The functions of the female sex pheromones of Ephestia cautella (Walker) (Lepidoptera,Phycitidae)

The sex pheromone complex of female Ephestia cautella contains three known components. Field trials on the attractiveness to males of the three synthetic compounds (and their combinations) are described. (Z,E)-9,12-tetradecadienyl acetate is shown to be the major attractant in the complex. (Z)-9-tetradecenyl acetate has no attractive effect on its own but there is a possibility that it may act as a synergist to the major attractant. (Z,E)-9,12-tetradecadienol also has no attractive effect alone but is shown to inhibit the attractiveness of the major attractant when the two compounds are presented together. The possibilities for use of these synthetic compounds in the control and survey of E. cautella infestations are discussed.     

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.     

The suitability of dried fruits, almonds and carobs for the development of Ephestia figulilella Gregson, E. calidella (Guenee) and E. cautella (Walker) (Lepidoptera: Phycitidae)

In experiments at 30°C, 70% r.h. and a light régime of 16 hr light/8 hr dark 30 freshly-hatched larvae were placed singly on ripe carob pods obtained direct from Cyprus, and almonds, dates and raisins bought from a shop. The raisins had been treated commercially with paraffin oil prior to export. All 3 species thrived on ground carobs and dates. Between 17 and 26 individuals of each of these species completed development and emerged as adults on these foods. The particle size of carobs had a considerable influence, for only 13 E. calidella and 8 of each of E. figulilella and E. cautella completed development on carob pieces. Only 1 adult of E. calidella was bred from almonds, and 2 from raisins; 9 adults of E. figulilella were bred from almonds, and 16 from raisins, whilst E. cautella gave 17 adults on almonds and 3 adults on raisins.

The shortest mean developmental period for E. figulilella was 34 days on ground carobs, for E. calidella it was 37 days on carob pieces and for E. cautella 35 days on almonds. The longest mean developmental periods were 56 days for E. figulilella and 59 days for E. calidella, both on almonds, and 84 days for E. cautella on raisins.

The significance of these laboratory results in relation to field and warehouse observations is discussed.     

Radiation-induced sterility in Ephestia cautella (Walker) (Lepidoptera: Pyralidae): Recovery of fertility during five generations after gamma irradiation

Male Ephestia cautella were exposed to 0, 10, 20 or 30 krad of gamma irradiation and mated with untreated females. There were no offspring from males treated at 30 krad. Some of the offspring from the other three treatments were paired and the remainder paired with untreated adults of the opposite sex. This procedure was repeated for a further five generations for all the lines that yielded offspring, no further individuals being irradiated. Data on the reproductive behaviour of control males and their progeny through five generations were statistically homogeneous between generations. The offspring of the irradiated males were predominantly male, but this became less marked in the succeeding generations from those irradiated at 10 krad, and more or less disappeared by the fourth. Sex ratio distortion appeared to be correlated with reduced reproductive rate. A partially sterilizing dosage of 20 krad given to the male E. cautella parents induced complete sterility in their first progeny. The practical significance of radiation-induced inherited sterility to control or suppress the moth is further discussed.     

The influence of delayed mating on the reproduction of Ephestia cautella (Walker) (Lepidoptera: Phycitidae)

The influence of delayed mating on reproduction was studied for its possible value in the control of Ephestia cautella. When mating of both sexes was delayed for progressively longer periods, fecundity and fertility were both reduced correspondingly until no adult progeny were produced when mating was delayed for 8 days. Fecundity was also reduced where mating was delayed for females only. Female longevity increased from 6.8 days with no delay to 11.4 days with an 8-day delay. The period during which females could lay fertile eggs nevertheless was reduced from 5.4 days with no delay to 3.0 days with a 6-day delay. The number of eggs laid within 1 or 3 days after mating was also reduced as the delay was increased.Physiological causes of reduced fecundity in the female are discussed. Delayed mating induced by causes such as high background levels of sex pheromone is considered in relation to the control of E. cautella.     

Ecological aspects of digestive enzyme covariation in almond moth larvae, Ephestia cautella (Walker) (Lepidoptera, Phyticidae)

In this paper we examine the correlations between activity levels of several digestive enzymes measured simultaneously in larvae of the almond moth, Ephestia (=Cadra) cautella (Walker). This study is unique in that we measured enzyme activity in each individual larva, not in samples pooled from several individuals as is the usual procedure in physiological studies of insects. This enabled us to take individual variation in size and enzyme activity into consideration and to calculate the correlation between different enzymes. We demonstrate that inter-enzyme correlations are affected by the diet on which the larvae feed.

