Phosphine resistance, respiration rate and fitness consequences in stored‐product insects

Abstract

Resistance to fumigants has been frequently reported in insect pests of stored products and is one of the obstacles in controlling these pests. The authors studied phosphine resistance and its physiological basis in adult insects of 12 populations of Tribolium castaneum (Herbst) (Tenebrionidae), ten populations of Rhyzopertha dominica (F.) (Bostrichidae) and eight populations of Oryzaephilus surinamensis L. (Silvanidae) from Brazil, and the possible existence of fitness costs associated with phosphine resistance in the absence of this fumigant. The bioassays for the detection of phosphine resistance followed the FAO standard method. The production of carbon dioxide and the instantaneous rate of population increase (r(i)) of each population of each species were correlated with their resistance ratios at the LC(50). The resistance ratio at LC(50) in T. castaneum ranged from 1.0- to 186.2-fold, in R. dominica from 2.0- to 71.0-fold and in O. surinamensis from 1.9- to 32.2-fold. Ten populations of T. castaneum, nine populations of R. dominica and seven populations of O. surinamensis were resistant to phosphine. In all three species there was significant association (P < 0.05) between respiration rate and phosphine resistance. The populations with lower carbon dioxide production showed a higher resistance ratio, suggesting that the lower respiration rate is the physiological basis of phosphine resistance by reducing the fumigant uptake in the resistant insects. Conversely, populations with higher r(i) showed lower resistance ratios, which could indicate a lower rate of reproduction of the resistant populations compared with susceptible populations. Thus, management strategies based on the interruption of phosphine fumigation may result in reestablishment of susceptibility, and shows good potential for more effective management of phosphine-resistant populations.

Spread of phosphine resistance among brazilian populations of three species of stored product insects

“…Of the 19 samples tested, five could be diagnosed with weak resistance and 14 with strong resistance suggesting that resistance was widespread and apparently at a high level. Therefore, our results are in accordance with earlier surveys of phosphine resistance in Brazil (Lorini et al 2007, Pimentel et al 2007, 2009) and also show evidence of resistance, but requiring further investigation for these species studied here.…”

“…In addition, the frequent unsuitable storage management added to poor fumigant application techniques has probably enhanced the selection pressure for resistance , Lorini et al 2007, Pimentel et al 2007. Another factor that can influence the evolution of phosphine resistance is the movement of insects due to the commodity trade (Benhalima et al 2004, Fragoso et al 2003b.…”

“…Moreover, phosphine resistance in stored-product insects is documented in several neighboring South American countries (Champ & Dyte 1976. Except for the global survey undertaken by FAO (Champ & Dyte 1976) , Lorini et al 2007, Pimentel et al 2007, 2009.…”

Prevalence and potential fitness cost of weak phosphine resistance in Tribolium castaneum (Herbst) in eastern Australia

“…However, effective management of this pest is threatened by phosphine resistance which has been reported from many parts of the world (e.g. Champ and Dyte, 1976;Price and Mills, 1988;Herron, 1990;White and Lambkin, 1990;Rajendran, 1994;Benhalima et al, 2004;Pimentel et al, 2007;Opit et al, 2012). Studies on the inheritance of phosphine resistance in T. castaneum show that there are two broad levels of resistance (weak and strong) in this species, with two major genes (rph1 and rph2) controlling their expression (Bengston et al, 1999;Jagadeesan et al, 2012).…”

“…Therefore, knowing if there are fitness costs associated with phosphine resistance could help in resistance management. Fitness has been investigated in a range of insect pests of stored grain using different experimental approaches (Pimentel et al, 2007;Schlipalius et al, 2008;Sousa et al, 2009;Pimentel et al, 2011;Jagadeesan et al, 2012Jagadeesan et al, , 2013Daglish et al, 2014). Some studies have used the population cage approach in which susceptible and resistant strains are hybridized and the resulting populations are reared in the absence of phosphine selection.…”