Study of Effect of Temperatures on the Natural Death and the Biotic Potential of Potato Tuber Moth, Phthorimaea operculella (Zeller), (Lepidoptera: Gelechiidae) and Used of some Plant Extracts as Insect Repellents Against Potato Tuber Moth Under Lab. Cond

Mohammed Y. Ibrahim


The changes in the different stages of the potato tuber moth, Phthorimaea operculella (Zeller) at three constant temperatures, 15,25 and 35°C., and 60±5 RH% were studied. It was found that the shortest period for the mean of generation time at 35°C., was 18.4 days while this duration was quite long (88.1 days) at 15°C. The mean generation time, however was 34.12 days at 25°C.

The highest number of deposited eggs was 147.4 eggs, while the lowest number of eggs was 24.5 at 35°C. The natural mortality of the insect as its average was 45.4, 25 and 6.1% for egg, larval and pupal stages, respectively. Upon relaying on the analysis of the dynamic of the insect numbers, which we called the analysis factors (K), this indication expressed the logarithmical difference for the precedent and succeeding insect stage. It is known that when the insect population has a biotic equilibrium then (Log F= K). If the potential is weak then (Log F<K)but if the biotic potential is strong then (Log F> K); where:

F= Fertility, K= Death during one generation

It was proved that Log F= 1.22, 1.56 and 0.74, K= 0.61, 0.61 and 0.66. Thus, the difference between them were 0.61, 0.95 and 0.08 which means that the population of the potato tuber moth was very strong and had the capacity of high biotic potential.

Plant extract of cumin, lemon, camphor, mint, Basil, thyme and lantana were evaluated for their repellency of potato tuber moth, Phthorimaea operculella (Zeller) (Gelechiide: Lepidoptera).

Acetone extract of Lantana leaves (6.3) gave the highest percentages (93.4%) followed by Camphor (86.2%), while the lowest percentages 44.6 and 50% were observed with Mentha microphylla and M. piperita, respectively. However, hexane extract of Lemon caused 82.5% repellency followed by lantana and camphor 47.7 and 43.9%, respectively.

Meantime, using distilled water, 86.0, 72.3, 68.0 and 59.1% of repellency were observed when lantana, thyme, cumin and M. piperita were used, respectively. The lowest percentages of repellency, 5.6 and 10.5% were obtained when distilled water and hexane extracts of basil leaves were tested, respectively.

الكلمات المفتاحية

Biotic Potential Dynamic, Natural Mortality, Potato Tuber Moth, Phthorimaea operculella (Zeller).

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