Date: August 5 2006
From: ProMED-mail <promed@promedmail.org>
In this report (oldest 1st)
[1] 1st report
[2] Containment, commercial aspects

[1] First report
Date: May 2006
From: ProMED-mail<promed@promedmail.org>
Source: biosecurity.govt.nz [edited]
<http://www.biosecurity.govt.nz/pest-and-disease-response/surveillance-risk-response-and-management/response-and-management/incursion-update> 

Boil smut [also known as common smut - Mod.JAD] is a large visible tissue growth (gall) containing powdery reproductive spores. It was detected on 13 Jan 2006 on an isolated block of maize in the Gisborne area. There have been no other reports of boil smut infections to date. Overseas boil smut is not considered a major disease, but yield losses in some maize crops can be significant from year to year. Evidence suggests that the smut has not been present at the infected Gisborne location for very long. Biosecurity New Zealand has placed a restricted place notice on the infected property to contain the disease while investigations continue. Through the crop health scouting program, other local maize crops have been investigated. No other incidence of boil smut has been recorded.

Relevant industry groups have been informed. The infected site will be grassed to stabilise the soil and protect against flood events. Next summer the affected area will be solarized by covering it with polythene to kill any spores. The restricted place notice will remain for 5 years and the site will probably be left fallow for 5 to 8 years. These measures will be followed by restricting maize growing in the affected field for years to come.

[2] Containment, commercial aspects
Date: 27 Jul 2006
From: ProMED-mail<promed@promedmail.org>
Source: stuff.co.nz [edited]
<http://stuff.co.nz/stuff/0,2106,3745755a3600,00.html>

A serious disease, common smut, discovered in a Gisborne maize paddock in January -- but not publicly announced -- has raised concerns about overseas perceptions of New Zealand's biosecurity.

Genetic Technologies general manager Phil Evans said today it was a very ugly and easily spread disease and could potentially close some export markets in parts of Australia where there is no boil smut.

Biosecurity New Zealand has said it may have to expose the infected soil to fumigants and sunshine, and leave the area fallow for 5 to 8 years.

The disease has the potential to severely affect overseas perceptions of New Zealand's sweetcorn and maize industry if eradication measures are unsuccessful.

Also known as boil smut, the fungal disease was found growing on sweetcorn in a paddock in the Makauri area.

Although key industry players, major growers and neighbouring growers were told about the incursion soon after it was found, there was no public announcement. The quick action of a Gisborne crop manager, who had seen the disease in the United States and knew it was not in New Zealand, led to biosecurity officials being notified. After the discovery, the infected plants and soil beneath them were removed and destroyed by incineration.
The remainder of the crop was removed and placed in covered compost heaps.

The field was then direct-drilled with grass to stabilise the soil over the winter months. Because there is a chance of spores surviving in the soil, eradication measures against the fungus will continue in the field in spring and summer.

Gisborne is a major maize and sweet corn growing area and sweetcorn is big business for the district's major food processor Cedenco. Cedenco's agricultural manager, Luke Hansen, said it was hard to define the economic significance if the disease were to establish in New Zealand. "The yield ability of any plant that gets it is destroyed so it would depend how many plants in any crop were infected." Education of growers, so there were more eyes to recognise the disease it if it did appear again, would help prevent it from establishing here in the future, he said.

The fungus affects only corn and maize plants and is present in most of the corn-growing areas around the world. There is no known reliable treatment but work is being done on developing a resistant cultivar across both maize and sweetcorn.

Biosecurity officials traced the Gisborne infection to 2 batches of imported seed and the remainder of the seed that was not planted in the paddock was destroyed. The original seed consignment met the relevant import health standard, had been fungicide-treated and was inspected.

The fungus can be dispersed by wind but they said the disease found in the Gisborne corn crop appeared to be from infected seed rather than wind-distributed spores because of the distribution of the infected plants.

--
ProMED-mail
<promed@promedmail.org>

[The crop plants maize (_Zea mays_) also known as corn, is a cereal grain.
It is called corn in the United States, Canada, New Zealand, and Australia, but in other countries that term may refer to other cereal grains.
Varieties have been bred and selected for both animal feed and human consumption. Sweet corn / sweetcorn is invariably grown for human consumption and is usually shorter than field-corn/maize varieties grown for feed.

_Zea mays_ develop symptoms of the disease boil smut (also known as common
smut) when infected by the fungus _Ustilago maydis_. _U. maydis_ is common where maize is grown but has not been previously detected in New Zealand.
Boil smut is easily recognized by the tumor-like galls that form on any above-ground plant part. The conspicuous galls that replace kernels are covered with a greenish-white papery tissue. As the galls mature, the interior darkens and turns into masses of powdery, dark olive-brown to black spores. Ear galls may reach several inches in diameter. Galls that form on other plant parts, including the tassels and leaves, are much smaller. Although no maize variety is immune, some hybrids and varieties are more resistant than others. Seed treatments are not very effective and the disease is generally difficult to manage.

Boil smut was detected on 13 Jan 2006 on an isolated block of maize in the Gisborne area of New Zealand. A report appeared in the May edition of a government web site maintained by Biosecurity New Zealand (see item 1 in this report). The maize industry in the Gisborne area, where the crop is important, was informed. The news was not made public until newspaper articles began to appear in late July 2006, one of which is included as item 2 in this report. These articles pointed out the possible quarantine implications of the discovery. It is noteworthy that in a report issued in 2000 the Australian Quarantine and Inspection Service identifies boil smut as having quarantine concern to Australia (3rd link in "Links").

This initial infection appears to be an isolated case and appropriate short and long-term plans seem sufficient to minimize the impact on New Zealand maize production. No further incidence of the disease has been reported.

In Mexico common smut is called huitlacoche , sometimes spelled cuitlacoche, and is considered a delicacy, even being preserved and sold for a higher price than maize cobs from uninfected plants. For culinary use, the galls are harvested while still immature - fully mature galls are dry and almost entirely spore-filled. The immature galls, gathered 2 to 3 weeks after an ear of maize is infected, still retain moisture and, when cooked, have a flavor described as mushroom-like, sweet, savory, woody, and earthy. Flavor compounds include sotolon and vanillin, as well as the sugar glucose. Interest in having smutted maize for culinary purposes results in some conflict between departments of agriculture and chefs in countries other than Mexico, including the USA.

There are no previous postings on ProMED-mail on common / boil smut.

Map:
<http://www.map-of-newzealand.co.uk/map-of-gisborne.htm>
Pictures:
<http://www.broad.mit.edu/media/images/ustilago.jpg>
<http://www.gov.mb.ca/agriculture/news/images/Vegetables/Common%20smut%20August%2019.jpg> 

Links:
<http://www.ipm.ucdavis.edu/PMG/r113100311.html>
<http://vegetablemdonline.ppath.cornell.edu/factsheets/Corn_Smut.htm>
<http://www.dpie.gov.au/corporate_docs/publications/pdf/market_access/biosecurity/plant/scorndira.pdf> 

<http://en.wikipedia.org/wiki/Maize>
<http://en.wikipedia.org/wiki/Corn_smut> - Mod.JAD]