Sorption and desorption of sulfuryl fluoride by wheat,flour and semolina

Sulfuryl fluoride (SF) has been developed as a fumigant for control of insect pests in stored grain. However, there is very limited information on the sorption behaviour of this fumigant, which can be critical to its bioactivity, application and potential for residues. We undertook a comprehensive laboratory study of the sorption and desorption of SF by wheat (bread and durum), flour and semolina at 15, 25 and 35 °C, moisture contents 12% and 15%, and concentration × time combinations at CT = 1500 mgh/L (4.167 mg/L × 360 h, 8.928 mg/L × 168 h and 31.25 mg/L × 48 h).At each dosage, sorption rate increased as commodity temperature and moisture content increased. The highest rates of sorption occurred at 35 °C and 15% m.c., and lowest rates at 15 °C and 12% m.c., and the rate was independent of initial concentration. Sorption followed first order reaction kinetics described by the exponential decay equation, C_t = C₀·e^−k*t, where k is the sorption rate constant. The most important factors determining the rate of sorption were commodity particle size (exposed surfaces) and temperature. Little sorption of fumigant occurred within the first 24 h whereas longer fumigation times resulted in significant sorption. Unbound SF was rapidly lost from the commodity upon aeration with no further desorption detected under any of the test conditions.SF possesses a number of characteristics that recommend it as a commodity fumigant. It is sorbed slowly by commodities relative to methyl bromide and carbonyl sulphide although it is sorbed about 4–5 times faster than phosphine. It desorbs rapidly upon aeration, and the lack of continued desorption has practical workplace health and safety benefits. On the other hand, sorbed SF appears irreversibly bound to the commodity matrix indicating the need to be alert to the possibility of excessive residues, particularly in longer term fumigations.     

Sorption of tritiated phosphine by various stages of Tribolium castaneum (Herbst)

When various stages of Tribolium castaneum were fumigated with 0.14–1.69 mg/l of tritiated phosphine for 5 hr the uptake of the fumigant was found to be considerably greater in larvae and adults than in pupae or eggs. Mature larvae absorbed 2–3 times as much phosphine as pupae at all concentrations tested and mortality was appeciably higher. Uptake by 1-day-old adults was about two fold that of the mature pupal stage from which they had emerged and increased with age so that 14-day adults absorbed about twice as much as newly emerged adults. Uptake by pupae followed a U-shaped curve somewhat similar to the characteristic pattern of oxygen uptake by pupae of different ages. Eggs retained only a small proportion of the radioactive fumigant they absorbed. A considerable amount remained at the surface of the eggs and was converted to soluble compounds that could be washed off with water. The results suggest that the higher tolerance of both eggs and pupae to phosphine may, at least partially, be attributed to the lower uptake of fumigant as compared to larvae and adults.     

Tolerance of the diapausing stages of four species of Lepidoptera to methyl bromide

The diapausing stages exposed to methyl bromide were larvae of Ephestia elutella (Hübner) and Plodia interpunctella (Hübner), pupae of Pieris brassicae (L.) and eggs of Bombyx mori (L.). Diapausing larvae of Ephestia elutella were highly tolerant, a few surviving to the adult stage after exposure to concentration-time (CT) products of up to 150 mg hr/l at 25°C and 260 mg hr/l at 15°C. Diapausing larvae of Plodia interpunctella were tolerant at low temperatures but quite susceptible at 25°C. In both species, larvae in diapause were four to six times more tolerant than other larvae at 15°C or below, and strains recently collected from the field were more tolerant than laboratory reared stocks.In E. elutella, differences in the method of induction, maintenance or termination of diapause did not affect tolerance to fumigation. P. interpunctella larvae reared at high population density were more susceptible than those reared at low density. Among strains of these species, a correlation was observed between the duration of larval diapause and tolerance to methyl bromide. Adults emerging after fumigation of diapausing larvae were of lowered fertility but rarely sterile. The CT products required for the complete control of moths in diapause were higher than those currently recommended for the disinfestation of stored products.Diapausing pupae of an outdoor species Pieris brassicae required the very high CT product of 403 mg hr/l for complete control at 25°C and were at least six times more tolerant than non-diapausing pupae. Diapausing eggs of Bombyx mori required 179 mg hr/l for complete control, while non-diapausing eggs were all killed by 125 mg hr/l.     

