By Isabelle Piche, Crops Summer Student, Moose Jaw
Aphids belong to the Order Hemiptera; all members of this group have piercing-sucking mouthparts and are fluid feeders. Some aphids feed on the sap in peas and lentils, which can cause wilting and a reduction in seed size. Plants with adequate moisture can compensate aphid pressure; control measures may be required when populations are very high and/or dry conditions persist. Physical disturbance such as wind or rain can knock these insects from plants. For this reason, scouting during calm periods is preferred.
Scouting should include 20 180-degree sweeps per location, and at least five locations per field. For lentils, the action threshold (average number per sweep) is 30 to 40 aphids. For peas, the action threshold is nine to 12 aphids per sweep, or two to three aphids on the top 20 cm of the plant. Sites should be revisited two days later. If the population is increasing, control may be required; if the population is decreasing or maintained, natural enemies are having an effect and control may not be warranted. Beneficial insects or natural enemies of aphids include predators like lacewings, lady bugs and parasitoids (tiny, parasitic wasps). The latter can be seen as dried husks of aphids, called "mummies". Once pod elongation is complete, the economic benefits of control are no longer realized. For further information and registered products, consult the Guide to Crop Protection.
One of the sessions at the 2019 Crop Diagnostic School focused on cereal aphids and the Cereal Aphid App. Aphids typically begin to appear in cereal crops during the third week of July, at which point the head is out and anthesis is occurring or finishing. There are two main species of aphids that attack cereals in Saskatchewan: the English grain aphid and the birdcherry-oat aphid. Both of these species can cause yield loss. Agriculture and Agri-Food Canada has taken the recommendations, economic thresholds, pictures of the main aphid species and beneficial insects and incorporated all of this information into a dynamic action threshold. What this means is that the action threshold for aphids will fluctuate depending on crop stage and which beneficial insects are in the field. Scouting for aphids begins by counting the number of aphids on the head and all the way down to the bottom of the plant. Sometimes the birdcherry-oat aphid stays in the flag leaf. Once the crop is in the hard dough stage, there is no economic benefit to control.
The Cereal Aphid Manager app can be used while scouting. Begin by scouting and counting the aphids and beneficial insects on five random tillers in a "W" pattern, at spots 30 paces apart. Aphids can also be detected by using a sweep net. Once you've input the information and crop stage, the app will provide you with a recommendation. The app has many photos of the major species of aphids and beneficial insects to help with identification. This app also keeps all previous scouting records and creates a graph illustrating the aphid population over time based on your scouting data. The Cereal Aphid Manager app is available through Google Play and the Apple App Store.