West central Michigan vegetable update – June 14, 2017

Asparagus harvest is drawing to a close over the next two weeks.

For all crops, as top or sidedress time approaches, note that coating urea with a urease inhibitor can slow losses of nitrogen to volatilization. This buys you some time, but irrigation or rainfall is still needed to move nitrogen into the soil.

There have been spotty issues with cutworm in brassicas, cucurbits and onions this spring. Many cutworm issues occur when there is attractive vegetation present in spring for caterpillars to develop on and moths to lay eggs on. This could be winter annual weeds like chickweed or a cover crop. Getting rid of this vegetation a few weeks before planting can help avoid a “green bridge” between it and your crop.

Temperatures are high enough that, if soil moisture is low, irrigating can help improve tip quality for asparagus. This happens as moisture evaporates from the soil surface to cool spears.

The pigweeds have remained a major challenge to control due in part to resistance. Below is a table of herbicides with pre-emergence pigweed activity, along with their mode of action and their Herbicide Resistance Action Committee code. For this code, products with the same numbers and letters have a similar mode of action. Resistance has been detected in Powell amaranth and redroot pigweed to some of the PSII (e.g. diuron) and ALS inhibitors. Some of these products are more suitable for pre-harvest or post-harvest application due to risk of injury and label restrictions, so make sure to talk with a trusted adviser and read the label.

Table 1. Herbicides for pigweed

Tradename

Common name

Mode of action

Spartan

sulfentrazone

PPO inhibitor (14(E))

Chateau

flumioxazin

PPO inhibitor (14(E))

Dual Magnum

S-metolachlor

Mitosis inhibitor (15(K3))

Prowl

pendimethalin

Mitosis inhibitor (3(K1))

Tricor

metribuzin

PSII inhibitor (5(C1))

Lorox

linuron

PSII inhibitor (7(C2))

Karmex

diuron

PSII inhibitor (7(C2))

Callisto

mesotrione

Carotenoid synth inhibitor (27(F2))

Sandea

halosulfuron

ALS inhibitor (2(B))

For cucurbits, striped cucumber beetle adults have been active.

For leafy cole crops, growers note that both flea beetles and imported cabbage worm have been active.

Onion thrips were present at two locations I visited over the past two weeks in onions. Note, the threshold for use of Movento is one thrip per leaf. In past years, first Movento applications have been made the about last week of June or the first week of July. With recent warm temps, keep an eye on populations and treat if they exceed threshold.

Aerial stem rot, black leg and tuber soft disease have been reported in Michigan potato fields. Seed sourced from Maine has been an issue. There is a newer pathogen that is causing these problems. Read the Michigan State University Extension article “Aerial stem rot, blackleg and tuber soft disease reported in Michigan potato fields” for more information.

For sweet corn, soil temperatures are very high right now in some parts of the state. With irrigation this means corn could be out of the ground in as little as three days. This means timely herbicide application is important.

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