Journal of Stored Products Research

CIMMYT and its network of collaborators in Mexico, conducted a series of experiments across agroecological zones of Mexico in 2017 and 2018 to evaluate the effect of different storage technologies on postharvest losses of maize. Experiments were conducted under “controlled” (i.e., managed by researchers) and “non-controlled” conditions (i.e., on-farm managed by extension agents). Each experiment compared the conventional storage technology (polypropylene bag with and/or aluminum phosphide or deodorized malathion) commonly used by farmers in the area to one or more other storage technologies (selected from hermetic metal silos, hermetic bags, recycled plastic containers, silage plastic bags, polypropylene bag with standard lime-calcium hydroxide- polypropylene bag with micronized lime). Data collected at the beginning and the end of each experiment included: (1) characteristics of the site of experiments (elevation, municipality, state, type of climate); (2) storage technologies evaluated; (3) grain characteristics (type of variety-hybrid or native-, moisture content, temperature); (4) grain damage data (percentage of grain impurities, percentage of insect-damaged grain, percentage of fungi-damaged grain, percentage of total damage, weight losses); (5) number of live insects per 500 g of sample (Sitophilus zeamais Motschulsky, Prostephanus truncatus Horn, Sitotroga cerealella Olivier); (6) storage time (in days and months) and average climatic data during storage period (minimum and maximum temperature, minimum and maximum relative humidity).

The irradiated garlic bulbs (0, 0.01, 0.06, 0.12 and 0.2 kGy) were stored under ambient conditions and physical and quality parameters were evaluated. Physical and chemical quality parameters include PLW (%), ROTTING (%), SPROUTING (%), TOTAL SOLUBLE SOLIDS (%), ASCORBIC ACID (mg/100g), FIRMNESS (N) AND ALLICIN CONTENT (μmol/mL). These were evalated after 15 days of storage interval.

