Michele Renee Warmund

Tomato (Solanum lycopersicum L.) plants are commonly injured by the off-target movement of synthetic auxin herbicides. A greenhouse and a field trial were conducted to determine the relative tolerance of eight fresh market tomato cultivars to drift-simulating rates of dicamba or 2,4-D. Tomato cultivars included ‘BHN 589’, ‘Celebrity’, ‘Florida 91’, ‘Mountain Merit’, ‘Primo Red’, ‘Red Deuce’, ‘Red Morning’, and ‘Skyway’. Dicamba (3,6-dichloro-methoxybenzoic acid) and 2,4-D (2,4-dichlorophenoxyacetic acid) were applied at 2.8 g ae ha⁻¹ and 5.3 g ae ha⁻¹-D, respectively. By 14 weeks after treatment (WAT), herbicide-treated plants of each cultivar produced less total and marketable yield than their respective nontreated control in the greenhouse trial. For most cultivars, dicamba-treated plants had less marketable yield than 2,4-D-treated plants in the greenhouse. Herbicide treatments also reduced total and marketable yields of each cultivar when compared with their control in the field study at 14 WAT, except for ‘Mountain Merit’. The severity of yield loss from herbicide treatments was cultivar-dependent. Field-grown ‘Skyway’ plants treated with dicamba produced the lowest marketable yield. In contrast, herbicide-treated plants of ‘Florida 91’ produced high marketable yields in the field, but ‘Red Deuce’ plants receiving 2,4-D were also highly productive. Herbicide residue in fruit sampled the third week of the harvest was nondetectable. Because the type of auxin herbicide drift is often unanticipated, ‘Florida 91’ may be the preferred cultivar for cultivation among those tested to maximize tomato production in the field.

The use of dicamba and 2,4-D products on herbicide-tolerant crops has resulted in numerous cases of off-target movement and injury to sensitive plants, including tomato ( Solanum lycopersicon L.). Two greenhouse studies were conducted to determine whether ‘Big Beef’ (‘BB’) or ‘Florida 91’ (‘FL’) tomato plants pretreated with an antitranspirant, including Moisture-Loc (ML) at 100 mL·L ⁻¹ , TransFilm (TF) at 50 g·L ⁻¹ , or Wilt-Pruf (WP) at 100 mL·L ⁻¹ , mitigated injury from synthetic auxin herbicides. Dicamba or 2,4-D was applied at a rate corresponding to 1/200 of the manufacturer’s labeled rate of 0.56 kg ae/ha or 1.06 kg ae/ha, respectively. At 2 weeks after treatment (WAT), plants treated with ML or WP before either herbicide exhibited injury symptoms, but they were always less severe than those treated with the herbicide alone for both cultivars. However, shoot length measurements indicated that none of the antitranspirants consistently provided protection against herbicide injury at 2 WAT. By 12 WAT, ML or WP used before either herbicide increased the number of live reproductive organs compared with dicamba or 2,4-D alone for both cultivars. Floral abortion on tomato plants was also reduced when ML or WP was applied before an herbicide treatment by 12 WAT. Although WP and ML did not provide complete protection against synthetic auxin herbicide injury, the concept of using film-forming barriers may be useful in mitigating some of the short-term effects of drift on plants.

