Preemergence, Soil-applied Treatments

isoxaben (Gallery 75DF, SC, 2.5DG and several others)

Perennial groundcovers and bulbs

Rate 0.495 lb ai/A (0.66 lb/A Gallery 75DF)

Time Late winter and early spring. 2 to 4 weeks after planting, before bulbs and annual weeds emerge. Also may apply after bulbs emerge but before they flower.

Remarks Activate with 0.5 inch water or shallow cultivation before weeds emerge. Chemical stability remains adequate when left on soil surface for 21 days. Primarily for broadleaf control.

Caution Not for commercial production sites. Not recommended on tulips taller than 0.75 inch, or on gladiolus before emergence, or if corms were less than 1 inch in diameter, or on bulbs while they are flowering.

Site of action Group 21: inhibits cell wall synthesis Site B

Chemical family Benzamide

oryzalin (Surflan AS)

Bulbous iris, daffodil, hyacinth, narcissus, tulip and others

Rate 0.75 lb to 1.5 lb ai/A (0.75 to 1.5 quarts/A) depending on target species and time of year applied.

Time Apply 2 to 4 weeks after planting ornamental bulbs but before annual weeds emerge.

Remarks For fall-planted bulbs, apply in late winter to weed-free soil.

Caution Do not apply to emerged tulips taller than 0.75 inch. Do not apply to gladioli corms prior to emergence or less than one (1) inch in diameter.

Site of action Group 3: microtubule assembly inhibitor

Chemical family Dinitroaniline

oryzalin + benefin (XL 2G)

Including bulbous iris, daffodil, hyacinth, and tulip

Rate Bulbs: use 75 to 150 lb/A depending on soil texture and time of year. Flowers: use 200 lb/A per application with at least 2 months between applications, not to exceed 600 lb/A per year.

Time Apply before target weeds germinate or immediately after cultivation. For bulbs, apply 2 to 4 weeks after planting but before weeds emerge.

Remarks Consult label for tolerant flowers and bulbs. (Inhibits cell division or mitosis, primarily in roots.)

Caution Do not apply to tulips emerged to 0.75 inch high or more, or to gladiolus before it emerges, or to plants less than 1 inch in diameter. Sensitive species include Douglas-fir, eastern hemlock, and begonia.

Site of action (both) Group 3: microtubule assembly inhibitor

Chemical family (both) dinitroaniline

oxadiazon (Ronstar 50 WSP)

Gladiolus bulbs only, and a few ground covers

Rate 2 to 4 lb ai/A (4 to 8 lb/A WSP) depending on target weed species.

Time Apply any time to weed-free soil and irrigate with 0.25 to 0.33 inch water immediately after applying for annual weed control.

Remarks Over the top or directed sprays. Apply anytime during the year, prior to weed seed germination. Rainfall or overhead irrigation after application will improve weed control activity.

Caution Applications of RONSTAR G must be made by a professional applicator only. Irrigate within 2 hr if applied over the top to wash herbicide from leaves. Weeds in the pink family (chickweed, mouse ear chickweed, and pearlwort) are resistant. Primarily broadleaf control.

Site of action Group 14: protoporphyrinogen oxidase inhibitor

Chemical family Oxadiazole

pendimethalin (Pendulum 2G, AquaCap 3.8ME, or several others)

Rate 2 to 4 lb ai/A (100 to 200 lb/A 2G) depending on desired length of weed control. For wildflowers up to 2.1 quarts/A Pendulum AquaCap

Time Apply before, during, or after planting bulbs. Apply to seeded wildflowers after flower seedlings have emerged but before weed seeds germinate.

Remarks May be applied to control susceptible weeds (primarily grasses) in bulbs (including crocus, daffodil, gladiolus, and tulip) and established wildflowers (including black-eyed Susan, California poppy, coreopsis, and oxeye daisy) listed on the label. Primarily for grass control.

Caution Granules may stain stone, wood, or other porous surfaces.

Site of action Group 3: microtubule assembly inhibitor

Chemical family Dinitroaniline

prodiamine (Barricade 65WG/4FL and several others)

See label for listed bulbs and wildflowers

Rate 0.65 to 1.5 lb ai/A (1 to 2.3 lb/A 65WG or 21-48 oz/A 4FL) depending on length of control desired, and number of applications per year.

Time In fall or spring before weeds germinate or after weeds are removed.

Remarks Irrigate soon after treatment to wash herbicide onto the soil surface and to activate it within the top layer of soil. Do not exceed 2.3 lb/A.

Site of action Group 3: microtubule assembly inhibitor

Chemical family Dinitroaniline

S-metolachlor (Pennant Magnum)

Many bulbs and flowers, except daffodil

Rate 1.24 to 2.48 lb ai/A (1.3 to 2.6 pints/A) depending on soil type and organic matter.

Time After transplanting

Remarks Apply when soil has firmed around plant. Irrigate shortly after planting to wash the herbicide from foliage and to activate the herbicide in the soil. Will not control emerged weeds. Existing weeds must be removed. Primarily targets grasses but controls some broadleaves and suppresses nutsedge. Inhibits seedling roots and/or shoots.

Caution Consult label for tolerant and approved species. Do not apply more than twice per year.

Site of action Group 15: inhibits very long chain fatty acid synthesis

Chemical family Chloroacetamide

trifluralin (Treflan 10G)

Rate 0.4 lb ai/A (40 lb/A)

Time Apply Trifluralin 10G to the soil surface 2 to 4 weeks after planting, but prior to the emergence of annual weeds. Trifluralin 10G may also be applied following bulb emergence. For fall planted bulbs, apply Trifluralin 10G again in late winter or early spring to weed-free soil surfaces.

Remarks Trifluralin must be activated by a single rain or overhead sprinkler irrigation of at least 0.5 inch. If not activated within 3 days, mechanically incorporate trifluralin with equipment that won't damage bulbs. Apply before weed seeds germinate; trifluralin will not control established weeds.

Caution Do not make preplant applications of Trifluralin 10G to areas where gladioli corms less than one inch in diameter will be planted or injury may occur.

Site of action Group 3: microtubule assembly inhibitor

Chemical family Dinitroaniline