The influence of photoperiod on the life-cycle of Ectomyelois ceratoniae (Zeller) (Lepidoptera: Pyralidae)

Diapause in fully grown larvae of Ectomyelois ceratoniae was induced by low temperature and short photoperiods. When larvae were reared at 30°C, 70% r.h. there was no diapause in a light regime of 12 hr light followed by 12 hr darkness (12L/12D), and only 20% entered a weak diapause in continuous darkness. However, at 20°C, 70% r.h. there was no diapause in 16L/8D but almost all larvae entered diapause in 12L/12D. At 20°C diapause delayed adult emergence by an average of 111 days, compared with about 50 days at 30°C. Survival to adult at 30°C was 75% or more at most photoperiods, but at 12L/12D and 13L/11D it was less than 50%. At 20°C survival was about 70% at the two photoperiods tested.

A slight effect of photoperiod on non-diapause growth rates was observed. Above 16 hr light longer photoperiods reduced the mean developmental period from egg hatch to adult emergence, by 4 days at 20L/4D and 6 days at 24L/0D.

The significance of diapause in this species in relation to its potential as a pest is discussed.     

Studies on three moth species in a Scottish port silo, with special reference to overwintering Ephestia kuehniella (Zeller) (Lepidoptera: Pyralidae)

During the winter of 1973–1974, enormous numbers of fully-fed, last instar larvae of Ephestia kuehniella (Zeller) were discovered in a large Scottish port silo where previously the endemic moth infestation had been almost entirely Endrosis sarcitrella (L.) and Hofmannophila pseudospretella (Stainton). E. kuehniella had previously been uncommon in this silo as in unheated silos elsewhere in Britain.

During 1974–1976 E. kuehniella was most abundant on the topmost floors of the silo, particularly inside the tops of grain bins where previously E. sarcitrella had been abundant. E. sarcitrella, however, was still the more abundant on the storage floors and at the bin bottoms. H. pseudospretella was widespread throughout the buildings, though less concentrated locally.

In September, most of the E. kuehniella larvae found were early instars less than half grown but by December the smallest larvae seen approached half grown. This gradual increase in mean larval length continued through the winter, although considerable mortality of large larvae occurred after December in some areas. However, some last instar larvae appeared to enter a diapause in the autumn and did not pupate until the following May. Adults of E. sarcitrella commenced to emerge in March, and of the other two species in June.     

Bioactivity of the essential oil extracted from Evodia rutaecarpa Hook f. et Thomas against the grain storage insects, Sitophilus zeamais Motsch. and Tribolium castaneum (Herbst)

The toxic, repellent and feeding deterrent activities of the essential oil extracted from Evodia rutaecarpa Hook f. et Thomas, were evaluated against Sitophilus zeamais adults and Tribolium castaneum larvae and adults. Contact toxicity assayed by topical application showed that S. zeamais adults were significantly more susceptible (LD₅₀=0.043 μg/mg body wt) to the essential oil than T. castaneum adults (LD₅₀=0.118 μg/mg body wt) and larvae (LD₅₀=0.093–0.126 μg/mg body wt). However, in the fumigation assays, S. zeamais (LC₅₀=41 μg/L air) was less susceptible to the essential oil than T. castaneum (LC₅₀=11.7 μg/L air). When compared with larvae of various ages, T. castaneum adults were more susceptible to the fumigant toxicity of the essential oil. Also, in the treated filter paper repellency test, the essential oil was more repellent to T. castaneum than to S. zeamais. A flour disk bioassay demonstrated that the essential oil of E. rutaecarpa had a weaker feeding deterrent action against T. castaneum adults than against T. castaneum larvae and S. zeamais adults. The reduction in growth rate of T. castaneum larvae and S. zeamais adults was mainly due to a behavioural (feeding deterrent) action rather than to post-ingestive toxicity of the oil.     

Development of Ephestia kuehniella (Zeller), Plodia interpunctella (Hübner) and Corcyra cephalonica (Stainton) (Lepidoptera: Pyralidae) on kernels and wholemeal flours of Fagopyrum esculentum (Moench) and Triticum aestivum L.

