I have included on this page all of the citrus tree diseases that are known to be in Maricopa County. Each disease is linked to a page on this site.


If you need me to look at your trees give us a call. I've been doing this for fifty plus's years.

Warner

 

 

 

Warner’s Tree Surgery is a family business that consists of my wife Pat, who manages the office and answers the phones, and me - Warner Working.

 

We currently serve - Mesa – Gilbert - Tempe - Chandler - Queen Creek - Scottsdale – Paradise Valley - East Phoenix Arizona.

 

These are the serious citrus diseases that are known to be in Maricopa County AZ. in 2018

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Alternaria brown spot

Disease cycle 

Alternaria is spread by airborne spores. Rain events or sudden changes in relative humidity also favor spore release. Spores are produced on older lesions formed on wilted twigs and mature leaves. Some spores come from fruit lesions but they are not a major inoculum source. Even the leaf contributes to the inoculum. Although the spores are airborne and carried by winds, alternaria brown spot is often spread among groves on nursery stock transported by humans.

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Quick Decline (QD) or Citrus tristeza virus (CTV)

CTV occurs in every citrus producing area throughout the world. Tristeza is vectored by several species of aphid the most efficient being the brown citrus aphid Toxoptera citricida (Kirklady). Where T. citricida does occur, Aphis gossypii (Glover), the cotton/melon aphid, is the primary vector. The aphid can acquire the virus after feeding on infected plants for 5-60 minutes; but loses the ability to transmit the virus after 24 hours.

 

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Citrus chlorotic dwarf virus

Disease cycle 

Vectored by bayberry whitefly (Parabemisia myricae (Kuwana)). It is transmissible by grafting on infected buds, slash inoculation from extracts of infected leaves and bark in phosphate buffer.

 

 

 

Bayberry whitefly was first discovered in the U.S. by California agriculture officials in 1978, and in Florida by agriculture officials in early 1984. Early dense populations caused defoliation in California citrus (M. Rose, pers. comm.), but this has not happened in Florida. The early finds in Florida were under natural biological control by hymenopterous parasites, including Eretmocerus sp. Apparently, the parasites were introduced with the whitefly. According to Mike Rose (pers. comm.) the Eretmocerus species present in Florida is the same as that found in California.

 

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Citrus scab [Fungus]

Disease cycle 

Conidia are produced on the surface of scab pustules. These spores spread to new susceptible tissue. There are two kinds of spores, clear oval shaped and colored spindle shaped (found in Florida and Brazil). The clear oval shaped type are spread by splashing rain and perish as soon as they dry, while the spindle-shaped form remain viable for a short time and are dispersed by wind for short distances.

 

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Citrus stubborn disease

Disease cycle 

CSD is caused by Spiroplasma citri, a phloem-limited, cell-wall-less bacterium. S. citri is transmitted in a propagative, circulative manner by several leafhoppers including Circulifer tenellus and Scaphytopius nitridus in citrus-growing regions of California and Arizona and C. haematoceps (syn. Neoaliturus haematoceps) in the Mediterranean region. The pathogen multiplies in the vector but no transovarial transmission occurs.

 

Spatial and temporal analysis of CSD incidence indicate only primary spread occurring and no or very limited secondary spread (citrus to citrus). Scaphytopius can develop on citrus but the population remains low to negligible throughout the season. C. tenellus and C. haematoceps have a wide host range which includes many natural hosts of S. citri but citrus is a non host of these leafhoppers. Citrus becomes infected when inoculative Circulifer vectors feed temporarily on citrus during migratory flights.

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Citrus Tristeza Virus (CTV)

Disease cycle

Tristeza is vectored by several species of aphid the most efficient being the brown citrus aphid Toxoptera citricida (Kirklady). Where T. citricida does occur, Aphis gossypii (Glover), the cotton/melon aphid, is the primary vector. The aphid can acquire the virus after feeding on infected plants for 5-60 minutes; but loses the ability to transmit the virus after 24 hours.

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Greasy spot

Disease cycle 

The major source of inoculum for greasy spot are wind-dispersed sexual spores (ascospores) produced during periods of wetness on decomposing fallen leaves. The disease cycle of this pathogen is unusual because most of the infection occurs on mature leaves. In areas with high temperature and high rainfall the disease cycle continues year round and infection may occur at any time.

 

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Huanglongbing (HLB)

Disease cycle 

Huanglongbing (HLB) is presumptively caused by a phloem limited bacteria. In citrus there are three forms of concern, the Asian, African and American forms. The Asian form of HLB expresses symptoms in both cool and warm conditions. The African form of HLB expresses symptoms only in cool conditions (20-250 C, 68-770 F). Both isolates can be vectored by the

 

 

Asian citrus psyllid Diaphorina citri (Kuwayana) and by the psyllid Trioza erytreae (Del Guercio). The American form was identified in Brazil in 2004 and is transmitted by D. citri there.

 

 

 

 

 

 

 

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Phytophthora

Disease cycle 

Phytophthora is a water mold (Class Oomycetes, formerly a fungus-like protist) that is found throughout the world. Under favorable conditions (high moisture and temperature) it produces large numbers of motile zoospores that can swim in water for short distances. These zoospores are the infective agents that may be transported in rain or irrigation to the roots. When zoospores contact roots they encyst, germinate and enter the root tip resulting in rot of the entire rootlet.

Foot rot or gummosis occur when zoospores splash onto a wound or bark crack around the base of the trunk. Additionally, there is an association of Phytophthora root rot when roots are damaged by citrus root weevils, particularly Diaprepes abbreviatus. Root stock susceptibility depends on which Phytophthora species are present and the presence of favorable soil, water and environmental conditions.

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Psorosis

Disease cycle 

Psorosis is transmitted by grafting. There is some evidence of natural spread, possibly by Olpidium brassicae which transmits other ophioviruses, or by an aerial vector. The incidence of psorosis has been reduced in many areas by using budwood certification programs.

Symptoms 

Leaf - foliar symptoms have a wide range and are best seen on young leaves nearing full expansion. Symptoms include chlorotic flecks that are irregularly distributed, leaf mottling, and round chlorotic spots. Symptoms may fade as leaves mature.

 


 

 

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Septoria

Disease cycle 

Septoria has saprophytic capabilities and pycnidia often form on dead twigs and leaves. Conidia from these pycnidia are spread by splashing water and may infect leaves and fruit. However, symptoms may not result for up to six months after infection.

 

 

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Sweet orange scab

Disease cycle 

Sweet orange scab forms spores on the surface of the scab pustules. This species of scab attacks mainly fruits. The conidia (asexual spores) are similar to those of E. fawcettii, require moisture for spore production and are primarily spread by splashing rain. Fruits are susceptible for 6 to 8 weeks after petal fall. The role of ascospores (sexual spores) is uncertain.

 

 

Citrus Pests is one piece of a multi-tool resource initiative to provide an accurate identification resource for pests and diseases of cultivated citrus in the United States. The resource includes three individual identification tools: Citrus ID Edition 2, Citrus Diseases, and Citrus Pests. All three tools are packaged into the comprehensive Citrus Resource

Citrus Diseases is one piece of a multi-tool resource initiative to provide an accurate identification resource for pests and diseases of cultivated citrus in the United States. The resource includes three individual identification tools: Citrus ID, Edition 2 , Citrus Diseases , and Citrus Pests (coming soon).  All three tools will be packaged into the comprehensive Citrus Resource.

We currently serve - Mesa – Gilbert - Tempe - Chandler - Queen Creek - Scottsdale – Paradise Valley - East Phoenix Arizona.