The list of disease reports is as follows:

Bacterial diseases (13 reports)

Bacterial wilt, banana - Uganda
Bacterial wilt, beans - Spain
Huanglongbing, citrus - USA (FL) (3 reports) Citrus canker - Australia (QLD) (2 reports) Citrus canker - USA (FL) (13 reports)

Fungal diseases (51 reports)

_Alternaria alternata_, tea - India (North Bengal) Apple core rot - India (Himachel Pradesh) Apple scab, races - Spain Soybean rust, Asian strain - USA (21 reports) Brown spot, tangerine hybrids - Iran: (1st report) Black rot, lettuce - Brazil (1st report) Black rot, peanut - USA (TX): (1st report) Black leg, canola - Argentina Botrytis blight, peanut - USA (GA) Cabbage leaf spot - Ukraine (Odessa) Canker and twig dieback, apple, pear - USA (WA) Downy mildew, cucurbits - Brazil (Minas Berais) Flag smut, bacterial leaf blight, rice - India (Punjab & Haryana) Frosty pod rot, cacao - Belize: 1st report Fruit rot, stored apples - Chile: 1st report Fruit spot, eggplant - USA (GA) Fusarium head blight, wheat - USA (MN, ND) Fusarium wilt, tomato - Mexico (Baja California Sur) Leaf rust, Septoria spp., wheat Kazakhstan Leaf rust, Septoria spp., wheat - Kazakhstan: corr.
Leaf rust, wheat, resistance change - India Leaf spot, fruit rot, eggplant - India (Andhra Pradesh) Panama disease, ladyfinger banana - Australia Phytophthora crown rot, peach - Chile Potato late blight - USA (AK) Potato smut - Chile Stripe rust, wheat - Australia Sudden death syndrome, soybean - USA (KY) Tan spot, cereals - Bulgaria: 1st report Verticillium wilt, eggplant - Italy Wheat diseases, cereals - USA (ND)

Virus diseases (27 reports)

Apple mosaic - Turkey (Anatolia)
Bean pod mottle virus, soybean - Iran (Golestan) Beet pseudo-yellows virus, cucurbit - Costa Rica Cucumber mosaic virus, banana - Iran Beet virus Q, sugar beet-Iran: 1st report Beet yellow vein virus, sugarbeet - Morocco: 1st report Bell pepper leaf curl virus - Pakistan: 1st report Cherry green mottle virus, sweet cherry - Poland East Africa cassava mosaic virus - Sudan ex Uganda French bean viruses - Iran : 1st report Grapevine viroids, China : 1st report Grapevine virus diseases - Iran Iris yellow spot virus, onion - Chile Iris yellow spot virus, onion - Spain: 1st report Leaf curl disease, tomato - Indonesia (Java) Iris yellow spot virus, onion - Spain: 1st report Major food crops monitored by ProMED-Plant Necrotic leaf spot, apple - Turkey (Isparta) Nomenclature error - ToLCV (2 reports) Tobacco streak virus, mung bean - India: 1st report Tomato chlorosis virus, tomato - Cyprus: 1st report Tomato criniviruses - France: 1st report Tomato leaf curl New Delhi virus, chilli - India Tomato leaf curl virus - Philippines (Mindanao) Tomato viruses - Ecuador Tomato yellow vein streak virus - Brazil (2 reports)

Viroid diseases (1 report)

Grapevine viroids, China : 1st report

Nematode diseases (3 reports)

Potato cyst nematodes - Russia (Kurgan)
Potato cyst nematodes, Russia (Altai Region) Stubby-root nematode, potato - USA (WA)

The data can be arranged in the following way to reflect the origins of virus diseases: those diseases that occurred in North America (Domestic) and those that occurred outside of North America (Foreign).

Bacterial diseases (13 reports)
Domestic - 4
Foreign - 16

Fungal diseases (51 reports)
Domestic - 29
Foreign - 22

Virus diseases (26 reports)
Domestic - 0
Foreign - 26

Viroid diseases (1)
Domestic - 0
Foreign - 1

Nematode diseases (3)
Domestic - 1
Foreign - 2

Summary of disease reports:

Domestic - 34
Foreign - 68

Included in the list of reports are 17 items that provide the 1st publication (1st report) of a new disease.

