Survey of Susceptibility to Abamectin of Pear Psylla (Hemiptera: Psyllidae) in Northern Italy

Abstract

The pear psylla, Cacopsylla pyri L. (Hemiptera: Psyllidae), is a relevant pest of pear, Pyrus communis L., trees in Emilia-Romagna region (northern Italy). The susceptibility to the insecticide abamectin was evaluated at different times of the year on C. pyri populations undergoing different control strategies within conventional, integrated, and organic farms. The tests performed were the egg spray and the topic and dip bioassay on adults. The larval mortality was evaluated by dip bioassay on treated leaves. The activity of P450-dependent monooxygenases, a relevant enzyme system involved in insecticide resistance of C. pyri, was also determined in adults by 7-ethoxycoumarin O-deethylation (ECOD assay). Tests on treated eggs and on larvae showed no significant differences in LC50 and LC90, although these values were always lower in individuals collected from organic farms in comparison with all other farms. Tests on overwintering adults revealed differences among populations, probably more related to collection time than to field pest control strategies. Unexpectedly, the ECOD assay on adults showed a slightly higher cytochrome P450 monooxygenase activity in the population undergoing organic control in comparison to others. Our results indicate that egg spray is the most reliable bioassay to verify data of open-field applications. Apparently, no resistance to abamectin has yet been developed by C. pyri in Emilia-Romagna.

The Past and Present of Pear Protection Against the Pear Psylla, Cacopsylla pyri L.

“…12 and Fig. 13), the stage target in C. pyri field treatments (Civolani et al, 2010). On adults, the abamectin topical tests performed in autumn 2007 and 2008 did not show significant differences among all populations tested, but the LC 50 values were apparently related to the adult collection dates, as previously reported (Civolani et al, 2010).…”

“…The egg spray test (LC 50 and LC 90 ) did not show relevant differences, although LC 50 and LC 90 values were always lower in the organic farm than in all others (Table 6). The results of leaf dip tests performed on young and old larvae were generally similar to the egg spray ones (Civolani et al, 2010). Overall, the tests data indicate that no apparent resistance to abamectin has been developed up to now in C. pyri populations of Emilia-Romagna.…”

“…13), the stage target in C. pyri field treatments (Civolani et al, 2010). On adults, the abamectin topical tests performed in autumn 2007 and 2008 did not show significant differences among all populations tested, but the LC 50 values were apparently related to the adult collection dates, as previously reported (Civolani et al, 2010). The egg spray test (LC 50 and LC 90 ) did not show relevant differences, although LC 50 and LC 90 values were always lower in the organic farm than in all others (Table 6).…”

“…Table 5. Response of C. pyri overwintering adult populations to topical applications of abamectin (2007 and 2008) in the province of Ferrara (Civolani et al, 2010). Table 6.…”

“…Table 6. Response of C. pyri to egg spray applications (2007 and 2008) in the province of Ferrara (Civolani et al, 2010). The values of LC 50 are expressed in mg l -1 of abamectin.…”