Tag: Corn

Week 13: Japanese Beetle

In Canada, Japanese beetle (Popillia japonica) is established in Ontario, Quebec, New Brunswick, Nova Scotia, and Prince Edward Island. It was detected in British Columbia in 2017. In BC, the BC Ministry of Agriculture and Food, CFIA, municipal governments (e.g., Cities of Vancouver, Kamloops, Burnaby, Port Coquitlam) and other stakeholders are collaborating to manage the Japanese beetle infestation. Their efforts have been quite successful so far.

Japanese beetle has not been found and is not established in Alberta, Saskatchewan, or Manitoba.

An adult Japanese beetle. Photographed by David Cappaert, Bugwood.org

Japanese beetle poses a threat to agriculture in Canada for several reasons. First, feeding by both adult and larval Japanese beetle cause damage to host plants. Larvae feed on the roots of plants, especially of turf and other grasses. Adults feed on the foliage, seeds, and fruits of host plants.

A Japanese beetle larva, or grub. The larvae are found in the soil and feed on the roots of turf and other grasses. Photographed by David Cappaert, Bugwood.org.

Second, Japanese beetles are generalists, known to feed on over 250 host plants. Some of its favourite host plants include field crops like soybean and corn, fruit trees and vines including grape vines, peach, cherry, plum, corn, deciduous trees like maple and elm, and ornamental plants including roses. Third, once established, it has been very difficult to effectively manage Japanese beetle populations.

Adult Japanese beetles and damage associated with adult feeding on plant foliage. Photographed by David Cappaert, Bugwood.org.

Japanese beetle is a regulated pest in Canada and is of concern in the United States. Therefore, the CFIA and USDA have developed regulatory requirements for Japanese beetle that are harmonized between countries. Each province/state has been assigned to one of four regulatory categories based on the risk of Japanese beetle introduction and establishment. The Canadian prairie provinces are in Category 4 – “Area not known to be infested/Unlikely to become established.” For more information about the regulatory status of Japanese beetle in Canada and the US, please check out this CFIA document published in June 2025.

Although risk of infestation and establishment of Japanese beetle in Alberta, Saskatchewan, and Manitoba is low, it remains important to be alert for possible infestation or introductions of Japanese beetle. Help protect the prairie region by reporting any potential Japanese beetle sightings to Dr. Meghan Vankosky (meghan.vankosky@agr.gc.ca) and by filing reports with the CFIA using their reporting tool.

For more information about the biology and damage caused by Japanese beetle, please check out the CFIA Japanese beetle factsheet, the BC Ministry of Agriculture Japanese beetle Pest Alert, and Invasive Species Centre webpage on Japanese beetle.

Wheat stem sawfly

Native to North America, the wheat stem sawfly is an economic pest depending on spring and durum wheat as its main crop hosts. These insects also target winter wheat, rye, grain corn and barley, in addition to feeding on native grass species. It is interesting to note that wheat stem sawflies do not feed on oat crops, as oats are toxic to wheat stem sawfly.

An adult wheat stem sawfly. Picture by Dylan Sjolie, AAFC-Saskatoon.

Wheat stem sawfly larvae feed on pith inside the stems of their host plant. Their feeding activity affects crop yield and quality. As infested host plants mature, the larvae travel down the stem to its base, where “V” shaped notches are cut into the stem a little above ground level. These notches leave plants vulnerable to collapsing or lodging, especially during wind events. Because wheat stem sawflies also breed and develop on native grass species, economic damage tends to be most prevalent around crop margins where native and agricultural plants are found close together.  

An adult wheat stem sawfly. Picture by Dylan Sjolie, AAFC-Saskatoon.

Adult wheat stem sawflies are 8–13 mm long with a wasp-like resemblance, due to their black body and yellow legs. Females have an egg-laying organ (an ovipositor) that extends from their abdomen. When resting on plant stems, these insects will point their heads downward. Mature larvae are 13 mm long and resemble whitish worms with brown heads. 

Biological and monitoring information related to wheat stem sawflies in field crops can be found on our Monitoring Protocols page as well as on provincial Agriculture Ministry pages (Manitoba, Saskatchewan and Alberta).