Comments on the disease reports

Bacterial diseases

2 bacterial diseases were of significant interest in the last 6 months of 2005. The 1st was citrus canker in Florida, which was battered by high winds and driving rains that spread the bacterium further afield. In Australia, it appears that citrus production in the Emerald area of Queensland, the main citrus production area, will come to an end. An Australian Senate inquiry into the outbreak has already been told that the owner of Evergreen Farms, where the disease was 1st detected, was allegedly illegally importing plant cuttings from overseas. There are also questions about how authorities handled the matter. Apparently, no one could provide definitive information on the source of the outbreak.

The 2nd disease, known as Huanglongbing (HLB), is a lethal disease of citrus caused by a phloem-limited bacterium (Candidatus _Liberibacter asiaticus_). It is one of the most severe diseases affecting citrus production in tropical and sub-tropical regions of the world, and has recently spread to citrus orchards in southern areas of Japan, Brazil and USA (Florida). HLB is found throughout East Asia, Saudi Arabia and India. The bacterium is transmitted by the Asiatic psyllid (_Diaphorina citri_). HLB could be a serious problem on the American continent if it is not controlled. A competitive PCR method has been developed which is less expensive than equipment used in real-time PCR systems.

Fungal diseases

Soybean rust: The major fungal disease in the last half of 2005 was the Asian strain of soybean rust (ASR) that erupted in the southeastern states of the USA, engendering 21 disease reports. At year-end, soybean crops in 33 Alabama counties were affected; other affected states and affected counties were Florida (23); Georgia (35); Mississippi (2); South Carolina (23); North Carolina (18); Louisiana (2); Texas (1); and Kentucky (1).

Government and industry spent millions of dollars last winter to prepare farmers for ASR, which could cost them thousands of dollars to control. But while the disease was found in southern states for a 2nd consecutive year, it never reached the Midwest. Kudzu (_Pueraria montana_), a host of ASR, is widely distributed in the southeastern states, where it serves as a susceptible host for the fungus and a generator of rust spores. 21 of the 51 fungal diseases recorded were due to ASR. Foreign reports of ASR were recorded in Uruguay, Brazil, and Argentina (4 reports).

Black rot and Botrytis blight were recorded in USA (TX) and Argentina, respectively, and canola black leg was reported from Argentina. Canola is the major oilseed crop grown in the Canadian Prairie Provinces and is an economically important and serious disease of canola (_Brassica napus_) in Australia, France, Germany, USA and the United Kingdom. Canola black leg is the most serious disease of canola/rapeseed in the prairies, and may cause major crop losses in some years. Disease management options include crop rotation, genetic resistance and seed treatment with fungicides which have proven to be effective. Combinations of genes, irrespective of whether they are major or minor, have been suggested as the best method for genetic control of leaf rust.

Cereal diseases

7 of the 51 disease reports involved cereals. Yellow rust, also known as stripe rust, is caused by _Puccinia striiformis_ f. sp. _tritici_ and is one of the most widespread wheat diseases worldwide. Leaf or brown rust caused by _Puccinia triticina_ is also one of the most important cereal diseases worldwide. Yield losses may reach 40 percent in susceptible cultivars, but it is generally in the range from 1-20 percent.

Development of genetic resistance to rust is the most efficient, cost-effective and environment-friendly approach to prevent the losses caused by rust epidemics. A major concern for leaf rust breeders is that the Lr 19 resistance gene for leaf rust no longer confers resistance against the fungus. Combinations of genes, irrespective of whether they are major or minor, have been suggested as the best method for genetic control of leaf rust.

Field crop diseases

Rhizomania, caused by Beet necrotic yellow vein virus (BNYVV), is one of the most destructive diseases of sugar beet, not only because it causes a severe loss in root yield and sugar content, but it is also difficult to control.