Three stored product moth pests, Ephestia kuehniella, Plodia interpunctella and Corcyra cephalonica were reared on the following five foods: whole buckwheat with pericarp, decorticated buckwheat, wheat var. “Centauro” (kernels), wholemeal wheat flour and whole buckwheat flour. Results showed that achenes of buckwheat with pericarp are a poor food for the development of these species. A low rate of survival to adulthood for E. kuehniella and P. interpunctella was recorded, with a considerable extension of post-embryonic development. Although the mandibles of larvae are strong, they have trouble in breaking the fibrous buckwheat pericarp. It was observed that when the seed was decorticated there was a higher percentage of adults emerged. The emergence of E. kuehniella began, according to the food given, 34–42 days after the eggs were laid. The susceptibility index (s.i.) of achenes without pericarp (s.i. 9.7) was higher than that observed on wheat (s.i. 8.6). The first P. interpunctella adults were found after 29 days on wheat and after 56 days on buckwheat with pericarp. The shortest mean period of development occurred on wheat (34 days) while the longest was on buckwheat with pericarp at 81 days. The highest susceptibility index was on kernels (s.i. 12.8), the lowest one was on buckwheat with pericarp (s.i. 2.3). C. cephalonica began to emerge, according to the food given, after 40–55 days. In this case, fewer adults were recorded from buckwheat with pericarp, but no significant differences among the means of emerged adults on wheat, wholemeal wheat flour and whole buckwheat flour were observed. The longest mean period of development was recorded on wholemeal wheat flour (72 days) while the shortest was on wheat kernels (58 days). The highest value for the susceptibility index was obtained for wheat kernels (s.i. 7.4) and the lowest one for buckwheat with pericarp (s.i. 4.5).     

Repellent, toxic and reproduction inhibitory effects of essential oil vapours on Acanthoscelides obtectus (Say) (Coleoptera: Bruchidae)

Thirteen essential oils (Apium graveolens, Citrus sinensis, Eucalyptus globulus, Juniperus oxycedrus, Laurus nobilis, Lavandula hybrida, Mentha microphylla, Mentha viridis, Ocimum basilicum, Origanum vulgare, Pistacia terebinthus, Rosmarinus officinalis, and Thuja orientalis) were tested in their vapour form against Acanthoscelides obtectus. Choice and no-choice tests revealed that most of them have a repellent action, reduce fecundity, decrease egg hatchability, increase neonate larval mortality and adversely influence offspring emergence. Furthermore, some oils were strongly toxic to A. obtectus, males appearing more susceptible than females. Among the essential oils tested, the most toxic for males were those of M. microphylla and M. viridis whereas the most toxic against females were those of L. hybrida and R. officinalis.     

Fumigant toxicity of three essential oils on the eggs of Acanthoscelides obtectus (Say) (Coleoptera: Bruchidae)

Fumigant toxicity of the essential oils from Lavandula hybrida, Rosmarinus officinalis and Eucalyptus globulus against the eggs of Acanthoscelides obtectus was assessed. The essential oil vapours were toxic to eggs with LC₅₀ values ranging between 1.3 and 35.1 μl/l air, depending on egg age and the essential oil. In all cases, the young eggs (3-day old) were more tolerant to essential oil vapours than the older ones (4-day old). Apart from the inhibition of hatching, the exposure of eggs to essential oil vapours increased the subsequent mortality of hatched larvae. The influence of length of exposure to essential oil vapours on egg hatchability was also significant.     

Bioactivity of selected plant-derived essential oils against Zabrotes subfasciatus (Coleoptera: Bruchidae)

The common bean Phaseolus vulgaris L. (Fabaceae) is an important vegetable protein source and constitutes a significant part of the diet in many tropical countries. The Mexican bean weevil Zabrotes subfasciatus (Boheman) (Coleoptera: Bruchidae) is one of the main pests affecting stored beans: it causes extensive qualitative and quantitative grain loss. We investigated the bioactivity of the essential oils extracted from Chenopodium ambrosioides L. (CA-EO), Ocimum gratissimum L. (OG-EO), and Schinus terebinthifolius Raddi (ST-EO) against Z. subfasciatus. After 12-h treatment, CA-EO and OG-EO at 20.0 μL/L of air killed 100% Z. subfasciatus, whereas ST-EO at 100.0 μL/L of air afforded 100% Z. subfasciatus mortality after 24 h. CA-EO provided the lowest 24 h LD₅₀ (0.8 μL/L of air) and displayed efficient repellent activity against Z. subfasciatus. Our results demonstrate that CA-EO is a potentially economical and environmentally friendly alternative to manage Z. subfasciatus in stored beans.     