Week 11: Western Bean Cutworm

Western bean cutworm, Striacosta albicosta, is native to North America, where it has traditionally been found in the United States (western Great Plains, including Idaho, Montana, Colorado, Utah, Arizona, New Mexico, Texas). Since 2000, the range of western bean cutworm has expanded to the east in both the United States and Canada, and is now found in Ontario, Quebec, and Nova Scotia (as of 2017).

Western bean cutworm is not present or established in Alberta, Saskatchewan, or Manitoba.

Larva of western bean cutworm. Photographed by Adam Sisson, Iowa State University, Bugwood.org.

It is important for farmers in western Canada to be on the lookout for western bean cutworm because this insect is a serious pest of corn and of dry edible beans (Phaseolus spp.). Larvae of western bean cutworm feed on developing corn ears and bean pods, resulting in direct injury to the harvested parts of these crop plants. In beans, the first and second instar larvae also feed on the leaves and flowers. In corn, damage can be observed on the silk, as well as the cobs and kernels. Damage caused by western bean cutworm increases the susceptibility of the plants to fungal infection, which can further decrease seed quality and yields.

Adult of western bean cutworm, with distinctive tan-coloured markings on the forewings. Photographed by Adam Sisson, Iowa State University, Bugwood.org.

In the adult stage, male and female western bean cutworm can be distinguished from other cutworm moths by a pale tan band on the leading edge of the forewing and by a spot and comma-shaped mark in the same pale tan colour located near the middle of the forewings. Adult moths are most active in mid- to late July and fly mostly at night. Eggs are laid in masses, with about 50-80 eggs on average. The eggs are white when first laid and darken to a light tan colour and then to a purple colour just before hatching. Larvae, especially from the 4th instar on, are characterized by the presence of 2 black stripes behind the head. The larvae are smooth and fairly hairless.

For more information and pictures, please refer to the Canadian Corn Pest Coalition factsheet and the Ontario Ministry of Agriculture, Food and Agribusiness factsheet on western bean cutworm.

Please report insects or damage resembling western bean cutworm to Dr. Meghan Vankosky (meghan.vankosky@agr.gc.ca).

Information for this Insect of the Week post was summarized from an Open Access paper: Smith, J.L., C.D. Difonozo, T.S. Baute, A.P. Michel, and C.H. Krupke. 2019. Ecology and management of the western bean cutworm (Lepidoptera: Noctuidae) in corn and dry beans – Revision with focus on the Great Lakes Region. Journal of Integrated Pest Management 10: 27 https://doi.org/10.1093/jipm/pmz025

Week 15: European Corn Borer

European corn borer, Ostrinia nubilalis, is a generalist pest of a variety of crops, including corn, potatoes, beans, sugar beets, tomatoes, quinoa, and millet. European corn borer is an occasional pest of crops in western Canada; as many of its hosts are grown in western Canada, it is important to monitor for European corn borer. In eastern Canada, European corn borer is an important pest and its populations are monitored by the Great Lakes and Maritimes Pest Monitoring Network and by the Réseau d’avertissements phytosanitaires in Quebec.

European corn borer larva and feeding damage on a plant stem. Picture by Jocelyn Smith, University of Guelph.

In western Canada, European corn borer has one generation per year. Adult female moths lay eggs in clusters on the underside of leaves in June, July and August. Larvae can typically be found feeding on leaves starting in July. Larval feeding continues until the larvae reach the fifth instar, which overwinters.

External plant symptoms of European corn borer feeding damage on corn. Picture by Jocelyn Smith, University of Guelph.

Early instar European corn borer larvae eat the leaves of their host plants. As the larvae grow, they tend to begin feeding on the midrib of leaves and on plant stems by tunneling into these plant structures. In corn, the growing larvae can mine into and feed on the corn tassels. Damage to the leaves and stems caused by European corn borer larvae can cause dieback, especially to young plants. Damage to the stems caused by tunneling larvae can weaken the plants, leaving them prone to breakage during storms or in windy conditions. Damage to the stems also interrupts nutrient cycling in infested plants, which can affect the quality and quantity of yield.

European corn borer damage to millet. Note the pile of frass (insect feces) in a pile below the affected millet plant. Picture by John Gavloski, Manitoba Agriculture.