It is widely distributed in most sugar beet-growing areas worldwide.
The virus is vectored by the plasmodiophorid fungus _Polymyxa betae_ (Pb). The presence of rhizomania could result in a total loss of a sugar beet crop.

The primary source of spread is through the movement of infested soil or beets. 3 pathotypes of BNYVV have been reported. During a survey on soilborne viruses in sugarbeet, a rod-shaped virus from Germany was shown to be a distinct virus, subsequently named Beet virus Q
(BVQ) and found to be transmitted by Pb. Although its contribution to rhizomania remains a matter of debate, it is not uncommon to find BVQ associated with rhizomania-infested fields. BVQ has been found in Bulgaria, Belgium, France, Germany, Hungary, Italy, and the Netherlands, but not from Turkey.

The most effective control measure is to use partially resistant sugar beet cultivars based upon single dominant genes. Once a field becomes infested with Pb, crop rotation will not appreciably reduce disease risk because of the long-term survival of viruliferous cystosori (spore balls).

However, some soil fumigants, such as those containing 1,3-dichloropropene, may kill enough cystosori to reduce disease development to acceptable levels, but it is very expensive. BVQ has been repeatedly observed by immunoelectron microscopy during the past decade in sugarbeet samples from various areas in Germany and abroad, indicating that it is widely spread. Another virus, Bean pod mottle virus, (BPMV) caused significant crop losses in soybean in North America. It is spread primarily by the bean leaf beetle _Cerotoma trifurcata_ and other beetle species. Yields from infected plants are lowered by 10-40 percent, grain quality is reduced both in oil and protein, and seed germination is lower. Delayed maturation results in a condition known as "green stem." BPMV has been reported in Iran, suggesting that infected seed may have been used for planting.

Banana and plantain diseases

Banana and plantain are the most important agricultural products in the tropics, with annual production of over 100 million metric tons.
Of the various pathogens encountered in the tropics, Panama disease [PD] (aka Fusarium wilt), is the most significant. PD is caused by the fungus _Fusarium oxysporum_ f.sp _cubense_ [FOC]. PD was considered a major threat to banana production in the 1940s-1950s, but planting of a PD-resistant banana cv. Gros Michel was a breakthrough. Over time, Gros Michel was replaced by the Cavendish-type cultivar, which has remained in production to date. A new variant of FOC, tropical race 4 (TR4), has been responsible for the Southeast Asian outbreaks. Unlike subtropical outbreaks that affect cold-stressed Cavendish in Australia, the Canary Islands, and South Africa, TR4 affects Cavendish in the absence of predisposing factors. Although it is found only in Southeast Asia, TR4 continues to spread in that region. The great fear is that FOC will spread to the Americas and Africa, where it could have a great impact on production of export bananas and plantains that normally resist PD.

Pulse crop virus diseases

Leguminous food crops such as peas, beans, chickpeas and lentils are major mainstays of modern agriculture. 3 virus diseases were reported in this period. Bean pod mottle virus (BPMV) caused significant crop losses in soybean. It is spread primarily by the bean leaf beetle _Cerotoma trifurcata_ and other beetle species. Yields from infected plants are lowered by 10-40 percent, grain quality is reduced both in oil and protein, seed germination is lower, and delayed maturation results in "green stem." BPMV spreads in the North American region.
The fact that BPMV has been reported in Iran suggests that BPMV-infected seed may have been used for planting soybean in Iran.

The 2nd virus disease, Southern bean mosaic virus (SBMV) and its various strains, can cause severe mosaic symptoms in bean (_Phaseolus
vulgaris_) and other important leguminous food crops. SBMV is transmitted by beetles (_Ceratoma trifurcata_ and _Epilachna
variestis_) and can also be transmitted by seed (3-7 percent) in _Vigna unguiculata_ cv. Early Wilt Resistant Ramshorn. It has been reported from Africa, North America, South and Central America, and France. SBMV probably entered Iran via infected seed. Disease management involves managing the bean leaf beetle. Growers should consider a later planting of soybean, especially if BPMV was a yield-limiting factor in previous years. Late planting can result in an increased risk of soybean aphid activity at a sensitive growth stage.

