Insect Control: Biological and Synthetic Agents - Index of

50 2: Indoxacarb and the Sodium Channel Blocker Insecticides
Table 3 Potency of indoxacarb to pest insects in the laboratory: larval ingestion and contact vs. adult contact
Insects
2.5. Biological Potency of Indoxacarb
2.5.1. Spectrum and Potency of
Indoxacarb in the Laboratory
Laboratory assays show that lepidopteran, hemipteran,
and homopteran pests are inherently very
sensitive to indoxacarb, and are significantly more
affected when indoxacarb is ingested (Wing et al.,
2000). When treated plant leaves were fed to a
variety of lepidopterous larvae, this resulted in
50% lethal concentration (LC 50) values ranging
from 0.3 to 7.7 ppm when evaluated 3 days posttreatment
(Table 3). These values are similar to
LC50 values published by other researchers (Seal
and McCord, 1996; Pluschkell et al., 1998; Liu
and Sparks, 1999; Liu et al., 2002; Giraddi et al.,
2002; Smirle et al., 2002; Ahmad et al., 2003; Liu
et al., 2003), and indicates the high toxicity of
this compound to Lepidoptera. Indoxacarb halts
insect feeding within 4 h after ingestion. Insect mortality
generally takes place within 2–4 days, and it
is critical to evaluate both mortality after 72 h and
feeding damage to assess the compound’s true effectiveness.
Trichoplusia, heliothines, and Spodoptera
are the most sensitive among the lepidopterans
while Plutella and Cydia are somewhat less sensitive.
Variation in activity among species may be due
to the rate of bioconversion of indoxacarb to the
active metabolite DCJW or to the amount of product
consumed. Insecticidal activity of indoxacarb
against the sucking insects Empoasca fabae and
L. lineolaris in the laboratory are similar to that
of the lepidoptera (Table 3). Lepidopteran adults
were also effected when they ingested a sugar
water solution with indoxacarb.
The ingestion activity of indoxacarb to lepidopteran
larvae is about three to nine times greater
than its dermal contact activity (Table 3). For some
Insecticidal potency of indoxacarb (LC50 values, ppm)
Direct spray contact
Ingestion Larvae Adults a
Heliothis virescens 1.47 12.96 56
Helicoverpa zea 0.68 2.55
Spodoptera frugiperda 0.61 5.25
Spodoptera exigua 1.96 7.66
Trichoplusia ni 0.28 45
Plutella xylostella 3.69 30
Empoasca fabae 1.11
Cydia pomonella 7.68
Lygus lineolaris 1.46
a Toxicity measured with methylated seed oil (1%) or vegetable oil plus organosilicone surfactant (0.5%) at 7 days posttreatment.
insects however, such as Lobesia botrana, the potency
of the two modes of entry is almost equivalent
(Anonymous, 2000). Indoxacarb shows negligible
activity when insects walk on a dried residue, and
has no activity as a fumigant.
Indoxacarb was also significantly less active as
a direct contact spray to moths compared to larvae;
however, it is still effective. Directly spraying
lepidopteran moths with indoxacarb plus methylated
seed oil at 1% or a vegetable oil plus organosilicone
surfactant at 0.5% resulted in LC50 values
ranging from 30 to 56 ppm for lepidopteran adults
at 7 days post treatment (Table 3). The ability of
indoxacarb to provide moth control or suppression
in the field will contribute to overall pest
suppression.
Indoxacarb has inherent toxicity to select coleopteran
(Parimi et al., 2003), hemipteran (Lygus),
homopteran (Myzus, Empoasca, Nephotettix, Nilaparvata),
and dipteran (Chen et al., 2003) pests after
feeding on treated leaves or artificial diets (Wing
et al., 2000) (Table 3). Indoxacarb has low water
solubility; however, leaf penetration and translaminar
activity are responsible for controlling certain
sucking pests and is enhanced by inclusion of
oil-based formulations or tank-mixed adjuvants.
Indeed, the compound is toxic in the field to plantbugs,
fleahoppers, and leafhoppers; however, it is
ineffective against species such as aphids because
of poor systemicity and low phloem oral bioavailability.
Overall, indoxacarb’s utility as a field insecticide
active against sucking insects is constrained
by its very limited systemicity, compared to many
neonicotinoids.
Indoxacarb exhibits ovilarvicidal activity on
Lepidoptera such as L. botrana, Eupoecilia ambiguella,
Heliothis armigera, and Cydia pomonella
(Anonymous, 2000). Laboratory data indicates