Urban Forestry Professionals

Palm Management: A Key to Common Landscape Palm Disorders and Diseases

  1. Symptoms affecting the entire canopy (all leaves)
    1. wilting
      1. fungal conk present on trunk - Ganoderma butt rot
      2. no fungal conk on trunk
        1. older leaves dying and hanging against trunk: leaves may first become chlorotic or discolored - lethal yellowing (symptoms primarily on 'Malyan dwarf' coconuts') [leaf symptoms of LY vary greatly with palm species]
        2. top of root system is not found within top 6 to 12 inches of soil - palm planted too deeply
        3. soil is water logged - poor soil aeration
        4. cross - sections of trunk show rotting or discoloration of wood
          1. discoloration confined to lowest 4 feet, usually located in the center of trunk - Ganoderma butt rot
          2. trunk discoloration at any height and usually concentrated on one side of trunk - Thielaviopsis trunk rot
        5. dying leaves show necrotic leaflets on only one side of the rachis - Fusarium wilt (on Phoenix canariensis and possibly P. dactylifera)
    2. leaves reduced in size
      1. leaves uniformly light green or yellow in color - nitrogen deficiency
      2. leaves chlorotic and necrotic - late stage potassium deficiency
    3. canopy growth at sharp angle to trunk axis - boron deficiency
    4. collapse of crown
      1. a. crown falls off trunk
        1. without warning - Thielaviopsis trunk or bud rot
        2. preceded by wilting and leaf discoloration
          1. cross section through trunk reveals rotted or discolored wood - Thielaviopsis trunk rot
          2. cross section through trunk does not reveal any sign of wood rotting or discoloration - lethal yellowing
      2. rapid (1 to 2 days) collapse of crown - lightning damage
      3. moderately fast (more than 4 days) to slow collapse of crown
        1. cross - section through crown area shows crumbly trunk tissue (actually insect frass) and possibly 3/4 to 1 inch long gray caterpillars - Opogona (banana moth) larvae damage
        2. cross -section through crown reveals galleries packed with frass, sometimes with white beetle grubs or pupae - palmetto weevil
        3. cross - section through crown area show rotted, but no crumbly trunk or bud tissue - Thielaviopsis trunk or bud rot
    5. leaves tattered - wind damage
    6. leaflets missing or partially missing from leap tips - boron deficiency
    7. chlorosis or necrosis of distal portion of leaves close to high voltage power lines - powerline decline
    8. leaves uniformly light green - nitrogen deficiency
    9. 'spotting' on leaves
      1. uniformly - colored necrotic spots accompanied by leaflet tip necrosis - foliar spray toxicity
      2. 1/8 to 1/3 inch raised black, diamond - shaped 'spots' (actually fungal structures), often accompanied by leaflet tip necrosis - diamond scale (only Washingtonia filifera in CA and AZ)
      3. 'spots' not raised and range in size and in color from yellow to black - leaf spot diseases (e.g., Exserohilium, Bipolaris, Calonectria, Pestalotiopsis, etc.)
    10. reddish - brown to brown, or black streaks or lesions on petiole or rachis; necrotic segments in fan palm leaf blades or uneven death of pinnate - leaved palm fronds - rachis blight (caused by one of several fungal pathogens); small fungal spore structures may be present on surface of lesioned petiole)
    11. leaf bases (and often dead leaf blades) covered with light salmon - pink spores - Gliocladium blight
  2. Symptoms most severe on oldest leaves
    1. chlorosis
      1. one or more older leaves uniformly yellow to yellow - orange in color (typically accompanied by skirt of dead leaves hanging down against trunk: yellowed leaves may originate mid-canopy in some cases) - lethal yellowing
      2. chlorosis confined to margins of leaves or leaflets; central portion of leaves or leaflets distinctly green - magnesium deficiency
    2. leaves discolored, but not necessarily chlorotic; usually shades of red to dark brown or gray - lethal yellowing [Note: leaf symptoms of LY vary with palm species and coconut cultivars]
    3. leaflets of oldest living leaves wilted or necrotic on one side of rachis only and petiole/rachis have reddish - brown or black streak and vascular discoloration evident in longitudinal section of petiole - Fusarium wilt (primarily Phoenix canariensis, but may occur on P. dactylifera)
    4. tip or marginal leaf or leaflet necrosis
      1. leaflet tips necrotic and curled - potassium deficiency
      2. leaflet tips not curled
        1. leaflet tips often broken off - potassium deficiency (Phoenix spp.)
        2. leaflet tips not broken off
          1. leaflets have translucent yellow/orange or necrotic spotting or yellow/orange discoloration - potassium deficiency
          2. leaflets do not have translucent yellow/orange or necrotic spotting or yellow-orange discoloration - can be potassium deficiency, soil salt injury, micronutrient or other chemical toxicity, or water stress (often requires leaf nutrient analysis, soil analysis, or knowledge of plant environment of management history to differentiate)
    5. chlorotic and/or necrotic, brown, or black 'spotting'
      1. very small- less than 1/16 inch raised 'spots' (actually fungal structures) - Graphiola leaf spot (false leaf smut) (Phoenix spp.)