Later instar larvae often begin feeding on the reproductive structures of the host plant: the pods, fruits, or ear shanks. Larval feeding to these structures affects the marketability of the crop; in many crops, including sweet corn and peppers, there is zero tolerance for European corn borer damage.

The Insect Community of Practice, a committee of the Canadian Plant Health Council has developed a harmonized monitoring protocol for European corn borer. This protocol can be used in any of the many crops that European corn borer can infest, not just corn.

For more information, please read the European corn borer page in Field Crop and Forage Pests and their Natural Enemies in Western Canada, also available in French. You can also find information from Manitoba Agriculture, OMAFRA, and the Canadian Corn Pest Coalition.

True armyworm

Similar to diamondback moth, the true armyworm, or just armyworm (Mythimna unipuncta or Pseudaletia unipunctata) is a migratory pest in Canada. After arriving from the United States, true armyworm can have two generations of larvae before cool temperatures in the fall stop their development. True armyworm caterpillars feed along leaf margins of their hosts, leaving damage that could be misdiagnosed as grasshopper or bertha armyworm damage. Preferred hosts include native grasses, wheat, rye, corn, oats, and barley. Other hosts can include crucifer vegetables (e.g., cabbage) and alfalfa.

Phermone traps have been deployed by the Saskatchewan Ministry of Agriculture and Manitoba Agriculture and by their collaborators and volunteers in both provinces to detect the arrival of immigrating true armyworm. Access the Provincial Insect Pest Report for Wk09 for updates.

The economic threshold for true armyworm larvae in cereals is 10 larvae/m2. If scouting in the evening or at night, beat plants in a 1 m2 area and count the dislodged larvae. True armyworm larvae are more likely to be on the ground during the day, so look under leaf litter and other debris around the plants in a 1 m2 area and count the larvae. For more information and tips for scouting, refer to the armyworm pages of the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” (2018) accessible as a free downloadable PDF in either English or French on our new Field Guides page OR access Manitoba Agriculture’s scouting guide.

True armyworm

Similar to diamondback moth, the true armyworm, or just armyworm (Mythimna unipuncta or Pseudaletia unipunctata) is a migratory pest in Canada. After arriving from the United States, true armyworm can have two generations of larvae before cool temperatures in the fall stop their development. True armyworm caterpillars feed along leaf margins of their hosts, leaving damage that could be misdiagnosed as grasshopper or bertha armyworm damage. Preferred hosts include native grasses, wheat, rye, corn, oats, and barley. Other hosts can include crucifer vegetables (e.g., cabbage) and alfalfa.

Phermone traps have been deployed by the Saskatchewan Ministry of Agriculture and Manitoba Agriculture and by their collaborators and volunteers in both provinces to detect the arrival of immigrating true armyworm. In Saskatchewan, true armyworm have been caught by pheromone traps in the northeast and central parts of the province. In Manitoba, true armyworm have been caught in all five regions.

The economic threshold for true armyworm larvae in cereals is 10 larvae/m2. If scouting in the evening or at night, beat plants in a 1 m2 area and count the dislodged larvae. True armyworm larvae are more likely to be on the ground during the day, so look under leaf litter and other debris around the plants in a 1 m2 area and count the larvae. For more information and tips for scouting, refer to the armyworm pages of the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” (2018) accessible as a free downloadable PDF in either English or French on our new Field Guides page OR access Manitoba Agriculture’s scouting guide.

True armyworm

Similar to diamondback moth, the true armyworm, or just armyworm (Mythimna unipuncta or Pseudaletia unipunctata) is a migratory pest in Canada. After arriving from the United States, true armyworm can have two generations of larvae before cool temperatures in the fall stop their development. True armyworm caterpillars feed along leaf margins of their hosts, leaving damage that could be misdiagnosed as grasshopper or bertha armyworm damage. Preferred hosts include native grasses, wheat, rye, corn, oats, and barley. Other hosts can include crucifer vegetables (e.g., cabbage) and alfalfa.

