John Gavloski Entomologist, Manitoba Agriculture

Transcription

1 From large spiny caterpillars to small sap suckers: Insects on Crops in Manitoba in John Gavloski Entomologist, Manitoba Agriculture

2 Variability in Insect Populations Some insects do not overwinter well or at all in Manitoba and may blow or migrate in. Insect Populations can be affected by: Food Availability Temperature precipitation dry Natural Enemies High levels of some.

3 Purpose of Presentation To review the insects of greatest abundance and concern in field crops in Manitoba in Discuss key drivers of population levels.

4 Flea Beetles on Canola Most canola seed with neonicotinoid seed treatment. Many fields received additional insecticide applications. Some reseeding in Central region. Slow emergence and growth due to cool weather and dry soil increased injury from flea beetles in some areas.

5 Cutworms Dingy Cutworms Redbacked cutworms Still a concern in many crops in 2017.

6 Alfalfa Weevil (Hypera postica) Feeding from larvae common in many alfalfa fields. Some alfalfa for hay was cut early. Insecticides applied to some alfalfa fields. Alfalfa weevil control started in early-june and extended into early-july.

7 Level of parasitism of alfalfa weevil at 4 Manitoba sites in % 50.0% 40.0% 30.0% 20.0% 10.0% Percentage Alf Weevil Larvae Parasitized (2017) Bathyplectes Oomyzus Unknown 0.0% Winnipeg Fannystelle Fisher Branch Arborg Graph by David Ostermann, Manitoba Agriculture

8 Aphids on Cereals Began to be noticed in early-june. Some populations above economic threshold in July. High levels of natural enemies noted in some fields. Incidents of barley yellow dwarf reported from some fields in the Central region.

9 Cereal Aphid Manager Phone app. Will incorporate aphids, natural enemies, plant staging (Zadoks scale) and other factors into the model. The app will use slightly different growth rates for different species of aphids. Photo: Tyler Wist

10 Pea Aphid (Acyrthosiphon pisum) Above economic threshold in many pea fields in Most control occurred in mid- to late-july.

11 Soybean Aphid (Aphis glycines) First noticed in early-july. Economic populations became widespread beginning the last week in July. High levels of predators in some fields.

12 Aphid Advisor Uses: aphid numbers natural enemy numbers expected population growth rates, to indicate whether there are enough natural enemies to keep aphid populations below action thresholds.

13 Diamondback moth (Plutella xylostella) Larvae of diamondback moth first started to be noticed in early-june. In July and early-august insecticide applications for diamondback moth occurred in canola fields in the Southwest, Northwest and Central regions.

14 Diamondback Moth What the traps forecasted Highest cumulative trap counts in MB in 2017 Nearest Town Region Trap Count Minitonas Northwest 197 The Pas Northwest 129 Teulon Interlake 107 Howden Central 86 The Pas Northwest 80 Whitemouth Eastern 75 Note- highest total in Southwest was 13 For comparison - highest trap counts in 2016 were 237, 184, 174, , there were no reports of control for dbm being needed in canola in highest counts in 2016 were also in Minitonas and The Pas.

15 Mortality Factors for Diamondback Moth Rainfall can be a major mortality factor of eggs and early instars of diamondback moth. Harcourt Memoirs of the Ent. Soc. Canada Kobori and Amano Applied Entomology and Zoology Parasitoids.

16 Surprises within the silky case - Parasitoids of Diamondback Moth Cocoons with Diadegma Photo from Mildred Valentino, Manitoba Agriculture

17 Bertha Armyworm (Mamestra configurata) Levels of larvae were high in the western part of Manitoba, with insecticide applications needed in some fields in August.

18 Bertha armyworm (Mamestra configurata) Highest cumulative counts for bertha armyworm in MB in 2017 Nearest Town Region Trap Count Risk Category Benito Northwest 605 Uncertain Tilston Southwest 413 Uncertain Durban Northwest 371 Uncertain Benito Northwest 329 Uncertain Durban Northwest 297 Low Glenboro Central 294 Low 86 out of 90 traps were in the low risk category (<300 moths) For comparison - Trap counts from 2017 were generally lower than in 2016 (12 traps over 300). - In 2016 economic populations of berths armyworms were not widespread.

19 Overwintering of Bertha Armyworm Depth of snow can affect how successful bertha armyworm overwinters. Pupae did not survive a Manitoba winter in snow-free field plots, but 55% survived in plots with 5 or 10 cm of snow. Lamb et al., The Canadian Entomologist 117,

20 Thistle Caterpillar (Vanessa cardui) The caterpillars and their webbing are very visible and caused concern in some soybean and sunflower fields..

21 Painted Lady Butterfly / Thistle Caterpillar A migratory species. Thistle, when present, a major food source for larvae.

22 Summary Dry weather may have had an impact on some crop-feeding insects. Some unexpected migrants. High levels of some species natural enemies.

23 Insect Pest Summaries Western Committee on Crop Pests Summaries of Insect Pests in Crops in Manitoba:

24 Discussion and Questions? John Gavloski Entomologist Manitoba Agriculture Phone: (204)