Cane dieback and foliar necrosis caused by an unknown pathogen were observed in elderberry ( Sambucus nigra subspecies) plantings in early Spring 2016. Studies were conducted to identify the causal organism and determine the effects of infection on vegetative growth and fruiting of selected elderberry cultivars under controlled conditions. A Heterophoma sp. was isolated from symptomatic ‘Ranch’ elderberry canes growing in a commercial planting in Missouri. In the subsequent 2017 experiments, all canes of ‘Bob Gordon’ plants inoculated with this Heterophoma isolate had reduced cane lengths, reduced numbers of leaves and leaflets, and failed to produce fruit. In a study using ‘Scotia’, none of the 32 inoculated canes had symptomatic tissue; but in a subsequent study, one of 16 inoculated canes had slight cane dieback, indicating a potential difference in cultivar susceptibility to the pathogen. In 2018, seven elderberry cultivars (‘Adams II’, ‘Bob Gordon’, ‘Marge’, ‘Ozark’, ‘Scotia’, ‘Wyldewood’, and ‘York’) were inoculated with the same Heterophoma isolate, which was subsequently reisolated from the boundary of symptomatic and asymptomatic tissue, thereby confirming pathogenicity of the fungus. The fungus was tentatively identified as H. novae-verbascicola (Aveskamp, Gruyter & Verkley) Q. Chen & L. Cai based on analysis of genomic DNA from the internal transcribed space (ITS) region. Only two of 16 ‘Scotia’ inoculated canes had cane dieback in 2018, whereas inoculated canes of all other cultivars developed symptoms. Cane and foliar growth of each inoculated cultivar was less than the associated noninoculated control at 14, 30, and 60 days after treatment (DAT). Among inoculated symptomatic plants, ‘Marge’ canes produced more vegetative growth than all other cultivars, and ‘Adams II’, ‘Ozark’, and ‘York’ canes generally produced the fewest number of leaves and leaflets at 60 DAT. Flowering was observed on canes of noninoculated control plants, but not on inoculated symptomatic canes by 60 DAT. Thus, the newly reported cane dieback disease of elderberry, caused by Heterophoma sp., adversely affected plant growth and fruiting of Sambucus nigra subspecies. However, ‘Scotia’ elderberry plants were less susceptible to the fungal infection than other cultivars, indicating that it may be possible to use ‘Scotia’ to develop new elderberry cultivars with improved resistance to infection by Heterophoma.

Elderberry rust ( Puccinia sambuci Schwein.) Arthur (= P. bolleyana ) (Arthur, 1921) disease is frequently found in commercial American elderberry ( Sambucus nigra L. subsp. canadensis L.) plantings when an alternate host, Carex sp., is present. To evaluate potential infection periods of P. sambuci on elderberry plants, micrometeorological conditions were monitored. Rust symptoms were observed on elderberry on 5 Apr. 2016, and conditions favorable for possible infection were 9 to 18 °C, ≥3 hours of continuous leaf wetness, and ≥85% relative humidity. Studies were also conducted to ascertain whether P. sambuci with varying pustule numbers affects fruiting, berry puree quality, or vegetative growth. Fruit yield was reduced by 31% when potted ‘Bob Gordon’ elderberry averaged six rust pustules per plant compared with noninfected plants. In another experiment, field-grown ‘Wyldewood’ plants averaging 137 rust pustules/cane at harvest had 47% less fruit weight on canes than uninfected canes. Titratable acidity of fruit puree from plants was lower when plants had either 690 rust pustules/plant or 137/pustules/cane, but soluble solids and pH of puree were unaffected by P. sambuci infection. The effect of rust infection on vegetative growth of elderberry plants also varied with pustule numbers. With a low infection level (six pustules per plant), P. sambuci did not induce premature leaf loss on ‘Bob Gordon’ plants or adversely affect shoot dry weight at the end of the growing season. When P. sambuci infection on ‘Wyldewood’ plants was more severe (137 pustules/cane), greater leaf loss occurred on infected canes than on uninfected canes. At very high infection levels (690 pustules/plant), ‘Bob Gordon’ plant dry weight was reduced. Because of the potential for fruit yield loss on elderberry plants, control of P. sambuci at relatively low infection levels on this plant may be warranted. Strategies that eliminate or suppress the alternate host would likely reduce the P. sambuci inoculum and limit the potential for elderberry plant infection.

