Feeding Performance and Effectiveness of Ladybird Beetles (Coleoptera: Coccinellidae) for Cowpea Aphid
(Aphis craccivora Koch) Control.
ByD.K Murahwi
Supervisors: Mr. Matsiga Prof. Mvumi
BACKGROUND
Many farmers in Zimbabwe are relying on pesticides for control of crop pests, (Mudimu et al. 1995).
Pesticides tend to have a non-selective effect on insects, (Ali et al. 2011).
There is a global shift towards organic and sustainable agriculture.
BACKGROUND CONT’
Ladybird beetles are the perfect candidate as biological control agents, since they are voracious predators (in both larval and adult stage), (Brewer & Oswald II 1995).
Can supplement their diet with pollen, nectar, or honeydew, (Cranshaw, 2014).
Although slow this method is effective in both curative and preventative measures of dealing with phytophagous insects.
RESEARCH PROBLEM and JUSTIFICATION
Research ProblemAphids are a major crop pest and tend to develop resistance to pesticides.
There are side effects associated with chemical pesticides
Thus chemical control being pushed out especially in the wake of organic farming
Justification Berlandier et al, (1998) research on aphid effect on lupin plants.
The beneficial aspects of insects outweigh the detrimental effects, (Goodwin 2014).
OBJECTIVES
Broad DetermineTo determine feeding performance and effectiveness of ladybird beetles for the control of cowpea aphids.
Specific1. To evaluate the feeding of native ladybird beetles on
cowpea aphids.2. To evaluate the feeding of native ladybird beetles
possible alternative diets.3. To identify the native ladybird species most suited to
effectively control cowpea aphids.
HYPOTHESES
1. H1: Native ladybird beetles are effective consumers of cowpea aphids.
2. H1: Ladybird beetles can survive on possible alternative food sources.
3. H1: Different native ladybird beetle species have different consumption rates of cowpea aphid.
MATERIALS AND METHODSGENERALUZ Crop Science Dept. cowpea plot in Natural Region 2a (18o12’S, and 31o 05’E) for the aphid and ladybird beetle source.
UZ Crop Science Dept. Entomology Laboratory averaging 26oC and 42% RH for food source experiments 1, 2, 3 and 4.
Study design had 3 treatments (Cheilonomes geisha, Hippodamia variegata and Cheilonomes lunata) and blocking by day for all 4 experiments.
Feeding samples were taken for each treatment and the weight changes averaged for the specific day to the particular treatment.
MATERIALS AND METHODS
30mg of food source was presented to the test subjects and after a 2 hour period the weight change of the food source was measured and recorded.
This was repeated for each day the experiment was run.
MATERIALS AND METHODS
OBJECTIVE 1Experiment 4 using cowpea aphid as the food source was done (02/03/15).
OBJECTIVE 2Experiment 1, 2 and 3 using Bee Pollen (07/01/15), Dried Ground Chicken Liver(13/03/15) and Shredded Tuna (18/03/15) respectively as the alternative diets.
OBJECTIVE 3Experiment 4 on cowpea aphid as the food source (02/03/15).
DATA COLLECTION AND ANALYSIS
Weight changes were measured at 2 hour intervals for the feeding samples which were ranging from 3 to 20 and averaged for each particular species.
This was done each day the experiment was run.Statistical package Minitab16 was used for analysis of the generated data.
Friedman’s test was carried out for test of significance and box plots used for graphical display of significance.
RESULTS
Figure 4.1: C. geisha, H. variegata and C. lunata
EXPERIMENT 1
Table 4.2: Friedman’s Test on Bee Pollen Data
Species Weight Changes (mg)
C. geisha 29.1
H. variegata 29.3
C. lunata 29
Grand median 29.1
P value 0.202
EXPERIMENT 2
Table 4.4: Friedman’s Test on Dried Ground Chicken Liver
Species Weight Changes (mg)
H. variegata 29.25
C. lunata 28.35
Grand median 28.8
P value 0.564
EXPERIMENT 3
Table 4.6: Friedman’s Test on Shredded Tuna
Treatments Weight Changes (mg)
Control 5.8667
H. variegata 6
C. lunata 5.2333
Grand median 5.7
P value 0.529
EXPERIMENT 4
C.lunataH.variegataC.geisha
30
28
26
24
22
20
18
16
Species
Weig
ht C
hang
e (mg
)
Boxplot of Weight Change
Figure 4.3: Box Plot of Aphid Consumption.
EXPERIMENT 4
Figure 4.4: Line graph of Ladybird Beetle Field Population
DISCUSSION
In this study, the ladybird beetles could not be reared on the possible alternative food sources Bee Pollen, Dried Ground Chicken Liver and Shredded Tuna.
Smith (1960) successfully reared ladybird beetles on corn pollen.
Kariluoto et al. (1976) and Kariluoto (1980) in Da Silva et al. (2010; pg 15) reveal diets based on pig liver have been developed.
DISCUSSION
The ladybird beetles were effective feeders of aphids. C. lunata was the heavier aphid feeder among the three species followed by H. variegata and C. geisha was the least.
Ladybird beetles are voracious feeders of aphids influenced prey and predator attributes, (Ferran & Dixon 1993).
In North Dakota in the period June and July of 1949 successful control of aphid infestation in wheat (Munroi & Somsen 1949).
CONCLUSION
The native ladybird beetle were found to be effective cowpea aphid feeders.
Although an alternative diet for rearing was not found in the current study, C. lunata was observed to be most suitable for control of Aphis craccivora Koch.
RECOMMENDATION
Maize pollen and cowpea pollen should be considered for research as alternative diet.
Research on possible artificial diets for the mass laboratory production of C. lunata would be important for cost effective production of the biological control agent for successful control of Aphis craccivora Koch
ACKNOWLEDGEMENTS
Peace Mujuru for the source of aphidsMrs Mutisi and Mr Vengai from Entomology Department of DR&SS for species identification
Dr David Icishahayo for statistical aidDr Mabasa for technical and technological assistanceDepartment of Crop Science Staff for their time and dedication
My Colleagues for moral and academic support
Thank you