The first objective of this study was to assess the effects of coconut shell biochar in propagation substrate on seed germination and seedling growth of Coreopsis grandiflora (Hogg ex Sweet) ‘Early Sunrise’, Leucanthemum ×superbum (Bergman ex J. Ingram) ‘Silver Princess’, and Eschscholzia californica (Cham.). Cornell seed germination mix was amended with the biochar (0%, 5%, 10%, 20%, or 40%, v/v). Seed germination and seedling growth were determined during a 21-day period in two germination rooms. This particular biochar amendment did not affect final germination percentage for any of the species. All three species had seedling shoot and primary root length growth with low to moderate positive correlation (r = 0.33–0.54) with coconut shell biochar amendment volume. Coreopsis seedling dry weight was significantly higher with 40% biochar than the control (P ≤ 0.05). The second objective of the study was to compare digitally collected data with manually collected data. Two-dimensional scans of Coreopsis and Leucanthemum seedlings were collected. Seedling dry weight (mg) and seedling length (mm) predicted seedling two-dimensional area for Coreopsis (R2 = 0.73, P < 0.001) and Leucanthemum (R2 = 0.87, P < 0.001). Digitally traced shoot and root lengths were strongly positively correlated (r = 0.99–0.97) with manual ruler measurements, suggesting that digital imaging could replace manual length measurements. The results of this study suggest inclusion of this particular coconut shell biochar in seed germination, and establishment substrates can have neutral or positive effects on herbaceous perennial germination and establishment.
Indole-3-butyric acid (IBA) is frequently used to promote adventitious root development in plant propagation from cuttings. We evaluated the effects of 0, 1000, or 3000 ppm IBA applied as a liquid foliar spray or talc-based basal dip on adventitious rooting of wall germander (Teucrium chamaedrys) cuttings. An initial experiment was conducted in Fall 2016, followed by a replication in Spring 2017. Two-dimensional root area, primary root count, root dry weight, and a rooting index (0 to 5 scale) were assessed as measures of root growth. By all metrics and for both experiments, cuttings benefited from IBA application and exhibited equal or greater root growth after the foliar spray treatment compared with the talc dip. In both experiments and for all metrics, the talc dip method achieved no greater root growth at 3000 ppm IBA than the foliar spray method at 1000 ppm IBA. These results suggest that for wall germander, IBA application by the foliar spray method is equal or superior to the talc dip method presently in widespread use in the horticulture industry.
The susceptibility of fraser fir (Abies fraseri), canaan fir (A. balsamea var. phanerolepis), and nordmann fir (A. nordmanniana) to phytophthora root rot (PRR) incited by Phytophthora cactorum or P. drechsleri was assessed in two experiments in central Pennsylvania. In an 8-week greenhouse study, seedlings and transplants growing in soilless substrate were inoculated with Phytophthora in flooded and non-flooded settings. In an 8-week outdoor study conducted in raised planting boxes filled with soil, transplants were inoculated with Phytophthora species in well-drained and poorly drained soil. Based on foliar disease ratings, mortality rates, and dry shoot and root weights, differences in susceptibility to P. cactorum and P. drechsleri existed between these true fir (Abies) species. Fraser fir was very susceptible to P. cactorum and P. drechsleri. Canaan fir had strong resistance to P. cactorum and P. drechsleri in well-drained settings but was susceptible in poorly drained settings. Nordmann fir had very strong resistance to P. cactorum and P. drechsleri in both well-drained and poorly drained settings.
The most serious disease problem in fraser fir (Abies fraseri) Christmas tree production is phytophthora root rot (PRR). The efficacies of six fungicide treatments in preventing PRR incited by Phytophthora cactorum and P. drechsleri in 2-year-old fraser fir seedlings were evaluated in 2010 and 2011 in central Pennsylvania. The study examined five fungicide drench treatments [dimethomorph, fosetyl-aluminum (fosetyl-Al), hydrogen dioxide, mefenoxam, propamocarb hydrochloride] and one soil spray treatment (mefenoxam) in raised planting boxes. Dimethomorph applied on 14-day intervals prevented foliar disease symptoms and mortality in fraser fir seedlings exposed to either P. cactorum or P. drechsleri. One-time application of fosetyl-Al or mefenoxam were effective at times in preventing foliar disease symptoms and mortality in fraser fir seedlings exposed to P. drechsleri but were not as effective against P. cactorum.