Agriculture and Agnculture et
Agri-Food Canada Agroalimentaire Canada
Research Direction generale
Branch de la recherche
1999
Corn Pest Survey Report
Xiaoyang Zhu, Lana Reid, Daniel Presello and Tsegaye Woldemarian
Eastern Cereal and Oilseed Research Centre (ECORC)
Agriculture and Agri-Food Canada Ottawa, ON
In August and September 1999, ECORC conducted a corn pest survey in Ontario and Quebec. The main purpose of this survey was to determine the distribution of the bacterial disease called Stewart's wilt (Pantoea stewartii=Erwinia stewartii) and of virual diseases, such as Maize Dwarf Mosaic Virus (MDMV), Maize Chlorotic Dwarf Virus (MCDV), Maize Chlorotic Mottle Virus (MCMV), Maize White Line Mosaic Virus (MWLMV) Wheat Streak Mosaic VirUs (WSMV), and Barley Yellow Dwarf Virus (BYDV). We also recorded the distribUtion and severity of other diseases and insects including eyespot (Aureobasidium zeae), northern leaf blight (Exserohilum turcicum), common rust (Puccinia sorghi), common smut (Ustilago maydis), stalk rot (Fusarium spp.), ear rot (Fusarium spp.), European corn borer (Ostrinia nubilalis) and corn rootworm (Diabrotica longicornis and/or D. virgifera). As well, we were scouting for new diseases in Canada.
At
each of the 69 locations we visited between August 19 and September 10, we
recorded the incidence of each pest and the severity of the predominant pest.
At the same time, we collected Stewart's wilt samples and virus-like leaf
samples. If no virus-like plants were found, then 10-18 leaves (1 leaf/plant)
were randomly collected from the location. ELISA tests for Stewart's wilt
and viruses were done in the laboratory by using AGDIA antibodies and methods.
Eyespot,
common smut, common rust, European corn borer and corn rootworms were the
most common pests found at most locations (Table 1). Stalk rot and ear rots
were found at all locations in which the corn was mature; some locations were
not mature enough to observe rot symptoms.
1.
Eyespot
- Severe eyespot was found in Quebec in the counties of Acton, Les Maskoutains,
and Montcalm and in Wellington County, ON. High susceptibility was found in
25 hybrids.
2.
Common Rust - Some
highly susceptible inbreds were found at the University of Guelph, ECORC (Ottawa),
and seed company breeding nurseries. Severe rust symptoms were only found
on hybrids in Renfrew County, ON. Eleven hybrids exhibited severe susceptibility.
3.
Northern Leaf
Blighf
- Northern
leaf blight was found at 28 locations. Seven hybrids appeared to be susceptible
to northern leaf blight in Elgin County, ON. One particular hybrid was highly
susceptible at a farm in St-Philippe, Argenteuil County, QUE., resulting in
a yield loss of about 20% on 4.4 hectares. Despite this northern leaf blight
was well controlled on this farm this year following several suggestions we
made after observing a major outbreak in 1998.
4.
Common Smut - In
several locations, seven hybrids were consistently susceptible to common smut
with more than 25% of the plant having smut galls, including on the lower
nodes. Overall, smut infection in 1999 was lower than that in 1998
5.
Stalk Rot - Stalk
rots were not very apparent at the time we visited these locations, but some
severe outbreaks were reported later in the season in Ottawa-Carleton County,
ON and Vandreuil-Soulanges County, QUE.
6.
Ear
Rot - As
with stalk rot, we did not observe much ear rot at the time of the survey;
however, we did observe some high susceptibility in Vaudreuil-Soulanges County,
QUE with more than 30% plants having ear rot symptoms.
7.
European Corn Borer - Severe
European corn borer damage was found in Pakenham and Kinburn, ON. In Pakenham,
one field had an infestation of 70%
with 36%
of the plants broken. In Kinburn, a non-Bt hybrid had 62% plants with ECB
borer damage while a Bt hybrid had only 6% damage.
8.
Corn Rootworm – No
severe corn rootworm damage was found this year at the time of the survey.
9.
Stewart's Wilt - Three
kinds of bacterial diseases, Stewart's wilt, Goss' bacteria wilt (Clavibacter
Michiganensis subsp. Nebraskensis = Corynebacterium nebraskense), and Holcus
leaf spot (Psedomonas
syringae) were found
in Ontario. As shown in Table 1, bacterial wilt was found at 32 locations,
mostly in southern Ontario. Different symptoms were found at different locations
and with different hybrids. A total of 67 wilt-like samples were collected
from 30 locations from 12 Ontario counties and 2 Quebec counties.
