Grass Seed Crops: Pest Management Thomas G Chastain CSS 460/560 Seed Production
Diseases of the Seed Ergot is a fungal disease of the seed - caused by Claviceps purpurea. Ergot replaces the seed, and reduces seed yield by reducing seed number. Ergot also increases seed cleaning costs and causes lost international marketing opportunities. Control measures for ergot include planting sclerotia-free seed, and fungicides (Tilt). Only Tilt is registered for ergot control. Ergot is a problem in all grass seed crops except orchardgrass and is most severe in Kentucky bluegrass. Kentucky bluegrass fertile tiller infested with ergot (top left), ergot sclerotia and Kentucky bluegrass seed (bottom left)
Diseases of the Seed Ergot and seed quality in Kentucky bluegrass (Chastain, 1992). Characteristic Low ergot incidence High ergot incidence Seed weight (mg) 0.35 0.34 Total weight produced per tiller; seed + sclerotia (mg) 26.0 25.4 Seed produced per tiller (mg) 25.6 20.4 Weight allocated to seed (%) 98.5 80.3 Seed germination (%) 83 78 Accelerated aging (%) 65 57 Kentucky bluegrass seed contaminated with ergot sclerotia
Diseases of the Seed Blind seed is caused by a fungus known as Gloetinia temulenta. Blind seed kills the embryo and reduces seed germination. Spread in field by ascospores and conidia in spring rainfall. Blind seed is a problem in perennial ryegrass and tall fescue. This disease can be a major problem and was one of the primary reasons for the implementation of field burning in Oregon. Field burning, and timely harvest reduce the number of seeds that act as sites for the over-wintering of the disease. Nitrogen nutrition of the plant is thought to play a role in the development of the disease as well. Plant disease-free seed. Electron micrographs of apothecia on seed (top), conidia (bottom) (Alderman, 2001)
Diseases of the Seed Grass seed endophyte is caused by a fungus known as Neotyphodium coenophialum in tall fescue and N. lolii in perennial ryegrass. Both fungi grow within plants and the infected seed produces plants that are also infected. Alkaloids produced by the pathogen - ergovaline and lolitrim B, cause poor performance and sickness in grazing livestock and abortion in horses. Grass seed endophyte is undesirable in forage seed, but the alkaloids may impart insect and drought resistance in infected plants. The endophytes are desirable in turf seed. Screenings and straw may be contaminated with alkaloids. New endophytes have been identified that do not produce toxic levels of alkaloids and are safe for forage seed. Grass seed endophyte hyphae in tall fescue (Ron Welty photo)
Foliar and Stem Diseases Foliar and stem diseases are not controlled by crop rotation or field burning, only fungicides and genetic resistance are effective. Stripe rust is caused by Puccinia striiformis and is found in Kentucky bluegrass and orchardgrass. The pustules are arranged in stripes on leaves and on the leaf sheath. Crown rust is caused by Puccinia coronata and is found in tall fescue, perennial ryegrass, Kentucky bluegrass, and orchardgrass. The disease gets its name from its teliospores, which have a crown-like structure but the disease is not specifically associated with the plant s crown. Heavy stem rust infestation in tall fescue panicle
Foliar and Stem Diseases Stem rust is caused by Puccinia graminis subsp. graminicola and is found in perennial ryegrass, tall fescue, Chewings fescue, orchardgrass, and Kentucky bluegrass. Stem rust was not observed on tall fescue in the Willamette Valley until 1989, but is now widespread. Pustules are dark red or brown and are irregularly distributed, but late in the season appear in groups on leaves and leaf sheaths, and on the inflorescence. Brown leaf rust is caused by Puccinia brachypodii var. poae-nemoralis and is found in Kentucky bluegrass. Brown to yellow pustules occur mainly on the lower surfaces of leaf blades but also develop on leaf sheaths. Stem rust pustules Cynthia Ocamb photo
Foliar and Stem Diseases Rust infestations continue in fields from one season to the next by overwintering on infected plants. The infestation can expand to epidemic proportions with warming temperatures in spring. Early warm springs tend to favor development over cool, wet springs, which tend to retard development of a rust epidemic. A model-based management tool has been constructed to determine the best application timing for rust control based on development of the crop and rust fungi. Rust on tall fescue plants in fall
Foliar and Stem Diseases A broad range of fungicides are available for controlling the rusts in grass seed production. These include Abound, Bumper 41.8 EC, Bravo Ultrex, Echo 720, Echo 90DF, Folicur 3.6 F, Headline, JMS Stylet-Oil, Laredo EC, Quilt, Tilt, Muscle 3.6 F, Orius 3.6 F, and PropiMax EC. Seed yield is reduced when the flag leaf is not protected. Multiple applications may be required and are needed more frequently for protectants than for systemics. The seed weight component of yield is significantly reduced in perennial ryegrass when the crop was not treated with a fungicide. Stem rust in tall fescue panicle
Foliar and Stem Diseases Eyespot is a disease caused by Mastigosporium rubricosum and is found in orchardgrass and bentgrasses. Scald is a leafspot disease caused by Rhyncosporium orthosporum and is found in orchardgrass, tall fescue, and perennial ryegrass. Can infect the flag leaf and the inflorescence, control with fungicide Bravo Ultrex. Drechslera leaf blight is a leafspot disease caused by Drechslera spp. and is found in perennial ryegrass, tall fescue, Kentucky bluegrass, fine fescues, and orchardgrass. Forms net blotch symptoms in some grasses while in fine fescues it forms small dark spots. Leaf scald in orchardgrass
Insects and Mites Sod webworm (Crambus spp.) damages crown and root systems in Kentucky bluegrass, orchardgrass, fine fescues, and tall fescue. Billbug (Hyalopteroides dactylis) damages crowns and roots of Kentucky bluegrass and orchardgrass. Grass gelechiid (Chinodes psiloptera) damages roots, crowns, and lower stems of Kentucky bluegrass. Sod webworm immature (top), damage in Chewings fescue (middle), sod webworm adult (bottom) Ken Gray photo.
