Non-bearing Apple Trees Research Articles

Control of insect pests using trunk injection in a newly established apple orchard

ABSTRACTWe evaluated the potential for using preplant trunk injections of emamectin benzoate in nonbearing apple trees. Trees were evaluated for pest injury and emamectin residues throughout the planting season and into the following year. Injections into the trunk best delivered emamectin benzoate to the canopy compared with injections into the taproot, and the higher rate reduced insect pests more than the lower rate. In the following year, differences in insect control between trunk and root injections were less pronounced, but the higher rate of emamectin benzoate persisted longer and better reduced pests relative to the other treatments.

Effects of Orchard Host Plants on the Oviposition Preference of the Oriental Fruit Moth (Lepidoptera: Tortricidae)

Recently, the oriental fruit moth, Grapholita molesta (Busck) (Lepidoptera: Tortricidae), has emerged as a major problem on apples (Malus spp.) grown in the mid-Atlantic and midwestern United States, despite its historically important and frequent occurrence as a peach (Prunus spp.) pest. It is possible that host-driven biological phenomena may be contributing to changes in G. molesta population dynamics resulting in outbreaks in apple. Studies were designed to examine the effects of host plants on oviposition behavior, in an effort to clarify the host association status of eastern U.S. populations and also to gain insight into how pest modeling and management efforts may be altered to take into account various host-associated effects. G. molesta adults exhibited ovipositional preference for nonbearing peach trees over nonbearing apple trees in close-range choice tests conducted in the field, regardless of the larval host origin. A significant preference for peach shoots over apple shoots was observed on six of 12 sampling dates with a wild G. molesta population at the interface of adjacent peach and apple blocks. Numbers of eggs found on apple fruit were higher after peach fruit were harvested and apple fruit began to approach maturity (during the flight period for third and fourth brood adults). Possible implications for population modeling and integrated management of G. molesta are discussed.

Effects of Orchard Host Plants on the Oviposition Preference of the Oriental Fruit Moth (Lepidoptera: Tortricidae)

Recently, the oriental fruit moth, Grapholita molesta (Busck) (Lepidoptera: Tortricidae), has emerged as a major problem on apples (Malus spp.) grown in the mid-Atlantic and midwestern United States, despite its historically important and frequent occurrence as a peach (Prunus spp.) pest. It is possible that host-driven biological phenomena may be contributing to changes in G. molesta population dynamics resulting in outbreaks in apple. Studies were designed to examine the effects of host plants on oviposition behavior, in an effort to clarify the host association status of eastern U.S. populations and also to gain insight into how pest modeling and management efforts may be altered to take into account various host-associated effects. G. molesta adults exhibited ovipositional preference for nonbearing peach trees over nonbearing apple trees in close-range choice tests conducted in the field, regardless of the larval host origin. A significant preference for peach shoots over apple shoots was observed on six of 12 sampling dates with a wild G. molesta population at the interface of adjacent peach and apple blocks. Numbers of eggs found on apple fruit were higher after peach fruit were harvested and apple fruit began to approach maturity (during the flight period for third and fourth brood adults). Possible implications for population modeling and integrated management of G. molesta are discussed.

Effects of root-zone temperature on nitrogen accumulation by non-bearing apple trees

SummaryNon-bearing, potted, apple plants were subjected to root temperature of 8.6.1(LRT) or 23.6.18C (HRT) and irrigated with 100 ml of water containing 20 mg of N as NH4NO3, in which both ammonium and nitrate-N fractions were enriched in 15N (10 atom%). The root system of each plant was pressurized (325 kPa) at day 1, 2, 4, and 8 after15 N application to evaluate the transport of nitrogen derived from fertilizer (NDFF) through the xylem. This technique was used to investigate N absorption. LRT reduced the rate of N uptake the day after 15N application relative to HRT. Two, 4 and 8.d after fertilization, the rate of exudation and consequently the uptake rate was similar for LRT and HRT. The total amount of N removed by plants after 8.d was not affected by root treatments. Carbon dioxide assimilation, transpiration rate and stomatal conductance were lower for trees subjected to LRT during the time course of the experiment. We suggest that the delay in N absorption was related mostly to the lower activity of root nitrate reductase detected at the lower root temperature, which increased the nitrate xylem sap concentration and diminished the rate of N uptake.

