Browsing Plant Diseases by Issue Date
Now showing items 1-20 of 36
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Nondormant Alfalfa Varieties for Arizona 2017Alfalfa varieties differ in fall dormancy, defined as growth during the fall. Nondormant alfalfa varieties are usually planted in mild winter areas for their ability to grow in the fall. However, fall growth of nondormant alfalfa may be undesirable in areas subject to repeated frosts or freezes. Nondormant, very nondormant, and extremely nondormant alfalfa varieties (fall dormancy class 8, 9, and 10) are adapted to elevations below 4000 feet in Arizona. Other dormancy classes not included in this publication are moderately nondormant varieties (fall dormancy class 7) which may be grown from 3000 to 5000 feet, and semi-dormant and dormant varieties (fall dormancy 6 and below) which are adapted to colder winter areas above 4000 feet.
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Biology and Management of Downy Mildew of LettuceThis publication describes the factors affecting development of downy mildew of lettuce and provides disease management strategies.
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Control of Brown Wood Rot in Lemons with Low Pressure Injection 2013-14We injected AGRA PHOS (Potassium Phosphite) 0-2.4-2, Propiconizole – 0.05%, Zn, Mn and Fe 0.105, 0.112, and 0.10% respectively, Zn, Mn and Fe 0.210, 0.220, and 0.200% respectively and Propiconizole – 0.05% + Zn, Mn and Fe 0.105, 0.112, and 0.10% respectively using a low pressure injection system for the control of Antrodia sinuosa in lemon trees. No treatment led to a significant reduction in fungal growth.
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Biology and management of Fusarium wilt of lettuceThis publication provides information on the development and management of Fusarium wilt of lettuce. Topics covered include the characteristics of the plant pathogen, disease development, and disease management considerations.
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Cultural Practices for Karnal Bunt ControlEnvironmental conditions between awn emergence and the end of flowering is the overriding factor in disease development. 2 The University of Arizona Cooperative Extension Cultural practices may be partially effective in controlling Karnal bunt but cannot eliminate the disease completely. Karnal bunt is most likely to be found in areas where lodging or water ponding have occurred.
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Pine Bark BeetlesPine bark beetles in Arizona are generally of the genus Ips or Dendroctonus. Fading foliage in the tree is often the first sign of a beetle attack. Prevention is best practiced since control is not possible once the beetles have successfully colonized the tree. Colonization is dependent upon trees being in a vulnerable condition caused by stress from various agents and site conditions.
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Cotton (Texas) Root RotThe most important disease of woody dicotyledonous plants in Arizona is Phymatotrichopsis root rot (Cotton or Texas root rot) caused by a unique and widely distributed soil-borne fungus, Phymatotrichopsis omnivora. The fungus is indigenous to the alkaline, low-organic matter soils of the southwestern United States and central and northern Mexico.
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Control of Brown Wood Rot in Lemons with Low Pressure Injection 2012We injected AGRA PHOS (Potassium Phosphite) 0-2.4-2, Propaconizole – 0.05%, Propaconizole plus Azoxystrobin – 0.117 and 0.135% respectively, Zn, Mn and Fe 0.105, 0.112, and 0.10% respectively, and Azoxystrobin – 0.137% using a low pressure injection system for the control of Antrodia sinuosa in lemon trees. The Propaconizole + Azoxystrobin treatment, the Azoxystrobin treatment, and the Zn + Mn + Fe treatment led to significantly less fungal lesion growth when applied prior to the introduction of the fungus, as compared to their application after fungal introduction.
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Susceptibility of Mesquite Species to Powdery Mildew in ArizonaMesquite (Prosopis sp.) is a popular tree in landscapes in Arizona because of its drought tolerance and attractive growth habit. Powdery mildew has been observed from late summer until early spring on mesquite leaves. It has been identified as Pleochaeta polychaeta based on morphological descriptions and comparison to herbarium specimens. Surveys were conducted in fall 2008 through winter 2009 at two locations in southern Arizona to determine the susceptibility of different mesquite species to powdery mildew. Twelve mesquite trees representing two species were sampled at Texas Canyon near Willcox, AZ, and 177 trees representing eight species were sampled at the University of Arizona campus in Tucson, AZ. The North American mesquite species P. glandulosa var. glandulosa and P. velutina were infected with powdery mildew at the University of Arizona campus and P. velutina at the Texas Canyon site. No powdery mildew was observed on P. alba, P. cinerea, P. nigra, P. chilensis, P. pubescens and P. chilensis x flexuosa. The powdery mildew affects the aesthetic value of severely infected trees but seems to have little effect on long term tree health.
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True MistletoesTrue mistletoes are parasitic flowering plants with characteristic clumps of growth that are easily visible on the host plant. They reduce the growth of infected hosts, but it usually takes many years for true mistletoe infections to kill a mature tree or shrub. This article gives information about the disease cycle, the symptoms and prevention and control methods for true mistletoes.
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Root-knot nematodeNematodes are microscopic round worms found in many habitats. They are the most abundant multicellular organisms on earth. Most are beneficial memebers of their ecosystems, but a few are economic parasites of plants and animals. There are several plant parasitic nematodes that cause problems on landscape and garden plants in Arizona and the most widespread and economically important are the root-knot nematodes. This article discusses the hosts and environmental conditions, symptoms and disease of root-knot nematode, and the prevention / control method to it.
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Sooty CankerSooty canker causes cankers and dieback in tree branches. This article briefly explains the host, symptoms, environmental conditions, disease and preventing / controlling method for sooty canker.
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Verticillium WiltVerticillium Wilt causes wilting and yellowing of leaves, death of limbs, often on one side or a portion of the plant. This article provides information on the disease caused by Verticillium Wilt including the host, symptoms, environmental conditions, disease and the preventing / controlling method.
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Dwarf MistletoesDwarf mistletoes are parasitic flowering plants that grow within host plants for about two years before producing characteristic yellow to orange or green to brown leafless aerial shoots on the outside of infected host tissue. They occur only on conifers in the pine family in Arizona and are usually host specific. This article gives information about the disease cycle, the symptoms and prevention and control methods for dwarf mistletoes.
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Damping OffDamping off is caused by several different fungi under different environmental conditions. The fungi include Pythium, Rhizoctonia solani, and Thielaviopsis basicola. This article discusses the symptoms, environmental conditions, diseases, prevention and control methods for the damping-off caused by fungi.