Ross Weiss, David Giffen, Sandra Younie, Owen Olfert and Meghan Vankosky
This past week (August 6-12, 2019) prairie temperatures were almost 3 °C cooler than last week (Fig. 1). The warmest temperatures were observed in southern AB and MB and eastern AB.
Across the prairies, 30 day (July 13- August 12, 2019; Fig. 2) average temperatures were slightly cooler than long term climate normals (Fig. 3). Temperatures were warmest across MB.
Growing season temperatures (April 1-August 12, 2019) continue to be approximately 1 °C cooler than average (Fig. 4).
Significant rainfall amounts were reported across parts of the northern Peace River region, southern AB and SK (Fig. 5). Across the prairies, rainfall amounts for the past 30 days have been lowest across the southern prairies (Fig. 6).
Growing season rainfall amounts (Fig. 7) have been below average across southern regions of AB and west-central SK (Fig. 8).
The growing degree day map (GDD) (Base 5 ºC, April 1-August 11, 2019) is below (Fig. 9):
The growing degree day map (GDD) (Base 10 ºC, April 1-August 11, 2019) is below (Fig. 10):
The lowest temperatures (°C) observed the past seven days ranged from at least 12 down to below 0 °C in the map below (Fig. 11).
The highest temperatures (°C) observed the past seven days ranged from at least 20 up to at least 32 °C in the map below (Fig. 12).
The maps above are all produced by Agriculture and Agri-Food Canada. Growers can bookmark the AAFC Drought Watch Maps for the growing season.
Ross Weiss, David Giffen, Owen Olfert and Meghan Vankosky
Grasshopper Simulation Model Output – Grasshopper development is progressing and populations are primarily in the adult stage (Fig. 1). Based on model runs, approximately 65% of the population should be in the adult stage (50% last week). Grasshopper development continues to be slower than average development. Based on climate data, 80% of the population would be expected to be in adult stage. Model output indicates that oviposition has begun in southern areas prairies (Fig. 2).
Bertha armyworm (Lepidoptera: Mamestra configurata) – Important – Watch for updates from your provincial monitoring networks who are compiling cumulative pheromone-baited trap interceptions to assess risk levels in Alberta, Saskatchewan (updated 07Aug2019), and Manitoba (locate table on pg 6). Regions in all three prairie provinces are reporting “uncertain” risk based on pheromone-baited unitrap cumulative counts. SCOUT NOW to confirm in-field larval counts and REMEMBER that LARVAL DENSITIES CAN VARY DRAMATICALLY even between adjacent fields! Scout to protect @FieldHeroes and avoid economic losses! Use the Field Heroes’ scouting guide for bertha armyworm and be sure to read more at their website! Biological and monitoring information related to bertha armyworm in field crops is posted by the provinces of Manitoba, Saskatchewan, Albertaand the Prairie Pest Monitoring Network. Also refer to the bertha armyworm pages within the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” which is a free downloadable document as both an English-enhanced or French-enhanced version.
Refer to the PPMN Bertha armyworm monitoring protocol for help when performing in-field scouting. Use the images below (Fig. 1) to help identify egg masses and the economically important larvae in canola.
Figure 1. Stages of bertha armyworm from egg (A), larva (B), pupa (C) to adult (D).
Photos: J. Williams (Agriculture and Agri-Food Canada).
Now is the time to do in-field scouting for this insect pest. Review the Insect of the Week which features bertha armyworm and its doppelganger, the clover cutworm!
Reminder – Feeding channels on the upper surfaces of the flag leaf in wheat were reported and evening scouting revealed the culprit!
Field scouting was performed in the evening from 8:30-10:30pm. As the temperatures decreased, the slugs moved up the wheat stems, climbing to the topside of the flag leaf and onto the wheat heads although they did not appear to feed at the developing kernels. Wheat was hand-collected by clipping stems ~20cm above the ground to later reveal a density of 1.04 slugs per stem (n=465 stems) causing the above damage (Fig. 2).
Specimens were forwarded to L. Luong (U of A) who identified the slugs from the above field as one species, Deroceras reticulatum, the grey field slug. The majority were juveniles. The grey field slug is the most common to occur in the home garden.
Thanks to Dr. John Gavloski (Manitoba Agriculture) who prepared the following in relation to slugs in field crops:
Slugs are a complicated problem because most general insecticides don’t work well on them.
