1. The effect of water stress on oviposition and feeding in the flea beetle, Lysathia n.sp
Chad Keates Supervisor: Dr Weyl Rhodes University Zoology and Entomology Department

2. Parrots feather: why does it matter?
Parrot’s feather, Myriophyllum aquaticum, is an alien invasive water weed.
Found in Eastern Cape, Western Cape, Mpumalanga
and the North West
Occurs in aquatic and moist terrestrial environments
Originates from South America
Mechanical and herbicidal removal have proven unsuccessful.

3. The introduction of Lysathia n. sp
Lysathia n.sp is a South American flea beetle.
Lysathia feeds on the emergent parrots feather shoots.
Sustained and cumulative feeding by the beetle results in longer recovery times for the plants.
Lysathia n. sp is considered a highly successful biological control agent for parrots feather.
However

4. Field sites indicate good control under aquatic conditions however limited control on muddy substrate. Similar to the alligator weed situation in Australia

5. Aims:
This study will test in two phases the effects of water-stress on Lysathia n.sp by determining whether:
Phase 1: Female Lysathia n.sp are capable of ovipositing on water-stressed parrots feather
Phase 2: Lysathia n.sp survive and are capable of feeding on water stress parrots.
This study is important because it will determine whether Lysathia n.sp is capable of limiting both aquatic and terrestrial growth of parrot’s feather or whether additional biological control agents need to be introduced in South Africa

6. Methods Phase 1: Oviposition experiment Experimental setup
30 tubs setup in the biocontrol tunnels
60 cups with 2 sprigs per cup
2 treatments: Choice and no choice
Each tub received 6 adult Lysathia n.sp for 2 days
Choice
10 tubs containing 1 water-stressed and 1
non-stressed cup each
No choice
stressed treatment-10 tubs, 2 water-stressed
cups in each
Non-stressed treatment-10 tubs, 2
non-stressed cups in each

7. Methods: Oviposition experiment
Data collection
After 2 days all the cups were
removed from their tubs
Each sprig was examined and amounts of eggs were counted per sprig
Statistical analysis
Choice- data was analysed using
non-parametric Wilcoxin rank test
No choice- data was analysed
using non-parametric Mann Whitney U test

8. Results: Oviposition experiment
The female Lysathia n.sp showed a significant preference for non-water-stressed parrots feather when given a choice between stressed and non-stressed parrots feather sprigs (Z(1,40)= 3.823, P= 0.000)
Fig 1: Average number of Lysathia n.sp eggs found per sprig when females were given a choice between water-stressed and non-stressed parrots feather sprigs. (Standard error bars have been supplied).

9. Results: Oviposition experiment
The female Lysathia n.sp showed a significant preference for non-water-stressed parrots feather when not given a choice between stressed and non-stressed parrots feather sprigs (U(1,80)= 396.5, P= 0.000).
Fig 2: Average number of Lysathia n.sp eggs found per sprig when females were not given a choice between water-stressed and non-stressed parrots feather. (Standard error bars have been supplied).

10. Discussion
The females in the oviposition showed a significant preference for non-stressed parrots feather conditions when choosing an oviposition site.
There was virtually no damage on stressed plants when parrots feather had a choice but under choice conditions there was higher levels of damage on stressed parrots feather.
This finding forms the basis of our second phase feeding experiment which serves to determine whether Lysathia are able to defoliate and thus reduce the density of parrots feather under stressed conditions when given no condition between plant conditions.

11. Methods Phase 2: Feeding experiment Experimental setup
Set up in bio-control tunnels
Parrots feather was placed in 20 plastic tubs
Each tub got 50g of parrots feather.
10 replicates received 8 Lysathia n.sp each
4 treatments with 5 replicates in each:
Water + Lysathia n.sp
Water + no Lysathia n.sp
Mud + Lysathia n.sp
Mud + no Lysathia n.sp

12. Methods: feeding experiment
Data collection
The total number of growth tips within a quarter of each replicate will be counted each week
Damage analysis will be done and parrots feather will be separated into 1 of 4 categories, namely: none, minor, moderate and fully damaged.
Statistical analysis
Amounts of growth tips- the data was analysed using a non-parametric multiple comparisons Kruskal-wallis ANOVA
Damage levels- the data was analysed using a non-parametric Mann Whitney-U test

13. Results: feeding experiment
The average amount of growth tips rarely differed between treatments however there were several occurrences of significant differences.
Significant difference found between all 4 treatments in:
Week 2: (H(3,20)= 7.844, P= 0.049)
Week 4: (H(3,18)= , P= 0.043)
Week 6: (H(3,18)=10.084, P= 0.018)
Fig 3: Average number of growth tips found per m² in treatments over a period of seven weeks. (Standard error bars have been supplied).

14. Results: feeding experiment
There was no significant difference recorded between damage levels in the two treatments
It is however important to note the original lag in week 2 which resulted in damage being observed later in the water stressed treatment (U(1,10)= 7.5, P= 0.180).
It was not significant but supported hypothesis resulting to oviposition preference
Fig 4: Comparison of the percentage feeding damage of two treatments over a period of seven weeks. (Standard error bars supplied).

15. Discussion
According to studies done on insect feeding guilds, free living chewers usually perform poorly on water-stressed plants.
Our study showed that Lysathia n.sp can defoliate and thus feed successfully on both stressed and non-stressed parrots feather
The lag phase observed in this experiment corroborated findings in the oviposition experience which found that females show preference for non-stressed parrots feather.
The almost similar levels of damage found at the conclusion are thought to be the result of the females confinement to particular treatments

16. Conclusion
The absence of Lysathia n.sp damage from terrestrial parrots feather in the field is likely the product of the females preference for non-stressed plants.
This preference thus drives females to disperse in search of more favourable conditions
The dispersal leaves stressed parrots feather free of biological control agents

17. Thank you