Repellent and fumigant activity of essential oil from Artemisia vulgaris to Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae)

Repellent and fumigant activity of the essential oil of mugwort, Artemisia vulgaris, against the stored-product insect pest, Tribolium castaneum was investigated. Artemisia vulgaris oil had a very strong repellent activity to adults and was significantly repellent at a 0.6 μL/mL (v/v) and higher in a filter-paper arena test. The oil had high fumigant activity against adults and larvae with adults much more susceptible than larvae. At 8.0 μL/mL, mortality of adults reached 100%, but with 12-, 14- and 16-day larvae, mortalities were 49%, 53% and 52%, respectively. The oil also had high-fumigant activity against eggs and toxicity progressively increased with increased exposure time and concentration. At dosages of 10, 15 and 20 μL/L air and a 96 h exposure period, mortality reached 100%. Regression analysis of data on individuals fumigated in the larval stage confirmed that the percentage of larvae reaching the pupal stage and the percentage of pupae that reached the adult stage, decreased significantly with increase in dosage concentration. No larvae, pupae and adults were observed following a 60 μL/L dosage.     

The influence of temperature and humidity on the life-cycle of Ephestia kuehniella Zeller (Lepidoptera: Pyralidae)

The development of Ephestia kuehniella was followed carefully on white flour at constant temperatures ranging from 7.5° to 31°C at humidities from 0 to 75% r.h. The lower limit of temperature for complete development was about 12°C although a few adults of a stock collected recently emerged at 10°C. Adults emerged at 28 but not at 31°C. Generally, development took longer and survival was poorer at 40 than at 70% r.h. However, at 20 and 25°C survival was good even at 15% r.h., and at 25°C, 18 out of 50 larvae reached the adult stage at a humidity near 0% r.h. Development was fastest at 25°C, 75% r.h., taking a mean of 74 days from oviposition to adult emergence.Oviposition occurred at 7.5 but not at 5°C. Mating was unsuccessful at 12.5°C. Eggs hatched at all temperatures between 12 and 31°C at every r.h. used. A few eggs from two field stocks hatched at 10°C but none did so at 7.5°C.At 12 C no larvae pupated at humidities below 70% r.h., and none pupated at 31°C at any humidity. Larval development was most rapid at 25°C, 75% r.h., taking about 60 days. The shortest mean pupal period, 9 days, occurred at 28°C, 70% r.h. In an experiment with field stocks, many larvae pupated at 10°C but none at 7.5°C.This study confirms E. kuehniella as essentially a temperate species that prefers heated premises such as bakeries and mills for rapid development. Its ability to develop on food at a low e.r.h. fits it further for life in flour mills.     

Efficacy of essential oil of Ocimum basilicum L. and O. gratissimum L. applied as an insecticidal fumigant and powder to control Callosobruchus maculatus (Fab.) [Coleoptera: Bruchidae]

Essential oils from sweet basil, Ocimum basilicum, and African basil, O. gratissimum, (Labiatae) grown in Guinea were obtained by steam distillation. Following exposure of newly emerged adult beetles (Callosobruchus maculatus) to 12 h of fumigation using pure essential oils at a dose of 25 μl/vial, 80% mortality was recorded for O. basilicum, 70% for O. gratissimum and 0% in the control. A significant difference was observed between the responses of males and females with males exhibiting greater sensitivity. When 1 g of aromatized powder was applied to adults, a 50% lethal concentration at 48 h was found to be 65 μl/g for O. basilicum and 116 μl/g of O. gratissimum oils. The essential oils from the two plant species exhibited a significant effect both on the egg hatch rate and on the emergence of adults. The egg hatch rate was reduced to 3% with O. basilicum and 15% with O. gratissimum using an essential oil concentration of 30 μl, whereas the egg hatch rate for the control was 95%. When compared with the control (97%), adult emergence dropped to 0% with O. basilicum and to 4% with O. gratissimum. Storage bioassays were run to assess the long-term effect of powders aromatized with essential oils of Ocimum. Complete protection was observed over 3 months starting at a dose of 400 μl in the case of both oils. From a germination test, it was concluded that aromatized powders have no significant effect on the seed germination rate. After 5 d, a rate of 88% germination was seen in seeds treated with aromatized powder and protected from insects, compared with 97% for untreated seeds that were not exposed to insects.     

Cross-resistance of a chlorpyrifos-methyl resistant strain of Oryzaephilus surinamensis (Coleoptera: Cucujidae) to fumigant toxicity of essential oil extracted from Eucalyptus globulus and its major monoterpene, 1,8-cineole

The fumigant toxicities of eucalyptus essential oil and 1,8-cineole, the major component of eucalyptus oil, were tested against a chlorpyrifos-methyl resistant strain and a reference strain of the sawtoothed grain beetle, Oryzaephilus surinamensis (L.). The resistant strain showed 1.9- and 2.2-fold higher tolerance against essential oil and 1,8-cineole fumigation toxicity, respectively, relative to the susceptible strain. The increased tolerance for the essential oil may be the result of cross-resistance. The resistance mechanisms in the resistant strain are discussed in relation to elevated detoxifying enzymes such as cytochrome P450 and esterases.     

