Weed Management in StrawberriesMatthew Cutulle

Overview of Weed Management

“If you know the enemy and know yourself, you need not fear the

result of a hundred battles. If you know yourself but not the

enemy, for every victory gained you will also suffer a defeat. If you

know neither the enemy nor yourself, you will succumb in every

battle” –Sun Tzu (Art of War)

https://www.clemson.edu/cafls/research/weeds/index.html

Understanding Critical Weed Free Period

Weed and crops are not competing

Weed interference will not Impact crop yield

When Weeds Become a Problem?

Weeds as Indicators of Poor Growing Conditions

Condition Indicator Weed(s)

Low Soil pH Red Sorrel

High Soil pH Plantains

Droughty Soils Prostrate Spurge, Black Medic, Knotweed, Woodsorrel,

Lespedeza, Bracted Plantain

Wet Soils Sedges, Poa annua, Alligatorweed, Moss, Algae, Goosegrass

Poor (Sandy) Soil Quackgrass, Poorjoe, Sandspur

High Nematodes Spurges, Pusley, Knotweed

Compacted Soil Goosegrass, Poa annua, Knotweed

Low Soil N Legumes (Clover, Chickweed, Black Medic, Chicory,

Speedwell), Broomsedge, Yellow Sneezeweed

High Soil N Poa annua, Chickweed, Moss, Ryegrass

Weeds as Indicators of Poor Growing Conditions

Stale Seed Bed Technique

• A stale seedbed is a seedbed where the non-dormant weeds in the germination zone (shallow soil layers from which weeds can emerge) are killed before crop planting. Weed emergence from the germination zone depends on weed species, soil type, tillage, and soil physical characteristics.

Prevent Seed Rain

Plasticulture

Impact of mulch color on yield

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Yellow = black plastic (Hassell)

Effect of non-fumigant treatments on weed densities compared to MeBr

Treatment Rate kg/ha Total Weed Density

Untreated Control 69.9 a

Methyl Bromide 392 12.8 b

Steam 70 C for 20 minutes 7.8 b

Mustard Meal 2242 58.1 a

Fludioxonil + Mefenoxam + oxyflurofen

0.28 + 0.56 + 0.56 6.9 b

Mefenoxam + Thiophanate-methyl + oxyflurofen

0.56 + 1.57 + 0.56 8.5 b

Pre-Plant Burn Down Herbicides for Strawberries

Herbicide Weeds Controlled Rate/Acre Comments

Goaltender 2XL Many annual broadleaf weeds.

1-2 pt Must be applied at least 30 days prior to transplanting. The soil must be worked to a depth of at least 2.5 inches prior to transplanting the crop. No control is provided after the crop is planted.

RoundUp Ultra Most emerged weeds 1-5 qt Must be applied to emerged weeds at least 30 days prior to transplanting. For annual weeds, good soil preparation will also control these weed species

Aim EC Most small-mediumemerged weeds

2 oz Apply alone or with other herbicides or fertilizers as a burndown treatment at least 24 hours before transplanting.

Preplant Residual HerbicidesHerbicide Weeds Controlled Rate/Acre Comments

(pendimethalin)Prowl H20Satellite Hydrocap

Annual Grasses and small seeded broadleaf weeds

1.5-3 pt Prowl: Use before planting strawberries. Apply to the soil surface before planting to prevent the establishment of most annual grasses as well as suppressing several broadleaf weeds such as velvetleaf and purslane. Moisture is required to activate the herbicide, and it can be applied through an overhead irrigation system or shallowly incorporated. At least one day must elapse between application and planting, unless protective gear is worn. Only the H2O formulation of Prowl is labeled for strawberries. No more than 6 pints are to be used in any one season. Prowl H2O should not be used if plastic mulch will be applied.

(sulfentrazone)Spartan 4F

Annual broadleaf weeds 4-8 oz- most of SC soils would be closes to 4.

Apply prior to planting or just after planting but before new growth appears. May cause severe damage to new growth. Strawberry varieties vary in sensitivity. Provides control of many broadleaf weeds, including field pansy, groundsel and nutsedge.

