POSTEMERGENT WEED CONTROL AND LABEL UPDATES IN ALMONDS 2008 North San Joaquin Valley Almond Day January 22, 2008 Kurt Hembree UCCE, Fresno County

Treatmentlb ai/A15 DAT30 DAT15 DAT30 DAT15 DAT30 DAT 1. Roundup 1, Gramoxone 1, Rely Venue 1, ACB D33 1, Scythe Roundup+Venue 1, Roundup+ACB D33 1, Roundup+Chateau 1, Roundup+Scythe Rely+Venue 1, Rely+ACB D33 1, Rely+Chateau 1, Postemergent Weed Control Trial in Almonds Fresno County *Horseweed (8 leaves - bolted), yellow nutsedge (2-6 leaves), crabgrass (2-4 leaves) Spray volume at 40 gpa, 1 AMS added at 8 lb/100 gal, 2 Agridex at 1% v/v Horseweed* Y. Nutsedge* Crabgrass*

4/2/07 – day of application

5/6/07 – 30 DAT RoundupGramoxone RelyVenue

ACB D33Scythe 5/6/07 – 30 DAT

Roundup + VenueRoundup + ACB D33 Roundup + ChateauRoundup + Scythe

5/6/07 – 30 DAT Rely + VenueRely + ACB D33 Rely + ChateauUntreated

Summary of Postemergent Treatments Since 2005: Rely applied alone seems to give the most consistent control of horseweed, fleabane and other broadleaves, but is somewhat weak on grasses and sedges. Adding other contacts improves control slightly. With the recent price drop of Rely, tank-mixing Rely and Roundup may be the way to go for the most consistent control. The PPO herbicides (Shark, Venue, Chateau) should not be used alone, unless you only have annual broadleaves, and they are very, very small. Gramoxone usually gives equal to better control. Success with the PPO products seems to be related to weather conditions. Keeping the spray volume up with complete coverage is important. ACB D 33 gave exceptional control of horseweed and fleabane when used alone or mixed with Roundup or Rely.

Herbicide Label Updates and Improving Product Performance: Chateau SW (Valent) Matrix FNV (DuPont)

Stanislaus County - May 2007 Roger Duncan

Early signs of wilt Shoot dieback Dieback with mottled leaves Roger Duncan

Technical bulletin added to the label in Oct 2007 for Merced, Stanislaus, and San Joaquin Counties

Improving preemergent performance of Chateau: A clean soil surface prior to application maximizes control. Apply in a spray volume of no less than 30 gpa. Using 12 oz in the fall mixed with Prowl H 2 0 or other preemergent will help broaden the control and get the “toughest” flush of horseweed and fleabane. If horseweed or fleabane are emerged at that time, adding 2,4-D or other contact should do the job, making spring weed control much easier. Where purslane is a problem, a second application or delaying application to just before petal fall can extend control later. Don’t expose tree roots to direct contact with the herbicide. If replanting into treated areas, use clean soil around roots.

Matrix FNV Application Info. Tree age: 1 year Timing: preemergence is it’s strength (2-3 months) Soil surface: free of trash Rate: 4 oz/A/year (broadcast), split-application allowed (2 oz + 2 oz) if banded and <50% area treated Spray volume: gpa Spray Tank pH: Activation: ½ inch rainfall ≈14 days. (apply to moist soil) Chemigation: through micro-sprinklers only Tank-mix partners: other preemergents (Prowl H 2 0); permit if GWPA regulated product is added; postemergents (RU, Gramoxone, Rely, etc.) Tree injury: likely if under poorly drained conditions and direct root contact?

Weeds controlled preemergence with Matrix FNV: Annual Broadleaves: Dandelion (seedling) Filaree Groundsel Henbit Mallow Mustards Shepherd’s-purse Fleabane Horseweed Pigweeds Purslane Puncturevine Spurge Lambsquarters* Nightshades* Velvetleaf* Annual Grasses: Barnyardgrass Crabgrass Foxtails (yellow, green, giant) Volunteer cereals* Perennials: Yellow nutsedge* Field bindweed* Johnsongrass* *Suppression