Studies On Development Of Resistance To Carbon Dioxide And Combination Of Phosphine Plus Carbon Dioxide In The Red Flour Beetle (tribolium Castaneum Herbst):

Adel Mohamed Abd El-lattf

The main objective of the present work was to study the development of resistance in the red flour beetle (Tribolium castancumHerbst) to phosphine, carbon dioxide and their mixture. Also to investigatesome biological characteristics of the resistant strain to a combination ofphosphine plus carbon dioxide in comparison to the parental stock.This work was conducted at the Plant Protection Dept., Faculty ofAgriculture at Moshtohor, Zagazig University. Data obtained could be summarized as follows : 1- Development of resistance in T castancum - adults to phosphine, carbon dioxide and a combination of the two gases:Adult populations of ’Lcastancum were exposed in the laboratory for 16 generations to a fixed concentration of 40 vpm phosphine (56.52 /.lgil) a controlled atmosphere containing 46% carbon dioxide and acombination of 40 vpm PH3 + 46% CO2 at varying exposure periods, 26 ±1°C and 6 ± 1°C,.in order to select strains resistant to phosphine, carbondioxide and their mixture. Selection pressure was carried out at the medianlethal dose/time inducing mortalities ranged from 50-70%. I.I-Development of resistance in T.castaneum adults tophosphine, Results indicated, that the lethal time values (LT50 LT 90, LT99)were significantly higher at the lower temperature 6 ± 1°C than at thehigher one (26 ± 1°C) and at the 16th generation, the lethal times neededfor a certain kill were markedly longer for the phosphine resistant strainthan the laboratory strain.Results of selection indicated that T castancum adults have thegenetic potential to develop resistance to phosphine and the treatment ofthe successive generations of this insect with the median lethal dosages ofphosphine produced insects with increased tolerance to the fumigant at the two test temperatures. The adults of the 16th generations showed 15.J-foldresistance to phosphine at 26 ± 1°C and 10.2 - fold resistance at 6 ± 1°Cwhen compared with the laboratory stock at the LT50 - level.1.2 - Development of resistance in T.castaneum to carbondioxide : Results indicated that at the 16th generation. the lethal time valuesachieved for certain mortality were significantly higher at the two testtemperatures, when compared with the laboratory strain. The adults of the 16th generation showed at 26 ± IOC 1.8 and 1.9 fold at LT50 and LT90 - level. respectively. At 6 ± 1°C the 16th generation revealed 1.7 and 1.8 fold at LT50 and LT90 -level, respectively.This result indicated that T.castaneum adults was capable to develop low resistance to an atmosphere contained 46% CO2. 1.3- Development of resistance in T.castaneum to acombination of phosphine + carbon dioxide : Results showed that the lethal time values recorded to obtain certain kill were significantly higher for the 16th generation at the two testtemperatures than for the laboratory strain (Parent). At the 16th generation,the adults of Ticastaneum showed 19.4 - fold resistance to a combinationof phosphine plus carbon dioxide at 26 ± 1°C and 18.5 - fold resistance at6 ± ] °C when compared with the laboratory stock at the LT 50 - level.This result indicated clearly that ’Lcastaneum adults have thegenetic potential to develop resistance to an atmosphere containing acombination of 40 vpm PH3 + 46% carbon dioxide. 2.1. The biological characteri tic of the re i tant train ofT.castaneum to a combination of P 3 + C02 in compari on to the parental stock.Results showed that, the resistant strain of T’castaneum (F 12)selected to a mixture of 40 vpm phosphine + 46% carbon dioxide laidignificantly higher number of eggs than the laboratory strain. But nosignificant differences were found between the laboratory and PH3 CO2resistant strain (F 12) of 7: castaneum in the average pre-ovipostion periodand sex ratio. The total developmental period was significantly longer forthe laboratory strain than the PH3 + CO2 - resistant strain. The averageincubation period was significantly longer in the laboratory strains than the PH ... + CO2 resistant strain. The larval mortality was considerably higherfor the PH3 + CO2 resistant strain. The average hatching rate of the eggssignificantly increased for the PH3 + CO2 resistant strain. The mortalityrate of the larval instars was significantly higher for the PH3 + CO2 -resistant strain than for the laboratory strain. It was also observed that the emergence rate of the adults was unaffected and amounted to 100% for the two strains.2.2. The population dynamics of Tribolium castaneum resistant strains (PH3 - RS, PH3 + C02 - RS) in comparison to theparental stock (laboratory strain).Results revealed that the mean adult mortalities were 2.23%, 4.44%and 13.63% for the laboratory, PHrRS, and PH3 + C03 - RS,respectively. These values were obviously higher in case of the PH3 +CO2 - RS than the other strains. The population growth rates were 0.054,0.053, and 0.053 for the labortory, ~H3 - RS and PH3 + CO2 - RSrespectively. It is evident that his value was slightly greater for thelaboratory strain than the other strains.The maximum number of the alive adults recorded in the foodduring an observation period of six months was 1090 805, 664 for theparental stock, phosphine resistant strain, and PH3 + CO2 - RS. resistantstrain, respectively. These values were reached after 120 days in all testedstrains.Although the resistant strains to phosphine and the strain resistant toa combination of PH3 + CO2 laid significantly higher numbers of eggs incomparison to the laboratory strain, the adult populations recorded duringthe observation period of six months were in contrary lower for the tworesistant strains than the laboratory strain.Thi could be due to the lower hatchability of egg in the phosphineresistant strain and higher mortalities during the various developmentaltages of the two resistant strains in comparison with the parental stock.