Fumigant toxicity of allyl isothiocyanate to populations of the red flour beetle Tribolium castaneum

The phasing out of methyl bromide as a fumigant, the phosphine resistance problems in stored product insect-pests, and the ever-growing concerns with human health and environmental safety have been guiding the search of alternative fumigants. Allyl isothiocyanate (AITC) is the main component of mustard oil with reported pesticide activity and potential as a fumigant of stored foodstuffs. The fumigant toxicity of AITC was assessed in adults of 18 populations of the red flour beetle Tribolium castaneum (Coleoptera: Tenebronidae). These populations were all susceptible to AITC with negligible variation among them. Two of these populations were further used to test the AITC susceptibility of eggs, larvae (early and late instars), and pupae of T. castaneum. All of the developmental stages of both populations were similarly susceptible to AITC. No cross-resistance between phosphine and AITC was observed. Despite the significant variation in body mass, respiration rate, and fitness among the populations of T. castaneum, they were not correlated with AITC susceptibility. Larvae and adult malformations were observed when larvae and pupae were exposed to AITC. These results show the potential of AICT as an alternative fumigant against stored product insects.     

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 tolerance of immature stages of four stored product moths to methyl bromide

Eggs, last instar larvae, and pupae of the Pyralid moths, Ephestia elutella (Hübner). E. kuehniella Zeller, E. cautella (Walker) and Plodia interpunctella (Hübner) reared at 25°C were exposed to methyl bromide over a wide range of concentrations and times at 10–30°C. One laboratory stock, and one field stock of each species were tested, but differences between stocks of the same species were small.P. interpunctella required lower CT products than the other species for complete kill of each stage. At 10°C, larvae of the field stock of E. cautella required a CT product of 110 mg h/l. for complete control. All stages of all species succumbed to a CT product of 64 mg h/l. at 15°C. When exposed at 20°C or above, pupae aged 0–3 days were more tolerant than other stages. Eggs aged 2 days or over were more tolerant than younger ones.The fertility of survivors from fumigated eggs resembled that of controls, but that of some individuals fumigated as pupae was depressed. For fumigated eggs of E. elutella and P. interpunctella at 15°C, the CT relationship held over concentrations from 4·2 to 10·8 mg/l. and exposure periods from 1 to 16 h.     

Effect of environmental conditions on the permeability of high density polyethylene film to fumigant vapors

Soil fumigation in greenhouses or agricultural fields often includes tarping the soil surface with polyethylene (PE) films to contain the fumigant in the soil and reduce emissions to the atmosphere. Previous research has demonstrated that PE films are permeable to methyl bromide and other fumigant compounds. In these experiments, the effect of temperature, fumigant mixtures, condensed water, and field aging on the permeability of high-density polyethylene (HDPE) was determined. Mass transfer coefficients (h, a measure of permeability) of the fumigants methyl bromide, 1,3-dichloropropene, propargyl bromide, and chloropicrin across HDPE films were determined. In these studies, temperature and HDPE film type had the largest impact on the h of fumigant compounds across HDPE films. Other factors investigated, including fumigant mixtures, condensed water on the film, and field aging of UV-stabilized film, did not have a significant impact on h. The results of these experiments suggest that the permeability of an intact piece of an agricultural film will increase with increasing temperature but is relatively constant despite changes in other environmental conditions.     

Lethal effects of sulfuryl fluoride on eggs of different ages and other life stages of the warehouse moth Ephestia elutella (Hübner)

Sulfuryl fluoride (SF) is a fumigant used for the control of stored-product pest insects and is a feasible alternative to some uses of methyl bromide. SF was first registered in Germany in 2004 for disinfestation of emptied flourmills, emptied food storages and dried fruit. One- to 4-day-old eggs, larvae and pupae of the warehouse moth, Ephestia elutella (Hübner) (Lepidoptera) were investigated for their susceptibility to SF under different conditions. Each life stage was exposed for 18 h, 24 h or 48 h, to 11.6 g/m³ or 21.3 g/m³ at 15 °C, 20 °C or 25 °C and 65% relative humidity. A Fourier transform infrared (FTIR) spectrometer was used to determine the concentrations of SF. Within 18 h of exposure, all larvae and pupae of E. elutella died at 11.6 g/m³ at all three temperatures. The 1 and 2- day-old eggs were generally more susceptible, whereas the 3 and 4-day-old eggs were more tolerant to the SF treatment. All eggs of all ages were controlled within 48 h of exposure to the concentration of 21.3 ± 1.3 g/m³ at temperatures of 20 °C and 25 °C.     