The 3rd disease, Tobacco streak, (TSV), infects Blackgram (_Vigna mungo_), and other important pulse crops in India, Nepal, Bangladesh and Myanmar. During the kharif season (a strong southwest land wind during the monsoon), a new disease was observed in the majority of the blackgram-growing areas of India. Alternate hosts may also play role in disease epidemiology, since TSV infects many widely distributed weeds. TSV infects a wide range of hosts in India. It is transmitted by _Frankliniella occidentalis_ and _Thrips tabaci_; _Thysanoptera_ (possibly by allowing virus particles from the surface of infected pollen to enter through feeding wounds). TSV is readily transmitted via seed at high levels in bean. Disease management depends mainly on planting virus-free seed.

Tomato virus diseases

Begomoviruses are inflicting heavy damage on tomato crops in Asia.
For example, in Bangladesh tomato is cultivated over ca. 40 000 acres annually. Tomato leaf curl virus disease (ToLCVD) normally reduces tomato production significantly, often causing up to 100 percent yield loss. Apparently Asia is a hot spot for the evolution of new virus isolates, as indicated by the isolation of new virus strains. 7 isolates of another begomovirus, Tomato leaf curl New Delhi virus
(ToLCNDV) have been reported from India and 2 from Thailand during this period. Recombination or pseudo-recombination are driving forces in the evolution of new begomoviruses, especially in tropical regions.

Disease management of ToLCNDV depends, in part, on preventing movement of the insect vector (_Bemisia tabaci_) on infested plants (e.g. tomato transplants) to virus-free areas. Various control options include removal of infected plants (roguing), removal or burial of infected crop residues, and intercropping in combination with chemical insecticides and the use of available resistant cultivars. Use of plastic UV-absorbing screening material to exclude Bt is another method. Genetic resistance to begomoviruses has been reported in some wild _Lycopersicon_ species such as _L. hirsutum_ and _L. peruvianum_, which might be transferred to tomato. In Pakistan, resistance to Tomato leaf curl virus has been incorporated into tomato and chili cultivars. Natural hosts of ToLCV include tomato, pepper, eggplant, okra, tobacco, beans, cotton, cucurbits and other solanaceous crops.

Cassava mosaic disease

Cassava mosaic disease (CMD) occurs in all cassava (_Manihot esculenta_)-producing regions of Africa, India and Sri Lanka, resulting in annual yield losses estimated at 1 billion pounds sterling [USD 1.776 billion]. CMD is caused by viruses in the genus _Begomovirus_ of the family _Geminiviridae_. They are transmitted by the whitefly _Bemisia tabaci_ [Bt] and spread through infected cuttings, which is the usual mode of cassava propagation. 3 groups of cassava mosaic viruses have been identified based on serological relationships. Group A is limited to West Africa, Burundi, Chad, Uganda and the western part of Kenya, whereas group B occurs in Malawi, Madagascar, Zimbabwe and the eastern parts of Kenya and Tanzania. Group C is restricted to India and Sri Lanka. Because of considerable differences in their nucleotide sequences, these groups of viruses are now identified as different virus species and are named African cassava mosaic virus (ACMV), East African cassava mosaic virus (EACMV) and Indian cassava mosaic virus (ICMV), respectively.

Cassava is one of the most common crops in sub-Saharan Africa, accounting for over 50 percent of world production with over 90 million tons of fresh product, more than any other crop in Africa.
Cassava is vital to the livelihood of over 200 million people and plays a key food security role for rapidly expanding rural and urban populations and has huge potential for commercialization, income generation, and poverty reduction.

