Chemical and Biological Control of Dracaena marginata Leaf Spots in Northern Egypt

Abstract

Six common fungicides, Dithane M45, Kocide 2000, Ridomil Gold Plus, Score, Equation Pro and Kemazed were tested for controlling the draceana leaf spot fungi. All the tested fungicides significantly decreased the in vitro growth of the tested dracaena leaf spot fungi. Percentage of inhibition on colony diameter ranged between 49.64% with Dithane M45 to 82.18% with Score which was followed by Kemazed (69.15%). However, inhibition of spore germination was the highest (72.8%) by Dithane M45, while inhibition of germ tube reached 89.91% with Kemazed. Meanwhile, in the in vivo tests, treatment with Kemazed decreased disease incidence of leaf spots on potted plants to 16.67% compared to 100% for the untreated inoculated control. On the other hand, the bacterial and fungal biocontrol agents tested proved to be effective against the dracaena leaf spot fungi. The in vitro assays conducted showed that the bacterial biocontrol agents namely, Stenotrophomonas maltophilia, Pseudomonas ultimum, P. fluorescens, P. putida, P. aeruginosa, Bacillus subtilis, B. megaterium, significantly decreased colony growth diameter (76.84-45.69%) of dracaena leaf spot fungi as well as spore germination (48.80-23.20%) and length of germ tube (88.77-65.65%) of the germinated spores compared to untreated control. Treatment with S. maltophilia showed the most consistent highest inhibition effect, followed by P. ultimum, B. subtilis, and B. megaterium, respectively. The in vivo tests of the most effective bacterial bioagents supported the in vitro results. Treatment with S. maltophilia showed the highest effect as it decreased disease incidence and disease index to 29.33% and 7.6%, respectively in comparison with 100% and 83.6% for the untreated inoculated control in the potted dracaena plants (cv. Bicolor). Meanwhile, the in vitro tests of the three Trichoderma spp., i.e. T. harzianum, T. hamatum and T. album showed significant inhibition effect on colony growth diameter of the tested dracaena leaf spot fungi in which T. harzianum showed the highest inhibition effect (75.02%), while T. album was most effective to inhibit spore germination (48%) and germ tube (90.21%) of the germinated spores. The in vivo tests of the fungal biocontrol agents supported the in vitro results. T. album (Bio-Zeid) showed the highest effect and decreased disease incidence and disease index on potted plants to 19.99% and 4.39%, respectively compared with 100% and 92.8% for the untreated inoculated control.

Occurrence of Stem and Leaf Spots on Lucky Bamboo (Dracaena sanderiana hort. ex. mast.) Plants in Vase and its Cure with Safe Means

“…Commercial name and formulation The in vitro inhibition effect of bioagents and Kemazed: According to Hilal et al (2016), before hardening the PDA medium, the Kemazed at the recommended rate (0.075g/100ml) was added. After the PDA had solidified, each dish was centrally inoculated with a mycelial disc (1 cm) of the tested fungi.…”

“…One disk came from the tested fungi margins of seven-day-old advancing cultures, while the other came from Trichoderma spp., on the plate's opposite sides both plugs were positioned 1.5 cm from the edge of the plate. At the end of the test, the colony growth of the tested fungi was determined in every treatment and the percentage reduction in the tested fungi's colony growth was calculated using the formulas of Ferreira et al (1991) and Uribe and Loria (1994) as follows: Also, according to Hilal et al (2016), bacterial powder of the commercial product of Bacillus subtilis 0.4 g/100ml and B. megaterium 0.25 g/ 100ml was grown on nutrient agar and incubated at 30±2°C for 24 hours. Then streaking solid PDA medium plates, then at a distance of 25 mm, on the opposite side, one disc (0.5 cm) from a 7-day-old culture of one of the tested fungi was placed.…”

“…However, several fungal diseases, including Antharacnoses caused by, Colletotrichum gloeosporioides, C. dracaenophilum, C. petchii and C. boninense, have been reported to affect bamboo plants in Egypt, as well as other countries around the world (Bobev et al, 2008, Liu et al, 2014, Macedo and Barreto, & Morsy and Elshahawy, 2016 subglutinans as a result of stem rot, while leaf spots were caused by Aspergillus niger and Alternaria alternata (Abbasi andAliabadi, 2008 andHilal et al, 2016).…”

“…Morsy and Elshahawy (2016) found that using a systemic fungicide (Kemazed ® ) in combination with other fungicide formulations can effectively control Colletotrichum dracaenophilum on bamboo diseases. Siddique et al (2014) and Hilal et al (2016), stated that although chemical control of plant diseases may be the simplest and quickest method, the environment, health risks, and the ongoing development of new strains of pathogens resistant to the chemicals used call for safer alternatives.…”