Phermone traps have been deployed by the Saskatchewan Ministry of Agriculture and Manitoba Agriculture and by their collaborators and volunteers in both provinces to detect the arrival of immigrating true armyworm. In Saskatchewan, true armyworm have been caught by pheromone traps in the northeast and central parts of the province. In Manitoba, true armyworm have been caught in all five regions.

The economic threshold for true armyworm larvae in cereals is 10 larvae/m2. If scouting in the evening or at night, beat plants in a 1 m2 area and count the dislodged larvae. True armyworm larvae are more likely to be on the ground during the day, so look under leaf litter and other debris around the plants in a 1 m2 area and count the larvae. For more information and tips for scouting, refer to the armyworm pages of the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” (2018) accessible as a free downloadable PDF in either English or French on our new Field Guides page OR access Manitoba Agriculture’s scouting guide.

True armyworm

Similar to diamondback moth, the true armyworm, or just armyworm (Mythimna unipuncta or Pseudaletia unipunctata) is a migratory pest in Canada. After arriving from the United States, true armyworm can have two generations of larvae before cool temperatures in the fall stop their development. True armyworm caterpillars feed along leaf margins of their hosts, leaving damage that could be misdiagnosed as grasshopper or bertha armyworm damage. Preferred hosts include native grasses, wheat, rye, corn, oats, and barley. Other hosts can include crucifer vegetables (e.g., cabbage) and alfalfa.

Phermone traps have been deployed by the Saskatchewan Ministry of Agriculture and Manitoba Agriculture and by their collaborators and volunteers in both provinces to detect the arrival of immigrating true armyworm. In Saskatchewan, true armyworm have been caught by pheromone traps in the northeast and central parts of the province. In Manitoba, true armyworm have been caught in the central, eastern, and Interlake regions.

The economic threshold for true armyworm larvae in cereals is 10 larvae/m2. If scouting in the evening or at night, beat plants in a 1 m2 area and count the dislodged larvae. True armyworm larvae are more likely to be on the ground during the day, so look under leaf litter and other debris around the plants in a 1 m2 area and count the larvae. For more information and tips for scouting, refer to the armyworm pages of the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” (2018) accessible as a free downloadable PDF in either English or French on our new Field Guides page OR access Manitoba Agriculture’s scouting guide.

WESTERN BEAN CUTWORM – WILL THE RANGE EXPANSION REACH THE PRAIRIES?

Western bean cutworm (Striacosta albicosta) is a native North American insect that, at high levels, can be a pest of corn and dry beans. However, the way they feed is different than some of the other cutworms many may be familiar with. Western bean cutworm feeds on the reproductive parts of plants (corn tassel, silks, and kernels, or dry bean pods and seeds). This can result in yield loss, and spread ear mold. In Ontario, injury by western bean cutworm has been shown to increase mycotoxin production in grain corn.

Range Expansion: The historical geographic range of the western bean cutworm covered the western Great Plains states including Colorado, Nebraska, and Wyoming but, over the past two decades, its distribution has been more easterly rather than north to the prairies. A report from the 1950s of western bean cutworm in Alberta has instead been confirmed as a misidentification of another species. Currently, it has not been detected in the Canadian prairie provinces. Since 1999, the geographic range of the western bean cutworm has rapidly expanded eastward across the U.S. Corn Belt and eastern Canada. Western bean cutworm adults have been collected in 22 additional states and provinces since 1999, spreading from western Iowa to the east coast of the United States and Canada. It was first found in Canada in Ontario in 2008. Keep an eye open for this insect when scouting for crop pests in corn or dry beans this summer.

Figure 1. Detailed expansion of western bean cutworm distribution into the eastern Corn Belt between 2000 and 2017. From: Smith et al. 2019. Journal of Integrated Pest Management. Volume 10, Issue 1, pg. 1-19.

Appearance and monitoring tips:
Larvae:
• There are six stages (instars) of the larvae, and appearances vary.
• Older larvae are a light tan colour, with an orange head. The pronotum (the shield-like structure just behind the head) has two broad dark brown stripes.
• You may find young larvae on the silks of corn. Older larvae may be on the ears of corn, but you may have to peel back the husks to find them (Fig. 2).

Figure 2. Western bean cutworm feeding on corn. Photo: Jocelyn Smith, University of Guelph.


