earlier than in the conventionally pruned vines. This led to earlier reduction in leaf photosynthesis, reduced berry growth earlier during the cell division period and later and eventual partial defoliation in the drier sites. Numbers of live shoots the following year in the minimally-pruned vines was reduced as was the subsequent crop, while the subsequent crop of conventionally-pruned vines was only slightly reduced.

Improved cultural practices in grape require a better understanding of root growth and physiology. Seasonal root dynamics were examined in mature `Concord' vines with balanced or minimal-pruning, and with or without supplemental irrigation in Fredonia, N.Y. Fine roots were continuously produced during the growing season starting in mid-June around time of bloom. Roots began to die in September at verasion. Minimal-pruned vines produced more roots than balanced-pruned vines, with the minimal-pruned/unirrigated vines producing the most roots. Irrigation and pruning delayed fine root production at the beginning of the growing season. Peak fine root flush was 16 June to 21 July 1997 for the minimal-pruned/unirrigated treatment, while peak flush was 7 July to 2 Sept. 1997 for balanced-pruned/irrigated treatment. In minimal-pruned vines, many roots were observed down to depths of 120 cm. In contrast, balanced-pruned vines had very few fine roots deeper than 40 cm. From initial observations, median lifespan of fine roots was 5 to 9.5 weeks, depending on treatment and depth in soil. Fine roots lived longer in the top 15-cm than in the 16- to 30-cm layer of soil in all treatments. Both minimal pruning and irrigation increased root lifespan. Fine roots had the shortest lifespan in the balanced-pruned/unirrigated treatment and the longest lifespan in the minimal-pruned/irrigated treatment.

Productivity of Concord vines infested with endemic populations of Eastern grape leafhopper, Erythroneura comes Say, was compared with that of uninfested vines in three field experiments from 1990 to 1995. Responses of vines to infestation levels ranging from 100 to 577 leafhopper days and peak leafhopper densities ranging from two to 14 leafhopper nymphs per leaf varied. Mean crop weight in vines not treated with insecticides was reduced by up to 4.9 kg/vine compared to sprayed vines. Effects on productivity sometimes carried over to subsequent crop years, but response of yield components to injury varied. In the season of injury, berry weight was the yield component most strongly affected. In subsequent years, leafhopper injury reduced bud fruitfulness, as measured by the number of berries per cluster and clusters per retained node. Soluble solids, adjusted for crop weight, were significantly affected in only one cropping cycle (out of 22). Yield reductions were only weakly correlated with infestation levels, as measured by leafhopper days and leaf injury ratings. Availability of adequate soil moisture and vine reserves is hypothesized to be an important determinant of the impact of leafhopper injury on Concord productivity in northeastern North America.

The effects of three levels of pruning severity, two rates of soil applied nitrogen, and a three spray regime of foliar nutrients were investigated at a commercial `Concord' vineyard during the 1991 and 1992 growing seasons. While increased node number resulted in higher yields of less mature fruit, yield, vigor and fruit maturity were unaffected by rate of soil applied nitrogen. In both years, while yield was significantly reduced by the application of foliar nutrients growth and fruit maturity was unaffected.

In two 4-year studies, `Concord' (Vitis labruscana, Bailey) cane pruning weight, yield, and soluble solids content were similar for vines growing under herbicide and cultivation treatments. In a vineyard with shallow soil, vines grown under mulch had a significantly greater increase in cane pruning weight than did vines grown with sod middles. Growth suppression of sod-managed vines occurred only in relatively dry years. While there was annual variation in vine response to herbicide and cultivation treatments, the cumulative responses over the 4-year study were similar for these treatments. A second vineyard where soil was less restrictive for root growth did not respond to the replacement of clean cultivation with herbicide treatments. In both experiments, there was no apparent advantage of two instead of a single herbicide application, and there was no difference between the budbreak, as opposed to bloom timing, of herbicide application.