Insect Control: Biological and Synthetic Agents - Index of

82 3: Neonicotinoid Insecticides
including N. cincticeps (green rice leafhopper), Laodelphax
striatellus (smaller brown planthopper),
and also mid- and late-season hopper species, like
Sogatella furcifera (white-backed planthopper) and
Nilaparvata lugens (brown planthopper). Benefits
of such nursery box applications include, reduced
labor input, longer residual effect, and reduced side
effects against nontarget organisms when compared
to surface treatments.
Based on 5-year field trials, a use pattern for
imidacloprid against the main rice pests has been
established. When applied as a granule, 2 granular
GR with 1 g a.i. per nursery box (¼ 200 g a.i. ha 1 )
0–3 days before transplanting, the product gives full
protection for 50–90 days against different hoppers
species. By controlling L. striatellus, a 91% reduction
of the rice stripe virus was observed. An excellent
residual effect was detected up to 50 days after
transplanting against L. oryzophilus, and up to
60 days against L. oryzae.
Apart from the seedling box application, imidacloprid
can be used as a granule for water surface
application, as a wettable powder (WP) or as a dust
formulation for foliar treatment, and also as a seed
dressing to control the above mentioned pests on rice.
Under field conditions of such use, no apparent effects
from imidacloprid treatments were observed against
populations of the spiders Pardosa pseudoannulata
and Tetragnatha vermiformis.
Therefore, imidacloprid can be regarded very effective
against rice insects and flexible to use, but it
is most efficient in nursery box application. It outperforms
other conventional insecticides due to its
broader efficacy and lower dose rates. Virus diseases
are suppressed through effective vector control, and
low toxicity has been observed against important
beneficials in rice.
3.4.2.2. Cotton The main cotton pests in the mid
South of the USA are Thrips tabaci, Lygus lineolaris
(tarnished plant bug), Neurocolpus nubilis (clouded
plant bug), Anthonomus grandis (boll weevil),
Heliothis virescens (tobacco budworm), and Helicoverpa
zea (bollworm). Other pests such as Pseudatomoscelis
seriatus (cotton fleahopper), Aphis gossypii
(cotton aphid), Spodoptera exigua (beet armyworm)
and S. frugiperda (fall armyworm) are of lesser
importance in this region.
Thrips tabaci attacks the terminal bud and two to
four true leaves. The plant is damaged by a reduced
stand, retarding growth, killed buds, and delayed
fruiting, with significant yield reduction. Lygus lineolaris
damages by feeding on pinhead squares,
which causes young squares to shed. Terminal bud
injury leads to multiple branched plants (‘‘crazy
cotton’’). Symptoms caused by N. nubilis are similar
to those of L. lineolaris.
It is thus evident that damage caused by earlyseason
pests, such as thrips and bugs, can be very
important. Loss of first-position squares can have
detrimental effects on the yield potential of the
plant. If normal fruiting of cotton plants is prevented,
this can cause a delay in maturity, which in turn
necessitates additional late-season insecticidal applications
to control bollworms, tobacco budworms,
and boll weevils.
A 480 FS formulation (Gaucho Õ ) is applied for
seed dressing, against early infestations of thrips
and aphids, at 250 g a.i. per 100 kg cotton seed
(37 g a.i. ha 1 ). Against bugs and later attack of
aphids, three foliar split applications at low dose
rates are recommended (Provado Õ 1.6 F, 3 15 g
a.i. ha 1 (Table 4). These should be done as band
sprays at intervals of 7–10 days. The first application
starts 30 days after emergence of the five leaf
stage, subsequent to the Gaucho Õ protection period.
The Heliothis–Helicoverpa complex is controlled
by conventional insecticides in mid-season, whereas
boll weevil and armyworms are controlled by
azinphos-methyl or cyfluthrin, respectively.
3.4.2.3. Vegetables Virus diseases have been
the main factors affecting the tomato and chilli production
in Mexico during the past 20 years,
and these diseases have led to significant yield reductions
in many regions. These crops are grown
on approximately 160 000 ha with constant virus
infestation in 30–35% of the fields, with persistent
viruses being the most important in Mexican agriculture.
In tomato crops, viruses can infest up to
100% of the crop. The damage depends on the
type of virus, the population density of vectors,
and the developmental stage of the crop. Protection
by conventional insecticide treatments under plastic
covered greenhouses, however, has not given
satisfactory results (Elbert and Nauen, 2004).
3.4.2.4. Cereals The traditional method in
controlling virus vectors in Europe is regular monitoring
of aphid attack of young wheat and barley
plants after emergence in autumn. If the threshold of
10% infested plants with at least one aphid per
plant has been surpassed, usually a pyrethroid will
be sprayed. Monitoring has to be continued,
because the residual effect of the treatment may be
insufficient for vector control. Depending on climatic
conditions and the duration of the aphid attack, a
second or a third application may be required. This
rather time consuming and difficult procedure can
be avoided by a seed treatment with imidacloprid.