Eastern black walnut ( Juglans nigraL.) seeds typically require a long period of stratification and often have low germination. A study was conducted to evaluate the effect of three formulations of gibberellic acid at 250 mg·L -1or tap water as a soaking treatment for ‘Thomas’ black walnut seeds for 24 h before stratification for 30, 45, 60, 75, or 90 d. Gibberellic acid treatments included 1) GA 3(ProGibb®); 2) GA 4+7(Provide®); and 3) 6-benzyladenine (BA) + GA 4+7(Promalin®). Percent walnut shoot emergence 60 days after planting, days to 20% and 80% shoot emergence (E20 and E80), and early seedling growth from black walnut seeds were evaluated. Percent shoot emergence was always higher for seeds soaked in GA 4+7or BA + GA 4+7when compared with other treatments. Shoot emergence for some seeds soaked in GA 4+7and BA + GA 4+7occurred with 30 d stratification and percent emergence increased with longer stratification periods. Seeds soaked in GA 3had higher percent shoot emergence than those soaked in tap water only. Also, seeds soaked in GA 3had fewer days to 20% shoot emergence when stratified for 45 or 60 d than those soaked in tap water and stratified for the same period of time. Addition of BA at 250 mg·L -1apparently did not enhance percent shoot emergence, E20, E80, or seedling height or weight. With timely harvest, hulling, seed selection, and soaking walnuts with 250 mg·L -1GA 4+7followed by 90 d stratification, 82% shoot emergence (i.e., germination) was attained.

Development of nitrogen (N) fertilization guidelines for Chinese chestnut trees in North America has been hampered by the paucity of research-based information. Thus, a study was conducted to determine the effect of selected annual N application rates (56, 84, 112, 140, or 168 kg·ha -1) on vegetative growth and fruiting of young ‘Peach’ Chinese chestnut ( Castanea mollissimaBl.) trees applied in four sequential years. Foliar N and other macro-and micro-nutrient levels were also determined to establish survey ranges for North American-grown Chinese chestnut. Cumulative nut yield, nut number, and trunk circumference increased linearly as the rate of N increased. Estimated net profitability during three years of nut production increased by 43% when annual N applications were increased from 56 to 168 kg·ha -1. Foliar N of chestnut trees producing the greatest cumulative nut yields during the early years of cropping ranged from 2.23 to 2.51%. The survey range was 0.09 to 0.16% for phosphorous (P) and 0.36 to 0.63% for potassium (K). Macro- and micronutrient survey ranges reported herein from leaves of ‘Peach’ Chinese chestnut trees provide baseline data for assessing their nutritional status.

Various elderberry ( Sambucus sp.) cultivars, including Bob Gordon, Marge, Ocoee, Ozark, Wyldewood, and York, have been selected primarily for plant productivity in North America and are most often processed into juice-based products. This study was conducted to quantify juice characteristics and to evaluate sensory attributes of juice from six elderberry cultivars using descriptive analysis. Hue angle values of ‘Bob Gordon’ and ‘York’ juices were low as compared with others tested. Soluble solids and titratable acidity of juices from ‘Wyldewood’ and ‘York’ were lower than those from other cultivars. Trained panelists identified 24 terms for descriptive analysis of elderberry juices. Of these 24 attributes, juices were highly characterized by a processed aroma, and several flavors, including processed, elderberry, fruity, and sweet. Unique juice descriptors for North American–grown elderberry cultivars included apple, beet, caramelized, fermented, processed, and pomegranate flavors, as well as astringent mouthfeel. Juices from elderberry cultivars differed in intensity ratings of nine attributes, including fruity, floral, sweet aromatics, bitter, sour, and sweet flavors, bitter and sweet aftertastes, and astringent mouthfeel. ‘York’ juice generally had high intensity ratings for sweet aromatics and sweet flavors, and relatively lower ratings for bitter aftertaste and astringent mouthfeel as compared with juices from other cultivars. This study provided key elements for future elderberry sensory research in the development of a formal lexicon for juice with defined attributes.