Predation by Blattisocius tarsalis (Berlese) (Acari: Ascidae) on eggs of Ephestia kuehniella Zeller (Lepidoptera: Pyralidae)

The mean predation rate of female B. tarsalis on eggs of E. kuehniella was determined at 15°C, 21°C, and 27°C with prey densities of 3, 5, 10 and 15 eggs. Young eggs less than 24 h old were used as prey. Under all experimental conditions most eggs were only partially consumed, confirming the general theory that predatory mites leave most of the food content unutilized. A mean predation rate of 2.2-7.0 eggs destroyed in 24 h was found, reflecting that a large proportion of the available prey was destroyed. The result supports the view that the predatory mite B. tarsalis could be a relevant biological control agent against E. kuehniella in flour mills. It was further demonstrated that frozen moth eggs can be considered as an appropriate food source.     

The incidence of diapause in seventeen populations of the flour moth, Ephestia kuehniella Zeller (Lepidoptera: Pyralidae)

Samples of Ephestia kuehniella were examined for diapause at 20 and 25°C in continuous darkness, continuous light and three other photoperiods. The samples came from five flour mills and five unheated stores in England, and from Scotland, Egypt, Finland and Japan, together with three laboratory reared stocks. Some larvae entered diapause in all but three of the English stocks, in all stocks from other countries, and in a 10-yr old laboratory stock from Japan but not in two other stocks reared in the laboratory for over 30 yr. In continuous darkness at 25°C, the incidence of diapause exceeded 10% in eleven stocks, 25% in eight, and 50% in three stocks, while in darkness at 20°C the proportions were usually much smaller. In other light regimes there was a much lower incidence of diapause, 10% being reached in only six experiments out of more than eighty. Markedly more larvae entered diapause when reared on the maize or wheat flour available in mills than on a nutritious laboratory diet of wheatfeed, glycerol and yeast.     

Composition,cytotoxicity and antimicrobial activity of essential oil from Dictamnus dasycarpus

The composition of the essential oil from Dictamnus dasycarpus was analysed by GC–MS; 47 constituents (88.9% of the total oil) were identified. The main compounds were syn-7-hydroxy-7-anisylnorbornene (29.4%), pregeijerene (15.5%) and geijerene (11.4%). The antimicrobial activity of the essential oil was evaluated against nine microorganisms using disc diffusion and broth microdilution methods. The oil showed the strongest bactericidal activity against Staphylococcus aureus ATCC 25923 and methicillin-resistant S. aureus. The in vitro cytotoxicity of the oil on six human cancer cell lines was also examined. The cytotoxicity of the oil on three human breast cancer cell lines was significantly stronger than on other cell lines.     

Effect of particle size of soft wheat flour on the development of Ephestia kuehniella Zeller (Lepidoptera: Pyralidae)

The effect of soft wheat flours, characterized by different particle size, protein and starch content, on the development of Ephestia kuehniella was studied. The attractiveness of the substrata to first and third instar larvae was also considered.The different protein content of the flours did not significantly affect the development of E. kuehniella, nor did it affect the ability of the flours to attract larvae. In tests with soft wheat flours with the same nutritional value but different particle size, the highest mean number of adults and the shortest developmental period were recorded on samples with greatest particle size (250-419 μm).In order to test the attractiveness of soft wheat flour to larvae, a one-way olfactometer was used. There were no significant differences observed in the number of first and third instar larvae found on flours with different protein composition and particle size. Larvae of this species show limited mobility, in fact few individuals of either instar can reach the flour from a distance of 2 m. No larvae of either instar contacted the different substrata from a distance of 2.5 m.     

Effect of high temperatures on larvae of Ephestia elutella (Lepidoptera: Pyralidae) in diapause

Diapausing larvae of Ephestia elutella (Hb.) were exposed at 40, 43 or 45°C and then transferred to 25°C to observe subsequent development and survival. All larvae died after 96 hr at 40°C, 24 hr at 43°C or 16 hr at 45°C. However, about 80% of larvae exposed to 40°C for 8 hr each day for 18 days and about 50% of larvae exposed at 43°C for 8 hr each day for seven days survived. At 45°C all larvae died after two 8-hr or three 6-hr exposures given on successive days, but eight 4-hr exposures failed to kill more than 25% of larvae exposed. When the gap between 6 and 8-hr exposures was increased from 1 day, some larvae survived, indicating that recovery from heat exposure could occur. Adults emerging after high temperature exposure of diapausing larvae proved fertile. In contrast adults from larvae pupating without diapause at 30°C are known to be infertile.

