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Beneficials on the rise against soybean aphids, root rot, fusarium in fields

Manitoba Insect & Disease Update for August 2

Diamondback moth continues to be a concern in some areas, although it is the pupa stage that is now dominant in some fields.

Soybean aphids surpassed economic threshold in some fields. In some soybean fields natural enemy populations seem to be building in response to the soybean aphids.

Bertha armyworms are being monitored, and high levels of larvae have been reported from the Holland and Austin areas.

Phytophthora root rot reports in soybeans continue to come in from across the province.

Fusarium head blight symptoms are evident in some fields, but overall incidence remains low.

Phytophthora Root Rot

Reports of root rot, suspected be Phytophthora, have continued to come in from across the province. In severe cases, up to 50 per cent of plants have shown disease symptoms. Plants infected with Phytophthora root rot (PRR) will typically completely senesce and not produce yield. The spores of the causal pathogen are long-lived in the soil, so rotation alone will not be enough to manage the disease in future years. Seed treatments can be used to manage disease early in the season, and resistant varieties are key to managing PRR. Provincial surveys have indicated what races of PRR are present in Manitoba and resistant varieties are indicated in Seed MB with what resistance gene they carry.

Fusarium Head Blight

The provincial survey for Fusarium head blight (FHB) in spring wheat is underway and almost complete across the province. In most fields, infection is extremely low. Symptoms are more easily observed in fields that received a rainfall in early July. FHB ratings are also performed in MCVET trials across the province which do not receive a fungicide application. Disease levels in these trials in 2017 have also been low overall.

To report observations on insects or plant pathogens that may be of interest or importance to farmers and agronomists in Manitoba, please send messages to:

Visit the insect pages on the Manitoba Agriculture website at www.gov.mb.ca.

Click here to view the complete Manitoba Insect & Disease Update on the Manitoba Agriculture website.

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