Tag: Soybean

Aphids in field crops

Aphid populations can quickly increase at this point in the season and particularly when growing conditions are warm and dry. Access the Provincial Insect Pest Report for Wk12 to remain alert to areas and crops suffering from aphid pest pressure.

Figure 1. Pea aphid adults (each 3-4 mm long) and nymph. Photo: M. Dolinski.

Biological and monitoring information (including tips for scouting and economic thresholds) related to aphids in field crops is posted by:
• Manitoba Agriculture (aphids on cereals, aphids on flax, soybean aphid, aphids on peas)
• Saskatchewan Pulse Growers (aphids in pulse crops or access the PDF copy)
• Saskatchewan Flax Development Commission
• Manitoba Pulse and Soybean Growers (soybean aphids: identification, scouting and management or access the PDF copy)
• The Canola Council of Canada’s “Canola Encyclopedia” section on aphids
• or check your provincial commodity group’s insect pest webpages for more detailed information.

Alternatively, several aphid pest species are described in the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” (2018) and is accessible as a free downloadable PDF in either English or French on our Field Guides page. PDF copies of the individual pages have been linked below to access quickly:
• Corn leaf aphid or Rhopalosiphum maidis (Fitch)
• English grain aphid or Sitobion (Macrosiphum) avenae (Fabricius)
• Oat-birdcherry aphid or Rhopalosiphum padi (Linnaeus)
• Pea aphid or Acyrthosiphon pisum (Harris)
• Potato aphid or Macrosiphum euphorbiae (Thomas)
• Soybean aphid or Aphis glycines (Matsumura)
• Turnip aphid or Lipaphis erysimi (Kaltenbach)
• Sugar beet root aphid or Pemphigus betae Doane
• Russian wheat aphid or Diuraphis noxia (Mordvilko)

Over the years, both the Weekly Updates and Insect of the Week have included aphid-related information but also important natural enemy details to support in-field scouting. Review the list below so pest and beneficial insects can be distinguished readily when scouting fields:
• Aphidius wasp (Insect of the Week; 2015 Wk15)
• Aphids in canola (Insect of the Week; 2016 Wk13)
• Aphids in cereals (Insect of the Week; 2017 Wk09)
• Cereal aphid manager APP (Weekly Update; 2021 Wk07) that presently is available only for iOS
• Ladybird larva vs. lacewing larva (Insect of the Week; 2019 Wk18)
• Ladybird beetles and mummies (Weekly Update; 2020 Wk15)
• Lygus bug nymphs vs. aphids (Insect of the Week; 2019 Wk16)
• Hoverflies vs. bees vs. yellow jacket wasps (Insect of the Week; 2019 Wk19)
• Pea aphids: a persistent problem for legume growers (Insect of the Week; 2021 Wk12)
• Soybean aphids and aphid annihilating allies (Insect of the Week; 2022 Wk07)
• Syrphid flies (Insect of the Week; 2015 Wk16)

Aphids in field crops

Aphid populations can quickly increase at this point in the season and particularly when growing conditions are warm and dry. Over the years, both the Weekly Updates and Insect of the Week included aphid-related information so here’s a list of these items to access when scouting fields:

• Aphidius wasp (Insect of the Week; 2015 Wk15)
• Aphids in canola (Insect of the Week; 2016 Wk13)
• Aphids in cereals (Insect of the Week; 2017 Wk09)
• Cereal aphid manager APP (Weekly Update; 2021 Wk07) that presently is available only for iOS
• Ladybird larva vs. lacewing larva (Insect of the Week; 2019 Wk18)
• Ladybird beetles and mummies (Weekly Update; 2020 Wk15)
• Lygus bug nymphs vs. aphids (Insect of the Week; 2019 Wk16)
• Hoverflies vs. bees vs. yellow jacket wasps (Insect of the Week; 2019 Wk19)
• Pea aphids: a persistent problem for legume growers (Insect of the Week; 2021 Wk12)
• Soybean aphids and aphid annihilating allies (Insect of the Week; 2022 Wk07)
• Syrphid flies (Insect of the Week; 2015 Wk16)

Week 11: Lygus Bugs

The Lygus bug pest complex includes at least 5 species, including the tarnished plant bug (Lygus lineolaris), Lygus keltoni, and Lygus borealis. Lygus bugs have an upside down triangle on their backs and adults are about 5-6 mm long; their colour varies depending on the species and their stage of development. Lygus bugs have a fairly wide host range, but canola, soybean and alfalfa are prone to yield losses resulting from Lygus feeding damage.

