natural-products-in-plant-pest-management

Phytochemicals as Natural Fumigants 181Table 8.6. Fumigant activity of the essential oil SEM76 extracted from Labiatae species onvarious developmental stages of Callosobruchus maculatus.Stage treatedAgeConcentration(µl/l)No. ofeggsNo. ofadultsF 1Eggs developed toadults (%)Egg 20–24 h 0.5 20 0 0Larvae outside 0–1 day 0.5 20 0 0the seedLarvae inside 2 days 1.0 20 3.5 17the seed1.5 20 4.5 22Larvae 3 days 1.5 20 10.5 533.0 20 8 40Larvae 7 days 1.5 20 14 703.0 20 13 63Larvae 11 days 1.5 20 17.5 883.0 20 16.5 83Pupae4–5 daysbefore1.53.0202012116055emergencePupae1–2 days0.5 20 4 20before1.5 20 1 5emergence 3.0 20 0 0Control 0 20 17 85Twenty unsexed adults were used for each test. The data are an average of three duplicateexperiments. Exposure time was 24 h.8.5 Distribution of a-Terpineol in the Fumigation ChamberMost of the research to study the potential of essential oils and their constituents(terpenes) for the control of insect pests was done using space fumigation,without paying attention to the amount of the fumigant available to thetreated insects. As a model, we studied the distribution of the terpenoidα-terpineol in the fumigation chamber among the air in the chamber space,filter paper and the flask walls. Using concentrations of 3, 5, 10 and 15 mg/lair and stirring at 20°C, only minor differences in the amount of the terpenoidin the chamber space was measured: 0.710, 0.676, 0.782 and 0.897 mg/lair, respectively. The rest was found on the filter paper and the flask walls(Table 8.7). At a higher temperature of 25°C, a higher amount of the terpenoid,50–60%, was recovered in the chamber space compared to the amountrecovered at 20°C (Table 8.7). No pronounced change of the terpenoid in thechamber space was measured at a different intensity of stirring or when nostirring was applied (Table 8.8). It should be mentioned that stirring causeda higher concentration of the terpenoid on the glass walls compared to thefilter paper, and the opposite if no stirring was applied (Table 8.8). Usingstirring at 20°C, we could show that after 2 h of fumigation the air in thefumigation chamber was already saturated (Table 8.9).