Low temperature tolerance of Plodia interpunctella, Sitophilus oryzae and Sitophilus zeamais: The prevalent pests of stored maize in Serbia

Abstract

Insect's bionomics and development are highly dependent on the environmental temperature. For centuries, this fact has been used for the control of storage pests. However, the temperature threshold depends on the species, life stage, acclimation and exposure period. This work assessed the effects of low temperatures (4,-4,-10,-15 and-18°C) and exposure period (10, 30, 60, 120 and 180 min) on the survival and development of Plodia interpunctella larvae, and adults of Sitophilus oryzae and S. zeamais, the prevalent maize pests in Serbia. Data were analysed using one-way and two-way ANOVA. Additionally, Probyt analysis was performed to determine the LT 50 and LT 99. The first significant effects were recorded at-4°C for S. oryzae when the mortality was 41% after 120 and 52% after 180 min of exposure. At-10°C, the mortality of S. zeamais was significant after 180 min (52.5%) and increased with the exposure period. The significant mortality of P. interpunctella larvae was at-15°C after 10 min (55.5%). At-18°C, P. interpunctella larvae were the most susceptible and 98% of mortality was recorded after 10 min, while 77.5% of S. oryzae and 68% of S. zeamais was recorded after 10 min. Two-way ANOVA showed that both factors (temperature and exposure) significantly affected the mortality of tested species, but the first factor was the most influential. These results indicate that temperature and exposure period should be adjusted to specific pest, while in combined infestations the temperature should be adjusted to the most tolerant one.

Razviće insekata je visoko uslovljeno temperaturom životne sredine. Vekovima je ova činjenica korišćena u kontroli brojnosti skladišnih štetočina. Međutim, temperaturni pragovi zavise od vrste, životnog stadijuma, aklimatizacije i trajanja ekspozicije. U ovom radu ispitivani su uticaji niskih temperatura (4, -4, -10, -15 i -18°C) i trajanja ekspozicionog perioda (10, 30, 60, 120 i 180 min) na nivo preživljavanja i razviće larvi Plodia interpunctella i imaga Sitophilus oryzae i S. zeamais, dominantnih štetočina uskladištenog kukuruza u Srbiji. Dobijeni podaci su analizirani korišćenjem one-way i two-way ANOVA. Dodatno, urađena je i Probyt analysis radi utvrđivanja LT50 i LT99. Prvi značajni efekti niskih temperature registrovani su na -4°C za imaga S. oryzae sa registrovanim uginućem od 41% posle 120 i 52% posle 180 min ekspozicije. Na -10°C uginuće imaga S. zeamais bilo je značajno posle ekpozicije od 180 min (52,5%) i raslo je sa trajanjem ekspozicionog perioda. Značajna smrtnost larvi P. interpunctella registrovana je na -15°C posle 10 min (55,5%). Na -18°C larve P. interpunctella bile su osetljivije i 98% smrtnost registrovana je posle 10 min, a u istim uslovima 77,5% kod imaga S. oryzae i 68% kod S. zeamais. Two-way ANOVA ukazuje da oba faktora (temperatura i ekspozicija) značajno utiču na smrtnost testiranih štetočina, ali je temperatura uticajniji faktor. Dobijeni rezultati pokazuju da temperatura i ekspozicija predstavljaju manipulativne faktore koje treba prilagoditi vrsti, dok u kombinovanim infestacijama treba ih prilagoditi najtolerantnijoj štetočini.