MSc Thesis - Marcia Valbusa - Instituto Biologico (Brazil), 2017

2.1. InsectsFour to six-week-old T. variabile and T. inclusum were sexed or mixed-sex adults were used for the experiment to mimic natural populations at food facilities. Trogoderma variabile and T. inclusum were obtained from the field in Kansas in 2016 and 2012, respectively. Both species were fed 300 g of ground dog food (SmartBlend, Lamb flavor, PurinaOne, Nestlé Inc., St. Louis, MO, USA) with oats and a moistened, crumpled paper towel on the surface in a 950 ml mason jar. Colonies were maintained at 27.5°C, 65% RH, and 14:10 (L:D) h photoperiod. For both species, adults were sexed based on body size and antennal segments as mentioned above and they were observed under the stereoscope microscope at between 10–100× magnification (SMZ18, Nikon, Tokyo, Japan).2.2. TreatmentsThe LLIN in this study consisted of a polyethylene netting (2 × 2 mm mesh, Vestergaard, Inc., Lausanne, Switzerland) with 0.4% deltamethrin, or control netting without insecticide but otherwise identical in physical properties, including mesh size and material composition. These were used with the movement assay.2.3. Food and pheromonal semiochemicalsWe assessed the movement in the vicinity of important pheromone and food kairomones after exposure to the deltamethrin-based LLINfter) or control netting. Food stimuli included 0.01 g of whole, organic, unbleached flour (Heartland Mills, Marienthal, KS, USA), and pheromonal stimuli consisted of a broad spectrum, multi-species lure with the sex or aggregation pheromones for six stored product species (Plodia-Trogoderma-Lasioderma [PTL] lure, IL-108-10, Batch# 1288200321, Insects Limited, Westfield, IN), including Trogoderma spp. pheromone. We disassembled the lure and used a single bead out of the 15 beads present in each replicate, and affixed it in place so it did not move in a Petri dish using a 1 × 1 mm square of parafilm followed the similar procedure as in the study of Ranabhat et al. (2024). We used a fresh lure for each replication of testing.2.4. Movement assaySingle-sex or mixed-sex adult T. variabile and T. inclusum were exposed to LLIN and their behaviors were compared to a those exposed to control netting. Cohorts of 5 adults were exposed for 1 min to the control net or LLIN affixed to a 24 × 24 cm Petri dish in the laboratory. Effects on the movement of exposed adults in response to food cues (using 0.01 g of flour) or with conspecific sex pheromones as described above were assessed either immediately or after being held for 24 h in Petri dishes under the same environmental chamber conditions as the colonies but without supplemental food, and then assayed using the video-tracking combined with Ethovision video-tracking system software (v.14.5 Noldus Inc., Leesburg, VA, USA). Only alive or affected adults were tracked, and placed in the center of arenas for experiments. We used the definitions in Ranabhat et al. (2022), but shortly alive adults were defined as moving with normal speed and activity and able to right themselves if flipped, while affected adults exhibited sluggish or drunken movements, could not right themselves if flipped, and some or all of their limbs exhibited twitching. Dead adults showed no signs of movement. The network camera (GigE, Basler AG, Ahrensburg, Germany) was suspended 76 cm above and centered over six replicate 100 × 15 cm (D:H) Petri dish arenas held in place with a foamboard on an artist’s light box (LPB3, Litup, Shenzhen, China). Arenas were lined with a piece of filter paper (85 mm D, Ahlstrom-Munksjo Filtration, LLC, Mt. Holly Springs, PA, USA) adhered with four pieces of double-sided tape (CHI4050, Permanent, Skillcraft, USA) placed equally on cardinal side of the arena. A small 1.1 cm hidden stimulus zone encircled each stimulus, midway and centered on each half of the arena wherein movement was tracked separately from each half of the arena (Figure 1). A hidden zone is one in which the system assumes that when a walking insect enters it, the insect disappears from view and the amount of time it spends within and frequenting the zone is tracked (Noldus et al., 2002). The advantage of a hidden zone is that it allows a stimulus to be placed within it without creating artifacts in tracking. A hidden zone can also double as a normal zone when the insect is visible within the boundaries of the zone, Ethovision assumes that it is on top of it and not inside the zone. In the case of the current study, the stimulus treatment zone was a hidden zone where either pheromone or food stimuli were placed so they would not be tracked with the Ethovision software, and the control stimulus zone was left empty. The total distance moved (cm), instantaneous velocity (cm/s), frequency of entering each half of the petri dish and stimulus zone, cumulative duration spent in each zone (s), and latency of entering each zone (s) over a 30 min trial period was logged after exposure to a given treatment. A 30-min period was chosen to be comparable with prior data (Ranabhat et al., 2024). The control side of the arena remained empty. We included the response variables of total distance moved (cm) and instantaneous velocity (cm/s), because they are very well-studied variables, these variables can be compared with the prior work, and they accurately describe overall patterns in movement that often translate to the field for stored product insects (Morrison et al., 2018; Wilkins et al., 2020; Wilkins et al., 2021). Other response variables such as frequency of entering each half of the petri dish and stimulus zone, cumulative duration spent in each zone (s), and latency of entering each zone were included because they accurately depict aspects of arrestment and are generally understudied but important components of behavior. A total of 12–16 replicate beetles were run per combination for both species for each combination of sex or mixed population, species, and treatment.