In most of the research on insect digestive physiology, investigators have concentrated on a single enzyme. But in the insect alimentary canal, different enzymes do not work in isolation. We demonstrate some patterns of activity correlations of different enzymes measured in extracts from the same individual larva which may suggest possible mechanisms of enzyme activity regulation.     

Release-recapture estimates of the population density of Ephestia cautella (Walker) in a commercial peanut warehouse

Seasonal trends in adult Ephestia (= Cadra) cautella (Walker) population density in an in-shell peanut storage facility were estimated from suction trap catches adjusted for recapture rates. Recapture rates the 1st day after release were 7% of females and 20% of males in an unstocked warehouse and 31% of males in a stocked warehouse; total recoveries were 11, 32 and 50%, respectively. Mating frequencies were generally between 46 and 75%. However, low mating frequencies (21–35%) during periods of low population density could have been partially due to the trapping of males.

Every 4 weeks the E. cautella population increased roughly two-fold in the unstocked ware-house (scattered peanuts remaining) and 37-fold in the stocked warehouse. Since breeding was continuous, generations overlapped.     

On the ability of Ephestia cautella (Walker) to mate in confined spaces in stacks of cocoa

The oviposition behaviour of adults of Ephestia cautella (Walker) which emerge within cocoa stacks was studied using glass tubes of various dimensions to simulate the sizes of spaces which normally occur between bags in a stack. When the moths were able to leave the stack they would do so, but when they were unable to leave the stack they could mate and lay eggs within it unless the size of the space was too small. When mating was not possible only sterile eggs were laid.     

Suppression of laboratory populations of Ephestia cautella (Walker) (Lepidoptera: Pyralidae) by release of males with cytoplasmic incompatibility

Unidirectional cytoplasmically incompatible males of Ephestia cautella (Walker) were substituted for irradiation-sterilized males in a modification of the sterile-male release technique. Laboratory populations were greatly suppressed or eliminated by single releases of incompatible males at ratios of 14:1 or greater. Isolated populations in nature (i.e., within a closed warehouse) could probably be eliminated by using this technique, but release ratios as high as 100:1 might be necessary.     

Orange-eye: A sex-linked recessive mutation in Ephestia cautella (Walker) (Lepidoptera: Pyralidae)

A new eye color mutant, orange eye (O), is described for Ephestia cautella. Preliminary data revealed that this mutation was inherited as a sex-linked recessive. The character is generally recognizable in only the late pupae and adult stages. The viability and reproductive potential of this strain are not significantly different from the wild type.     

Laboratory observations on the ability of Ephestia cautella (Walker) (Lepidoptera: Phycitidae) to locate,and to oviposit in response to a source of grain odour

Grain odour influenced oviposition behaviour was investigated amongst free-flying, gravid Ephestia cautella females. Females released into a 5 m³ or 10 m³ cage readily located, and oviposited in the vicinity of, small sources of diffusing grain odour or grain odour in an airstream. Oviposition increased at the odour source when 30% of an airstream carrying grain odour was replaced by CO₂, whereas it decreased when 95% was replaced by N₂, and did not change when 60% was replaced by either CO₂ or N₂. Females released into a wind-runnel responded to grain odour by increased frequency of upwind flight and by landing at the odour source. These responses are discussed in the context of grain stores sealed for treatment with controlled atmospheres or fumigants.     

A practical trial of pyrethrins-in-oil surface sprays for the protection of bagged grain against infestation by Cadra cautella (Wlk.) (Lepidoptera, Phycitidae) in Kenya

Two formulations of synergized pyrethrins in technical white oil were tested as monthly protective sprays on stacks of fumigated bagged wheat, primarily against Cadra cautella (Wlk.) but also against Sitophilus oryzae (L) and Tribolium castaneum (Hbst.), under warm-temperate storage conditions in up-country Kenya. The formulations were: 0·4% pyrethrins with 2·0% piperonyl butoxide, applied at 50 ml/m², and 0·4% pyrethrins with 0·4% piperonyl butoxide at 20 ml/m².

Results were assessed by recording infestation in samples taken from each stack after 18 weeks storage and five spray applications.

Both treatments gave reasonably good protection against C. cautella but were not satisfactory against S. oryzae or T. castaneum. There was no evidence of any taint in bread made from the treated grain, but the higher application rate caused excessive staining of the bags.

It is concluded that satisfactory control of reinfestation by C. cautella can be expected in practice using 0·4% pyrethrins in oil with only a minimal quantity of added piperonyl butoxide, and that 20 ml/m² is a suitable rate for application to bagged produce.     