      2. no raised spots - potassium deficiency
    6. gummy exudates ('bleeding') from multiple small, 1/5 to 1/3 inch wounds in palm crownshafts - weevil damage (e.g. Metamasius spp.)
    7. old to middle - aged leaves have necrotic 'skeletonized' patches with only veins and surface layers of leaf intact; underside of leaf necrotic patches typically covered in tubes of insect frass - leaf skeletonizers
    8. leaf kinks and hangs parallel to trunk
      1. leaf remains healthy - wind damage
      2. leaf dies
        1. multiple small, 1/5 to 1/3 inch, wounds in leaf base - weevil damage (e.g. Metamasius spp.)
        2. no wounds and palm is Adonidia merrillii - lethal yellowing
  3. Symptoms affecting youngest leaves only
    1. spear leaf (i.e., youngest unopened leaf) discolored or collapsed
      1. spear leaf hanging down, but otherwise healthy - boron deficiency
      2. spear leaf pulls out easily
        1. on cold - damaged palm - secondary bacterial bud rot [Note: cold damage occurred weeks prior to symptoms]
        2. on otherwise healthy palm
        1. pulled out spear leaf base has distinct foul smell - Phytophthora bud rot
        2. not foul smell at base of pulled spear leaf - Thielaviopsis bud rot; lethal yellowing (Phoenix dactylifera, Borassus flabellifer)
    2. no new leaves emerging, but older leaves still green - bud rot (bacterial, Phytophthora or Thielaviopsis) or non - pathogenic bud damage
    3. new leaves chlorotic
      1. necrotic streaking present - manganese deficiency
      2. no necrotic streaking present - iron deficiency
      3. green spots superimposed on chlorotic new leaves - iron deficiency
      4. leaflets of chlorotic new leaves becoming necrotic and palm is Roystonea spp. - royal palm bug
    4. new leaves reduced in size, but older leaves full - sized
      1. leaves mostly necrotic
        1. leaflets curled or fizzled; leaflet necrosis more severe towards base of leaf - manganese deficiency
        2. leaflets not curled or fizzled - pre-emergent herbicide injury
      2. new leaves not necrotic, but crumpled and greatly reduced in size - boron deficiency
      3. new leaves have truncated tips
        1. leaflet tips necrotic - manganese deficiency (Cocos only)
        2. leaflet tips not necrotic - boron deficiency
    5. new leaves have sharply hooked leaflet tips - boron deficiency
    6. spear (and often other new leaves) fail to open normally - boron deficiency
    7. transverse puckering or transverse translucent streaking on leaflets - boron deficiency
  4. Symptoms affecting flowers and fruits
    1. flower stalks have blackened tips - boron deficiency, lethal yellowing (look for other symptoms to separate disorder from disease)
    2. premature nut drop in Cocos spp.
      1. stem ends blackened and water soaked - lethal yellowing
      2. stem ends green to brown and not water soaked - boron deficiency
  5. Symptoms affecting trunk
    1. gummy sap flowing from trunk ('bleeding')
      1. bleeding from multiple small, 1/5 to 1/3 inch, wounds in crownshaft - weevil damage (e.g., Metamasius spp.)
      2. bleeding from single larger wound with evidence of wood rot
        1. light salmon pink spores present on trunk - Gilocladium trunk rot
        2. light salmon pink spores not present - Thielaviopsis trunk rot
      3. bleeding from one or more widely dispersed areas throughout the trunk - lightning injury
    2. holes in trunk at any location along trunk
      1. large holes (5.8 inch) - borer (Dinapete) damage
      2. many small 1/5 inch holes, often in rows - woodpecker feeding damage
      3. small holes (1/16 inch), randomly dispersed; typically having sawdust plugs protruding out of hole - Ambrosia beetle damage
    3. holes or wounds in crownshaft or trunk near canopy - weevil damage (e.g., Metamasius spp.)
    4. longitudinal splitting of trunk
      1. palm obviously dying - lightning injury
      2. palm appears to be otherwise healthy - excessive water uptake
    5. tapering of trunk
      1. leaves chlorotic, and/or necrotic
        1. leaves chlorotic, but no necrosis present - nitrogen deficiency
        2. leaves chlorotic and/or necrotic - reduced vigor due to routine overpruning, prior cold temperatures, or other environmental stress
    6. shriveling - water stress (may be caused by waterlogged soils or deep planting)
    7. fungal conk on trunk - Ganoderma butt rot (leaves often wilted; cross - sections reveal internal rot at base of trunk)
    8. trunk collapses on itself - Thielaviopsis trunk rot