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True Armyworm larvae photo

Watch for Armyworm in spring cereals and mixed forages

By Tracey Baute

Armyworm has been spotted at low levels in a few winter wheat fields, though being so close to harvest, it is really not a concern in that crop. However, it does indicate a need to keep an eye out for them in spring cereals, as well as mixed forages (as they like to feed on grasses). True armyworm larvae can vary in colour from green to reddish-brown but all have white-bordered stripes running laterally along the body. True armyworm also have dark diagonal bands at the top of each abdominal proleg and a yellowish-brown head with a network of dark-brown lines creating a mottled pattern.

True Armyworm larvae photo

True Armyworm larvae. Photo by T. Baute, OMAFRA.

Scouting Guidelines: Scout every 4 days to stay ahead of any potential invasions. The best time to scout for true armyworm is shortly after dusk when larvae are actively feeding.  In cereals and mixed forages, examine 10 areas of the field, assessing the number of larvae per 30 cm x 30 cm (1 ft2). Pay particular attention to the border area directly adjacent to other grassy host crops. During the day, if it is cloudy and overcast, you might be lucky enough to see larvae on the head of the plant but on sunny days, they will be down on the ground among the crop debris or under soil clods. Brown frass may also be present on the plants and on the soil surface. Birds diving into your field is a good indication that there are good eats there so take a look.

True-Armyworm-parasitized-by-tachinid-fly-J-Smith-UGRC-pointing-to-egg_01

True Armyworm parasitized by Tachinid fly. Photo by J Smith UGRC pointing to egg.

When you do find larvae,  look for any white eggs that may be attached to the backs of the armyworm larvae. This is a sign that the larvae have been parasitized by one of its parasites which have done the job for you. Avoid treating with insecticides when large numbers of parasitized larvae are present as they have already been controlled by parasitoids or when larvae are close to 2.5 cm in length, as insecticides will no longer be effective and the larvae will soon stop feeding.

Threshold for Mixed Forages: Control is warranted when five or more larvae (smaller than 2.5 cm) per square foot are found. In seedling crops, two to three larvae (smaller than 2.5 cm) per square foot may warrant control.

Threshold for Cereals: Chemical control is warranted if there are 4 to 5 un-parasitized larvae per 30 cm x 30 cm and the larvae are smaller than 2.5 cm. If a significant amount of wheat head clipping is occurring, spray may be warranted if larvae are still actively feeding, are smaller than 2.5 cm and as long as pre-harvest intervals have not been reached.


Source: Field Crop News

Corn Nitrogen Response Curve

Nitrogen stabilizers

Nitrogen management has always been a challenge in high nitrogen demand crops such as corn and winter wheat.

The three pathways that can contribute to significant nitrogen loss are:

  • Volatilization (loss of ammonia nitrogen to the atmosphere from the soil surface),
  • Denitrification (which occurs when soils are saturated and in an anaerobic environment) and
  • Leaching (downward movement of nitrate nitrogen out of the rooting zone due to excessive rains)

The challenge has always been to make nitrogen available when the crop needs it and minimize the exposure of nitrogen to the weather scenarios that contribute to N loss. Consider the nitrogen response relationship for corn and winter wheat (below):

Corn nitrogen response curve

(Adapted from Richie, et.al, 2005, How a Corn Plant Develops).

Corn Nitrogen Response Curve

We often apply nitrogen early in the season before the crop actually utilizes it. For example, the demand for nitrogen in corn is at its peak at about the V10 growth stage (often around early to mid-July). Split-applying nitrogen has been a reasonably effective way to reduce the risk of nitrogen loss, however, with added application costs. Read more

winter wheat stand

Nitrogen on winter wheat

Nitrogen on winter wheat

Cereals are very responsive to nitrogen. However, over-application of nitrogen or applying too early on a thick stand of wheat can cause lodging, resulting in reduced yield, quality, and harvestability. The optimum rate of nitrogen for a particular field will depend on the type of wheat grown, past applications of manure or fertilizer, soil type, and crop rotation. Use general recommendations as a starting point but combine them with observation of crop growth and lodging tendency. The idea is to ensure nitrogen is available early and consistently though the major uptake period (which is node development though booting). Read more

Assessing winter wheat survival

Assessing winter survival in wheat

Assessing winter survival in wheat Factors affecting winter survival in wheat The ability of winter wheat plants to survive winter often depends on each plant’s ability to tolerate low temperatures. Winter wheat plants go through a process called ‘cold acclimation’ in the fall during which each plant acquires the ability to withstand the cold temperatures […]

Managing Fusarium Head Blight at harvest

Fursarium Spores WheatThe less infected kernels that go into storage the better, and the greater of a chance a grower will have for not getting docked to a lower grade of wheat.

Combine tips and notes

  • Higher fan speeds are needed to blow infected kernels out the back. Ridgetown College has done studies on fan speeds, and there is a tenfold decrease in the amount of Fusarium damaged kernels in a sample when the fan speed is at maximum blast. But with that comes challenges of losing good healthy kernels.
  • Research from Ohio State showed combine fan speeds between 1375 and 1475 RPM and the shutter opening at 3.5 inches received the lowest discounts at elevators from FHB damaged wheat kernels and DON levels in the harvested grain.
  • Reduce combine speed. Having the combine traveling at a slower speed, will allow better separation between the good and bad kernels.
  • In fields which are severely affected by leaf diseases, the lower test weight of the grain may make it more difficult to separate normal kernels from Fusarium damaged kernels.

Read more

Snow mould in winter cereals


Holly Loucas, Agronomist, DOW Agroscience

What is snow mould?

Snow moulds are cold-loving fungi that can attack many economic plants under a cover of snow.

Pathogen biology

WinterMouldChartThe important species of snow moulds that infect winter wheat are Microdochium nivale and Typhla spp.

Gray snow mould (Typhula spp) is the less damaging form of snow mould. It is able to survive throughout hot summer months as sclerotia under the ground or in plant debris.

Pink snow mould (Microdochium nivale) is usually more severe than gray snow mould. It can survive the summer months in decayed plant debris as spores or mycelium. Read more

Wheat field

Late Planted Winter Wheat

During years when soybeans are harvested later than expected or environmental conditions delay field work, winter wheat is generally skipped in the rotation or planting is rushed. When planting winter wheat later than the recommended planting dates, even more care should be taken to ensure yield potential is not lost.

Planting date

In general, delaying planting past the recommended planting window can cost a producer from 0.6 to 1.1 bu/day. It is best to strive to plant around these dates (See figure 1).

planting dates map

Figure 1: Optimum Planting Dates in Ontario.

Read more