1. Attractants and Behavioral Ecology of Oviposition in
Scarab Beetles
Alexandre Rutikanga (Alex)
Master of Science: Agricultural Entomology (Makerere Univ.)
Master of Advanced Studies: ICM (Neuchatel Univ. Swiss)
Bachelor of Science: Crop Production and Horticulture (Univ. of Rwanda)
Research Scientist: IPP-Chinese Academy of Agricultural Sciences
A. Lecturer: University of Technology and Arts of Byumba (Rwanda, East Africa)
Beijing, China 30 May 2016
2. CONTENT
Background
Chemical communication in Beetles
Application of knowledge of Chemical Ecology in Pest Management
Behavioral Ecology of Scarab Beetles
Oviposition Attractants for Scarab beetles
Key Materials and Methods for Experiments
Future Prospects
Work Plan , Review Paper
3. THE WORLD POPULATION GROWTH- FEEDINGTHE HUNGRY PLANET
vs ONE GREEN PLANET’SVIEW & PESTS AND DISEASE PRESSURE
• Food production need to be kept up with
population growth
• 45 percent of land worldwide is already
occupied by animal agriculture and another
33 percent is used just to grow livestock
feed
• If we hope to sustain our population, we
need to shift from meat, eggs and dairy and
rely on protein from plants
• Need to have in mind that,‘Pests and
disease pressure= threat to crop
production’
www.onegreenplanet.org
4. BACKGROUND
Scarab beetles, 91% belongs to the family, Scarabaeidae
This study will focus on:
Holotrichia parallela Motschulsky (Coleoptera: Scarabaeidae: Melolonthinae)
Holotrichia oblita Falderman (Coleoptera: Scarabaeidae: Melolonthinae)
Anomala corpulenta Motschulsky (Coleoptera: Scarabaeidae: Rutelinae)
Postosia brevitarsis Lewis (Coleoptera: Scarabaeidae)
In China they are reported as pest of many crops (peanuts, soybean, potato) and turf grass
Resulting yield losses have been estimated in the range of 15-20%
Little is known on these scarab beetles in terms of Oviposition attractants and Behavioral ecology of
oviposition
Knowledge of these will help in the formulation of IPM strategies
Luo et al., 2008
5. CHEMICAL COMMUNICATION IN BEETLES
Behavioral responses in insect can be a result of membrane-bounding receptors that are triggered by
the presence of ligands
Odorant-Binding Proteins (OBPs), soluble proteins secreted in the sensilla lymph of insect, are
sophisticated chemical sensors and key driver in chemical communication
OBPs are important in chemical communication of insects and have therefore been characterized
from a range of insects including scarab beetles
Mueller et al., 1990; Vogt et al., 1991, 1999, Laughlin et al., 2008
6. USE OFTHE KNOWLEDGE ON CHEMICAL COMMUNICATION TO MANAGE
BEETLES
State - of - the Art
Chemical communication has a significant role in the interaction host plants- insect pests and this can
be manipulated to design insect traps or other management options
Pheromone-based traps: traps baited with methyl antranilate (plant lure) helped to catch 5 times as
many A. rufocuprea than synthetic sex pheromones
Plant volatiles can be used to monitor spread of an insect and directly used for its control
For example a three-component lure: phenethyl propionate + eugenol + geraniol (3:7:3) was more
effective for the control of the Japanese beetle
Ladd et al., 1975, Imai et al., 1997, Zhou et al., 2009
7. FEEDING AND MATING ATTRACTANTS FOR SCARAB BEETLES
Case of Holotrichia parallela
Holotrichia parallela responds to volatiles of plant such as elm trees for food
Volatiles associated with response of H. parallela
OCIMENE, Farnesol, Lauric acid, E-2-Hexen-1-ol, Limonene, α-pinene, 3-Hexen-1-ol, acetate, Benzaldehyde
(Plant volatiles )
L-isoleucine methyl ester (LIME) and Linalool (sex pheromones)
Sun et al., 2008; Ju et al., 2012
8. BEHAVIORAL ECOLOGY OF OVIPOSITION IN SCARAB BEETLES
Scarab Beetles have oviposition preferences
Phyllophaga cuyabana (Moser) lays larger number of eggs in plant species such as soybean Glycine max (L.) and
sunflower Helianthus annus (L.) compared to cotton Gossypium hirsutum L.
Female beetles of the species Diloboderus abderus Sturm do not to feed but prefer to oviposit in fields
containing soybean residual biomass which was not the case of maize biomass
This means oviposition preference for more suitable hosts that could stand their offspring survival
Such a behavior can tentatively be supported by the evolutionary hypothesis of variation in resource
quality for offspring performance
Studies on behavioral ecology of species such as H. parallela … can build on this knowledge
Craig et al., 1989 ; Oliveira et al., 2007
9. OVIPOSITION ATTRACTANTS FOR SCARAB BEETLES
it seems unclear which plant volatiles are associated with the oviposition of scarab beetles such as H. parallela,
however,
adults of the beetle Phyllophaga cuyabana, can distinguish species of same genera (e.g.: Crotoralia spectabilis and
C. juncea) based on composition and concentration of 2ndry chemical compounds (pyrrolizidine alkaloids)
P. japonica can discriminate between the quality and quantity of resources as more eggs were laid in soil blocks
with larger diameter stems or a higher number of stems per soil bloc
Soil-borne cues (e.g.: Metarhizium anisoplae) influence female beetles (e.g.: P. japonica) in post-alighting
oviposition decisions
Organic fertilizers (broiler litter, cow manure, hay, …) attract both adults and grubs of the Green June Beetle
(Cotinis nitida L.)
