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Weed Management

Weeds damage safflower yields in several ways. Early weeds may compete with safflower for moisture, sunlight, and nutrients, lowering production and increasing cultivation costs. Heavy infestations of weeds later in the season may interfere with mechanical harvesting, and in extreme cases cause abandonment of fields. Since safflower often matures before many common weed species, green weed matter taken in by the harvester impairs quality and must be cleaned at the grower's expense.

Cultural control of weeds. The most effective weed control is achieved by practicing a sound crop rotation, which reduces weed numbers and minimizes the accumulation of weed seed in the soil. It is good practice to allow weed seeds to germinate with winter rains or a pre-irrigation before any initial tillage. Spring operations then can be timed to destroy one or two crops of germinating weed seeds before planting.

Planting date also is important in weed control. Early winter seeding, especially in the Sacramento Valley, will prolong the period when safflower grows slowly, and winter weeds may develop ahead of the safflower and smother it. It is better to plant later, after the winter weeds are destroyed and before the summer weeds are established.

If a field is not heavily infested and if perennial weeds are not a serious problem, adequate weed control can be achieved with well-timed crop cultivation. Safflower planted in rows can be cultivated two or three times, or as often as necessary, until just before flowering. It is very important that the last cultivation be made as late as possible, but without causing mechanical damage to the crop. When safflower is planted with a grain drill, precluding cultivation between rows, shallow harrowing or light cultivation has been used both to control seedling weeds before the safflower emerges, and in young stands when the safflower is 3 to 6 inches (7.5 cm to 15 cm) high. Harrows which disturb the soil surface yet do not uproot the safflower plants can be used perpendicular to the safflower rows. Damage will occur if safflower plants are turgid and brittle. Cultivation should be done later in the day and only on warm days so that the safflower plants are less turgid and more flexible.

The use of herbicides. The currently labeled herbicides for safflower in California are listed in Table 5. Two, Trifluralin and EPTC are most commonly used. They usually provide effective control of early season weeds, after which competition by the safflower itself reduces or eliminates further weed germination and growth. Trifluralin (Treflan) is the most commonly used herbicide. It is available in liquid and granular formulations. It controls annual grasses such as barnyard grass, green and yellow foxtails, crabgrass, wild oats, and broad leaf weeds including velvetleaf, wild mustard, and wild sunflowers. It resists leaching and can present a carryover problem to sensitive crops such as grain sorghum, corn, and sugarbeets.

Table 5. Herbicides registered for use on safflower in California, 1997
Trade name	Chemical name/description	Type
Dual	Metolachlor 2-chloro-N-(2 ethyl-6-methylphenyl) -N-(2-methoxy-1-methylethyl) acetimide	Preemergence, selective
Eptam (EPTC)	S-ethyl dipropylthiocarbamate	Preemergence, selective
Goal	Oxyflourfen 2-chloro-1-3-(3-ethoxy-4-nitrophenoxy) -4-(trifluoromethyl) benzene	Preemergence, selective
Gramoxone	Paraquat	Fallow weed control
Roundup	Glyphosate Isopropyl salt of N-(phosphoro- methyl) glycine	Fallow weed control, preplant; may be used up to 30 days before planting for some specialty safflower markets
Treflan, Trilin, Trifluralin	Trifluralin a,a,a-Trifluro-2,6 dinitro-N,N- dipropyl-p-toludine	Preemergence, selective
Note: Restrictions governing the use of pesticides change frequently. Check with the County Agricultural Commissioner, Cooperative Extension Farm Advisor, or a licensed pest control adviser. Always follow the directions on the label with respect to application, reentry, and disposal of residual material and containers.

EPTC (Eptam) is a preplant incorporated material that controls many kinds of grasses, including barnyard grass, crabgrass, green and yellow foxtails, fall panicum, witch grass, several broad leaf weeds such as pigweed, lambsquarter, and yellow nutsedge. This herbicide should be incorporated immediately after application by multiple discing or use of a power-driven rotary tiller. EPTC has a short residual in the soil and should not present a carryover problem to following crops.

For fallow season weed control, and for dry land systems before planting in the spring, Glyphosate is commonly used. Pesticide labels are constantly changing. Current information about the registration status of a particular pesticide is available to those with access to the Internet from the California Department of Pesticide Regulation at http://www.cdpr.ca.gov (listed by active ingredients only), or from U.C. Cooperative Extension personnel, or licensed pest control advisors.

Safflower Contents | Insects [11]

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Modified: 10 Feb 2000 Comments to webmaster@agric.ucdavis.edu