Take Advantage Of Fall Weed Management In Blueberries

Fall can be an important time to control weeds. Here are a few tasks that should pay off in the future.

– Scout your fields

Spend some time after harvest walking fields and recording weed pressure and determine how successful your spring preemergent herbicides were. Note where control was good and poor and which weeds are present, particularly where perennial weeds have become established. Birds drop seeds of many noxious perennials (Virginia creeper vine, grapevine, poison ivy) in blueberry fields, so even clean fields need to be monitored for new weeds. Is weed pressure related to the soil type or herbicides used last spring?

This information will help in formulating a weed management program for next spring. Are rows completely devoid of weeds in the fall? This might indicate too much herbicide was used the previous spring. Some annual weeds should begin establishing in the fall if rates are optimum.

– Treat tough perennial weeds

Late summer and fall are good times to work on tough-to-control perennial weeds such as Virginia creeper vine, grapevine, milkweed, goldenrod, poison ivy and brambles. These perennials generally do not respond to soil applied herbicides, but can be managed by careful applications of glyphosate late in the summer. Glyphosate is effective on these weeds, but can also kill blueberries. Perennial weeds are killed because the chemical moves to below-ground plant parts. Treat before weed leaves senesce. Virginia creeper vine, for example, drops leaves early in the fall. For spot spraying perennials:

– Use 2% glyphosate solutions.
– Add ammonium sulfate to improve absorption.
– Avoid all green blueberry tissues.
– Apply when weeds are still green.
– Spray at low pressure to limit drift.

Use extreme care not to contact green blueberry tissues (stems and leaves) with glyphosate. Glyphosate absorbed by blueberry leaves and green bark moves within the bush and can kill whole canes or bushes. Weeds such as blackberry, Virginia creeper, and grapevine may need to be pulled out of bushes so they can be treated safely. This may seem too slow to be practical, but consider what these weeds cost in lost income. Bushes covered by Virginia creeper vine may yield just 20% of their potential. This easily equates to a $5 to $10 loss per bush. The loss is incurred each year and increases as the vines spread to neighboring bushes. Investing 15 minutes to carefully pull vines out of that bush and safely treat them on the ground is money well spent.

For more information, click here to see the full article on Michigan State University’s Extension News for Agriculture website.