The effect of 1-pentadecene on Tribolium castaneum behaviour: Repellent or attractant?

BACKGROUND: Movement of the red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae), in stored products is mediated by food volatiles and other semiochemicals. RESULTS: In two-way olfactometer assays, T. castaneum was more attracted to wheat bran previously infested with conspecifics than to uninfested bran. Chemical analysis showed that 1-pentadecene was present in the headspace of T. castaneum-infested wheat bran, but not detectable in the headspace of uninfested bran. An olfactometer was used to test the effect on T. castaneum behaviour of 1-pentadecene, and of volatiles from wheat bran with and without 1-pentadecene. The lowest concentration of 1-pentadecene exhibited an attractive effect, compared to the control (n-hexane). Slightly higher concentrations showed a neutral effect, while the highest concentrations repelled T. castaneum. Wheat bran with a low 1-pentadecene concentration was more attractive than wheat bran alone, whereas higher concentrations of 1-pentadecene were repellent. CONCLUSION: The results provide important information on intraspecific, semiochemical-mediated behaviour in T. castaneum, which could potentially be used to develop new methods to monitor the flour beetles in stored products. © 2021 Society of Chemical Industry.

Biological Features and Population Growth of Two Southeastern European Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae) Strains.

A study of the biological features and the potential population growth between two laboratory strains of the confused flour beetle, Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae) from Greece and Serbia is conducted on cracked barley and cracked white rice. The results show that, at a species level, T. confusum is able to complete development on cracked barley but not on cracked white rice. Therefore, cracked white rice proves to be an unsuitable commodity for T. confusum. Larval development on cracked barley is significantly shorter for the Serbian compared to the Greek strain (37.7 and 49.7 days, respectively), but pupal development does not differ between the two strains (6.2 days for both strains). Additionally, male longevity does not differ between the Greek and Serbian strains (144.4 and 151.4 days, respectively), while female longevity is significantly shorter for the Serbian (151.7 days) compared to the Greek strain (186.6 days). Fecundity does not differ between the two strains (11.3 and 17.7 eggs/female for the Greek and the Serbian strain, respectively), whilst survival is higher for the Serbian strain on both tested commodities. The values of the net reproductive rate, the intrinsic rate of increase and the finite rate of increase on cracked barley are significantly higher for the Serbian (7.27 females/female, 0.025 female/female/day and 1.026, respectively) compared to the Greek strain (2.91 females/female, 0.014 females/female/day and 1.014, respectively). It therefore is expected that different strains of T. confusum may exhibit variable phenology as well as potential population growth. Additionally, we expect our results to have bearing on the management of this species.

Behavioural responses of Tribolium castaneum (Herbst) to different types of uninfested and infested feed.

Tribolium castaneum is one of the most economically important insects that damages stored products. The effects of several infested or uninfested raw feed materials (wheat bran, coarse wheat meal, corn feed flour), feed products (compound feed for pigs and for laying hens) and flour mixed with brewer's yeast on the food-searching behaviour of T. castaneum adults were studied in a total of 48 combinations. Preference and olfactometer tests revealed that all the tested uninfested and intraspecific infested substrates were significantly more attractive to T. castaneum than the control (represented by part of an arena or olfactometer arm without substrate). We determined that all infested substrates were 2-9 times more attractive than uninfested in the preference test, while in the olfactometer test, they were 3-8 times more attractive. In comparing the attractiveness of the infested and uninfested substrates, in both tests wheat bran was found to be the most attractive substrate to T. castaneum adults and coarse wheat meal the least. The results of the present study contribute to our knowledge of how raw feed materials and products influence the behaviour of T. castaneum and their susceptibility to infestation, and indicate the possible utilization of wheat bran in monitoring processes of T. castaneum in pest management programmes.

Insecticidal potential of natural zeolite and diatomaceous earth formulations against rice weevil (Coleoptera: Curculionidae) and red flour beetle (Coleoptera: Tenebrionidae).

Insecticidal potential of natural zeolites and diatomaceous earths originating from Serbia against Sitophilus oryzae (L.) and Tribolium castaneum (Herbst) was evaluated. Two natural zeolite formulations (NZ and NZ Modified) were applied to wheat at rates of 0.50, 0.75, and 1.0 g/kg, while two diatomaceous earth (DE) formulations (DE S-1 and DE S-2) were applied at rates of 0.25, 0.50, 0.75, and 1.0 g/kg. A bioassay was conducted under laboratory conditions: temperature of 24 +/- 1 degrees C, relative humidity in the range 50-55%, in tests with natural zeolites, and 60-65%, in tests with DEs, and in all combinations for progeny production. Mortality was assessed after 7, 14, and 21 d of insect contact with treated wheat, and the total mortality after an additional 7-d recovery on untreated broken wheat. Progeny production was also assessed after 8 wk for S. oryzae and 12 wk for T. castaneum. The highest mortality for S. oryzae and T. castaneum was found after the longest exposure period and 7 d of recovery, on wheat treated with NZ at the highest rate and DEs at rates of 0.50 -1.0 g/kg. Progeny reduction higher than 90% was achieved after 14 and 21 d of contact of both beetle pests with wheat treated with DE S-1 at 0.50-1.0 g/kg and DE S-2 at 0.75-1.0 g/kg, while the same level of reduction was achieved only for T. castaneum after its contact with the highest rate of NZ formulation. NZ Modified, applied even at the highest rate, revealed much lower insecticidal potential.