Be prepared for cutworms and grasshoppers this season, and that includes knowing which you need to spray and which you don’t.
That was the message from Jennifer Otani, an Agriculture Canada entomologist based in Beaverlodge, speaking to the FarmTech conference in Edmonton.
Forecasts based on surveys last year have been issued — see the accompanying map for grasshoppers, and similar forecasts for wheat midge and sawfly can also be found at www.agriculture.alberta.ca/app21/loadmedia.
“We strongly encourage people to look at the risk associated with their area,” said Otani. “This does not mean that you will have to spray, but it gives you an idea of the risk. You’re looking for moderate, severe and very severe densities.”
The Alberta Pest Surveillance Network has several people monitoring throughout the year and produces the forecasts using data from the previous year, combined with modelling reports.
The 2012 forecast is showing some severe pockets of grasshoppers in Alberta. Last year’s open fall resulted in a lot of egg laying for adult grasshoppers. “What that means is that we have more eggs than normal and they’re probably at different stages,” said Otani. “This spring, the grasshoppers will likely emerge over a longer period, which will make monitoring a little more difficult.”
“The limitation is that this is produced in January and what happens at the end of May and beginning of June can really vary depending on weather,” Otani said.
There are four species of grasshoppers considered economic pests. Red-legged grasshoppers are not considered a pest species, because they don’t cause a lot of damage.
“The big issue is to monitor very early and to get out there and look for the nymphs very early,” Otani said.
Nymphs are much easier to control with insecticides than the adult species.
“You really want to look for the younger ones before they have time to be doing a lot of feeding,” Otani said.
Producers also need to keep a sharp eye for cutworms, Otani said. The diversity of cutworms species in the province has rapidly changed and some haven’t been seen for more than 15 years.
“It’s starting to be a bit of an issue and a bit of a cause for concern,” Otani said. “The real concern with this group is that the adults look very similar.”
Otani said the diversity of species presents a challenge for control, as not all of the species can overwinter at the same stage and do not cause damage at the same time. Some feed above ground and some below.
Red-back cutworms come above ground in the evening to feed, but pale western and glassy cutworms are subterranean. Some species have a host plant preference while other insects will eat just about anything. Control methods vary widely as a result.
Cutworm eggs can remain on plant material or in soil over winter. Some small larvae, which are generally brownish grey and about 10 to 25 millimetres in length, can survive through the winter. The insects are damaging when they are in the larval stage.
After the larval stage, the insects turn into pupae and then into flying moths. Cutworms caused the most damage in the early part of May up in the Peace country and even earlier in central and southern Alberta.
Cutworm damage may increase in late-seeded fields with a lot of regrowth.
“We’re trying to advise people to watch for regrowth and try to manage it if at all possible,” Otani said. “This presents a bit of a risk for the next season.”
As with other insects, scouting is important. Otani said producers should scout in the seed row, down below the soil surface, no deeper than about 10 centimetres. “Stay near to the live plant or plant material that is showing damage,” she said. “Don’t dig where you’re already missing stuff.”
Cutworms tend to be easiest to spot early in the morning, or in the evenings. “We really encourage people to look in several different places too,” Otani said.
If a specimen is found, producers should keep it intact and get some good pictures to help an entomologist identify it. Unusual patterns, damaged plants, plants that have fallen over or browning off may be signs of cutworms.