Adults:
• Each forewing has a white or tan band running along the edge or margin of the wing (Fig. 3). Inside this band are 2 distinctive markings: a brown circle and a brown kidney bean shape, both surrounded by a tan border.
Note – Other moths across the Canadian prairies, such as redbacked cutworm, have similar markings.

Figure 3. Western bean cutworm adult. Photo: Jocelyn Smith, University of Guelph.

Please help – When monitoring in the Canadian prairies, adults or larvae suspected to be western bean cutworm can be directed to your provincial entomologist for species verification. New and confirmed sightings of this species are important and will help mobilize research and pest management strategies.

Additional information on western bean cutworm can be found in the publication “Western Bean Cutworm” by the Canadian Corn Pest Coalition: https://cornpest.ca/corn-pests/western-bean-cutworm/

Did you know? Bt corn with the Vip3A protein effectively controls western bean cutworm, but some of the Bt corn products for European corn borer will not.

Reference:
Ecology and Management of the Western Bean Cutworm (Lepidoptera: Noctuidae) in Corn and Dry Beans—Revision With Focus on the Great Lakes Region. 2019. J. L. Smith, C. D. Difonzo, T. S. Baute, A. P. Michel, and C. H. Krupke, Journal of Integrated Pest Management, Volume 10, Issue 1: 1-19.

EUROPEAN CORN BORER: A GENERALIST PEST OF CROPS

Despite its common name, the European corn borer (Ostrinia nubilalis) feeds on many crop and non-crop plants including beans, potato, quinoa, millet, hemp, wheat, many vegetables and some flowers. European corn borer is occasionally an economic pest of crops such as corn and potatoes in Manitoba, where there is one generation per year. In parts of Ontario and eastern Canada, there are univoltine (one generation per year) and bivoltine (two generations per year) strains. How prevalent and damaging European corn borer is to many of its host crops is still not clear.

  • European Corn Borer larva in millet. Photo credit: John Gavloski, Manitoba Agriculture

European corn borer has traditionally been monitored in corn fields, and more recently in potato fields. However, a new harmonized protocol can be used to monitor for European corn borer in multiple crops. Anyone participating in insect monitoring on any potential host crop can access the harmonized protocol online or using the Survey123 app.

The protocol can be used to report the presence of European corn borer eggs, larvae, and crop damage. Anyone monitoring populations or encountering noticeable levels of European corn borer or their injury to any crop is highly encouraged to add this data. For more information about the harmonized protocol and to submit monitoring data, please click here to access all needed links. Information collected from across Canada will be used to better understand the distribution, feeding habits, and abundance of this pest.

European Corn Borer egg masses. Photo credit: John Gavloski, Manitoba Agriculture

Access these resources to find more information:
• Review the European corn borer page within the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” (2018) also accessible as a free downloadable PDF in either English or French on our new Field Guides page.
• Review the Manitoba Agriculture fact sheet for the European corn borer.
• Review the Ontario Ministry of Agriculture, Food, and Rural Affairs fact sheet for European corn borer.

Nationwide monitoring pilot project for European corn borer

The European corn borer (ECB; Ostrinia nubilalis), has been an important pest of corn and other crops in eastern Canada for nearly a century now but is also known to be a sporadic pest in western Canada. Despite its name, ECB is actually a generalist feeder, having a wide range of hosts. With so many new emerging crops being grown in Canada that are also hosts for ECB (eg. hemp, cannabis, quinoa, hops, millet and others), there is no better time to look at this pest across the Canadian agricultural landscape.

To monitor for ECB nationwide, the Surveillance Working Group of the Canadian Plant Health Council has developed a harmonized monitoring protocol for European corn borer in both English and French. The project aims to generate real-time reporting and annual maps – access a full description of the project and list of key contact persons. The protocol can be used to report ECB eggs, larvae or damage in any host crop across Canada. This harmonized protocol has been designed to complement protocols already in use to make management decisions in order to generate data to compare ECB presence across all of Canada and across host crops.

