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Stockholm School of Economics
January 9, 2016
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and saved in 70% alcohol for
Data Analysis. All analyses were
the linear mixed model procedure
2010). Data from the ve sample
sites within a plot
were averaged before analysis, and
delays or prevents the rebound of
pest populations that is a
significant factor in natural
biological control. A two-year field
sampling of 10 cotton arthropod
showed that spiders (27%) were
the most dominant foliage dwelling
in the Rolling Plains region of Texas,
and Slosser et al.
(1998) observed that lady beetles
comprised 62% of the
total predators in dryland cotton
during a five-year study
in the Rolling Plains region.
However, the proportion of
lady beetles in the total
Cowger, C., and C. Mundt.
2002. Effects of wheat cultivar
mixtures on epidemic progression
of Septoria tritici blotch
and pathogenicity of
Edwards, P. J., and S. D.
Wratten. 1983. Wound induced
transgenic Bt monoculture
treatment were signicantly
dampened in both years compared
with that in
Fig. 3. Temporal dynamics of
cotton aphids in two monoculture
pure stands (transgenic Bt
SZNC20B and non-Bt 93Fu56)
and 3:1 mixture of both genotypes,
aphid population dynamics trends
were observed in
plots of different mixture patterns
(Fig. 3A, B), peak
cotton aphid abundances differed
years. In 2008, peak densities were
23 June (Fig. 3A), whereas in 2009,
that diverse predator communities
juvenile predators than did singlepredator-species
communities, which is supported
by enhanced abundances
of larval ladybirds and larval
lacewings in this
One limitation of this study was
failure to r
on undamaged tissues (Edwards
1983). Thus, factors leading to the
mirid bugs and sweetpotato
whiteies were likely
reduced competition and lower
from cotton aphids and pests of
other species in
mixture plots. Al
emigration of apterous individuals
or alates (Wu
and Guo 2003). Owing to arearestricted movement
in monoculture setting, cotton
aphid seasonal abundance
is largely dependent upon earlystage colonization.
Contrary to expectations, mixtures
crops correlated with wide-scale
adoption of Bt cotton in
China. Science 328: 1151.
Luttrell, R., G. P. Fitt, F. S.
Ramalho, and E. S. Sugonyaev.
1994. Cotton pest management:
part 1. A worldwide perspective.
Annu. Rev. Entomol. 39: 517526.
Mahmood, T., D
Zheng). Arthropod species were
sampled by visually
inspecting 20 cotton plants at ve
sampling sites in each plot (100
plants per plot), in situ.
Thus, on any sampling date, the
total number of
nymphs and adults inhabiting 100
mid-July with a second peak in late
August (2008) or
early September (2009) (Fig. 2).
Arthropod Pests. Of the cotton
insect pests measured,
cotton aphids occurred in the
followed by mirid bugs, and
whitey biotype B.
Cotton Aphids. Altho
DEPARTMENT OF ECONOMICS
2016 WI Peterborough
Dr. M. Arvin
Room 351, Gzowski College
Telephone: 705-748-1011 Ext. 7299
(Office hours: please see page 4)
Newton, A., G. S. Begg, and J.
S. Swanston. 2009. Deployment
of diversity for enhanced crop
function. Ann. Appl.
Biol. 154: 309322.
Parajulee, M., and J. Slosser.
1999. Evaluation of potential
relay strip crops for predator
enhancement in Texas cotton.
data related to the predatorprey
convergent lady beetle and cotton
of a decision rule system for a
given predator or predator
guild will be the necessary first
step toward further development
of a biologically and
of various species and also withinspecies developmental
stages, however there were
exceptions, such as
larval ladybirds. Furthermore,
differed signicantly between
years, and there was
signicant variation in the
interactions between yea
the maximum densities occurred
on 23 August (Fig.
4A), whereas the maximum
densities in 2009 occurred
on 3 August (Fig. 4B).
Sweetpotato Whiteflies. Crop
(F_220.1; df_2, 15; P_0.0001) and
df _ 1, 15; P _ 0.0001) signicantly
predator abundances in mixed
plots versus monoculture
elds. Enhanced predator numbers
linked to correlation between prey
diversity, and plant diversity.
analyses of our data suggested
that prey abundance
and mixture pattern was noticed (F
_ 1.3; df _ 2, 15;
P_0.31). In contrast to cotton aphid
bug densities were signicantly
higher in the cotton
variety mixture treatment (SF)
compared with that in
monoculture plots (S and F),
Date 9, 99 26.61d 74.73d 12.32d
7.40d 263.71d 25.72d
a P _ 0.05.
b 0.05 _ P _ 0.01.
c P _ 0.01.
d P _ 0.001.
ENTOMOLOGY Vo9l9. 41, no. 4
Weare grateful to Marvin Harris
and Yunfeng Zhang (Institute o
Randomly selected 10 plants per
observed visually in the field and
pest and predator numbers
were recorded. Ten predator
species were sampled
that included predaceous bugs
(minute pirate bug Orius
spp., damsel bug Nabis spp., bigey
linear mixed model by using year
as a random factor.
Data were log(x_1) transformed to
satisfy analysis of
variance assumptions of normality
of variance before analysis.
Treatment means were
compared with the least signicant
mixture pattern was signicant
only for disease
severity (F _ 79.9; df _ 1, 15; P _
In each growing season, similar
incidence rate and
disease index trends were
observed in plots of different
measured cotton variety mix
patterns (Figs. 12).
which kill naturally occurring
predators and parasitoids
and pyrethroids also physiologically
interacts with cotton
leaves enhancing cotton aphid
reproduction (Kidd &
2012 Institute of Zoology, Chinese
Academy of Sciences
2 R.B. Shrestha & M.N. Par
lady beetle larva (2nd instar),
medium larva (3rd instar),
and adult (1 week after adult
emergence) specimens were
used in this aphid consumption
study. Large larvae were
not evaluated because most of
them pupated by the end
of the experiment. Six small l