Impact of host plant resistance on emergence, body parameters, and supercooling point of Cylas formicarius elegantulus (Coleoptera: Brentidae)

Sweetpotato weevil, Cylas formicarius elegantulus (Summers) (Coleoptera: Brentidae), an in-field and storage pest of sweetpotato, is the primary insect constraint to sweetpotato production in tropical and subtropical regions. Feeding by adult and larval sweetpotato weevil induces terpenes, rendering storage roots unmarketable. To reduce storage root damage and sweetpotato weevil populations, the present experiment tested the impact of sweetpotato cultivar on developmental time, adult emergence, body length, weight, and supercooling point of sweetpotato weevil. The cultivars tested were 'Beauregard' and 'Evangeline,' both orange fleshed cultivars susceptible to sweetpotato weevil, and 'Murasaki; a white fleshed cultivar known to be resistant to sweetpotato weevil. There were no differences in developmental time with most adult sweetpotato weevils emerging 34 to 44 d after oviposition. However, the number of adult sweetpotato weevil that emerged from Beauregard (38.9 +/- 3.3) and Evangeline (48.4 +/- 6.2) roots were greater than numbers emerging from Murasaki (11.1 +/- 3.5), indicating resistance is due to antixenosis. Although fewer in number, adults (male and female) emerging from Murasaki were heavier than males and females emerging from Beauregard and males from Evangeline. Supercooling points of sweetpotato weevil males emerging from Murasaki (-17.9 +/- 0.4 degrees C) were significantly lower than Beauregard (-16.3 +/- 0.5 degrees C) but similar to Evangeline (-17.1 +/- 0.4 degrees C). Host plant resistance expressed by Murasaki may reduce sweetpotato weevil populations significantly, but those that emerge may be better suited to survive the cold.

Automated summary

This study tested the impact of different sweetpotato cultivars on the developmental time, adult emergence, body length, weight, and supercooling point of the sweetpotato weevil. The results showed that the Murasaki cultivar exhibited strong resistance, with fewer but more cold-tolerant adults emerging.