“Ambers” is a term used to describe poorly filled, shriveled eastern black walnut ( Juglans nigra L.) kernels with a dark brown or black-colored pellicle that are unmarketable. Studies were conducted to determine the incidence of ambered black walnut kernels and to ascertain when symptoms were apparent in specific tissues. The occurrence of ambered kernels was evaluated in fruit harvested from mature ‘Football’ trees growing at three sites within a commercial black walnut orchard in 2008 to 2010. Mature walnut fruit sampled from trees at Site 2 had greater odds for ambered kernels than those on trees at two other sites within the same orchard with 27% of the walnuts sampled exhibiting symptoms when examined in October. Also, black walnut fruit in 2010 had more ambered kernels than those examined in Oct. 2008 or 2009. Cropload, soil type, ambient temperatures, or precipitation was not apparently associated with a high incidence of ambered kernels. When black walnut fruit from trees at Site 2 were examined from 25 June to 6 Oct. 2011, embryos were visible in 50% of the fruit without discoloration on the first date. Stenospermocarpy (e.g., aborted or rudimentary embryos after fertilization) was observed in fruit with discolored or ambered kernels as early as 7 July. Stenospermocarpic fruit with ambered kernels had shorter embryo axis lengths (root apex to shoot apex) than fruit with non-ambered kernels on 7 July and at successive sampling dates. Cotyledon widths of ambered kernels in stenospermocarpic fruit were narrower than those of non-ambered kernels on 21 July, but symptomatic cotyledons continued to enlarge until 15 Sept. All fruit enlarged during the growing season and nut diameters varied by only 3.4 mm at harvest. Thus, visible embryo degeneration, which was associated with ambered kernels in black walnut fruit, was detected in early July when shell hardening occurs and kernel tissues are enlarging.

Studies were conducted to characterize altered tissues of larvae-infested buds and stem and leaf galls induced by Dryocosmus kuriphilus Yasumatsu on Chinese chestnut trees ( Castanea mollissima Blume) and to describe gall inhabitants. Bud and gall samples were collected from chestnut trees growing in Mantua, OH, on 2 Mar. and 3 May 2012, respectively, and prepared for microscopy. Uni- and multilocular larval chambers containing one D. kuriphilus larva per chamber were observed in buds and stem galls. Evidence of insect-modified Castanea cells was present as a two-layer zone of hypertrophied plant cells adjacent to the larval chambers before budbreak on 2 Mar. By 3 May, stem and leaf galls were in the growth and differentiation stage of development. Within galls, torn cell walls and disorganized organelles were visible in the protoplasm of cells surrounding ovoid-shaped larval chambers. A continuous layer of nutritive cells with large nuclei and nucleoli, abundant lipid bodies and mitochondria, and fragmented vacuoles was contiguous to larval chambers. At the outermost region of the nutritive tissue, cells had recently divided. Larger vacuolated cells, with slightly thickened walls, were observed surrounding recently divided cells. Thin-walled parenchyma cells in the chestnut gall cortex had large vacuoles with fewer organelles than those of the nutritive layer. Vascular tissue within the gall was connected with that of the plant host tissue outside the gall. In some chestnut galls, a single parasitoid larva was found attached to a D. kuriphilus larva. Each parasitoid larva had six pairs of setae on its head capsule, a pair of clypeal setae, a notched labrum, a semicircular lobed labium, 13 post-cephalic body segments, and rows of long, erect setae on all body segments.

Grafting failure of Chinese chestnut ( Castanea mollissima Blume) trees is common. Some researchers have suggested that secondary phloem fibers in chestnut rootstock stems may interfere with graft union formation. Others suggest that high rootstock moisture content may reduce grafting success. This study was conducted to ascertain the precise arrangement of secondary phloem fibers in Chinese chestnut seedling rootstocks and to determine if they are associated with grafting failure. We also investigated the effects of moisture content of rootstocks and container growing medium on grafting success. Nodes on Chinese chestnut seedlings had 2/5 phyllotaxy with five alternate buds present in two revolutions around the stem. Vascular cambium in 1-year-old rootstock stems was arranged in a regular five-lobed cylinder in cross-sections. Primary phloem fibers were present in a discontinuous ring and secondary phloem fibers were usually clustered outside the cambium between the lobes. Grafts were successful when scion buds were placed on the rootstock disrupting secondary phloem fibers with cambia of the budded tissues aligned. Containerized rootstocks at 56% and 62% growing medium moisture content before grafting had 25% graft union success rates, whereas non-irrigated plants at 48% moisture had a 75% success rate.