Simple Summary: Insect pests of stored commodities cause harm not only to bulk grains but also to
many value-added food products in mills, processing plants, and other facilities where these products
are stored. In this study, the residual efficacy of an Insect Growth Regulator (IGR), novaluron, was
evaluated under laboratory conditions against larvae of three stored product insects, Oryzaephilus
surinamensis (L.), Tribolium castaneum (Herbst), and Trogoderma granarium Everts, on concrete, metal,
and wood surfaces to which IGRs are typically applied for pest control in such facilities. Statistically
significant reductions in emergence percentages of adults compared to a distilled water control
occurred for up to 12 weeks when novaluron was sprayed on concrete, metal, and wood at rates
between 0.053 and 0.209 mg/m2, the highest of which induces 100% mortality at 0 weeks after
treatment. Residual efficacy decreased with increasing time after treatment due to degradation and
sorption of novaluron into the surfaces. Novaluron residues were most persistent on metal and least
persistent on wood surfaces. Knowledge of novaluron residual efficacy on storage facility surfaces
can be helpful guidance for timing of postharvest insect pest management treatments as the costs of
commonly used pesticides increase along with insect resistance to such pesticides.
Abstract
The residual efficacy of novaluron on concrete, metal and wood was evaluated against last-
instar larvae of Oryzaephilus surinamensis (L.), Tribolium castaneum (Herbst), and Trogoderma granarium
Everts. The larvae and food provided for survival were exposed to surfaces pretreated at rates of
0.053, to 0.209 mg/m2 and bioassays were conducted from 0- to 16-weeks post-treatment. Percentage
emergence of adults was recorded after 30 days (d). On all surfaces at week 0, no O. surinamensis
or T. castaneum adults emerged, and ≤3.3% emergence of T. granarium was found at 0.209 mg/m2.
Novaluron significantly reduced the percentage emergence of adults of the three species compared
to a distilled water control for the first 12 weeks on all the tested surfaces as the residual efficacy
declined at a low rate during initial weeks and then at a high rate in the final weeks of the 16-week
study. Reductions to emergence were most persistent on metal surfaces, with mean percentages of
adult emergence of ≤18.3 in week 12, followed by concrete (≤32.5) and wood (≤45.0) for all species
at novaluron application rates of 0.209 mg/m2. For >4-weeks protection, higher application rates
would be needed to avoid buildup of pest populations and reductions in profitability. Such results
can be helpful for the management of O. surinamensis, T. castaneum, and T. granarium as the costs of
commonly used insecticides against postharvest insect pests and the resistance of these insects to the
pesticides gradually increase in mills, warehouses, and food storage facilities.
Introduction
Currently, the main strategies for the control of stored product insect pests are based
on fumigants (primarily phosphine) and residual insecticides that are applied as surface reatment or as grain protectants in food storage facilities [1,2]. However, most of these
treatments leave toxic residues, and their frequent use had led to the development of resis-
tance in stored product insects to the most-used insecticides [3–7]. In recent years, research
has been conducted on non-chemical control methods, e.g., botanicals, pheromones, or
hermetic storage [8–11], as well as alternative chemical insecticides with low toxicity to
mammals and humans [12–14]. Need remains, however, for further evaluation of methods
to apply alternative reduced risk insecticides in ways that provide effective, nontoxic
control of important stored-product insect pest
Insect growth regulators (IGRs) possess great pest-control potential and their adoption
in the food industry has been widely considered [12,15–17], particularly for control of
stored product insects [18–26]. A prominent use of IGRS is to spray them onto uncovered
metal, wood, or concrete surfaces, as in a study by Boukouvala and Kavallieratos [27]
that evaluated six different insecticides on concrete for control of Trogoderma granarium
Everts (Coleoptera: Dermestidae), including pyriproxyfen, sprayed at a rate of 2.3 mg/m2,
s-methoprene at 3 mg/m2, and deltamethrin at 1100 mg/m2. Surface treatment approaches
generally are less costly and more convenient, and they reduce levels of residues on food
commodities compared to direct application [13].