Pre-herbicides applied at or after planting

Herbicide Weeds Controlled Rate/Acre Comments

Devrinol Annual grasses and small seeded broadleaf weeds

2 - 4 lb2 gal8 lb

(Formulation Dependent)

Apply to weed-free soil after strawberry plants become established. Heavy rate after planting may inhibit rooting of daughter plants. This material must be activated with rainfall, irrigation, or shallow cultivation within 24 hrs.

Prowl Annual grasses and small seeded broadleaf weeds

1.5-3.0 pt Banded Application (between rows) if applied at or after transplanting

Chateau Broadleaf weeds, some grasses, and some suppression of perennial weeds

3 oz Apply as a banded spray with a hooded or shielded sprayer to row middles or between plastic. Do not contact the strawberry plants including daughter plants. Apply prior to weed emergence

Herbicide Weeds Controlled Rate/Acre Comments

Dacthal FDacthal 75W

Annual grasses and small seeded broadleaf weeds

8 - 12 pt8 - 12 lb

Weak on ragweed, smartweed, and galinsoga. Apply at transplanting or after cultivating. Irrigation, rainfall, or shallow cultivation after application will improve control.

Sinbar 80WP Broadleaf weeds, some grasses, and some suppression of perennial weeds

2 - 6 oz During the planting year, Sinbar may be applied at 2 to 3 ounces per acre after transplanting but before new runners start to root. If strawberry plants have developed any new foliage prior to application, irrigation or rainfall (0.5 to 1 inch) is required to wash the Sinbaroff the strawberry plants. or soils with at least 2% organic matter, there is no maximum amount per application; however, no more than 8 ounces of Sinbar can be applied per year. For soils with between 1 and 2% organic matter, a maximum of 4 ounces of Sinbar can be applied at any one time with an annual maximum of 8 ounces per acre.

POST HerbicidesHerbicide Weeds Controlled Rate/Acre Comments

(paraquat)*GramoxoneSL 2.0

Emerged annual grasses and broadleaf weeds.Suppression of emerged perennial weeds between rows.

2 pt

Contact herbicide. Use with a non-ionic surfactant. Direct spray between rows using a shield to prevent contact with strawberry plants. Do not apply within 21 days before harvest or more than 3 times in a season.

(clopyralid)Stinger

Selected emerged broadleaf weeds including dandelion, Canada thistle, clover, vetch, ragweed, and jimsonweed

2/3 pt

Make one application per crop year after harvest to emerged weeds. Apply uniformly with ground equipment in a minimum of 10 gallons of water per acre. Do not tank mix with any other herbicides. Only this clopyralid product is registered for strawberry, other similar products with other trade names are NOT registered in New England. Do not use any spray additives.

Select grasses 6-8 oz Effective on small, actively growing grasses. Improved activity over Poast on cool-season and perennial grasses. Add 1qt/100 gal spray of crop oil concentrate. Repeat application at 14 days for perennial grasses. Ammonium sulfate at 2.5 lb/acre may be added to improve activity on perennial grasses. Do not apply within 4 days of harvest.

18% v/v Suppress in water carrier pH of 2.82

Untreated Check

18% v/v Suppress in water carrier pH of 2.82

Untreated

Suppress Organic Herbicide

2,4 D application in Row Middles

• Use Ai nozzles if possible.

Alternative Row Middle Management

Ryegrass in row middles. Terminate with Select

Spider mites – biocontrol

Eating adult Eating egg

Mites live in weeds!

Mites live in weeds!

How could weed management impact spider mite biological control?

Weeds promote spider mites

But weeds are good for natural enemies!

Shelter

Alternative prey

This includes phytoseiids

So what happens when weeds are managed?

So what happens when weeds are managed?

Harmful effects of the herbicide?

No shelterNo floral resourcesNo alternative prey

Spider mites seek out new food

Are the predators still alive to follow?

Herbicide, Abiotic Stress or injury from a biological?

Credit Ontario Ministry of Agriculture

Chateau Drift

Nitrogen Deficiency

Photo courtesy of University of California

Pursuit Injury

Sinbar

Magnesium Deficieny

Magnesium Deficiency

Photo: Scot Nelson/Flickr)

Gramoxone

Mite Damage

Crabgrass Control

Control Method- Select or Poast

Mice in Strawberry

Lavender and Cats

Questions