When scouting corn, quinoa, hemp, millet, potatoes, apples, or other crops susceptible to ECB, the Surveillance Working Group of the Canadian Plant Health Council encourages the use of the harmonized monitoring protocol and reporting of the data from fields or research plots using the free Survey123 app (available for both desktop and mobile devices):
• Early to Mid-Season ECB Survey (Before July) – https://arcg.is/0qCCHH (applicable for use in eastern Canada).
• Later Season ECB Survey (July to Pre-Harvest) – https://arcg.is/fSODf (applicable for use in both eastern AND western Canada).

Nationwide monitoring pilot project for European corn borer

The European corn borer (ECB; Ostrinia nubilalis), has been an important pest of corn and other crops in eastern Canada for nearly a century now but is also known to be a sporadic pest in western Canada. Despite its name, ECB is actually a generalist feeder, having a wide range of hosts. With so many new emerging crops being grown in Canada that are also hosts for ECB (eg. hemp, cannabis, quinoa, hops, millet and others), there is no better time to look at this pest across the Canadian agricultural landscape.

To monitor for ECB nationwide, the Surveillance Working Group of the Canadian Plant Health Council has developed a harmonized monitoring protocol for European corn borer in both English and French. The project aims to generate real-time reporting and annual maps – access a full description of the project and list of key contact persons. The protocol can be used to report ECB eggs, larvae or damage in any host crop across Canada. This harmonized protocol has been designed to complement protocols already in use to make management decisions in order to generate data to compare ECB presence across all of Canada and across host crops.

When scouting corn, quinoa, hemp, millet, potatoes, apples, or other crops susceptible to ECB, the Surveillance Working Group of the Canadian Plant Health Council encourages the use of the harmonized monitoring protocol and reporting of the data from fields or research plots using the free Survey123 app (available for both desktop and mobile devices):
• Early to Mid-Season ECB Survey (Before July) – https://arcg.is/0qCCHH (applicable for use in eastern Canada).
• Later Season ECB Survey (July to Pre-Harvest) – https://arcg.is/fSODf (applicable for use in both eastern AND western Canada).

Doppelgangers: Cereal leaf beetle vs. Collops beetles

The case of the innocuous versus the evil twin: When making pest management decisions, be sure that the suspect is actually a pest. This can be challenge since insects often mimic each other or look very similar. An insect that looks, moves and acts like a pest may in fact be a look-alike or doppelganger.

Doppelgangers may be related (e.g. same genus) or may not be related, as in the case of monarch butterflies (Danaus plexippus) and viceroys (Limenitis achrippus).  Doppelgangers are  usually relatively harmless but sometimes the doppelganger is a pest yet their behaviour, lifecycle or hosts may be different.

Correctly identifying a pest enables selection of the most accurate scouting or monitoring protocol. Identification and monitoring enables the application of economic thresholds. It also enables a producer to select and apply the most effective control option(s) including method and timing of application.  For the rest of the growing season, the Insect of the Week will feature insect crop pests and their doppelgangers.

The case of the cereal leaf beetle versus Collops beetles: 

Cereal leaf beetle, Boris Loboda

Cereal leaf beetles (Oulema melanopus), both adults and larva, feed on leaves (oat, barley, wheat, corn, etc), but it is the larval damage that can reduce yield and quality, especially if the flag leaf is stripped. Adults are 6-8 millimeters (.25-.31 inches) long with reddish legs and thorax (middle section between head and abdomen) and metallic bluish-black head and elytra (wing coverings).

Collops beetle, cc-by-nd-nc 1.0 Ashley Bradford

They may be confused with beneficial beetles belonging to the Collops genus (adults feed on aphids, stink bug eggs, moth eggs, small caterpillars, spider mites, whiteflies). Roughly the same size, they may have a red or orange thorax with/without red markings on their elytra, depending on the species. One consistent feature that will help distinguish between the two species is that the cereal leaf beetle elytra are smooth and shiny whereas the Collops’ elytra are covered in hairs.

Specific information on the cereal leaf beetle can be found in the updated Field Crop and Forage Pests and their Natural enemies in Western Canada field guide.

Review previously featured insects by visiting the Insect of the Week page.

