Things are Heating Up for Insects

Tuesday, June 23, 2020

Insect development relies on the accumulation of heat throughout the season to progress through their life stages, allowing their development to be tracked with the use of degree day models specific to the insect. By tracking the degree days, the timing of key activities such as adult flight and egg hatch can be predicted, facilitating scouting and pest management activities. To calculate degree days for a particular insect, there are two pieces of information that need to be known: the base temperature (the minimum temperature required for the development of that insect), and the biofix date (the date on which degree day calculations for that insect will begin). The equation used to calculate degree days for insect development is:

GDD = ((Tmax + Tmin)/2) – Tbase

In the equation, Tmax and Tmin refer to the maximum and minimum temperatures on a single day. Using this equation, the growing degree days can be calculated anywhere that has daily temperature information available, making it possible to tailor the model to a particular geographic area. Being able to customize data is important in Nova Scotia where we have a number of microclimates with sometimes significantly different weather often caused by the geography and proximity to the Atlantic Ocean or the Bay of Fundy. Environment Canada lists all of the weather stations available in Nova Scotia both past and present, and can provide the temperature data needed to calculate degree days. Choose the closest weather station logging hourly data for the current year. It is important to note that while degree day modeling can be a useful tool, development models from other geographic areas are not necessarily validated for use in Nova Scotia. Degree day modelling should be used in conjunction with, not as a replacement for, regular scouting.

European corn borer (ECB) is a pest of a number of crops in Nova Scotia. There are two types of ECB, with significantly different development schedules. The univoltine type completes one life cycle in a growing season while the bivoltine type can have two lifecycles in a growing season, though in cool summers the second generation of the bivoltine corn borer may not be able to complete its development.

Mature larva in silk tunnel
European corn borer larva in a corn stalk. Photo:  

Both univoltine and bivoltine types of European corn borer use a base of 10°C and a start date of April 1st for degree day development models. As of June 21st, 239* degree days had been accumulated in Kentville and 190 in Debert. According to the model, at 231 degree days, about 5% of pupae are emerged for univoltine types, with egg laying starting to occur around 425 degree days. For bivoltine types, about 50% of 1st generation adults are emerged by  281 degree days, with a second generation starting their flight around 792 degree days.

For more information on European corn borer in Nova Scotia, check out Perennia’s new fact sheet!

*These numbers were generated with CIPRA software, AAFC, Saint-Jean-sur-Richelieu, Quebec.

How Perennia Agricultural Services is Adapting to Working in COVID-19

Friday, May 29, 2020

During this time of COVID-19 restrictions, members of the Perennia Ag Services staff are adapting how we work to ensure the health and safety of our staff and clients. Check out the following bulletin for details on how we're working to best serve you in these challenging times.

Upcoming Webinar on U-Pick and On-Farm Produce Sales

Wednesday, May 27, 2020

The recent announcement that u-picks will be allowed to operate this summer brings with it the task of figuring out how to make that happen while adhering to COVID-19 guidelines. On June 2nd from 4-5pm, join us for a webinar on “Strategies and Adaptations for U-Pick and On-Farm Produce Sales”. This will be an opportunity to discuss practical management strategies to reduce risks associated with COVID-19. Speakers include Perennia Horticulture and Food Safety specialists as well as Farm Safety Nova Scotia.

Representatives from Perennia’s Horticulture Team, Horticulture Nova Scotia and the Nova Scotia Department of Agriculture will also be on hand as we address your questions and concerns. There will be a question and answer session live during the webinar, so come prepared!

Please visit the following link to register for this informative session.
We look forward to having you there and working together to have a successful season!

Time to keep an eye out for cabbage maggot

Monday, May 25, 2020

With a cool start to the spring this year, insect pests have been a little later getting out and about than we would typically see. Now that there are warmer days upon us, it's important to pay attention to when those insect pests will be active so that control measures can be taken in a timely fashion.

Cabbage maggot (Delia radicum) is a particular challenge in brassica crop production. It overwinters in the pupal stage, emerging in the spring, usually coinciding with the bloom of yellow rocket and serviceberry. From a degree day perspective, emergence begins around 161 Degree Days (DD) at a base of 4°C, with peak flight occurring around 250 DD for the first generation of cabbage maggot. As of Friday May 22, 2020, 175 DD (base 4°C) had been accumulated in Kentville. Other Delia species, Delia platura (seedcorn maggot) and Delia florilega (bean seed maggot) are also on the move in the Valley.

Cabbage maggot larvae in soil. Photo UMass Extension.

