Asian citrus psyllid & the citrus disease huanglongbing:
Training for retail nurseries and garden centers
Psyllid
Huanglongbing
Matt Daugherty, UC Riverside
[email protected]
Photography: M. Rogers, M. Keremane, S. Halbert,
M. Hoddle, and E. Grafton-Cardwell
The psyllid (pronounced: síl - lid) is a
small insect, about the size of an aphid
Adult
It has an egg stage,
5 wingless juvenile
stages called nymphs,
and winged adults
Egg
5 Nymphal instars
Adult psyllids feed on young or mature leaves.
This allows adults to persist year-round
When feeding, the adult leans
forward and tips its rear end at a
characteristic 45o angle.
Yellow-orange eggs are tiny and tucked into the tips of new
shoots, making them difficult to see
Female ACP strongly prefer to lay eggs
on new leaves and shoots (“flush”)
Nymphs produce sugar-filled waxy tubules as they feed.
The tubules are unique and easily seen
Nymphs can only survive
on young, tender leaves
and stems.
Thus, nymphs are found
only when the plant is
producing new leaves.
As the psyllid feeds, it injects a salivary toxin that
damages flush. If leaves survive, they twists as they grow
Twisted, notched leaves are
an indicator the psyllid has
been there.
What plants does the psyllid attack?
All types of citrus and related plants in the family Rutaceae
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Citrus (limes, lemons, oranges, grapefruit, mandarins…)
Fortunella (kumquats)
Citropsis (cherry orange)
Murraya paniculata (orange jessamine)
Bergera koenigii (Indian curry leaf)
Severinia buxifolia (Chinese box orange)
Triphasia trifolia (limeberry)
Clausena indica (wampei)
Microcitrus papuana (desert-lime)
Others…..
Calamondin
The psyllid feeds and reproduces on plants that we don’t
think of as citrus, such as ornamentals
Plants that continuously produce new foliage, such as orange jessamine
(Murraya paniculata) are preferred by the psyllid. Nursery shipments of this
plant contributed to psyllid spread in Florida
Why are we so worried about this psyllid?
ACP can transmit the bacterium
that causes huanglongbing (HLB)
Bacterium blocks nutrient
transport, affecting tree growth,
survival, and fruit production
Candidatus Liberibacter asiaticus
Yellowing, poor quality fruit, tree decline, and death
Earliest symptoms include blotchy,
irregular yellowing of leaves
Fruit don’t develop properly: small,
deformed, poor flavor
HLB
Lack of tree vigor, stunting; excessive
fruit drop
Tree mortality in as little as 5 years
• No cure!
Zinc
Human-assisted spread of the psyllid and disease
in Florida
The psyllid was first detected in
1998, after which it spread rapidly
throughout the state
• assisted by shipment
of infested ornamentals
Within 3 years the disease
spread to all citrus
growing regions
• citrus production is ~1/2 of
what it was
• production costs 50% higher
ACP & HLB in Florida
Where are ACP and HLB in California?
ACP was found in San Diego in 2008
• now present throughout Southern
California (residential and
commercial citrus)
• parts of the Central Valley
• parts of the Bay Area
More than 20 cases of HLB have been
found in Los Angeles County
What is being done to manage ACP and limit
HLB in California?
1. Statewide monitoring for ACP and HLB
• residential and commercial trapping
• inspections of nurseries
2. Quarantine zones established around infested areas
• regulations on nursery shipments
3. Treatments of residential citrus
4. Biological control
5. Area-wide treatments of commercial citrus
How can nurseries help prevent spread of the
pest and disease?