Invasive species: Brown marmorated stink bug

This week’s Insect of the Week is the brown marmorated stink bug (Halyomorpha halys). Stink bugs get their name from the foul odour they release when threatened. Brown marmorated stink bug is not known to be established in the Prairies, but the species has been found in the Southern Interior of BC, in Ontario and Quebec. Feeding causes damage to seeds and seed pods, reducing yield. Nymphs and adults prefer field corn and soybean, but infestations have been reported on rape, pea, sunflower and cereals in the USA. They have also been known to attack tree fruits, berries, vegetables and many ornamental trees and shrubs.

Brown marmorated stink bug – adult (CC-BY 2.0 Katja Schulz)

Additional information and fact sheets for this insect have been posted by Ontario Ministry of Agriculture, Food, and Rural Development, and BC Ministry of Agriculture and Seafood. You can also check out our Insect of the Week page.

This insect is featured in our Field Crop and Forage Pests and their Natural Enemies Field Guide which is available for download from the Insect Field Guide page. 

Insect of the Week – Twospotted spider mite (Acarina: Tetranychus)

This week’s Insect of the Week is the twospotted spider mite. This tiny mite is 0.5 mm long and has eight legs. It has a greenish, yellowish to orange oval body with two dark spots on its abdomen. To the unaided eye, it looks like a small speck. they feed on corn, soybean, dry beans, alfalfa, vegetables and fruit.

These mites overwinter in protected sites as eggs, immatures or adults depending on food hosts and habitat. Immatures and adults move to emerging plant hosts in the spring. They create webbing on the underside of leaves where they puncture cells to feed on cell contents. This feeding causes stippling, yellowing or browning of the leaves. Leaves may dry and drop which can further reduce crop yields.

Infestations start at the field edge and move inwards. Extended hot, dry conditions favour rapid population build up and exacerbate feeding injury.

For more information on the twospotted spider mite, check out our Insect of the Week page!

Twospotted spider mite – adult closeup
David Cappaert, Michigan State University, Bugwood.org
Twospotted spider mite – stippling damage on bean
Whitney Cranshaw, Colorado State University, Bugwood.org

Insect of the Week – Darksided cutworm

It’s spring, so it’s cutworm season. This week’s insect is the darksided cutworm. Mature larvae are hairless, greyish with a prominent white stripe on either side just above their legs. It is a climbing cutworm with feeding occurring at night. They have a broad host range including cereals, canola, corn, flax, sunflower, vegetables berry and tree fruits.

Find out more about the darksided cutworm at the Insect of the Week page.  Other important species include dingy, army, redbacked and pale western cutworms (See Insect of the Week: 2017 – May 1, 8, 15 and 29).

Darksided cutworm
Photocredit John Gavloski, Manitoba Ministry of Agriculture

In addition, Cutworm Pests of Crops on the Canadian Prairies – Identification and Management Field Guide was recently published (2017). This new handy manual has chapters on general biology, history of outbreaks, scouting techniques, natural enemies and general control options. The meat of the manual is descriptions of 24 cutworm species, their lifecycle, hosts, damage, monitoring and economic thresholds. To download a copy, go to the Cutworm Field Guide page.

Insect of the Week – Glassy cutworm

This week’s insect is the glassy cutworm. The larva is greyish-white, semi-translucent and shiny (i.e. glass-like) with a orange-brown head. Since it overwinters as a larva, it is active as soon as the ground thaws. It feeds underground and rarely come to the surface. Their main host crop are grasses but will also attack wheat and corn. Corn planted following wheat may be particularly at risk.

Find out more about the glassy cutworm at the Insect of the Week page.

Glassy cutworm
cc-by Joseph Berger, bugwood.org

Other important species include dingy, army, redbacked and pale western cutworms (See Insect of the Week: 2017 – May 1, 8, 15 and 29).

In addition, Cutworm Pests of Crops on the Canadian Prairies – Identification and Management Field Guide was just published (2017). This new handy field guide has chapters on general biology, history of outbreaks, scouting techniques, natural enemies and general control options. The guide includes descriptions of 24 cutworm species, their lifecycle, hosts, damage, monitoring and economic thresholds. To download a copy, go to the Cutworm Field Guide page.

