Etapas reprodutivas do desenvolvimento da soja

Reproductive Soybean Development Stages and Soybean Aphid Thresholds

R2 Stage soybean plant (full bloom)

Open flower at one of the two uppermost nodes on the main stem with a

fully developed leaf.

Stage length 5 to 15 days: average 10

Action Threshold - 250 aphids/plant when population actively increasing.

This guideline incorporates an approximate 7-day lead time between

scouting and treatment to make spray arrangements.

R3 Stage soybean plant (beginning pod)

Pod is 3/16 inch long at one of the four uppermost nodes on the main stem

with a fully developed leaf.

Stage length 5 to 15 days: average 9

Action Threshold - 250 aphids/plant when population actively increasing.

In replicated trials conducted throughout the Midwest in 2003, the 250

aphids/plant action level worked best from late vegetative through R3 stages.

R4 Stage soybean plant (full pod)

Pod is ¾ inch long at one of the four uppermost nodes on the main stem with

a fully developed leaf.

The most critical time for soybean yield: Stress at this time can not be

recovered and results in more yield loss than at any other time.

Stage length 4 to 26 days: average 9

Thresholds not currently determined, but populations exceeding 250/plant

and actively increasing need monitoring and treatment at grower discretion.*

Photo © Iowa State University

soybean aphid

Aphid thresholds depend on actively increasing populations. Examine 20-30

plants once or twice weekly to determine population dynamics.

Action Threshold - 250 aphids/plant when population actively increasing.

R1 Stage soybean plant (beginning bloom)

One open flower at any node on the main stem.

A node is the part of the stem where a leaf is (or has

been) attached.

Stage length 0 to 7 days: average 3

David W. Fischer - Dane County UWEX Crops and Soils Agent

James Fanta - Dodge County UWEX Crops and Soils Agent

X1134

University of Wisconsin - Extension

*Thresholds for R4-R5 beans continue to evolve. Spraying at R4-R5 has been documented to protect yield. Growers and consultants are strongly advised to keep current with UWEX treatment recommendation updates.

Acknowledgements: Eileen Cullen and Bryan Jensen - UW Department of Entomology, Roger Borges - UW Department of Agronomy. Soybean aphid photograph by John Wedberg, remaining photographs not attributed to Iowa State University taken

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