Predictive Model Updates

Timing scouting activities is important. In addition to the Weekly Update, updated phenology models for insect pests on the Canadian prairies will be posted here during the growing season, especially when this information may help time scouting or management activities. Posts on this page will be accompanied by Twitter updates if you follow @vanbugsky.



Pest Risk Alert: Bertha Armyworm, June 3, 2019
Dymex alfalfa weevil model (Hypera postica– daily weather – base model)
Prepared by Ross Weiss (AAFC) on June 3. Posted by Meghan Vankosky (AAFC) on June 4. 

Recent warm conditions have advanced bertha armyworm (BAW) pupal development. Compared to last week, development is 2-6 days faster and development is 2 days ahead of normal (based on climate normals). Based on BAW model runs, pupal development is nearing 80% in some areas of southern and central AB and SK. BAW adults may begin to emerge within the next 10 days. It is advisable to place pheromone traps in fields when pupal development is 80% to capture the full extent of adult flight activity. Based on this value, traps should be put out in SK and AB fields this week.

Table 1. Predicted and average emergence dates for adult bertha armyworm at select locations across the prairie region. 
Location
Predicted emergence date
Average emergence date
Saskatoon
June 15, 2019
June 17
Brandon
June 16, 2019
June 15
Edmonton
June 17, 2019
June 23
Lethbridge
June 18, 2019
June 16
Grande Prairie
June 22, 2019
June 23
Avg
June 17, 2037
June 18




Figure 1. Predicted stage of pupal development of bertha armyworm based on temperature across the prairies in spring 2019. Adult emergence occurs when pupal development reaches 100% (indicating that pupal development is complete). 


Pest Risk Alert: Alfalfa Weevil for June 3, 2019
Dymex alfalfa weevil model (Hypera postica– daily weather – base model)
Prepared by Ross Weiss (AAFC) on June 3. Posted by Meghan Vankosky (AAFC) on June 4. 

Weather conditions continue to be favourable for development of alfalfa weevil, if alfalfa weevil are present in your area. First instar development is nearing completion and the more individuals in the population should be in the second instar stage. In alfalfa fields near Brooks AB and Swift Current SK, larvae should start to reach the third instar stage late this week. 

Figure 1. Percentage of alfalfa weevil population in the first instar, week of June 3, 2019. 


Figure 2. Percentage of alfalfa weevil population in the second instar, week of June 3, 2019. 

Figure 3. Predicted timing of alfalfa weevil development in spring 2019 near Swift Current, SK. 

Figure 4. Predicted timing of alfalfa weevil development in spring 2019 near Brooks, AB. 



Pest Risk Alert: Alfalfa Weevil for May 28, 2019
Dymex Alfalfa Weevil Model (Hypera postica- Daily Weather - Base Model) 
Prepared by Ross Weiss (AAFC) on May 28, Posted by Meghan Vankosky (AAFC) on May 29

Model output based on meteorological data up to May 27, 2019 and projected to June 15, 2019 indicates that alfalfa weevil larvae, if present in the Swift Current and Brooks regions, will reach the second instar in a few days and the third instar about one week later. Model predictions are based on meteorological data and the temperature requirements for alfalfa weevil development and do not reflect or predict population densities in these regions. Figure 1 predicts the development of alfalfa weevil over the next few weeks at Swift Current SK and Figure 2 for Brooks AB. 

The models are initiated with a randomly selected number of individuals (not reflective of actual insect numbers in alfalfa fields). In the figure, each developmental stage of alfalfa weevil is represented by a different coloured line. The ‘appearance’ of each successive developmental stage in the field is expected to occur when the number of individuals raises above zero. In Figure 1, alfalfa weevils are predicted to reach the second instar (dark blue line) beginning in early June and reach the third instar (green line) about a week later. 


Figure 1. Predicted timing of the development of alfalfa weevil at Swift Current SK in spring 2019. 


Figure 2. Predicted timing of the development of alfalfa weevil at Brooks AB in spring 2019.



Alfalfa Weevil oviposition and egg development update: May 13, 2019
Prepared by Ross Weiss (AAFC) on May 13, posted by Meghan Vankosky (AAFC) on May 14

A DYMEX model was developed for Alfalfa Weevil that can be used to predict the timing of developmental milestones based on abiotic conditions. Model output for May 13, 2019 indicates that alfalfa weevil oviposition is underway and initial embryonic development has begun. The oviposition index provides an indication of relative oviposition rates across the prairies. The model predicts that the most eggs have been laid around Winnipeg and Regina, as well as a large region in Alberta extending from the US border to fields east of Calgary (Figure 1). Across the region, embryological development is just beginning, with development ranging from 1 to 6.5% (Figure 2). The greatest development is predicted to have occurred in southern and central regions of Alberta and west-central Saskatchewan.


Figure 1. The oviposition index is used to indicate where the most Alfalfa Weevil eggs have been laid, where 0 indicates no eggs and 1 indicates high relative egg numbers.



Figure 2. Modelled embryonic development of Alfalfa Weevil eggs, ranging from 1 to approximately 6.5%. Egg hatch when embryonic development reaches 100%.