Nutritional characteristics of Hydrilla verticillata and its affect on two

Nutritional characteristics of Hydrilla verticillata and its affect on two

Influence of nutritional
characteristics of Hydrilla
verticillata on two biological
control agents
Judy Shearer
Michael Grodowitz
Jan Freedman
US Army Engineer Research and Development Center
Vicksburg, MS
Biocontrol for Nature Symposium
Hydrilla verticillata
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First introduced in Florida
1950’s – aquarium trade
Asia, Africa, Australia
Submersed plant
Rooted in sediment
Forms extensive mats
Tubers and turions
– Extended survival
• US Problem
– Southeast
– California
– East/West Coast
Rio Grande - Texas and Mexico
Lake Somerville, TX
Lake Okahumpka, FL
Nickajack Reservoir, AL
Biological Control Agents
Hydrellia pakistanae
Mycoleptodiscus terrestris
(Mt)
Herbivory
Disease
Efficacy
Herbivore
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Temperature
Parasitism
Predation
Water flow
Canopy formation
Physical characteristic
Nutrition
Disease
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Temperature
Ph
Density
Canopy formation
Physical characteristics
Water flow
Nutrition
Herbivore
Treatments
Fertilization
CO2
Grow Time
Fertilized
High
Short/Warm
Used
Low
Long/Cool
Nutritional composition of hydrilla following
growth under different treatment combinations
Hydrilla nutritional composition
100
80
% Ash
% Crude protein
% Lipids
% Crude Fiber
% N free extract
60
40
20
0
Short Short Long
Used Used Used
Low
High Low
Long
Used
High
Short Short Long
Fert
Fert
Fert
Low
High Low
Treatment
Long
Fert
High
Methods
• In each container:
– 40 g hydrilla
– 50 eggs
• Adults removed as emerged
• Small oviposition boxes
– Counted eggs
– Assessed crowding
– Determined fly weight
Days to First Emergence
Various fertilization levels
Days To First Emergence
20.5
20.0
19.5
19.0
18.5
18.0
17.5
17.0
16.5
16.0
Used
Fertilized
Fertilization
Correlation: r = -.8573
21
95% confidence
20
19
18
17
16
DAYS TO
15
2
4
6
8
10
12
14
16
% CRUDE PROTEIN
18
20
22
24
Eggs Per Female
Various fertilization levels
Eggs per female for different fertilization levels.
22
20
Eggs per female
18
16
14
12
10
8
6
4
2
Used
Fertilized
Fertilization
Correlation: r = .92688
0.60
95% confidence
0.55
0.50
0.45
0.40
0.35
0.30
0.25
% PHOSPHORO
0.20
0.15
0.10
2
4
6
8
10
12
14
16
% CRUDE PROTEIN
18
20
22
24
Correlation: r = .86985
26
24
95% confidence
22
20
18
16
14
12
10
EGGS PER FE
8
6
4
0.10
0.15
0.20
0.25
0.30
0.35
0.40
% PHOSPHOROUS
0.45
0.50
0.55
0.60
Nutritional influences
Model: Exponential growth (y=c+exp(b0+b1*x1+b2*x2 ....))
z=84.5538+exp(5.26134+(.081049)*x+(-.41639)*y)
Variance explained = 67%
350
300
– Low protein
250
• Smaller females
• Fewer eggs
200
150
– Crowding
– Negates protein effects
100
50
20
16
12
8
32
28
24
20
16
12
8
4
Pathogen Experiment
Nutritional composition of hydrilla grown under different
treatment regimes.
Hydrilla nutritional compostion
100
80
% Ash
% Crude protein
% Lipids
% Crude fiber
% N free extract
60
40
20
0
Fert
CO2
Fert
Air
Used
CO2
Treatment
Used
Air
Methods
• In each container:
• 250 ml flask
• 150 ml deionized water
• 1 to 5 cm hydrilla sprig
• Inoculated with:
• Liquid Mt
• Rate = 0.1 ml/L
Disease rating of hydrilla sprigs 14 days post inoculation
with Mycoleptodiscus terrestris: 4 = tissues disintegrated;
3 = chlorotic and flaccid; 2 = chlorotic; 1 = slight chlorosis;
0 = green and healthy
4
Disease rating
3
2
1
0
FERT
USED
CONTROL
Sediment Treatment
Mycoleptodiscus terrestris
• Two structures
– Spores
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Reproduction
Unicellular or multicellular
Reproductive
Distributional cells
– Microsclerotia
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Survival
Multicellular
Hard
Resistant
Resting body
Number of spores/ml water containing a hydrilla
sprig 14 days post inoculation with Mt
Number of spores/ml
25000
20000
15000
10000
5000
0
Fert/CO2
Fert/Air
Used/CO2
Treatment
Used/Air
Average number of microsclerotia/leaf
Average number of microsclerotia/leaf 14 days
post inoculation with Mt
25
20
15
10
5
0
Fert/CO2
Fert/Air
Used/CO2
Treatment
Used/Air
Model: Exponential growth (y=c+exp(b0+b1*x1+b2*x2 ....))
y=3.7951+exp(8.38821+(-.6504)*x)
40
35
Variance explained = 66.2%
30
25
20
15
10
MICROSCLEROT
5
0
-5
6
8
10
12
14
16
% CRUDE PROTEIN
18
20
22
24
20000
15000
10000
5000
0
Fert/CO2
Average number of microsclerotia/leaf
Number of spores/ml
25000
Fert/Air
Used/CO2
Used/Air
Fert/Air
Used/CO2
Used/Air
25
20
15
10
5
0
Fert/CO2
Plant nutrition
High protein
• H. pakistanae
• M. terrestris
• Increased eggs
• Increased spores
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• Increased disease
Increased damage
Plant Nutrition
Low protein
• H. pakistanae
• Fewer eggs
• Smaller females
• Promotes insect dispersal
• M. terrestris
• Fewer spores
• Fewer sporodochia
• Shift to survival mode
Acknowledgements
• Dwilette McFarland
• Harvey Jones
• Jenny Reeves