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Reviewing the Big Five Insect Threats of 2019

John GavloskiEntomologist, Manitoba Agriculture and Resource Development

Top Insect Concerns From 2019

• Flea beetles in canola• Cutworms• Grasshoppers

• Armyworms• Thistle caterpillar• Diamondback moth in canola• Bertha armyworm in canola

Flea Beetles on Canola• Most canola seed with neonicotinoid

seed treatment.• Some canola growers delayed seeding

to reduce risk from flea beetles.• Many fields received additional

insecticide applications.• Some reseeding due to flea beetles.• Additional stresses on canola seedlings in

some areas, such as frost, cool and dry weather, soil blasting and cutworms.

Seeding Dates and Flea Beetle Injury

1) MB: Earlier seeded tests suffered more damage by flea beetles.

Lamb. 1984. Can. Ent. 269-280.

2) ND: Early seeding increased injury by flea beetles.Knodel et al. 2008. J. Econ. Ent. 810-821.

3) AB: Early seeding reduced damage by flea beetles in southern Alberta, but increased damage in central and northern Alberta.

Carcamo et al . 2008. J. Appl. Ent. 623-631.

MAC Trivia 2019 - Which are Potential Cultural Controls to minimize Flea Beetle injury in Canola?

A) Seeding as shallow as available moisture will allow

B) Direct seedingC) Increasing seeding rateD) A and CE) All of the above (A, B, C)

Cutworms

• A concern in many crops in 2019.• Insecticides used, and some reseeding.• Some reports of multiple insecticide

applications.

Dingy Cutworms Redbacked cutworms

Can some plants compensate for cutworm feeding?

• Removal of some canola plants resulted in remaining plants producing more pods (which increased from 20-90 to as many as 600), and in some instances more seeds per pod and increased seed weight. – McGregor. 1987. Canadian Journal of Plant Science. 43-51.

• “The loss of only some flax plants at larval densities lower than 16 larvae per 0.5m2 results in a small but significant increase in per plant yield”.– Source: Ayre. 1990. The Canadian Entomologist. 21-28.

Cutworm Forecast for 2020? • Pheromones and light traps tested for

several species of cutworms, but not effective at predicting damage.

Overwinter:• As partially grown larvae: Dingy, glassy.• As eggs: Redbacked, darksided.

• Timely scouting in spring recommended.

Grasshoppers

• Population increasing over past few years.• Control along field edges and whole fields.• Later-season edge effects noted in some crops

(canola, soybeans, etc.).• Affected pasture regrowth in some areas.

Twostriped grasshopper Migratory grasshopper

Winter Weather and Grasshoppers

• Soil temperatures of -15°C required to cause substantial winter mortality.– Don’t usually occur because snow cover

insulates.– Eggs usually laid where snowfall

accumulates.

– Mukerji and Braun. 1988. The Canadian Entomologist. 1147-1148.

Effect of spring rains on grasshoppers

• “Impact of mid-May rain on grasshoppers will be negligible.”– Each egg has a nearly waterproof shell.

• “Plenty of rain between late May and mid-June will slow down the pest species of grasshoppers, and can kill a significant proportion”.

MAC Trivia 2019 - Which of the following is not a Predators of Grasshopper Eggs?

a) Bee fly larvaeb) Blister beetlesc) Ground beetlesd) Lady beetle larvaed) Field Crickets

• Consider management techniques that minimize harm to predators and parasites.

Thistle caterpillar / Painted Lady Butterfly(Vanessa cardui)

• Large amounts of painted lady butterflies noticed in early June in some areas.

Thistle caterpillar (Vanessa cardui)

• Insecticides applied to some soybean fields in the Northwest and Eastern regions to control larvae in early/mid July.

• Also noticed on Canada thistle, round leaf mallow, and sunflowers.

MAC Trivia 2019 -Parasitoids of Thistle caterpillar

What are these oversized house flies with bristly abdomens that kept emerging from my pet thistle caterpillars?

A) CotesiaB) Hover fliesC) Robber fliesD) Tachinid fliesE) Stiletto flies

Thistle caterpillar forecast for 2020?

• Adults migrate into the Prairies from overwintering sites in southern California and Mexico.

Armyworms(Mythimna unipuncta)

• Controlled in some fields of small grain in the Eastern, Interlake and Central regions in mid/late July.

• Also controlled in some forage grass seed crops in Eastern region.

Armyworms(Mythimna unipuncta)

• Cotesia pupal clusters noticeable on cereal heads in some fields.

Notice anything unusual about the armyworm in this photo?

What Didn’t Happen in 2019

• Soybean aphids– Outbreak years: 2006, 2008, 2011, 2017

• Aphids in cereals and flax.• Wheat midge• European corn borer• Aster leafhoppers

Insect Pest Summaries

• Western Committee on Crop Pests– http://www.westernforum.org/

• Summaries of Insect Pests in Crops in Manitoba:– http://www.gov.mb.ca/agriculture/crops/insects/index.html

Discussion and Questions?

John GavloskiEntomologistManitoba Agriculture and Resource Development

Phone: (204) 750-0594Email: John.Gavloski@gov.mb.ca