There
are many symptom-types that have been attributed to Stewart's wilt. Seventeen
samples were collected with typical Stewart's wilt symptoms (Symptom 1: long
streak lesions with wavy margins, Fig. 1) of which 15 (88.2%) tested positive
for Stewart's wilt with the ELISA test (Table 2).
Eighteen
samples were collected from plants with similar symptoms but shorter lesion
lengths (Symptom 2) 5 (27.8%) of these samples tested positive. Symptom 3
(Fig. 2) is called "top-fire" by some seed companies and consists
of shorter, irregular, yellow or red lesions restricted by veins. Fifteen
samples were collected with this symptom of which 5 (33.3%) tested positive.
Eleven samples were collected from plants with longer, irregular, wavy lesions, mostly around the leaf tips (Symptom 4); 8 (72.7%) tested positive. Two samples with general discoloration of the husk (Symptom 5) from plants exhibiting Symptom 3 lesions were collected, one of which tested positive. Two samples with symptoms similar to those of Holcus leaf spot (Symptom 6) were collected, but none tested positive for Stewart's wilt. One sample with fine, white stripes along the veins (Symptom 7) was collected and tested positive. One sample with brown stalk nodes from plants exhibiting Symptom 3 lesions (Symptom 8) was collected and tested positive.
Stewart's
wilt was identified at Durham, Elgin, Frontenac, Huron, Kent, Leeds and Grenville,
Middlesex, Ottawa-Carleton, Oxford, and Renfrew counties, ON. No Stewart's
wilt was found in Quebec. Very severe Stewart's wilt was
found
in Elgin and
Kent
counties, including at
the
OCC trials
at
these
locations. Twenty-six hybrids were highly susceptible, with more than 40%
of the leaf area wilted. Thirty-two hybrids possessed some resistance with
<10% of the leaf area wilted; all other hybrids were intermediate in symptoms.
10.
Red Leaf - Corn Virual Diseases
- Red leaf, possibly caused by BYDV, was found in 24 locations, again with
more in southern Ontario than other locations. Symptoms of MDMV were found
at 3 locations. in total, about 340 plant samples were analysed by ELISA for
MDMV-A, B, and O, MCDV-T, MCMV, MWLMV, WSMV, and BYDV-mav and rpv. BYDV-mav
was identified in Ottawa and Maynard. WSMV was also identified at Ottawa,
especially in grain samples with symptoms of kernel red streak. Overall, the
incidence of viral diseases in Canada was low in 1999.
11.
Other
Diseases and Insects
- Head smut (S
porisorium holci-sorghi = Sphacelotheca reiliana ) is
a systemic disease, with the symptoms apparent only on the ears and/or tassels,
unlike common smut which can have galls appearing all over the plant at the
Greenbelt Farm Ottawa, one field was found with head smut in 1998 where the
area infected was about 75 x 30 m; however, in 1999 it expanded to 300 x 100
m2,
most likely
due to
spread
by a combine. At another location in Kinburn in 1998, head smut caused about
65% yield losses on a 48 acre field of corn. After several suggestions made
by ECORC on this case study, head smut was well controlled in 1999.
Anthracnose
top-die back caused by Colletotrichum
graminicola,
was
found in Cobden and Ottawa.
At
the Cobden OCC trials, 25 susceptible hybrids had almost 100% diseased plants
while resistant hybrids had no symptoms.
Physoderma
brown spot (Physoderma
maydis) was
found at Strathburn, Elgin County, ON; and Holcus leaf spot (Pseudomonas
syringae) was
found at Walton, Huron County, ON.
The
corn flea beetle (Chaetocnema
pulicaria),
a
vector of Stewart's wilt, was found in southern and eastern Ontario. Aphids
and mites were found at most locations but mite damage was only found at Mosport,
Durham County, ON. Aphids were numerous in Ottawa-Carleton County, ON and
Le Haut-Richelieu and Acton counties, QUE. A significant amount of herbicide
damage was found in many locations.
Conclusions
Overall, 1999 had less com diseases than average due to the dry weather in July, August, and September. However, this kind of weather does favor some diseases such as Stewart's wilt. This is the second year ECORC has conducted a comprehensive corn pest survey in Ontario and Quebec. We plan to conduct this survey on an annual basis to build up a database of corn pests in Canada. This database will be used to monitor pest outbreaks, track emerging pests and develop prediction models.
For further information about our survey, or to report pest outbreaks for the next survey or obtain disease identifications, contact:
Mr. Xiaoyang Zhu / Dr. Lana Reid
Eastern Cereal and Oilseed Research Centre
Agriculture and Agri-Food Canada
CEF, Bldg. #99
Tel: (613)-759-1616 / 759-1619
Fax: (613)-952-9295
E-mail: zhuxyz@em.agr.ca or reidl@em.agr.ca
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