Effects of Root Zone Temperature on the Kinetics of Nitrogen Uptake of Non-bearing Apple Trees

Low root-zone temperature is one of the potential causes of low rate of plant nutrient uptake in spring. In this period, fruit trees are frequently supplied with nitrogen and a delay in root absorption could lead to an increase of nitrate leaching. In this study we assessed the effect of low root temperature on kinetic of nitrogen absorption of apple trees. One-year-old rooted cuttings of `Mark' apple rootstocks were subjected to two root temperature: 8 ± 1°C (LT) and 23 ± 1°C (HT). Four days after treatment imposition, the potted plants were supplied with 20 mg of N as NH4N03, enriched with 10 atom% of 15N. One, 2, 4, and 8 days after fertilization, tree root system was inserted into a Sholander bomb where a 0.325-Mpa pressure was applied to collect the xylem sap from the stem cross section. The sap exudation rate was always depressed by low root temperature. Nitrogen flow through the xylem vessel was highest in HT plants the day after fertilization (10-fold higher than LT), then decreased constantly. In LT plants, N flow was low the first and the second day after fertilization then reached the maximum 4 days after fertilization, when it was significantly higher than in HT plants. The amount of fertilizer-N found in leaves reflected the different movement rate of N observed in the two treatments. In HT trees fertilizer-N reached a plateau 2 days after fertilization, while in LT it linearly increased over time. This results suggest that root zone temperature of 8°C, although causes a delay (2–4 days) in nitrogen uptake, does not represent a serious limiting factor for N nutrition of tested apple trees.

Dry Matter Partitioning of Nonbearing Apple Trees Following Injury by European Red Mite (Acari: Tetranychidae)

Apple trees ( Malus × domestica Borkhauser) of ‘Bisbee Delicious’ (a spur type), ‘Triple Red Delicious’ (a nonspur type), ‘Golden Delicious’, and ‘Red Stayman 201’ were subjected to various levels of European red mite, Panonychus ulmi (Koch), injury for 3 yr after planting. Mite injury (as measured by the mean seasonal cumulative mite days for the 3 seasons) ranged from 35 to 1,821 for the experimental trees. Dry matter accumulation in tree partitions was measured at the end of the 3rd growing season, and the effect of mite injury was analyzed. All 4 cultivars tested responded to mite injury in a similar manner, although tree size was influenced greatly by intrinsic differences among cultivars. Reductions in dry matter accumulation in the tree as a whole, the aerial portions, and the root systems occurred as a result of mite injury. The percentage of reduction per 1,000 mite days was greatest for the root system (7-12%), whereas reductions in other partitions averaged about 6%. The effect of mite injury during the non bearing phase, although statistically significant, is not a likely critical factor in the establishment and early production of an orchard. The importance of establishing biological mite control with Stethorus punctum (LeConte) early in the life of an orchard outweighs any negative effects on early growth.

Effects and Control of Periodical Cicada (Homoptera: Cicadidae) Oviposition Injury on Nonbearing Apple Trees

Four netting and five insecticide treatments were evaluated for the protection of nonbearing apple trees from periodical cicada, Magtcicada septendecim (L.), oviposition injury. A green, tubular, 1-cm-mesh netting excluded cicadas and was the most effective treatment. Netting of larger mesh sizes permitted entry and oviposition injury comparable with that observed on controls. Oxamyl, methomyl, and esfenvalerate were similar in providing excellent knockdown of cicadas; however, only treatment with esfenvalerate resulted in a significant reduction in oviposition injury. Tree height, tree volume, number of scaffold limbs per tree after pruning, and percentage of change in trunk cross-sectional area were significantly and negatively correlated with the number of oviposition scars per tree. When all costs associated with the use of insecticides for cicada control are considered, tubular netting is about 15% more expensive than chemical control with handgun sprayer at all tree densities, but cheaper than control with airblast sprayer at a tree density of 250 per ha.

Growth Reduction in Nonbearing Apple Trees by Woolly Apple Aphids (Homoptera: Aphididae) on Roots

The effect of root-feeding populations of woolly apple aphids, Eriosoma lanigerum (Hausmann), on newly planted, nonbearing apple trees in an orchard environment was studied. Roots of two-thirds of the 351 ‘Red Delicious’ study trees were artificially infested with woolly apple aphids from a laboratory colony in 1986, 1 mo after planting. The artificial infestation resulted in 95% of the trees being infested (including controls), but did not produce more severe root infestations per tree than expected in natural infestations. The root infestation rating (mean = 0.35 on a scale of 0-1, SEM = 0.18) determined from destructive sampling of one-third of the orchard after three growing seasons was not correlated with population density above ground throughout the 3 yr of the study. Root feeding marginally reduced branch growth in the first and third year after infestation, crown length in the third year, and trunk diameter in the first and second years. Crown length was significantly reduced after 1 yr and trunk diameter was significantly reduced after 3 yr because of woolly apple aphid feeding on roots. Scion biomass also was significantly reduced by woolly apple aphid root feeding after 3 yr. We conclude that woolly apple aphid populations on roots have a slight, but significant, negative effect on growth of young non bearing apple trees in the orchard environment. We also conclude that, because of the lack of correlation between woolly apple aphid populations aboveground and on roots, sampling branch terminals and pruning scars yields no information on the density of woolly apple aphids on roots.

