By: Scott Hartley, PAg, Provincial Specialist, Insect/Vertebrate Pest Management
The 2016 growing season started with warm and dry conditions. In May and June, rain events allowed for good crop growth in most areas with some areas receiving high amounts of precipitation. Following a winter with higher than normal temperatures and low snowfall in most areas, insects such as flea beetles were expected to be problematic. Richardson’s ground squirrel populations were on the increase with the dry conditions and low run-off in the spring, and even caused significant damage to some crops.
Although there were reports of high feeding pressure by flea beetles in some areas in the latter part of May, overall it was a moderate year for them. In some cases where growing conditions were slow, canola plants in early stages were more vulnerable and foliar insecticide application was required. Producers were reminded to keep in mind any restrictions associated with the products, including maximum number of applications and maximum amount of chemical that can be applied per season.
Cutworms became the main insect of concern in the last two weeks of May, with reports across Saskatchewan in most crops, including pea, lentil, wheat, oats, barley and canola. Due to favourable climatic conditions, cutworms developed faster than in previous years’ cooler springs. Damage was so extensive in some situations that crops were re-seeded. Reports of cutworm infestations continued into the third week of June, typical of cutworm species that over-winter as eggs, such as red-backed cutworms.
Monitoring commenced early in 2016, with most traps set up by the end of April. One trap near Regina picked up a single diamondback moth in the second week of April. Although economic infestations on the Prairies are usually a result of blow-ins from the south, the mild winter likely allowed for better over-wintering success for the moths. Collection of data continued until the end of June. However, even with the early start, there were no significant infestations noted in the province.
Pea leaf weevil
A pea leaf weevil survey has been conducted in Saskatchewan in late May and early June since 2007, initially to determine distribution of the weevil and more recently to assess levels of damage. The survey of visual damage to pea plants has focused primarily in southwestern Saskatchewan but has expanded east and just north of the South Saskatchewan River. In 2016, based on the survey and additional reports, it now appears the pea leaf weevil has a much wider distribution east and north than previously known. The typical damage (notching) to the leaves of pea plants was noted southeast of Moose Jaw. Pea fields observed in the Outlook area (RM 284) had light levels of feeding, but faba bean plots at the irrigation centre (CSIDC) showed potentially economic levels of damage. There were also pea and faba bean fields with high levels of feeding near Kyle and Davidson, and at fields around Saskatoon.
Cabbage seedpod weevil
The cabbage seedpod weevil has become an annual pest in canola and mustard primarily in southern Saskatchewan, migrating into flowering crops near the end of June and into July. The distribution of the weevil now includes most of southern Saskatchewan to near the Manitoba border and north to Kindersley and Outlook in the west. A survey was conducted in 2016, with the results expected to be available in early December.
Grasshopper infestations were not expected to be severe in 2016, but by the end of June young grasshoppers were reported in high numbers in some areas. Agriculture and Agri-Food Canada bio-climatic models indicated the annual hatch was not complete in all areas by the middle of June. Some of the sentinel sites had higher populations of hatchlings than had been seen for over a decade, but infestations did not materialize, except in lentil, where the economic threshold is only two grasshoppers per square metre. A survey for adult grasshoppers was conducted by Saskatchewan Crop Insurance Corporation field personnel in August and early September.
Reports of aphids started in early to mid-July, first in lentil crops followed by pea, wheat and canaryseed. Initially most reports were a result of regular field scouting and aphid numbers were not at economic threshold levels. However, the humid conditions in July favoured the development of aphid infestations. Whether or not insecticide application was required depended on the stage of the crop. As in the previous year, there were widespread reports of the orange or red morph of the normally green English grain aphid in wheat. This colour variation is thought to be a result of climatic conditions.
Humid conditions in July favoured wheat midge infestations, which were reported throughout the eastern half of the province in 2016. Midge emergence was very high in many cases, prompting questions about an economic threshold for wheat midge in midge tolerant wheat. Initially released in red spring wheat, midge-tolerant wheat varieties are now available in durum and extra strong classes. This option for managing wheat midge has become widespread, with estimates of midge tolerant varieties contributing one-third of Canada Western Red Spring (CWRS) wheat in Saskatchewan.
Bertha armyworm emergence started by the end of June, earlier than noted in the past several years. Although this pest was not expected to be of concern in 2016, there were some higher numbers of moths collected by mid-July, especially in the central part of the province, as seen on the weekly risk map. Since the bertha armyworm is more predictable with peaks in their cycle every eight to 10 years, the high numbers were surprising and may have been a result of the mild winter. There were reports of insecticide application for control in a few areas.
Some other anomalies in 2016 included slugs and tent caterpillars. Slugs are not a common pest of field crops, although they have been noted in cereals and canola in some of the recent wet years in the spring. However, in late July and early August, slugs were found devouring some wheat heads in central and northern regions of Saskatchewan.
Tent caterpillars feed on tree and shrub species and are normally found in some areas of the province in any year. In 2016, however, they were reported in high numbers across the province. While they were primarily found in urban areas, parks and shelterbelts, tent caterpillars were also reported in alfalfa and canola. Feeding damage was not significant and the caterpillars were likely moving across fields from treed areas.