Cassava production in Africa faces new challenges from CMD. The disease has spread in recent years, bringing increased risk of food insecurity to millions of rural and urban households, particularly in eastern Africa. Research and extension programs have helped limit the geographic spread of CMD, but the potential magnitude of the problem threatens to overwhelm these efforts. CMD continues to be prevalent in all the main cassava-growing areas in the ECA (Economic Commission for Africa) sub-region and is regarded as the most important disease, causing between 20 and 90 percent crop losses based on the cultivar, viral strain and environmental factors.

Deterioration in the status of CMD is a fact in East Africa, Uganda, DR Congo, and Kenya. Lack of alternative propagation stock in disease-infected areas leaves farmers no choice but to use material from the previous harvest of infected plants as planting stock for the next generation. Environmental factors favoring the development and fecundity of Bt enhance disease spread, and spread of CMD is therefore highly linked to the vector. To alleviate the situation, a number of African countries (Kenya, Burundi, and Madagascar) have made significant progress in selecting resistant/tolerant clones, which are being evaluated within their different ecological zones.

Disease management of begomoviruses depends on preventing movement of _Bemisia tabaci_ [Bt] -infected plants (e.g. tomato transplants) to virus-free areas, where the virus can become established. Various control options include removal of infected plants (roguing, removal, or burial of infected crop residues) and intercropping in combination with chemical insecticides and use of available resistant cultivars.
Use of plastic UV-absorbing screening material to exclude Bt is another method.

Genetic resistance to begomoviruses has been reported in some wild _Lycopersicon_ species such as _L. hirsutum_ and _L. peruvianum_ which might be transferred to tomato. In Pakistan, resistance to leaf curl virus has been incorporated into tomato and chili cultivars.

Pepino mosaic virus disease

Pepino mosaic potexvirus (PepMV) was detected for the 1st time in Ecuador in wild populations of _Lycopersicon pimpinellifolium_ along the Pacific coast of South American. Potexviruses are extremely infectious, but they are not known to be naturally spread by vectors.
The virus is easily spread via contact with infected plants. PepMV has been detected in the potato cultivar Yungay growing in the Andes in Peru. Moreover, 14 percent of tested accessions in the potato germplasm at the International Potato Center in Peru are infected with PepMV. More research is required to determine the risks of PepMV infection in potato. Spread from tomato to potato may be possible under field conditions in southern Europe.

Disease management includes use of healthy transplants, planting of resistant or tolerant cultivars, and protection of seedlings with fine meshing to exclude whiteflies. Several insecticides such as imidacloprid or esfenvalerate are recommended and should be rotated to reduce build-up of insecticide-tolerant whiteflies. Contrary to experimental results in the UK, numerous field and several experimental observations in the Netherlands and a few other EU countries indicate that PepMV has only a very minor or a non-significant economic impact on tomato production on average. More damage might be expected if PepMV-affected plants are also attacked by the fungal species _Verticillium_.

Onion virus diseases

Iris yellow spot virus (IYSV) is transmitted by the onion thrips (_Thrips tabaci_), but does not appear to be transmitted by the Western flower thrips (_Frankliniella occidentalis_). It mainly infects onion, garlic and leek. The industry is concerned about the potential impact of IYSV in Washington State, particularly because it has been recorded as present in Colorado, Arizona, Utah and California. IYSV infection in onions cannot be cured. Infected plants should be removed and destroyed, along with cull piles and volunteers. Maintaining good cultural management practices will help to reduce stress on the plants, thus lessening the disease's effect.
Other management practices include maintaining good soil fertility and adequate irrigation supplemented with good management of thrips and weeds.

Onion thrips are best managed with chemical insecticides. Although no cultivars are known to be resistant to IYSV, research has shown that cultivars vary in their susceptibility to both the virus and the thrips vector. IYSV has been reported from North America for several years and recently in Australia. The virus is mainly transmitted by onion thrips (_Thrips tabaci_) and to some extent by the western flower thrips (_Frankliniella occidentalis_), which causes considerably more damage to the crop. Volunteer onions are often symptomatic in early spring in Colorado. The virus likely over-winters in perennial and winter annual weeds, over-wintering onion, and in adult thrips. Apparently, there is no biological control for IYSV.