Quarantines exist
for the psyllid
(blue lines) and the
disease (red line)
to limit spread
1. Help maintain the psyllid quarantine
• educate customers
2. Minimize infestations on nursery plants
• adopt a set of best management practices
The psyllid quarantine and plant tagging system
Quarantines:
1. Prohibit plant movement to areas
outside the quarantine
2. Requires insecticide treatment of plants
prior to shipping to retail. Retreatment
after 90 days
The color of a plant’s tag reflects its origin:
Blue: plant came from production
nursery outside of quarantine
Yellow: came from within the
quarantine zone
Inform customers about the pest and disease
1. Where they are relative to the
quarantine zone
• signage near citrus trees
http://www.cdfa.ca.gov/plant/pe/inte
riorexclusion/acp_quarantine.html
• explain tagging system
2. Psyllid & disease identification
• signage near trees
• provide brochures (quick tips)
3. Control options for psyllid
(insecticides, soaps, oil)
• shelf talkers
UC IPM “Quick Tips”
Monitor nursery plants regularly for pest and disease
Check plants for evidence of
the psyllid (especially flush)
Check leaves for blotchy
yellow disease symptoms
Isolate any infested or
suspected diseased plants
Report any psyllid finds or
suspected symptoms
Ensure turnover of host plant stock
Prior systemic insecticide treatments are effective for upwards of
three months
Trees can reside
at retail sites
much longer
35% > 1 yr
Long residencies
increase risk of
ACP infestation
Ensure turnover of host plant stock
Prior systemic insecticide treatments are effective for upwards of
three months
Encourage sale of ACP host plants before they become unprotected
1. Initiate a labeling program to
keep track of when plants arrived
• date or different colors
2. Distribute trees in a way that
encourages the sale of “older”
plants first
Use appropriate watering practices
Adequate water is important for uptake
of systemic insecticides. But,
overwatering is problematic
• contributes to pesticide runoff
• limits retention of systemic
insecticides in plants
Use water volumes that limit excess
runoff
• increase watering frequency
and reduce amount
Minimize psyllid access to host plants
1. Screening
• barrier to ACP establishment
• the most effective, sustainable
control measure
2. Place in shaded area
• ACP appears to prefer warm,
sunny areas
3. Move plants inside
• temporarily house flushing
plants in interior of store
Limit temporal overlap in nursery stock
If possible, encourage brief absence of citrus and other ACP host
stock
Absence of suitable host plants, even briefly, may limit ACP
populations
• no “reservoir” for insects
• limits spillover infestation
onto new plants
Encourage absence during
season when citrus stock is
normally low anyway
Conventional insecticides
Mandatory treatments for nursery stock in quarantine protect
plants for upwards of 90 days
• with appropriate watering may extend the effectiveness of
systemic insecticides
Retreatment may be necessary to protect plants for longer
durations
• treatments can be made using labeled foliar and systemic
insecticides
• if possible, consider retreatment by licensed applicator,
which are likely to provide a longer duration of effectiveness
Insecticidal soaps
Soaps can effectively kill ACP nymphs and
adults by contact
• little to no residual period
• not effective against eggs
Apply every 10 to 14 days when plants are
flushing
• helpful for other common pests
(mites, whiteflies)
Horticultural oils
Horticultural oils decrease attractiveness of trees for psyllids
• ACP avoid trees, reduce oviposition for up to a few weeks
after application
With adequate coverage, can
cause mortality of nymphs
and eggs
0.5% - 1% adequate to see
beneficial effects
Don’t apply more than every 6-8
weeks, depending on climate
Avoid removing new flush
Although pruning or hand
removal of new shoots may
temporarily decrease
attractiveness to ACP, citrus
responds by producing more
flush
• labor-intensive pruning
“treadmill”
May have a longer-term negative
effect on plant
Spray wash psyllids off plants
Moderately high-pressure hosing to
remove psyllid adults and nymphs
(“bug blaster”)
• may not effectively dislodge
psyllid eggs
• more effective if used in
conjunction with soaps or oils
Can contribute to overwatering or
plant damage if done too often or
too vigorously
Summary of Action Steps
• Inform customers about pest, disease, quarantine,
control options
• Inspect plants, isolate infested plants, and report
• Ensure prior insecticide treatments are effective
-encourage turnover of stock, don’t overwater
• Adopt supplementary control measures
-screening, insecticidal soaps, pray washing
Collectively these steps will minimize the potential for humanassisted spread of the psyllid and disease in California
http://www.ipm.ucdavis.edu/QT/asiancitruscard.html
Downloadable
brochure
General information
on psyllid and disease
biology, identification,
and control
Share with customers
Online ACP & HLB training course for retail nurseries
http://class.ucanr.edu/
ACP Distribution and Management
http://ucanr.edu/sites/ACP/