Sluggo Professional (PCP#30025) is registered for slugs in field crops. It is a bait, which must be consumed by the slugs to be effective but it could be expensive on a large field.
Often insecticides don’t work well on slugs and it may be related to the mucous coating slugs exude.
Be wary, if an insecticide is applied, the product will likely not affect the slugs but it will kill the ground beetles and other natural enemies that prey upon or parasitize slugs and could exacerbate the slug problem.
Growers using no-till or minimum till operations may consider tillage to help reduce future levels of slugs.
Health Canada has an overview of snails relating to gardening posted here.
The following is offered to predict when Culex tarsalis will begin to fly across the Canadian prairies (Fig. 1). Protect yourself by wearing DEET! This week, regions most advanced in degree-day accumulations for Culex tarsalis, the vector for West Nile Virus, are shown in the map below. As of August 11, 2019, areas highlighted orange are on the verge of approaching sufficient heat accumulation for mosquitoes to emerge. Areas highlighted red in the map below should now have C. tarsalis in flight.
Once adults emerge, the following map demonstrates how quickly a Culex tarsalis mosquito carrying WNV can become fully infective (i.e., when it has accumulated 109 base 14.3° degree days) – it’s a matter of days, depending on the region (Figure 2). For example, as of August 11, 2019, Foremost AB was predicted to only take 16-18 days for C. tarsalis to become fully infective.
The Canadian Grain Commission is ready to grade grain samples harvested in 2019. Register online to receive a harvest sample kit (by October 15, 2019). Samples are accepted until the end of November but send as soon a harvest is complete.
This is a FREE opportunity for growers to gain unofficial insight into the quality of their grain and to obtain valuable dockage information and details associated with damage or quality issues. The data collected also helps Canada market its grain to the world!
Provincial entomologists provide insect pest updates throughout the growing season so we link to their most recent information:
• Manitoba’s Crop Pest Updates for 2019 are posted here. Access Issue #13 posted August 13, 2019, noting continued grasshopper concern, the presence of new generation flea beetle adults in canola, and a repeated call for grasshopper surveyors.
Hoverflies are un-BEE-lievably good mimics of bees and yellow jacket wasps!
Mimicry is used by insects in several ways. Some insects, like the ambush bug and praying mantis, look like plants. These predators sit very still, blending into their surroundings, and wait very patiently for their unwitting prey to pass by. Other insects, use mimicry to avoid predation, often by taking on the appearance of species with clear markings that are known to be dangerous. Hoverflies (Diptera: Syrphidae) are some of the most convincing mimics of all of the insects. Even experts can have a difficult time distinguishing hoverflies from bees and wasps, especially when working in the field.
Bees (honeybees, solitary bees, native bees; Hymenoptera: Apidae): Bees are important pollinators, usually with distinctive black and yellow strips. Bees have two pairs of wings and are much fuzzier than wasps or hoverflies. Bees have stingers, but are not aggressive under normal circumstances. Some species of bees (e.g. honeybees) have barbed stingers that become lodged inside their victim. When this happens, the stinger is pulled out of the body of the bee and the bee dies. For this reason, bees with barbed stingers only sting as a last resort, in an effort to protect their colony. Bees are beneficial insects that will leave you alone if you leave them alone.
Yellow jacket wasps (Hymenoptera: Vespidae): Yellow jackets and some of their close relatives have colouring similar to bees. Like bees, wasps have two pairs of wings. Unlike bees, which are usually vegetarians, wasps are carnivores that eat other insects. Thus, wasps are beneficial insects, but they also have a bad reputation for harming people because they scavenge for food at our picnics and barbecues during the summer. Wasps also tend to be aggressive and will sting with little provocation.
Hoverflies (Diptera: Syrphidae): Hoverflies belong to a completely different order of insects than bees and wasps. Like bees, hoverflies are pollinators and are often observed hovering over flowering plants in fields and gardens. Unlike bees and wasps, hoverflies only have one pair of wings. Hoverflies do not have a stinger. They also do not have biting mouthparts, so they can do no harm to people. Hoverflies protect themselves from predators, and people, by mimicking bees and wasps. In addition to pollinating plants, hoverflies provide another important ecosystem service: their larvae are predators of small plant-dwelling insects like aphids!
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.