An adult Lygus bug, with the characteristic triangle on the back. Picture by AAFC-Saskatoon.
Lygus nymphs of different instars and an adult Lygus bug. Pictures by Hector Carcamo, AAFC-Lethbridge.

The nymphs and adults use piercing and sucking mouthparts to drink from their host plants. They prefer to feed on new growth and reproductive tissues, as these are more nutrient-rich than other plant structures. Feeding by Lygus bugs can result in bud-blasting, where developing buds or flowers do not continue to develop and drop from the plant. If Lygus bugs feed on developing seeds, the seeds become shriveled, reducing yield quality and quantity. Watch for circular, black scars on canola pods, as these are an indicator that Lygus bugs has been feeding on canola pods, and probably on the seeds inside the pods.

Top: A canola raceme with bud blasting symptoms typical of Lygus feeding injury. Bottom: Canola seeds damaged by Lygus feeding (left, middle) and healthy canola seeds (right). All pictures by R.A. Butts, AAFC-Lethbridge.

In addition to direct yield losses due to Lygus feeding damage, the wounds left by their mouthparts make plant tissues vulnerable to infection by pathogens. Because Lyugs bugs inject digestive enzymes into the plant to help break down plant tissues for consumption, they can also vector plant diseases.

Use a sweep net to scout for Lygus bugs in canola and alfalfa crops. The PPMN has a monitoring protocol available here.

In canola, scout as flowering is complete and pods are beginning to ripen. Take 10 sweeps at 15 locations in the field and estimate the number of lygus nymphs and adults per sweep. Recent research suggests that the economic threshold to avoid yield loss in canola is 2-3 Lygus bugs per sweep; check out the Canola Council of Canada, Manitoba Agriculture, and Alberta Agriculture and Irrigation Lygus pages for more information about Lygus bugs and economic thresholds in canola.

In alfalfa, scout at the start of the bud stage by taking 5 sweeps in at least 15 locations per field and estimating the number of Lygus nymphs and adults per sweep. In seed alfalfa fields, the economic threshold is 8 Lygus per sweep in at least 40 sweeps.

For more information about Lygus bugs, visit previous Insect of the Week articles and find the Lygus page in Field Crop and Forage Pests and their Natural Enemies in Western Canada, available in English and in French. SaskPulse also recently published an overview of Lygus impacts on pulse crops written by Jennifer Bogdan.

Painted Lady Butterfly

This week, Alberta Agriculture & Forestry’s Scott Meers noted painted lady butterfly larvae (Vanessa cardui).  The larvae are important to scout for because this species feeds on a wide range of host plants including soybean (Action threshold=>25% defoliation), sunflowers, borage and dry beans in addition to several species of thistles (including Canada thistle) and mallow. 

The “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” includes photos of both the larvae and adult.  The guide is available as an English-enhanced or French-enhanced version.  The Butterflies and Moths of North America website tracks confirmed sightings of V. cardui (screenshot provided below; retrieved 30May2019).

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 – Soybean aphid

This week’s Insect of the Week is the soybean aphid. This pest overwinters in the US and is blown into Canada, where winged females migrate to soybeans and produce several generations over the summer.

In 2016, 2.5 million acres of soybeans were planted in Alberta, Saskatchewan, and Manitoba. This amount is expected to rise in coming years. Thus, it is important to know how to scout for and manage soybean aphids.

For more information on soybean aphids, visit our Insect of the Week page.

Soybean aphid – adult (Robert J. O’Neil, Purdue University (wiki))



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