Fourth International Bemisia Workshop International Whitefly ...

Journal of Insect Science | www.insectscience.org ISSN: 1536-2442
mortalities ranging from 35 to 40%. The least effective
among the tested compounds, were Agri Sea-Green
and Iber-neem (causing mortalities around 20%). None
of the insecticides evaluated caused mortality to Er.
mundus significantly different than the control. On the
other hand, emergence of En. formosa adults from
pupae treated with Soapline 60 was significantly
greater than emergence from pupae treated with
Tec-Bom, Sunspray Ultrafine and Agri Sea-Green. En.
pergandiella proved very sensitive to all the tested
products and significantly fewer parasitoids emerged
from pupae treated with all the formulations when
compared with the control. To control B. tabaci
nymphs, our results demonstrate than some of the
called “biorational” insecticides (e.g. potassium soaps
or mineral oil) are as effective as conventional
insecticides, or even better. In contrast, to control B.
tabaci adults, the most effective products were the two
conventional insecticides tested (Actara and Calypso).
Therefore, since B. tabaci is difficult to control, it
could be useful to integrate biological control with safe
insecticides to natural enemies. To do so, our results
indicate that the impact on biological control of some
of the termed “biorational” insecticides should not be
neglected and, the integration of both control methods
will depend on the parasitoid species used.
Bemisia tabaci Biotype Q and its Natural
Enemies in Vegetable and Ornamental
Crops
Judit Arnó, J. Roig, and R. Gabarra
Departament de Protecció Vegetal. IRTA-Cabrils. Cabrils
(Barcelona), Spain.
Correspondence: judit.arno@irta.es
Vegetables in some Mediterranean areas are grown
mainly on small family operated farms. Vegetable
crops are grown year- round in open fields and
greenhouses built with metal frames, covered with
plastic films, and mostly unheated. Vegetable
production coexists with ornamental crops either in the
open field or in heated greenhouses. In this situation,
whiteflies reproduce all year with continuous
carry-over among different crops and environments.
For many years, Trialeurodes vaporariorum has been
one of the main pests. However, from the early 90’s,
populations of Bemisia tabaci have been increasing in
vegetable and ornamental crops. In the area of study,
the northeast of Spain, tomato, cucumber and
poinsettia crops are often heavily infested by B. tabaci.
This pest usually coexists with T. vaporariorum and
their relative abundance changes with crop and season.
Tomato is grown in three different crop cycles from
February to December in greenhouse and outdoors.
Cucumber is grown mainly in greenhouses in two crop
cycles from March to November. Finally, poinsettia is
grown for the Christmas market in heated greenhouses
from July to December. In tomato, biological control
of whiteflies, by conservation and augmentation of
native populations of the mirid bug Macrolophus
caliginosus, is used by many growers. In cucumber, no
specific biological control program is applied and,
although the crop is sprayed more often that tomato,
natural enemies can be preserved to a certain extent. In
poinsettia, releases of the parasitoid Eretmocerus
mundus to control B. tabaci populations together with
the use of soft insecticides began in 2003 in few farms
as an alternative to chemical control of the pest. In this
scenario, we wanted to determine the importance of
three B. tabaci sensitive crops (tomato, cucumber and
poinsettia) on the survival of this whitefly, and to
evaluate the natural enemies associated with B. tabaci
and T. vaporariorum. For this purpose, tomato crops
(IPM and non IPM) were surveyed: 9 in spring, and 7
in autumn 2003, and 11 in spring and 17 in autumn
2004. We also surveyed 7 cucumber greenhouses
during September 2004, 7 poinsettia greenhouses
during 2003 and 5 more during 2004. In these
poinsettia greenhouses, growers released Er. mundus
combined with the use of soft insecticides. Thirty
tomato leaflets, 30 cucumber leaf-disks (9.6 cm 2 ), and
30 poinsettia leaves were sampled to evaluate B. tabaci
infestation, parasitization and predation. Parasitized
pupae were isolated until the emergence of the
parasitoid to determine its species. In tomato,
Trialeurodes vaporarioum was the predominant
species in the spring crops whereas B. tabaci was the
most abundant in autumn crops. In cucumber and
poinsettia, B. tabaci was almost the only whitefly
present. In autumn 2004, although the infestation was
very different among greenhouses, average density of
B. tabaci on cucumber (3.43 nymphs/ cm 2 ) was
significantly greater than on tomato (0.13 nymphs/
cm 2 ) or poinsettia (0.08 nymphs/ cm 2 ) (F= 43.7; df
2,28; P