This knowledge provides a starting point to designing experiments on oviposition attractants for beetles such as
H. parallela, H. oblita …
Villani et al., 1994; Brandhorst-Hubbard et al., 2001; Szendrei & Isaacs, 2005; Oliveira et al., 2007
10. RELATIONSHIP OVIPOSITION PREFERENCE (adults) AND
PERFORMANCE (offspring) IN SCARAB BEETLE
Oviposition preference: hierarchical ordering of plant species by ovipositing females (expressed
as proportion of eggs laid on each of the plant species)
Offspring performance: survival at all immature stages (egg, larva, pupa), larval nutritional indices,
growth rate, pupal mass, resultant adult fecundity and longevity
Oviposition of female (e.g.: Deloyata guttata beetles) corresponds with the performance of their
offsprings, therefore, evolution of host specificity
Preference/performance relationship,: perceived as a strategy for selection of enemy-free space
Such relationship can be determined for the key scarab beetles (H. parallela, H. oblita, …)
Rausher, 1984; Futuyma and Peterson, 1985
11. KEY MATERIALS AND METHODS FOR LABORATORY :
Oviposition Preference among Plant Species, Bare Soil and Inert Materials
Plexiglas box (15x18x18cm)
Pieces of apple to feed beetles
Styrofoam (as inert walking floor) with openings to harbor
soil blocks
Soil blocks to support different oviposition resources
Oviposition resources (natural and artificial plant materials)
Adult Insects (beetles) collected from field
Ensure mating by placing males & females in screen cages
(1m3) for 2-3days
Separating females from males based on morphological
features
… Szendrei & Isaacs, 2005
12. KEY MATERIALS AND METHODS FOR LABORATORY :
Attractants- Grub Preferences as Exposed to Organic Odors
GlassY-Tube Olfactometer, jars and rubber stoppers (for 2 choices only)
Satellite chemometer (for multiple choice experiment) composed of Rubbermaid bowl and vinyl tubes
Third-instar grubs (60 grubs)
Different types of organic fertilizers
Brandhorst-Hubbard et al., 2001
13. KEY MATERIALS AND METHODS FOR OUTDOOR SCREEN HOUSE:
Oviposition Attracts from Organic Materials (Fertilizers)
Outdoor screen houses (3x4x2m)
Plastic pots (11-12 liters)
Organic fertilizers (Cow manure, broiler litter, grass hay, …)
Adults beetles (25 females) per screenhouse
Determination of the levels of N in each organic fertilizer
Sand-loam soil sifted to remove stones and large pieces of organic matter
Temperature 23-350C
Watering to keep soil and OM moist
Release females in screenhouse to oviposit and remove pots after a period of 5 days
Mosquito nets to keep pots in lab until eggs and larvae sifted from soil within 2 wks
Brandhorst-Hubbard et al., 2001
14. KEY MATERIALS AND METHODS FOR FIELD EXPERIMENTS:
Case of Dual-ChoiceTest for Oviposition and Adult Distribution
4 Outdoor nylon net cages (2x2x1m), the floor lined with transparent plastic, 120cm distant apart
6 Trays (30x50x15cm) in each cage for the main host and 6 similar trays for each of the alternate hosts
Adult beetles collected from filed during the first adult flight
Place trays side-by-side (simulating double mixed cropping)
Trays containing main host considered as control (simulating monoculture)
Release 30 couples of adult beetles in the middle of the cage
Observe for a period of 10 days adults that fly and land on different substrate, mark them on elytra, record adults that fail to
burrow into the soil, live ones marked on elytra and re-introduced in the middle of cages following morning and dead ones
discarded
Take a sample of 60 adults from the cages, maintain them in lab to estimate pre-oviposition period (1st egg expected 3 days after)
Seven days after 1st oviposition, remove trays from cages, record live, dead adults and eggs (remember also central pots), damaged
leaves also evaluated
Oliveira et al., 2007
15. CONCLUSION AND FUTURE PROSPECTS
Understanding the behavioral ecology, isolation and/or identification of attractants associated with
oviposition of scarab beetles (H. parallela, H. oblita,Anomala spp) can usefully be exploited in IPM
program for these soil insect pests
e.g.: Selective baits, mixed cropping and/or rotation
Attractants to the oviposition of scarab beetles such as H. parallela, can play a key role in biological
control, for example guiding the application of lures to attract (at the right time) specialized egg
parasitoids.