Winter Update – True armyworm

Earlier this summer (Week 14), the true armyworm (Lepidoptera: Noctuidae: Mythimna unipuncta) was reported on the lower west coast and a summary was provided by Tracy Hueppelsheuser (BC Ministry of Agriculture).

Tracy kindly provided an update to the situation…. The initial true armyworm damage reported earlier did not relent and a second generation of voracious larvae continued to cause damage in late August through to late September in southwestern British Columbia.  In addition to Vancouver Island (hit a second time), true armyworm larvae showed up south of Abbotsford, Sumas, Matsqui, Dereoche, as well as east through Chilliwack (Greendale, Rosedale), and west all the way to Delta and Westham Island.  The outbreak resulted in damage to grass fields and even corn was defoliated and cobs damaged!  

True armyworm pupae were observed mid-September and moths are expected over the next while in lower BC.  A third generation is anticipated but is not expected to cause as much damage owing to the cooler nights (~8°C) which should slow insect development and feeding.  Parasitism was noted which is good news in terms of natural enemies responding to the outbreak.  Also, lots of bird feeding activity has been observed although the birds’ seeking and feeding activities have also damaged grass fields!

The outbreak of true armyworm in lower BC appears to be part of a larger outbreak that has similarly afflicted western Oregon and Washington this year.  

Find more information on true armyworms in the NEW Cutworm Field Guide, free and downloadable in 2017!


Screenshots of true armyworm from the Cutworm Field guide are also shown below:




Insect of the Week – Cereal leaf beetle

This week’s Insect of the Week is the cereal leaf beetle. Wheat is their preferred host, but they also feed on oats, barley, corn, rye, triticale, reed canarygrass, ryegrass, fescue, wild oats, millet and other grasses. Adults and larvae feed on the leaf tissue of host plants. Yield quality and quantity is decreased if the flag leaf is stripped. It is also interesting to note that larvae carry all of their own fecal waste with them as protection from predators.


For more information on the cereal leaf beetle, see our Insect of the Week page.



Cereal leaf beetle larva (cc-by 2.0 Christophe Quintin)




Cereal leaf beetle damage (cc-by-nc-sa 2.0 CIMMYT)



Remember the NEW Cutworm Field Guide is free and downloadable in 2017!

Weekly Update – Small scarab beetle

Small scarab beetle (Coleoptera: Aphodius distinctus) – This is the time of summer that farmers will be seeing larvae of a small scarab beetle (Aphodius distinctus) in their fields.  There have been scattered reports each June of large numbers of beetle grubs in crops associated with crop damage (e.g., canola, corn, dry bean, onion, pea).


Please help researchers compile information related to this species so they might confirm its pest status!  Information is posted about the beetle and the survey.  Here’s how you can help:


1. Please send reports of high white grub densities and associated crop damage to Kevin.Floate@agr.gc.ca (403-317-2242). 


2. Live larvae accompanied by the following field information would be extremely helpful please – contact Dr. Kevin Floate if you have a sample!


3. Include answers to the following so the pest status for this species can be ascertained:  
     – Previous crop?
     – Legal land location or latitude+longitude?
     – Irrigated or not?
     – Was composted manure added this spring?
     – Surface residue in spring?

Insect of the Week – Tetrastichus julis

Tetrastichus julis (parasitoid)

Last year, the focus of the Insect of the Week was crop pests. This year, we’re changing things up and highlighting the many natural enemies that help you out, silently and efficiently killing off crop pests. [note: featured Insects of the Week in 2015 are available on the Insect of the Week page] 

This week’s Insect of the Week is Tetrastichus julis (sorry, no common name), an important cereal leaf beetle parasitoid. Where T. julis has become established, it can reduce cereal leaf beetle populations by 40 – 90%, preventing yield loss without using pesticides. See also the factsheet, Biological Control at its Best, Using the T. julis Wasp to Control the Cereal Leaf Beetle (French version).


For information about the cereal leaf beetle (p. 24) and other pests and their natural enemies, see the new Field Crop and Forage Pests and their Natural Enemies in Western Canada – Identification and Management Field Guide for identification, life cycle and conservation options (download links for field guide available on the Insect of the Week page).

T. julis adult parasitizing a cereal leaf beetle larva 
– Swaroop Kher, University of Alberta/AAFC