Toxic and antifeedant action of nutmeg oil against Tribolium castaneum (Herbst) and Sitophilus zeamais Motsch

The essential oil extracted from nutmeg seeds using steam distillation was tested against the stored product insect pests, Tribolium castaneum (Herbst) and Sitophilus zeamais Motsch., for contact toxicity, fumigant toxicity and antifeedant activity. Filter paper impregnation was employed for contact and fumigant toxicity studies, whereas a flour disc bioassay was used to investigate antifeedant effects. Adults of S. zeamais were about ten times more susceptible than T. castaneum adults to contact action (LC₅₀ values of 1.7 mg/cm² and 18 mg/cm² respectively). However, S. zeamais adults were only 1.7 times more susceptible than T. castaneum adults to fumigant action (LC₅₀ values of 4.5 mg/cm² and 7.7 mg/cm² respectively). Furthermore, the larvae (10–16 days old) of T. castaneum were more susceptible than the adults, but the susceptibility of the larvae decreased with age. Nutmeg oil also significantly (P < 0.05) affected the hatching of T. castaneum eggs and the subsequent survival of the larvae in the concentration range 1.4–3.2 mg/cm². The production of F1 progeny of both T. castaneum and S. zeamais exposed to media treated with nutmeg oil was significantly (P < 0.05) reduced at all concentrations tested. F1 progeny production was totally suppressed at nutmeg oil concentrations of 1.05 g/100 g rice for T. castaneum and 0.35 g/100 g wheat for S. zeamais. Nutritional studies showed that nutmeg oil significantly (P < 0.05) affected the growth rate and food consumption of both insect species, depending on the concentrations used, but the antifeedant activity was more pronounced against S. zeamaisthan against T. castaneum. At 20 g nutmeg oil/100 ml, the feeding deterrence index of T. castaneum was only about 7%, whereas that of S. zeamaiswas 33%. These results suggest that nutmeg oil may be useful as a grain protectant with contact, fumigant and antifeedant activities against these insects.     

Initial and delayed mortality of late-instar larvae, pupae, and adults of Tribolium castaneum and Tribolium confusum (Coleoptera: Tenebrionidae) exposed at variable temperatures and time intervals

Late-instar larvae, pupae, and adults of Tribolium castaneum (Herbst), the red flour beetle, or Tribolium confusum (DuVal), the confused flour beetle, were exposed for variable durations at 36-54 °C. Beetles were placed in laboratory ovens set at a baseline of 27 °C, the temperature was increased by 0.1 °C per minute until the target temperature was achieved, and beetles were then held for specified exposure durations. There was no mortality after initial exposure or after a 1-week holding period of any life stage of T. castaneum or T. confusum exposed for 32 h to 36, 39, or 42 °C. At 45 °C, there was no initial mortality of either species exposed for different time intervals except for those exposed for 28 h. However, there was a significant increase in mortality after the 1-week holding period of those beetles exposed initially for at least 16 h to 45 °C. There was a sharp increase in mortality after the initial exposures of 4 h at 48 °C; mortality of T. confusum larvae was 90.0±5.7% but was only 10.0±10.0% for larvae of T. castaneum, and no pupae of either species were dead. All life stages of both species were killed after the initial exposure of 12 h, and 1-week mortality of beetles exposed for 4 and 8 h was generally greater than initial mortality. At 51 and 54 °C, 2- and 1-h exposures, respectively, killed all life stages of each species. Mortality in conditions of gradual temperature increase was less than previous studies with sudden temperature increases.     

