The 2012 Drought. Common Weed Complaints in Musk Thistle 1/18/2014. Webster County Diversified Agriculture Conference Marshfield, MO

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1 The 2012 Drought 6 th worst drought in history Hottest year in history Sarah Kenyon University of Missouri Extension Agronomy Specialist KenyonS@missouri.edu The 2012 Drought Other Causes for Weedy Pastures Drought weakens the root structure as well as the forage availability Can impact total forage production next year Overgrazing Poor Fertility Common Weed Complaints in 2013 Musk Thistles Chickweed Henbit Red Sorrel Queen Ann s Lace Plantain Musk Thistle Spotted Knapweed Biennial Rosette 90% of life span Spines deter grazing Reduced pasture yield by 23% if left uncontrolled 1

2 Thistle Chemical Control Best results during the rosette stage (fall or early spring) Weedmaster/ Rangestar (a.i. 2,4 D + Dicamba) Grazon P+D (Picloram + 2,4 D) Milestone (Aminopyralid) GrazonNext (Aminopyralid + 2,4 D) PastureGard (Triclopyr + Fluoxypyr) Surmount (Picloram + Fluoxypyr) Tordon 22K (Picloram) Flower head weevil (Rhinocyllus conicus Forelich) Introduced from Europe in 1975 Rosette weevil (Trichosirocalus horridus Panzar) Introduced from Italy in 1979 Flower Head Weevils Introduction of flower head weevil An Integrated Approach Thistle Chemical Control Spray in the fall or early spring Mow in late summer Let weevils do the rest! Too late to spray Treat at this stage 2

3 Chickweed Henbit Red Sorrel Plantain Queen Ann s Lace Other Weeds Spray in fall or early spring Weedmaster/ Rangestar (a.i. 2,4 D + Dicamba) Grazon P+D (Picloram + 2,4 D) Milestone (Aminopyralid) GrazonNext (Aminopyralid + 2,4 D) Blackberries (Rubus spp.) Fertility Mowing Spray in Fall before the leaves fall off (October) Metsulfuron, Cimarron Max, Surmount, or Remedy Source: Dr. Kevin Bradley, MU Source: Dr. Kevin Bradley, MU Rubus spp. Do not mow during the year of herbicide application Plan on a follow up treatment the next year to control escape canes Horsenettle/Bullnettle (Solanum carolinense L.) Perennial Resistant to grazing spines present Fertility Frequent mowing Herbicides 3

4 Horsenettle Spotted Knapweed Grazon P+D, GrazonNext, Forefront, Milestone, Surmount, or Tordon 22K Apply at mid bloom through fruiting Control will take multiple years due to prolific seed production. Spray for 3 consecutive years to achieve % control. Biennial Allelopathic (Catechin) Prolific Seed Production An 63% reduction in cattle grazing (Butcher, 1984) Replacement of Grass by Spotted Knapweed Over Time Chemical Control Plants/m Grass Spotted Knapweed Years Graph adapted from: Sheley and Jacobs. Weed Technol. 1997: 11: pt/a Tordon 22K 5 oz/a Milestone Apply at late bud or rosette stage Chemicals will provide control for 2 3 years but spotted knapweed will reinvade the area unless other control techniques are adopted Montana State University & Colorado State University Cultural Control Irrigation to allow the forage to outcompete the knapweed Not tolerant of flooding or shade Grazing Colorado State University found that cattle grazing diffuse knapweed twice during the spring decreased seed production by 50% Mowing alone is not recommended. The plant can produce seed below the mowing height. For small areas hand pull/dig plant making sure to remove as much root stock as possible Knapweed Root Weevil Knapweed Flower Weevil UV Knapweed Seed Head Gall Fly 4

5 Photo Courtesy of: University of Arkansas UV Knapweed Seed Head Gall Fly Fly lays it eggs on the seed head and the larvae feed on the developing seed Study is ongoing at University of Arkansas Small populations are naturally occurring and not available for purchase MDC Cost Share Program Spotted knapweed weevils can be purchased online Knapweed Root Weevil $140/100 insects July to mid September Knapweed Flower Weevil $80/200 insects June to late July Knapweed Root Weevil Adults lay eggs near the roots on the soil surface, and developing larvea feed on roots Knapweed Flower Weevil Adults lay eggs on the flower and the developing larvae feed on developing seeds Can purchase online weedbustersbiocontrol.com Spotted Knapweed Control Photo Courtesy of: University of Arkansas CHEMICAL 1 pt/a Tordon 22K 5 oz/a Milestone BIOLOGICAL Knapweed Weevils UV Knapweed Fly CULTURAL Fertility Irrigation Grazing Mowing Hand Digging 5

6 Cultural Cultural Control Soil Fertility Reseeding Crop Rotation Timed Planting & Harvesting Purchasing Certified Seed Keys to Pesticide Use Biological Organism found in nature Usually specific to target plant Some Commercially Available Weed Control Chemical Mechanical Mechanical Control Mowing or Grazing Prevents Seed Production Depletes Carbohydrate Reserves of Perennials Identify pest Select the right product Time the application correctly Apply accurately Follow grazing and haying restrictions ALWAYS READ THE LABEL 34 Other Considerations Clover will be eliminated from pasture Newly planted grass seedlings may be damaged Grass seeds may not germinate Read label for restrictions Toxic to people, animals, or other plants Oncogenicity - tumors in laboratory animals Ground water concerns Grazon P+D Surmount Tordon 6

7 Private Pesticide Applicator Training Tuesday, March 4, :00 3:30 pm Webster County Extension Center $12 for Training Manual THANK YOU! Sarah Kenyon Agronomy Specialist