Exposures at high temperature significantly hastened the termination of diapause. In general, the higher the level of mortality in the sample, or the greater the number of exposures at high temperature, the sooner pupation occurred in long days at 25°C.     

The choice of probing sites by Bracon hebetor Say (Hymenoptera: Braconidae) foraging for Ephestia kuehniella Zeller (Lepidoptera: Pyralidae)

A direct behavioral assay was conducted to investigate the preferred habitat for host searching by the parasitoid Bracon hebetor (Hymenoptera: Braconidae). The effects of mating, feeding and post-emergence experience on female parasitoid choices of searching sites were also examined. B. hebetor appears to be directed to the habitat of its host through chemical cues originating from the host larvae, frass and adults. These cues elicit a series of directed responses by the female. Generally, the data showed that flour containing 30-day-old larvae was preferred by B. hebetor females. This was followed by the flour containing the frass, then the adult host, and finally the flour containing 10-day-old larvae. It appears that cues produced by young larvae were the weakest whereas cues produced by older ones were the strongest. Feeding seemed to be important in the location of the proper searching site. Although the cues were normally learned by the immature stages of the parasitoid, and were subsequently manifested in their responses as adults, adult experience increased the ability of the parasitoid to locate the suitable habitat for searching.     

Effects of gamma radiation on the progeny of irradiated Ephestia cautella (Walker) (Lepidoptera: Pyralidae) males

One-day-old P₁ males of Ephestia cautella, Baghdad strain, were treated with 0.15, 0.20 and 0.25 kGy of γ radiation and mated in groups (15 pairs) with untreated virgin females. Radiation effects were assayed by determining percentage of egg hatch, mating ability and F₁ sex ratio. Our results showed the greater the initial dose, the greater the reduction in the percent egg hatch, and the greater the male-to-female ratio. Radiation effects on F₁ males were greater than the effect on the P₁ males. Furthermore, the results showed that the effects on F₁ males were greater than the effects on F₁ females. These results were confirmed cytologically by examination of the developing meiotic germ cells of F₁ males which showed that the meiotic nuclei carried multiple translocations. Such chromosomal aberrations explain the sterility observed in the F₁ male generation.     

Chemical composition and antioxidant activity of the essential oil of Clinopodium vulgare L.

This study was designed to examine the chemical composition and in vitro antioxidant activity of the essential oil of Clinopodium vulgare. GC–MS analysis of the oil resulted in the identification of 40 compounds, representing 99.4% of the oil; thymol (38.9%), γ-terpinene (29.6%) and p-cymene (9.1%) were the main components. The samples were subjected to a screening for their possible antioxidant activity by using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and β-carotene-linoleic acid assays. In the first case, IC₅₀ value of the C. vulgare essential oil was determined as 63.0 ± 2.71 μg/ml. IC₅₀ value of thymol and γ-terpinene, the major compounds of the oil, was determined as 161 ± 1.3 μg/ml and 122 ± 2.5 μg/ml, respectively, whereas p-cymene did not show antioxidant activity. In β-carotene-linoleic acid system, C. vulgare essential oil exhibited 52.3 ± 1.19% inhibition against linoleic acid oxidation. In both systems, antioxidant capacities of BHT, curcumine and ascorbic acid were also determined in parallel experiments.     

Insecticidal effect of Steinernema feltiae (Filipjev) (Nematoda: Steinernematidae) against Tribolium confusum du Val (Coleoptera: Tenebrionidae) and Ephestia kuehniella (Zeller) (Lepidoptera: Pyralidae) in stored wheat

The confused flour beetle, Tribolium confusum, and the Mediterranean flour moth, Ephestia kuehniella, are important pests of stored grain products. The insecticidal effect of three strains (UK 76 [=Nemasys], USA/SC, and Hawaii) of the entomopathogenic nematode Steinernema feltiae was determined in the laboratory, in wheat, against these pests. The nematodes were applied at three dose rates: 100, 300 and 900 nematodes/insect individual. The Hawaii strain was most virulent against T. confusum adults and larvae, with a significant dose effect in the case of the larvae. Larval mortality of this species reached 79% and 100% after 7 and 14 d of exposure to the nematodes, respectively, at the highest dose applied. On the other hand, adult mortality of T. confusum did not exceed 66%. In the case of E. kuehniella larvae, USA/SC performed best causing 52% and 69% mortality after 7 and 14 d exposure, respectively, at the highest dose tested. Since very few data are available on the effect of entomopathogenic nematodes against these pests, it is concluded that the Hawaii and USA/SC strains of S. feltiae should be further investigated as promising biological control agents for T. confusum and E. kuehniella.