2.1. InsectsFour to six-week-old T. variabile and T. inclusum were sexed or mixed-sex adults were used for the experiment to mimic natural populations at food facilities. Trogoderma variabile and T. inclusum were obtained from the field in Kansas in 2016 and 2012, respectively. Both species were fed 300 g of ground dog food (SmartBlend, Lamb flavor, PurinaOne, Nestlé Inc., St. Louis, MO, USA) with oats and a moistened, crumpled paper towel on the surface in a 950 ml mason jar. Colonies were maintained at 27.5°C, 65% RH, and 14:10 (L:D) h photoperiod. For both species, adults were sexed based on body size and antennal segments as mentioned above and they were observed under the stereoscope microscope at between 10–100× magnification (SMZ18, Nikon, Tokyo, Japan).2.2. TreatmentsThe LLIN in this study consisted of a polyethylene netting (2 × 2 mm mesh, Vestergaard, Inc., Lausanne, Switzerland) with 0.4% deltamethrin, or control netting without insecticide but otherwise identical in physical properties, including mesh size and material composition. These were used with the movement assay.2.3. Food and pheromonal semiochemicalsWe assessed the movement in the vicinity of important pheromone and food kairomones after exposure to the deltamethrin-based LLINfter) or control netting. Food stimuli included 0.01 g of whole, organic, unbleached flour (Heartland Mills, Marienthal, KS, USA), and pheromonal stimuli consisted of a broad spectrum, multi-species lure with the sex or aggregation pheromones for six stored product species (Plodia-Trogoderma-Lasioderma [PTL] lure, IL-108-10, Batch# 1288200321, Insects Limited, Westfield, IN), including Trogoderma spp. pheromone. We disassembled the lure and used a single bead out of the 15 beads present in each replicate, and affixed it in place so it did not move in a Petri dish using a 1 × 1 mm square of parafilm followed the similar procedure as in the study of Ranabhat et al. (2024). We used a fresh lure for each replication of testing.2.4. Movement assaySingle-sex or mixed-sex adult T. variabile and T. inclusum were exposed to LLIN and their behaviors were compared to a those exposed to control netting. Cohorts of 5 adults were exposed for 1 min to the control net or LLIN affixed to a 24 × 24 cm Petri dish in the laboratory. Effects on the movement of exposed adults in response to food cues (using 0.01 g of flour) or with conspecific sex pheromones as described above were assessed either immediately or after being held for 24 h in Petri dishes under the same environmental chamber conditions as the colonies but without supplemental food, and then assayed using the video-tracking combined with Ethovision video-tracking system software (v.14.5 Noldus Inc., Leesburg, VA, USA). Only alive or affected adults were tracked, and placed in the center of arenas for experiments. We used the definitions in Ranabhat et al. (2022), but shortly alive adults were defined as moving with normal speed and activity and able to right themselves if flipped, while affected adults exhibited sluggish or drunken movements, could not right themselves if flipped, and some or all of their limbs exhibited twitching. Dead adults showed no signs of movement. The network camera (GigE, Basler AG, Ahrensburg, Germany) was suspended 76 cm above and centered over six replicate 100 × 15 cm (D:H) Petri dish arenas held in place with a foamboard on an artist’s light box (LPB3, Litup, Shenzhen, China). Arenas were lined with a piece of filter paper (85 mm D, Ahlstrom-Munksjo Filtration, LLC, Mt. Holly Springs, PA, USA) adhered with four pieces of double-sided tape (CHI4050, Permanent, Skillcraft, USA) placed equally on cardinal side of the arena. A small 1.1 cm hidden stimulus zone encircled each stimulus, midway and centered on each half of the arena wherein movement was tracked separately from each half of the arena (Figure 1). A hidden zone is one in which the system assumes that when a walking insect enters it, the insect disappears from view and the amount of time it spends within and frequenting the zone is tracked (Noldus et al., 2002). The advantage of a hidden zone is that it allows a stimulus to be placed within it without creating artifacts in tracking. A hidden zone can also double as a normal zone when the insect is visible within the boundaries of the zone, Ethovision assumes that it is on top of it and not inside the zone. In the case of the current study, the stimulus treatment zone was a hidden zone where either pheromone or food stimuli were placed so they would not be tracked with the Ethovision software, and the control stimulus zone was left empty. The total distance moved (cm), instantaneous velocity (cm/s), frequency of entering each half of the petri dish and stimulus zone, cumulative duration spent in each zone (s), and latency of entering each zone (s) over a 30 min trial period was logged after exposure to a given treatment. A 30-min period was chosen to be comparable with prior data (Ranabhat et al., 2024). The control side of the arena remained empty. We included the response variables of total distance moved (cm) and instantaneous velocity (cm/s), because they are very well-studied variables, these variables can be compared with the prior work, and they accurately describe overall patterns in movement that often translate to the field for stored product insects (Morrison et al., 2018; Wilkins et al., 2020; Wilkins et al., 2021). Other response variables such as frequency of entering each half of the petri dish and stimulus zone, cumulative duration spent in each zone (s), and latency of entering each zone were included because they accurately depict aspects of arrestment and are generally understudied but important components of behavior. A total of 12–16 replicate beetles were run per combination for both species for each combination of sex or mixed population, species, and treatment.