Disease management depends upon use of thrips-free transplants, utilization of crop rotation (at least 3 years between crops), elimination of culls and weed hosts of the vector, and avoidance of plant stress by providing appropriate irrigation, and avoidance of soil compaction and saline soils. There are no completely IYSV-resistant onion cultivars available, but some less resistant ones can be used. Thrips control may provide some reduction in Iris yellow spot, but thrips control alone is not sufficient to economically control the disease. Thrips resistance to commonly applied insecticides is widespread in Colorado and other onion production regions of the High Plains in the USA.

Crinivirus diseases

Criniviruses are an emerging genus worldwide containing new species that have evolved over time and are now evident as causal agents of new plant diseases. Their symptoms are easily mistaken for those of physiological or nutritional disorders or pesticide phytotoxicity, thus confounding their identification. Criniviruses remain confined to cells associated with the plant phloem, and symptoms are considered to result from plugging of the phloem with large viral inclusion bodies, thus likely interfering with normal vascular transport in infected plants. Both Tomato infectious chlorosis virus
(TICV) and Tomato chlorosis virus (ToCV) were 1st reported during the 1990s in the United States, and ToCV has been reported to occur in the Mediterranean countries, Portugal, Spain, and Italy.

4 crinivirus species transmitted by the greenhouse white fly (GHWF) have been identified to date, including Beet pseudoyellows virus (BPYV), ToCV and TICV. The latter viruses have exerted significant pressure on vegetable and fruit production in North America, Europe, and other parts of the world, affecting both greenhouse-grown crops as well as field crops. 2 viruses, primarily Beet pseudoyellows virus
(BPYV) and TICV, are transmitted exclusively by GHWF, and are currently responsible for economic damage to vegetable and fruit production. Although ToCV is transmitted by the GHWF and impacts tomato production, it is much more efficiently transmitted by Bt, biotype B, than by GHWF, and its incidence is associated more closely with the presence of Bt in fields and greenhouses than with GHWF.

The host range of BPYV is extremely broad. Disease management is straightforward; use of virus-free transplants, avoidance of susceptible hosts, especially weeds, roguing of infected plants and control of insects by chemical insecticides.

Currently, the most effective method for control of criniviruses is an effective insecticide-based control program. Imidocloprid-based products are most frequently used for whitefly control and can be applied as a foliar spray, a seed treatment or through drip application. While insecticides effectively reduce whitefly populations, they are inefficient for control of viruses, since whiteflies can transmit a virus before being killed by an insecticide. Most GHWF-transmitted criniviruses do not produce symptoms until 3 to 4 weeks after infection occurs, by which time it may be too late for implementation of control measures.

Nematode diseases

Potato cyst nematodes (PCN) are major pests of potato crops in cool-temperate areas of Russia. Because of the current pathotypes, no resistant cultivars are available for planting. The situation is more serious in the case of _G. pallida_ than with _G. rostochiensis_.
Plant damage, particularly in relation to the weight of tubers produced, is closely related to the number of nematode eggs per unit of soil. It has been estimated that approximately 2 t/ha of potatoes are lost for every 20 eggs/g soil. Up to 80 percent of the crop can be lost when nematode populations are grown under conditions of continual potato cultivation.

Control is traditionally by crop rotation, which in the absence of potato cultivation will reduce nematode populations significantly. 7 years without potatoes is a common recommendation. More recently, crop rotation has been supplemented by use of nematicides (fumigants or granular systemic compounds). Integration of these methods can be used to keep the nematode population levels below economic thresholds. Control on tomatoes is chiefly by application of recommended soil fumigants.

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[see also in the archive:
2005
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Major food crops monitored by ProMED_Plant 20050823.2484 Quarantine pests, new data - EPPO (02): Spain: 2004 20050714.2014 Quarantine pests, new data _ EPPO (03): Lithuania 2004 20051104.3226 Regulated plant pests, detection - July 2005: EPPO 20051105.3235 Regulated plant pests, detection, May 2005: EPPO 20051105l.3236]