Susceptibility of several varieties of soybean to Ephestia cautella (Walker) (Lepidoptera: Phycitidae)

Ephestia cautella (Walker) was reared on 39 varieties of soybean at 30 ± 1°C, 80 ± 5% r.h. and 12 hr light: 12 hr dark photoperiod. Larvae were reared individually on whole grains and flours of each variety and larval period, pupal period, per cent pupation and per cent adult formation were recorded. Larvae failed to develop on grains of 13 varieties while grains of Grant, Clark glabrous, Clark dense, Henry, Harrowmanchu and Hawkey-63 were highly susceptible to this pest. On the other hand larvae completed development successfully on all 39 varieties when seeds were ground into flours. It was also clear that UPSM-158 was somewhat tolerant to the attack of this pest while UPSM-120, Hawkey-63, Clark-63, Chippewa, UPSM-57, Harrowmanchu, Hampton, Goldsoy, Davis, Hood, and Kohachugatsu were also less efficient in supporting the development. Addition of 5% yeast to these varieties produced remarkable improvement in the quality of the diet which indicated that the flours of these varieties were deficient in one or more essential nutrients.     

Diapause in twenty populations of Ephestia cautella (Walker) (Lepidoptera: Pyralidae) from different parts of the world

Population samples of Ephestia cautella from difierent parts of the world were examined under various conditions of temperature and photoperiod for the incidence of diapause. In all but one of the twenty samples, larvae wandered for extended periods in search of sites to pupate, and diapause lasted over 50 days in some individuals from fifteen samples at 20°C, including five from the tropics. Some larvae of all fifteen samples diapaused in constant darkness but larvae from only eight, including just one from the tropics, diapaused in short photoperiods, and from only five of these, in constant light. Only one population, that in which diapause had previously been reported, diapaused at 25°C. Except in samples of this and three other populations, the proportion of larvae entering diapause did not exceed 50% under any of the conditions tested.The duration of diapause was in general quite short, mean times to pupation ranging from about 4–15 weeks. At 20°C, individuals from seven populations diapaused for longer than 12 weeks, and only a very few from three populations diapaused for over 20 weeks. Diapause is thus unlikely to enable E. cautella to overwinter in the UK in unheated premises.     

Effect of gamma irradiation of phosphine-fumigated dates on the development of Ephestia cautella (Walker) (Lepidoptera: Pyralidae)

Possible toxicological effects from interactions between gamma radiation (1 KGy at 46 rad/s) and phosphine residues in fumigated dates were studied when the dates were fed to Ephestia cautella. The results showed comparable development, fecundity and fertility of this insect when reared on a complete diet of fumigated, irradiated, fumigated irradiated or untreated dates.     

Gamma radiation effects on mating frequency and delayed mating of male Cadra cautella (Walker) (Lepidoptera: Pyralidae)

Gamma radiation doses of 0, 10, or 20 krad to 8-day-old pupae of Cadra cautella (Walker) did not significantly affect (P<0.05) the mating frequency of male moths kept constantly with female moths (1♂:5♀ per vial) for 72 hr but there were fewer matings by males exposed to 30 krad. When the opportunity of mating was restricted to 24 hr and delayed for 1–7 days, the mating frequency, and the numbers and fertility of eggs laid by young females all progressively declined with age. Increasing the radiation dose accentuated the reduction in male reproductive potential. Range of male longevity was not so critical as the period of significant male mating activity. Males in constant association with excess females had significantly lower (P < 0.01) mean longevity (4.25 ± 1.11 days) than did unmated and mated males (7.75 ± 1.99 days) in the delayed-mating studies; that was related to the increased mating frequency (maximum 8 ×) in the free-choice situation.     

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.     

Thermal-death kinetics of fifth-instar Amyelois transitella (Walker) (Lepidoptera: Pyralidae)

Information on kinetics for thermal mortality of navel orangeworm, Amyelois transitella (Walker) (Lepidoptera: Pyralidae), is needed for developing post-harvest phytosanitation thermal treatments of walnuts. Thermal-death kinetics for fifth-instar navel orangeworms were determined at temperatures between 46°C and 54°C at a heating rate of 18°C min⁻¹ using a heating block system. Thermal-death curves for fifth-instar navel orangeworms followed a 0.5th-order of kinetic reaction. The time required to achieve 100% mortality (N₀=600) decreased with increasing temperature in a logarithmic manner. Complete kill of 600 insects required a minimum exposure time of 140, 50, 15, 6, and 1 min at 46°C, 48°C, 50°C, 52°C, and 54°C, respectively. The reaction rate (k) was affected by treatment temperatures following an Arrhenius relationship. The activation energy for thermal kill of fifth-instar navel orangeworms was estimated to be between 510 and 520 kJ mol⁻¹.