Seasonal Life Tables for ACP in Southern CA

Erica J. Kistner, Nagham Melhem, Elizabeth Carpenter, Martin Castillo, and Mark S. Hoddle

UC-Riverside Dept of Entomology

Applied Biocontrol Research

ACP Life Table Studies• Life tables can be used to

assess mortality and survivorship rates for the different immature life stages of ACP– Eggs– Small nymphs– Large nymphs

• Mortality can be assigned to different causes– Parasitism– Predation– Harsh Environment

Developing Life Tables for ACP

1. Full Exclusion (625 holes per inch2 )

3. T. radiata access (156 holes per inch2 )

2. Walking enemies excluded (sticky

barrier)

4. No exclusion (No treatment)

ACP Life Table Studies• ACP Cohorts that are “born” at the

same time were studied across sites and through time– Three different sites in Riverside, CA

• Differ significantly in flora composition – Life tables for 116 ACP cohorts were

generated across seasons (2014-2015:

• Spring• Summer• Fall• Winter

UC-R Biocontrol Plot

Lochmoor (private property)

Jurupa (private property)

Collecting Survivorship and Mortality Data

• Every other day ACP life stages were counted on experimental plants:

• Number entering each stage is recorded

• Determine survivorship rates to adulthood

• Determine parasitism rates

• Identify predators trapped on sticky barrier and on ACP colonies

Eggs 1st-3rd Instars

4th-5th Instars

Adults0

0.10.20.30.40.50.60.70.80.9

1 Winter

D. citri Stage

Prop

ortio

n En

terin

g St

age

Eggs 1st-3rd Instars

4th-5th Instars

Adults0

0.10.20.30.40.50.60.70.80.9

1 Spring

D. citri Stage

Prop

ortio

n En

terin

g St

age

Eggs 1st-3rd Instars

4th-5th Instars

Adults0

0.10.20.30.40.50.60.70.80.9

1 Summer

D. citri Stage

Prop

ortio

n En

terin

g St

age

Eggs 1st-3rd Instars

4th-5th Instars

Adults0

0.10.20.30.40.50.60.70.80.9

1 Fall

D. citri Stage

Prop

ortio

n en

terin

g St

age

Mean ACP Survivorship Curves (2014-2015) at Riverside CountyWinter: Nearly all ACP die because of cold weather. 20% of Full exclusion ACP survive

Spring: About 29% of ACP reach adulthood when exposed to Tamarixia only. 99% ACP die when fully exposed to all natural enemies. 61% of Full exclusion ACP survive

Summer: About 46% of ACP reach adulthood when exposed to Tamarixia only. 96% ACP die when fully exposed to all natural enemies. 72% of Full exclusion ACP survive

Fall: About 66% ACP die when exposed to Tamarixia only. 96% ACP die fully exposed to all natural enemies 63% of Full exclusion ACP survive

Mean ± SE jackknifed treatment differences in ACP life table parameters (2014-2015)

Ro, net reproductive rate, (per capita rate of population growth), MT, mean generation time (in days) rm, instristic rate of increase, Td, doubling time (in days). Means within a column followed by a different letter are significantly different.

• If Ro > 1, then the population is growing

• ACP net reproductive rates (Ro) ↑ when protected from natural enemies (Kruskel-Wallis P < 0.001)

Treatment Net Reproductive

rate (Ro)

Generation time (Tc)

Intrinsic rate of increase (rm)

Doubling Time (Td)

No exclusion 8.20 ± 2.66a 27.14 ± 1.57a 0.03 ± 0.01a 17.12 ± 6.51a

Full exclusion 171.30 ± 20.04b 33.88 ± 1.75a 0.16 ± 0.01b 5.63 ± 0.49b

T. radiata access 76.64 ± 17.59c 32.81 ± 2.1a 0.11 ± 0.02bc 9.14 ± 3.00b

Walking enemies excluded

45.35 ± 12.23c 27.87 ± 1.60a 0.09 ± 0.01c 12.49 ± 4.67ab

What is killing ACP?

Fall Cohorts Only (n = 28)Life Stage Number entering stage

lx

Morality Factor

Number dying in stage dx

Full exclusion Walking insects excluded

T. radiata access

No exclusion

Full exclusion Walking insects excluded

T. radiata access

No exclusion

Eggs 1613 1471 1506 1537 Unknown 100 96 102 109Disappear 83 427 127 855

1st - 3rd instars 1430 948 1277 573 Unknown 122 120 420 136Disappear 20 99 85 155Predation 0 115 0 46

4th - 5th instars 1288 614 772 236 Unknown 158 109 64 33

Disappear 42 40 17 23Predation 0 0 0 114

Parasitism 0 105 159 0

Adults 1088 340 518 66

Form

icidae

Syrphidae

Chrysopidae

Coccinellid

ae

Aranae

Phytoseiid

ae

Aeolothripidae

Tamarixia

Anthocorid

ae

Forfi

culid

ae

Thripidae 0

50

100

150

200

250

300

350

400

ACP Natural Enemies and Allies

Tota

l Ins

ects

Obs

erve

d Common Arthropods on ACP Cohorts (2014-2015)

Invasive Argentine ants tend ACP nymphs and protect them from natural enemies

Summary• Natural enemies including Tamarixia reduced urban ACP net

reproductive rate (Ro) by 55-95%.– Parasitism rates peaked in the fall with parasitism comprising 21% of the

total ACP mortality (when ants are excluded).– Dominant predators include hover fly and green lacewing larvae (86% of all

observed predation mortality).– Mites, spiders?, and thrips may be causing high egg mortality.

• Argentine ant management is warranted especially in heavily infested urban areas (liquid baits)

• Minimizing pesticide use or utilize natural enemy compatible products for citrus pest control

Acknowledgements• Hoddle Lab Members: Christina Hoddle, Ruth Amrich,

Michael Lewis (photos), Kelsey Schall, Allison Bistline-East, Meghan Vankosky

• CRB: Brian Taylor• USDA: Greg Simmons• CDFA: David Morgan, Grace Radabaugh• UC-Riverside, Dept of Entomology: Matt Daugherty• Field help: Kathryn Vega, Victor Herrera