Effectiveness of short exposures of propylene oxide alone and in combination with low pressure or carbon dioxide against Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae)

Toxicity of the fumigant propylene oxide (PPO) alone and in combination with low pressure (100 mm Hg) or 92% CO₂ to all life stages of Tribolium castaneum using short exposure times (4 and 8 h) at 30°C was studied. Results indicated that PPO was moderately toxic with Ct products ranging from 120 to 608 mg h/l required to obtain complete mortality of the different life stages. A marked difference in susceptibility between life stages was recorded. Eggs were the most sensitive with a LD₉₉ value of 30.1 mg/l for 4 h, whereas pupae were the most tolerant with a LD₉₉ value of 146.5 mg/l. It was shown that an increase in exposure time from 4 to 8 h resulted in 23%, 42%, 48% and 47% reductions of LD₉₉ values for eggs, larvae, pupae and adults, respectively.There was no or very limited mortality of all stages except the egg (53% to 62%), when exposed to either 100 mm Hg or 92% CO₂ for 4 h. However, when 100 mm Hg or 92% CO₂ were combined with PPO, the LD₅₀ and LD₉₉ values for PPO in all stages except the egg were significantly reduced. Combinations of PPO with 100 mm Hg or 92% CO₂ produced equal reductions in the LD₉₉ value from 146.5 to about 22 mg/l for the most tolerant pupal stage. Both combinations also produced significant reductions in the LD₉₉ values for larvae and adults (6.3- to 6.6-fold) compared with those exposed to PPO alone. These results indicated that 100 mm Hg and 92% CO₂ each had a synergistic effect on the toxicity of PPO to T. castaneum. The combination of PPO with vacuum or CO₂ can thus provide a potential alternative to methyl bromide.     

Studies on the toxicity of phosphine to tolerant stages of Trogoderma granarium Everts (Coleoptera: Dermestidae)

Tests were conducted at 20 and 30°C at 60% r.h. to find the dosages of phosphine needed for control of diapausing larvae and eggs of Trogoderma granarium. At 20°C, 60% r.h., some larvae from each of four recently acquired field strains of T. granarium survived a 5-day exposure period at a concentration-time (Ct) product of 164 g hr/m³. Under these conditions laboratory stock larvae were killed by a 4-day exposure period of about 120 g hr/m³, and eggs by a 3-day exposure of about 50 g hr/m³. Eggs, aged 0–1 days, proved the most tolerant stage at 30°C, 60% r.h., surviving a Ct-product of 16 g hr/m³ over a 2-day exposure period. At 30°C the diapause of larvae became unstable and their tolerance of phosphine was low. Adults emerging after fumigation of larvae appeared normal and if sufficient numbers emerged together a second generation was produced.Complete control of larvae of several stocks (about 20 weeks in diapause) was achieved within a 4-day exposure at 20°C with a mixture of methyl bromide (2.0 g/m³) and phosphine (1.4 g/m³), whereas 6 days were required for these stocks using phosphine alone. To ensure elimination of all stages of non-resistant T. granarium, exposures to phosphine should last 7 days at 20°C and 4 days at 30°C.     

Does sorption of sulfuryl fluoride by wheat reduce its efficacy against adults and eggs of Rhyzopertha dominica?

Despite its growing importance as a fumigant for grain, there is no information on the impact of sorption on the efficacy of sulfuryl fluoride (SF) against target insect pests. Eggs and adults of a major grain pest, Rhyzopertha dominica, living in wheat (12% m.c.), were fumigated with SF at 0.5, 1, and 2 mg/L for 168 h at 25 °C. Sorption of the fumigant by the grain followed an exponential decay and reduced the mortality rates of both adults and eggs. The partition ratio (K), a measure of physical sorption, had a strong impact on mortality of both adults and eggs. The quadratic model showed the best fit to the data and turning points in the relationship indicated that although mortality increased as concentration increased, physical sorption removed fumigant resulting in a decrease in the mortality rate. There was a linear relationship between mortality and the rate of sorption (k) of SF by the wheat. At each concentration, mortality rate increased as k increased despite sorption continuing, indicating that the chemical sorption rate had little impact on mortality. Sorption of SF into the commodity has the potential to reduce the biological efficacy of the fumigant resulting in potential control failures. Concentration x time protocols may need to be revised to account for this phenomenon.     

