Ross Weiss, David Giffen, Owen Olfert and Meghan Vankosky
Weather synopsis – Temperatures (30 day average) continue to be warmest in southern AB and western SK (Fig. 1). Across the prairies, the monthly average temperature was slightly cooler than normal.
Rainfall (30 day accumulation) amounts have been well below average for most of the prairies (Figs. 2 and 3). Rainfall amounts (30 day) across southern SK are normal to above normal.
On March 27 and 28 significant snowfall amounts were reported for a number of locations across AB and southern SK (Table 1; Fig. 4). This has resulted in improved soil moisture amounts for the southern SK (Fig. 5).
Agriculture and Agri-Food Canada (AAFC) and Environment and Climate Change Canada (ECCC) have been working together to study the potential of trajectories for monitoring insect movements since the late 1990s. Trajectory models are used to deliver an early-warning system for the origin and destination of migratory invasive species, such as diamondback moth. In addition, plant pathologists have shown that trajectories can assist with the prediction of plant disease infestations and are also beginning to utilize these same data. We receive two types of model output from ECCC: reverse trajectories and forward trajectories.
‘Reverse trajectories’ (RT) refer to air currents that are tracked back in time from specified Canadian locations over a five-day period prior to their arrival date. Of particular interest are those trajectories that, prior to their arrival in Canada, originated over northwestern and southern USA and Mexico, anywhere diamondback moth populations overwinter and adults are actively migrating. If diamondback adults are present in the air currents that originate from these southern locations, the moths may be deposited on the Prairies at sites along the trajectory, depending on the local weather conditions at the time that the trajectories pass over our area (e.g. rain showers, etc.). Reverse trajectories are the best available estimate of the ”true” 3D wind fields at a specific point. They are based on observations, satellite and radiosonde data.
‘Forward trajectories’ (FT) have a similar purpose; however, the modelling process begins at sites in USA & Mexico. The model output predicts the pathway of a trajectory. Again, of interest to us are the winds that eventually end up passing over the Prairies.
Ross Weiss (AAFC), Meghan Vankosky (AAFC) and Serge Trudel (ECCC)
DATE: APRIL 30, 2019
1. Reverse trajectories (RT)
a. Pacific Northwest (PNW) – For the period of April 24-30 there have been 18 RTs (originating over ID, OR and WA) that have crossed over prairie locations. By comparison, for the period of April 17-23 there were 51 RT’s. The majority PNW RTs have been reported to pass over southern AB. Since March 23rd Lethbridge AB has reported the highest number of PNW RTs (n=22), Beiseker AB (n=15) and Olds AB (n=31).
b. Mexico and SW USA (TX, CA) – No trajectories, originating over Mexico or southwest USA have crossed the prairies for the period of April 24-30, 2019. Since March 23, 2019 there have been 5 reverse trajectories that originated over Mexico, CA and TX. All five occurred on April 7.
c. Texas and Oklahoma – No trajectories, originating over TX or OK have crossed the prairies for the period of April 24-30, 2019. Since March 23, 2019 there have been 18 reverse trajectories that have originated over OK and TX. Most of these trajectories have crossed eastern SK and MB.
2. Forward trajectories (FT) –
The following table reports the origin of forward trajectories predicted to cross the prairies over the next five days (Note: ‘InitialDate’ refers to when the forward trajectory crossed the source location. Trajectories are predicted to cross prairie locations within five days of the initial date).
In a continuing effort to produce timely information, wind trajectory reports will be available both DAILY and WEEKLY:
DAILY REPORTS, as they can be generated, will be put up as a downloadable PDF file on this page.
Cutworms (Noctuidae) – A field guide is now available to help growers scout and manage Cutworms! Cutworm Pest of Crops is available for free in either English or French and is posted on the Cutworm Field Guide page!
Several species of cutworms can be present in fields. They range in colour from shiny opaque, to tan, to brownish-red with chevron patterning. Cutworm biology, species information, plus monitoring recommendations are available in the Prairie Pest Monitoring Network’s Cutworm Monitoring Protocol. Also refer to Manitoba Agriculture cutworm fact sheet which includes action and economic thresholds for cutworms in several crops.
Scout fields that are “slow” to emerge, are missing rows, include wilting or yellowing plants, have bare patches, or appear highly attractive to birds – these are areas warranting a closer look. Plan to follow-up by walking these areas later in the day when some cutworm species move above-ground to feed. Start to dig below the soil surface (1-5 cm deep) near the base of a symptomatic plant or the adjacent healthy plant. If the plant is well-established, check within the crown in addition to the adjacent soil. The culprits could be wireworms or cutworms.
Flea Beetles (Chrysomelidae: Phyllotreta species) – Be on the lookout for flea beetle damage resulting from feeding on canola cotyledons but also on the stem. Two species, Phyllotreta striolata and P. cruciferae, will feed on all cruciferous plants but they can cause economic levels of damage in canola during the seedling stages.
Remember, the Action Threshold for flea beetles on canola is 25% of cotyledon leaf area consumed. Watch for shot-hole feeding in seedling canola but also watch the growing point and stems of seedlings which are particularly vulnerable to flea beetle feeding.
Estimating flea beetle feeding damage can be challenging. Using a visual guide to estimate damage can be helpful. Canola Watch circulated this article but also use the two images (copied below for reference) produced by Dr. J. Soroka (AAFC-Saskatoon) – take it scouting!
