Fourth International Bemisia Workshop International Whitefly ...

Journal of Insect Science | www.insectscience.org ISSN: 1536-2442
Mortality and Population Dynamics of
Bemisia tabaci within a Multi-Crop System
Steven E. Naranjo 1 , Peter C. Ellsworth 2 and Luis
Cañas 3
1 USDA-ARS, Arid-Land Agricultural Research Center, Maricopa,
Arizona, USA.
2 Department of Entomology, University of Arizona, Maricopa
Agricultural Center, Maricopa, Arizona, USA
3 Department of Entomology, Ohio State University, OARDC,
Wooster, Ohio, USA
Bemisia tabaci is a multivoltine insect with no
diapause that maintains population continuity by
moving from one host to another over the year. To
better understand the mechanisms governing
population development of this insect, whitefly
“ecosystems” were established in three geographically
and climatically distinct areas in Arizona. These
systems consisted of a sequence of six representative
hosts including winter broccoli, spring and fall
cantaloupes, summer cotton, perennial alfalfa, various
annual weeds, and the perennial ornamental, lantana.
No insecticides were used at any site. Source and rates
of natural mortality were quantified, in situ, on each
host plant by constructing life tables. The same
mortality factors were observed in all hosts at all sites.
The quantitative contribution of each mortality factor
varied among hosts and time of the year, but was
relatively consistent among geographic sites. Predation
and dislodgement from the plant surface were
consistently the largest sources of mortality, although
mortality from desiccation was high during the fall and
winter. Most mortality occurred during the 4th
nymphal stadium and the egg stage for most host
plants. Median generational mortality was generally >
90% except on spring-planted cantaloupe where
median mortality was ≈ 65%. Predation, dislodgement,
desiccation, and occasionally parasitism, were the key
factors depending on host plant, season and site. Low
mortality during the spring on cantaloupe appears to
act as a biotic release leading to outbreak populations
during summer months. Overall, an understanding of
the year round dynamics of this pest will greatly aid
the development of better pest management strategies
in all affected crops.
Greenhouse Whitefly Eggs and Nymphs
Density on Gerbera jamesonii under
Different Nitrogenous Fertilizer Regimes
Laura D. Ortega-Arenas 1 , D. A. A. Miranda 1 and M.
Sandoval-Villa 2
1 Programa en Entomología, Campus Montecillo, Colegio de
Postgraduados, Montecillo, Estado de México. México.
2 Programa en Edafología, Campus Montecillo, Colegio de
Postgraduados, Montecillo, Estado de México. México
The objective of the study was to evaluate the
influence of nitrogenous fertilization in three varieties
of gerbera (Gerbera jamesonii H. Bolus), on the
oviposition rate and population density of whitefly
nymphs, Trialeurodes vaporariorum (West.). An
evaluation was also made of the effect of nitrogen
concentration on indicators of flower quality (diameter
of capitulum, diameter of peduncle and length of
penduncle), yield and post-harvest life. Three varieties
of gerbera were used (Tzigana, Fallela and Marisol)
and three concentrations of nitrogen (8, 12 and 16 me
L −1 ), in a completely random design with factorial
arrangement of treatments. The effect of the treatment
was determined registering every two days, the
population density of whitefly eggs and nymphs, per
cm 2 of leaf, in two experiments: 1) free choice and 2)
no choice. The population density of eggs and nymphs
was higher in free choice assays. In these, the number
of eggs and nymphs increased significantly (p≤0.05) as
the supply of nitrogen increased. In the no choice
assays, however, the oviposition rate and nymphs
density were not notably influenced by the nitrogen
supply. In the three varieties, the highest density of
eggs and nymphs was related to the nitrogen content in
the leaves. The nitrogen supply did not effect the
diameter of the capitulum, the length and thickness of
the peduncle and the yield, but it did have an influence
on the post-harvest life of the flower. In the varieties
Fallela and Marisol, the post-harvest life was longer as
the nitrogen supply was increased; on the other hand,
in the Tzigana variety, the duration of the flower did
not show a direct relationship with the nitrogen
content.
Invasion and response: Impacts of bemisia
on worldwide agriculture
L. S. Osborne
Mid-Florida Research and Education Center, IFAS, University of
Florida, Apopka, FL, USA.
Correspondence: lsosborn@ufl.edu; www.mrec.ifas.ufl.edu/lso
The historical record reveals that Bemisia tabaci has
caused damage to agricultural crops for more than 80
years. However, this pest was generally considered a
minor or even a non-pest in most agricultural systems
until the late 1980’s and early 1990’s. During the past
20 years the impact this pest has had on agriculture has
been staggering. Why, after almost 80 years, has this
whitefly reached such a pest status that we are
attending the 4th International Workshop to discus its
management and biology? The two workshops in Duck
Key this week will address some of the issues that
have contributed to this heighten pest status. During
my presentation, I will discuss the impact this pest has
had on agriculture and why we should pay very close
attention to Bemisia tabaci. This insect should severe
as a model of an invasive species. Why has this pest
Journal of Insect Science: Vol. 8 | Article 4 37