European Earwigs (Dermaptera: Forficulidae) Fail to Control Apple Aphids on Bearing Apple Trees and Woolly Apple Aphids (Homoptera: Aphididae) in Apple Rootstock Stool Beds

Insectary-reared and wild European earwigs, Forficula auricularia L., provided with artificial daytime retreats on bearing apple trees infested with apple aphids, Aphis pomi DeGeer, failed to slow aphid population growth. The difference between this result and earlier success on nonbearing apple trees is not explained. Caged earwigs damaged a few apple fruits by feeding at the calyx end, but no damage to fruit and only minimal damage to leaves was observed when earwigs were allowed free movement. Earwigs released and caged on apple rootstock stool beds after suppression of apple aphids by insecticide treatment prevented resurgence of apple aphids but had no apparent effect on infestations of woolly apple aphids, Eriosoma lanigerum (Hausmann).

Effects of succinic acid-2,2-dimethyl hydrazide (Alar) or scoring on growth and flower initiation of young apple trees

Foliar sprays of the growth retardant succinic acid-2,2-dimethyl hydrazide (Alar) applied early in the spring on young non-bearing Delicious, Granny Smith, and Gravenstein apple trees reduced the extension growth and increased the amount of bloom in the following spring. Scoring (a knife cut completely around the trunk) in late October and during November on Granny Smith, and Gravenstein trees increased the amount of bloom in the following year. When scoring has performed in early December the response to flowering on Gravenstein variety was greatly reduced. Scoring reduced the extension growth on Granny Smith but not on Gravenstein variety. The use of either Alar or scoring offer practical ways of promoting earlier flowering and cropping of young non-bearing apple trees.

Sampling and Distribution of Summer Eye-spotted Bud Moth Spilonota ocellana (D. & S.), Larvae and Nests on Apple Trees

Summer larvae of the eye-spotted bud moth, Spilonota ocellana (D. and S.), appeared in unequal densities on certain portions of apple trees in Door County, Wisconsin. The resulting non-random distribution introduced a bias in data obtained of the summer larvae. This phenomenon has been reported in Quebec apple orchards (LeRoux and Reimer, 1959) where densities of summer larvae were consistently greater in the upper than in the lower tree levels, and quadrant differences often occurred in the number of eggs parasitized, spring and summer larval shelters, and pupal shelters. The present study was initiated to determine the extent of the uneven distribution of summer eye-spotted bud moth larvae and nests on young, non-bearing apple trees. Summer larvae appear shortly after the first of August when eggs begin to hatch (Oatman, 1960).

Absorption of essential nutrient elements by apple trees in water culture. 1

1. At the Horticultural Division of National Tohoku Agricultural Experiment Station, the authors have continued their attempt to culture apple trees in nutrient solution, and to grow normally throughout 4-5 years successively. 2. In 1951 and 1952, two-year-old non-bearing apple trees, of American Summer Pearmain, McIntosh, Jonathan, Starking Delicious, and Rall's Janett, grown in nutrient solution previously for a year, were cultured successively to study the sea-sonal nutrient (N, P, K) absorption. 3. 35-l grazed earthenware pots were used. During the season, the solution was aerated by bubbling method continuously, and was changed every other weeks at. the same time, chemical analysis of the solution and the measurement of plant growth(total weight, shoot length, etc.) were performed. The composition of the nutrient solution used were modified HOAGLANDS formula (Table 1), and in these solutions, enough residual nutrient ions were found even at the end of two weeks period. 4. It was proved from this study that, in water culture, apple trees are able to be grown more vigorously than the field condition, 5 years or more successively. 5. N absorption increased gradually from the time of growth start to midsummer, in parallel with the rising of atmospheric (water) temperature and growth increase, and reached its maximum at the time of the highest temperature (late July to early August). Then it decreased gradually with the descent of temperature, and, consequently, the N absorption after defoliation was little. Thus, seasonal absorption of N by apple trees in water culture was closely related to the change of atmospheric (water) temperature. 6. The seasonal absorption curves of K were quite different from that of the nitrogen. K absorption increased rapidly at the biginning of early growth, and reach its highest point in the early or middle June, when the shoots began their active growth. This highest level of K absorption continued for a while, till most shoots terminate their growth, however with several fractuations in the course. Then decline of absorption was apparent in accord with the decrease of shoot growth. Apparently, absorption of K related closely to the growth of shoots. 7. The absorption curve of phosphorous was quite analogous to that of N, but, in this case, there was no maximum and absolute amount of absorption was much less than that of N absorption. 8. The absorption process of water (transpiration) was almost identical with that of atmospheric temperature, accordingly this process was analogous to that of nitrogen. The quantity of the absorbed water throughout the season was unexpectedly great. 9. It seems to be found there are some correlations between the nitrate absorption and growth of fibrous roots. 10. With few exceptions, the nutrient absorptions, especially N, were closely related to the growth rate of trees. 11. The mean absorption ratio of N, P, K wereseparately 100:13. 3:46.3. 12. The varietal difference of nutrient absorption process could not be ascertained. 13. The model figure for the seasonal absorption process of N, P, K and water, and for growth process is shown in Fig. 11.