Once the first generation of adults has emerged in the spring, they take flight and lay their eggs. It is important to know when peak flight is taking place so that you have the opportunity to alter planting times or deploy control measures, such as insect netting, accordingly.  For scouting purposes, eggs can usually be found small clumps on the soil around the base of your seedlings. For more information on cabbage maggot, including concerns about pesticide resistance, check out Perennia’s fact sheets “Cabbage Maggot” and “Chloropyrifos Resistance in Cabbage Maggot”.

April Shower Bring May... Insect Pests

Tuesday, May 19, 2020

As we head into late May, things are finally feeling like spring and the soil is warming up. With warmer soils come more productive growing days, but also a cozier habitat for pests, including wireworm!

This time of year, wireworms move up to the warmer top layers of soil, feeding on newly seeded or transplanted crops. In fields you know to be problematic areas for wireworm, consider growing a less susceptible crop and practicing crop rotation. Consider cover crops such as brown mustard and buckwheat to combat existing populations. Avoid planting highly susceptible crops such as cereals or potatoes in problematic areas.

Wireworm attacking a lettuce transplant. Photo courtesy Rosalie Gillis-Madden, Perennia.

For more information about wireworms, including how to set up a bait trap, check out Perennia’s new wireworm fact sheet.

Combating Clubroot

Friday, May 8, 2020

Clubroot is a soil borne disease that can survive in the soil for very long periods of time. The spores can go dormant when a host plant is not present, leading to the need for long crop rotations between brassica crops to reduce spore load in the soil. Equipment is the main source of disease spread as the spore-containing soil gets picked up and carried from field to field on tires and tillage equipment.

Soil on equipment and tires transfers clubroot from field to field.
Photo: Canola Council of Canada.
At Horticulture Congress in January 2020, Dr. Mary Ruth McDonald from the University of Guelph spoke about research she is conducting on clubroot control. One of the points that really stood out was the use of grass cover crops to help with clubroot control. A grass cover crop will help to keep the soil in place, therefore reducing the spread of clubroot by equipment. Planting a grass cover crop on the headlands or at the entry to fields with a history of clubroot could be beneficial in reducing this spread.

The clubroot fungus causes abnormal growth of root tissue, resulting
 in clubbing. Photo: Rosalie Gillis-Madden, Perennia.    
There is also some evidence that certain species or varieties of grass cover crops could be contributing to the management of clubroot populations by acting as bait crops. Perennial ryegrass has been seen to stimulate the germination of resting clubroot spores, allowing them to be taken up into the root hairs of the grass, but preventing them from completing their lifecycles and being released back into the soil. Dr. McDonald reported the resting spore concentration of bare soil compared to soil that had been planted with grass cover crops. Three varieties of perennial ryegrass (vars. Norlea, All Star, Fiesta), one of smooth bromegrass (common lot), and one of meadow bromegrass (var. Fleet) were tested, resulting in significantly lower resting spore concentrations in the Fiesta perennial ryegrass and smooth bromegrass.

Further research conducted by Sarah Drury, masters student from the University of Guelph under the advisement of Dr. McDonald, tested the effect of several common cover crops on the clubroot resting spore concentration in soil. Under greenhouse conditions, soils were inoculated with resting spores and then seeded with barley, spring wheat, field pea and perennial ryegrass. One treatment was also left fallow. Post-planting spore concentrations were measured and showed a significant reduction in initial levels for the barley treatment. All others were comparable to the initial spore concentrations.

Perennial ryegrass has been shown to stimulate germination of resting clubroot spores, in some studies.
Photo: Sonny Murray, Perennia.

Other management strategies include liming to a pH of 7.2 or higher, which inhibits the germination of the resting spores, and crop rotations of at least 4-5 years while controlling alternate weed hosts.

Getting into the Weeds Workshop Series

Monday, April 27, 2020

The final installment of the "Getting into the Weeds" Workshop Series is now available on Perennia's YouTube channel:

In this webinar, Gavin Graham, New Brunswick Minor Use Coordinator, and Peter Burgess, Perennia Integrated Pest Management Specialist discuss recent changes in the last few years to pesticides. In addition, Angela Gourd, Nova Scotia Department of Agriculture Plant Protection Coordinator, takes participants through the results from strawberry, onion, and carrot weed surveys.

Be sure to check out the other videos in this series, including "Winter Greens Production" with David Blanchard of Pleasant Hill Farm, and "Food Safety Success" with Shelly MacDonald and Elaine Grant of Perennia's Food Safety Team.