4 Control:Take special care during transplanting to avoid excessive planting depth and wounding of stem and root tissue.Avoid excessive soil compaction during the transplant operation.Water carefully; avoid overwatering.Drench-applied fungicides can be effective in controlling this disease problem.
6 Phytophthora root rotPhytophthora root rot is caused by several species of fungi in the genus Phytophthora.Phytophthora cinnamomi is usually credited with causing the greatest damage to container- and field-grown woody ornamentals.P. parasitica, P. citricola, and possibly P. cactorum, are also known to attack woody plants, particularly azaleas and rhododendrons.Phytophthora cryptogea has been known to cause heavy damage on junipers in poorly drained landscape beds
7 Phytophthora Root Rot Symptoms: Phytophthora root rot greatly reduces the volume of the roots which are needed by the plant to absorb water and nutrients.The roots on diseased plants are brittle and brown to reddish-brown in color.A network of fine, discolored feeder roots may be confined to one area or include the entire root system. The fungus usually colonize the crown of the plants, often girdling the stem at or just above the soil line. A brown to reddish-brown discoloration of the tissues occurs just below the bark and may extend up the stem above the soil line.On some trees and large shrubs--such as dogwood--brown, water-soaked cankers oozing a dark-colored fluid or gum may develop at the soil line.
10 Phytophthora Root Rot Symptoms: These symptoms can easily be confused with those of a nutritional disorder, overwatering, drought stress, and a number of other factors and so can be overlooked by the grower.Slight yellowing of the leaves followed quickly by permanent wilting and plant death are the symptoms usually associated with Phytophthora root rot on container-grown azaleas and rhododendronsIn landscapes, established plants may show symptoms of general decline for one or more years before succumbing to root rot, while newly planted azaleas will quickly die.
11 Phytophthora Root Rot Symptoms: Symptoms vary according to the degree of root colonization by Phytophthora root rot fungi, plant age, plant susceptibility to root rot, and environmental stress.Typically, symptoms first appear on one plant and later on surrounding plants in both container areas and landscape beds. Some yellowing of the foliage, particularly at the shoot tips, leaf shed, slowed plant growth, and possibly limb dieback may occur in early stages of the diseaseHowever, it is not uncommon for liners or container-grown plants to remain almost symptomless until after transplanting into larger containers or landscape beds.
12 Phytophthora Root Rot of Gardenia Phytophthora nicotianae
13 Phytophthora Symptoms: The foliage of azaleas and rhododendrons may also be invaded by some Phytophthora root rot fungi.Irregular blotches which are first olive-colored and later brown, sometimes with a red margin, develop on the leaves.Diseased leaves are usually shed by the plant.Damage usually appears on limbs near the base of the plant.
17 Disease CyclePhytophthora spp. survive as resting structures (chlamydospores and oospores) and mycelia in diseased roots, crowns, and other crop debris.The resting structures are released into the soil or potting media from infested crop debris and are readily spread from pot to pot throughout propagation and container production areas by soil and splashing or flowing water.Recycled irrigation and runoff water has been implicated as a source of these fungi in rhododendron nurseries.
18 Disease CycleHeaviest losses to root rot in most container production nurseries usually occur on flat, poorly drained beds where water is allowed to stand around container basesOverwatering in the nursery or landscape will also contribute to losses from the disease.Phytophthora root rot is most commonly seen in field production nurseries and landscape plantings on poorly drained, waterlogged soils that are prone to flood. Disease development is usually slow or absent on well-drained sites.
19 Control:Prevention is the key to controlling Phytophthora root rot in commercial nursery stock. Once symptoms start to appear, much of the damage has already been done.No single control measure will ensure protection from Phytophthora.Several approaches must be directed at preventing the introduction and spread of these fungi and at preventing conditions favorable for disease development.These approaches include proper establishment and production practices, disease resistance and chemical control
20 Fusarium Stem Rot - Dieffenbachia Caused by Fusarium solaniInfection takes place at the soil lineThis is followed by the production of a brown spot.As the tissue dies, it becomes tan and falls away, removing tissue from the edge to the heavy center vein tissue
22 Fusarium Wilt Caused by Fusarium solani Infection takes place in the rootsLower leaves turn yellow and wilt, followed by overall plant wilting and death of entire plant. Lower portion of stem near soil line turns dark brown-to-black with brown discoloration in vascular tissues.
27 ManagementPlanting disease-free cuttings, sterilization of potting soil and benches offer best means of control.Do not injure plants at the soil line.Apply iprodione (Kidon, Rovral, Chipco 26019) or etridiazole (Truban, Terrazole) + Thiophanate-methyl (Banrot) to protect healthy plants.
28 Anthracnose and brown leaf spot Caused by (Colletotrichum spp. or Leptosphaeria spp.)Occur throughout the world in greenhouse and indoor landscapes.
29 Symptoms/SignsSymptoms of two leaf spots are very similar, with both occurring primarily during the cooler, winter months.Leaf spots are initially tan and water-soaked and may have a bright yellow halo.Fruiting bodies of the causal organism (Glomerella or Colletotrichum spp. [anthracnose]) or Leptosphaeria sp. (brown leaf spot) appear in concentric rings of tiny black specks within the leaf spot.