Insects and Mites European crane fly (Tipula spp.) larvae damage roots and crowns of plants. Wireworms (Ctenicera spp.) damages seedlings of grasses. Winter grain mite (Penthaleus major) damages leaves and causes reduced seed yield, plant vigor, and stand longevity in Kentucky bluegrass. European crane fly Ken Gray photo (top), Winter grain mite Ken Gray photo (middle), and wireworm Ken Gray photo (bottom).
Sweep net Insects and Mites Pest Management Approach 1. Monitoring pest populations is an important component of insect and mite pest management strategies. 2. Includes setting pheromone traps, conducting sweeps of fields to determine pest population levels. 3. Insecticide and biological control measures are used when applicable to prevent the pest populations from causing economic injury.
Slug Other Pests Seedgall nematode (Anguina agrostis) is a problem in bentgrass seed fields that causes losses in seed yield. Gray garden slug (Agriclimax reticulatus) and the gray field slug (A. laevis) are controlled in seedling fields of perennial ryegrass and tall fescue with metaldehyde bait applied in fall. Slugs are not as severe in established fields.
Other Pests Geese are highly localized problems for grass seed producers. Some species are federally protected, making control difficult. Geese in grass seed field
Other Pests Meadow voles are an cyclical problem for grass seed producers. Lack of crop rotation might be a factor involved in increasing vole populations in the valley. Meadow vole (top left vole.com photo), vole runways and holes, and damage caused by meadow voles in tall fescue seed field (bottom left)
Annual bluegrass Weeds Reasons for controlling weeds in grass seed crops 1. Seed quality. Weed-free seed can command a premium price. Seed certification prohibits certain weed seeds whereas limited numbers of other weeds seeds are allowed. 2. Competition. Weed plants compete with the seed crop for water, light, and nutrients and can reduce seed yield. 3. Seed conditioning costs. Weedcontaminated seed costs more to clean. Re-cleaning further increases costs. 4. Marketability. Marketability is reduced by weed seeds.
Weeds The volunteer crop and off-types of the same species are the most difficult to control weeds in grass seed crops. Failure to control volunteers can result in the loss of eligibility for certification. Plants of other grass seed crops and grass weeds including annual bluegrass (Poa annua), downy brome (Bromus tectorum), roughstalk bluegrass (Poa trivialis), rattail fescue (Vulpia myuros), California brome (Bromus carinatus), and wild oats (Avena fatua) are difficult to control. Broadleaf weeds are easier to control than grasses, but problems with wild carrot (Daucus carota) are increasing. Downy brome
Weeds Map Source: George Mueller-Warrant, USDA-ARS
Weeds California brome
Self-propelled sprayer (top), weed wiper (bottom, Smuckers Inc. photo), spot spraying crew in perennial ryegrass seed field (right) Weeds Weed management strategies: 1. Herbicides. Several broadleaf herbicides are available to control these weeds in grass seed crops. Selective herbicides must be used to control grass weeds in grass seed crops.
Weeds 1. Herbicides. Registration and availability of herbicides for grass seeds crop change frequently. Herbicide application techniques include broadcast spraying, row spraying, spot spraying, weed wiper, and charcoal banding. Row spraying results in roughstalk bluegrass seed crop in central Oregon (top left), Goal and Karmex damage in perennial ryegrass seed crop (bottom left).
Weeds 2. Field burning. Field burning destroys weed seeds and seedlings, but is limited in availability. 3. Good crop management. Must maintain vigorous, competitive crop growth to aid in the suppression of weeds in grass seed fields. Early canopy closure increases shading which can decrease weed seed germination, and also leaves fewer open niches for weeds. Vigorous growth and early closure of the crop canopy can be manipulated through changes in stand establishment practices. Nutrient and irrigation management are important aspects of general crop management that assist other methods of weed control.
Weeds 4. Crop rotation. Rotation can be an effective weed management tool where suitable rotation crops are available. Unfortunately, there are very few profitable rotation crops available for the wet grass seedproducing soils in the Willamette Valley. 5. Tillage/mechanical. Not widely practiced at this time, but may increase in the future. Wild oats