Weeds play host to soybean cysgt nematode - FW Daily News: Home

Weeds play host to soybean cysgt nematode

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Posted: Saturday, March 21, 2009 12:00 am | Updated: 5:36 pm, Tue Mar 12, 2013.

There are six winter annual weeds and one cool season perennial that have been identified as alternate hosts to soybean cyst nematode, according to the following information provided by Valerie Mock and Bill Johnson. We have observed that SCN can reproduce in the field on purple deadnettle. Fields with these weed hosts may be increasing SCN population densities at a faster rate than fields without weed hosts.A recent study in Indiana found that known SCN weed hosts were prevalent in 93 percent... There are six winter annual weeds and one cool season perennial that have been identified as alternate hosts to soybean cyst nematode, according to the following information provided by Valerie Mock and Bill Johnson. We have observed that SCN can reproduce in the field on purple deadnettle. Fields with these weed hosts may be increasing SCN population densities at a faster rate than fields without weed hosts.

A recent study in Indiana found that known SCN weed hosts were prevalent in 93 percent of the fields surveyed, indicating the possibility of a statewide increase in nematode population densities due to weeds. In Indiana SCN has been found in 82 of 92 counties. Most of these weeds can start to emerge during late August and September. So consider using this guide to scout fields and determine if you have these weeds present and if the density or future cropping plans would warrant fall treatments for winter annual weeds.

The purpose of this article is to identify characteristics of each of the six winter weed hosts and the one cool season perennial. We will discuss them in the order of strongest to weakest host.

Winter annual weed hosts:

• Purple deadnettle (strong host)

• Henbit (strong host)

• Field pennycress (moderate host)

• Shepherd’s-purse (weak host)

• Small-flowered bittercress (weak host)

• Common chickweed (weak host) Cool season perennial:

• Mouseear chickweed (weak host)

Purple deadnettle and henbit are strong hosts and it can be difficult to distinguish the two weeds when they are small.

Purple Deadnettle (Lamium purpureum)

Leaves: Cotyledons (the seed leaf) have a white tip, and are oval with a notch where the petiole (the stalk between the stem and leaf blade) connects to the cotyledon. Leaves have prominent venation, resulting in a crinkled look. Leaves at the base of the stem are hairy and circular in shape. Leaves at the top of the stem are hairy and triangular in shape.

Stems: Square and greenish-purple in color. Stems tend to branch at the base of the plant and have hairs that point downward.

Flowers: Blooms are purple, and occur in upper leaves in whorls of 3 to 6. Purple deadnettle blooms between April and October.

Henbit (Lamium amplexicaule)

Leaves: Cotyledons are oval, have a white tip, and notched where the cotyledon and petiole meet. Leaves are circular with rounded teeth along edges and slight venation which causes a crinkled look. Leaves have hair on their upper surfaces and hair along the veins on their lower surfaces. Leaves at the top of the stem wrap around the stem and are sessile (lacking a stalk).

Stems: Stems are square, tend to branch near the base of the plant, have hairs that point downward, and are green or purple.

Flowers: Flowers are purple to pink. Henbit can flower from March to November.

Field pennycress and shepherdspurse are weaker hosts than purple deadnettle and henbit. Much like purple deadnettle and henbit, these weeds can be difficult to distinguish from one another.

Tune in next week and I will continue with field pennycress. Below I

have a glossary of some words used in this article.

This is Hanson

Young, Purdue Extension Educator, have a good week.

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