Alfalfa Weevil (Hypera postica) – Degree-day maps of base 9°C are produced using the Harcourt/North Dakota models (Soroka et al. 2015). Models predicting the development of Alfalfa weevil (Hypera postica) across the prairies are updated weekly to help growers time their in-field scouting for second-instar larvae.
The AAW model runs indicate that oviposition has begun in fields near Swift Current SK (Fig. 1). Compared to last week, oviposition rates are predicted to have increased.
The larval stage of this weevil feeds on alfalfa leaves in a manner that characterizes the pest as a “skeletonizer”. The green larva featuring a dorsal, white line down the length of its body has a dark brown head capsule and will grow to 9mm long.
Alfalfa growers are encouraged to check the Alfalfa Weevil Fact Sheet prepared by Dr. Julie Soroka (AAFC-Saskatoon). Additional information can be accessed by reviewing the Alfalfa Weevil Page extracted from the “Field crop and forage pests and their natural enemies in western Canada – Identification and management field guide” (Philip et al. 2015). The guide is available in both a free English-enhancedor French-enhanced version.
Pea Leaf Weevil (Sitona lineatus) – The PLW model was run for Red Deer AB (Fig. 1) and Saskatoon SK (Fig. 2). The output suggests that PLW are beginning to become active and will begin to fly on warmer days (Figs. 1 and 2).
Pea leaf weevils emerge in the spring primarily by flying (at temperatures above 17ºC) or they may walk short distances. Pea leaf weevil movement into peas and faba beans is achieved primarily through flight. Adults are slender, greyish-brown measuring approximately 5 mm in length (Fig. 3, Left).
The pea leaf weevil resembles the sweet clover weevil (Sitona cylindricollis) but the former is distinguished by three light-coloured stripes extending length-wise down thorax and sometimes the abdomen. All species of Sitona, including the pea leaf weevil, have a short snout.
Adults will feed upon the leaf margins and growing points of legume seedlings (alfalfa, clover, dry beans, faba beans, peas) and produce a characteristic, scalloped (notched) edge. Females lay 1000 to 1500 eggs in the soil either near or on developing pea or faba bean plants from May to June.
Cereal leaf beetle (Oulema melanopus) – Model output indicates that CLB adults have begun to oviposit eggs near Lethbridge AB (Fig. 1).
Lifecycle and Damage:
Adult: Adult cereal leaf beetles (CLB) have shiny bluish-black wing-covers (Fig. 2). The thorax and legs are light orange-brown. Females (4.9 to 5.5 mm) are slightly larger than the males (4.4 to 5 mm). Adult beetles overwinter in and along the margins of grain fields in protected places such as in straw stubble, under crop and leaf litter, and in the crevices of tree bark. They favour sites adjacent to shelter belts, deciduous and conifer forests. They emerge in the spring once temperature reaches 10-15 ºC and are active for about 6 weeks. They usually begin feeding on grasses, then move into winter cereals and later into spring cereals.
Egg: Eggs are laid approximately 14 days following the emergence of the adults. Eggs are laid singly or in pairs along the mid vein on the upper side of the leaf and are cylindrical, measuring 0.9 mm by 0.4 mm, and yellowish in colour. Eggs darken to black just before hatching.
Larva: The larvae hatch in about 5 days and feed for about 3 weeks, passing through 4 growth stages (instars). The head and legs are brownish-black; the body is yellowish. Larvae are usually covered with a secretion of mucus and fecal material, giving them a shiny black, wet appearance (Fig. 3). When the larva completes its growth, it drops to the ground and pupates in the soil.
Pupa: Pupal colour varies from a bright yellow when it is first formed, to the colour of the adult just before emergence. The pupal stage lasts 2 – 3 weeks. Adult beetles emerge and feed for a couple of weeks before seeking overwintering sites. There is one generation per year.
Grasshopper Simulation Model Output – The grasshopper simulation model will be used to monitor grasshopper development across the prairies. Weekly temperature data collected across the prairies is incorporated into the simulation model which calculates estimates of grasshopper development stages based on biological parameters for Melanoplus sanguinipes (Migratory grasshopper).
This week we observed an adult grasshopper (female), Arphia conspersa, in Saskatoon. Model runs were conducted for Grande Prairie, Saskatoon, Swift Current and Lethbridge.
As of April 30, 2019, predicted development was 60% and is similar to long term average values. The following graph illustrates development for 4 prairie locations (Fig. 1). Hatch is expected to occur during the 3rd week of May (Saskatoon, Swift Current and Lethbridge) and early June in Grande Prairie.
Reminder – The Prairie Pest Monitoring Network’s 2019 Grasshopper Forecast Map was released in March. Review all the risk and forecast maps by linking here. While spring temperatures, soil moisture conditions, and precipitation can all have an impact on overwintered grasshopper eggs, areas highlighted orange or red in the 2019 forecast map should be vigilant this spring by performing in-field scouting to assess nymph densities.
Field scouting is critical – it enables the identification of potential risks to crops. Accurate identification of insect pests PLUS the application of established monitoring methods will enable growers to make informed pest management decisions.
We offer TWO generalized insect pest scouting charts to aid in-field scouting on the Canadian prairies:
Whenever possible, monitor and compare pest densities to established economic or action thresholds to protect and preserve pollinators and beneficial arthropods. Economic thresholds, by definition, help growers avoid crop losses related to outbreaking insect pest species.