Evaluation of chlorpyrifos and chlorpyrifos-methyl for control of Dermestes maculatus Deg. (Coleoptera: Dermestidae) on sheepskins

Chlorpyrifos and chlorpyrifos-methyl were compared to sodium arsenate for control of Dermestes maculatus Deg. on sheepskins.Laboratory experiments showed that sprays of chlorpyrifos depositing 24·5 mg/m² gave complete control of eggs whereas the standard rate of arsenate only gave 80% control. Almost complete knockdown of mixed instar larvae was obtained with sprays of chlorpyrifos depositing 49 mg/m² whereas the standard rate of arsenate only gave 60% knockdown.In laboratory experiments in which treated sheepskins were stacked to simulate bale conditions, chlorpyrifos deposits of 49 mg/m² gave more effective control of 4th–5th instar larvae at 1 day, 1, 2 and 3 months after treatment than did the standard deposit of arsenate. Chlorpyrifos and chlorpyrifos-methyl deposits of 49 mg/m² permitted less than 10% survival of 4th–5th instar larvae and adults on treated sheepskins at 2 months after treatment.     

Insecticidal activities of constituents identified in the essential oil from leaves of Chamaecyparis obtusa against Callosobruchus chinensis (L.) and Sitophilus oryzae (L.)

Analysis by gas chromatography-mass spectrometry led to the identification of 20 volatiles from the steam distilled oil of the leaves from Chamaecyparis obtusa Siebold et Zuccarni. Seven constituents of the oil were tested for contact and fumigant activity against adults of Callosobruchus chinensis (L.) and Sitophilus oryzae (L.). Responses varied with compound and dose rather than increasing exposure time beyond 1 or 2 days. In the impregnated-paper test with the constituents [bornyl acetate, (+)-limonene, myrcene, α-phellandrene, α-pinene, sabinene and terpinolene], at 0.1 mg/cm², bornyl acetate, α-phellandrene and terpinolene caused 97%, 97% and 87% mortality, respectively, against C. chinensis adults 1 day after treatment. At 0.05 mg/cm², moderate activity was achieved with bornyl acetate (56% mortality), α-phellandrene (75%) and terpinolene (55%). Against S. oryzae adults, at 0.26 mg/cm², terpinolene caused 93% mortality 2 days after treatment, whereas 80% mortality 4 days after treatment was observed with bornyl acetate and α-phellandrene. The toxicity of these compounds was significantly decreased at 0.18 mg/cm². In a fumigation test with S. oryzae adults, bornyl acetate and terpinolene were much more effective in sealed containers than in open ones, indicating that the insecticidal activity of these compounds was largely attributable to fumigant action. These naturally occurring materials derived from leaves of Chamaecyparis could be useful for managing populations of C. chinensis and S. oryzae.     

The effect of diurnally interrupted doses of phosphine over four days on egg mortality of susceptible and resistant strains of Sitophilus oryzae (L.)

Phosphine concentrations in stored grain are uneven and can undergo cyclic fluctuations caused by diurnal changes in solar heat exchange and wind. Experiments were conducted to investigate the influence of daily concentration variations on insect mortality. Values of LT₅₀ and LT_99.9 are presented for Sitophilus oryzae eggs in response to a range of diurnally interrupted phosphine treatments over four days. Egg mortality was determined for three insect strains that varied in susceptibility to the fumigant, at concentrations that ranged from 0.75 mg/L to 3 mg/L for 32-8 h respectively, giving the same Ct product for all treatment combinations. Effects on mortality were analyzed in terms of accumulated phosphine exposure over 4 days of treatment, and in terms of the total elapsed time of treatment. Results were compared to those obtained from continuous treatments having equivalent Ct combinations. Treatments that were interrupted daily extend the total elapsed time required for a given level of mortality and that time increased as concentration increased and daily treatment time decreased. Values of LT_99.9 for a susceptible strain were 67.6 h and 103.6 h, and for a resistant strain were 133.6 h and 179.5 h at concentrations of 1 mg/L and 3 mg/L respectively. However, diurnal treatments were more efficacious than continuous treatments when only dosage time was measured. Values of LT_99.9 for the susceptible strain were 21.0 h compared with 33.8 h and 11.0 h compared with 17.7 h, and for the resistant strain were 35.2 h compared with 57.4 h and 22.2 h compared with 44.3 h at 1 mg/L and 3 mg/L respectively. The findings show that the level of mortality during interrupted treatment is mainly due to the additional time that the fumigant is absent and not a combined affect including insect recovery during the intervening periods. In fact, the dosage time is reduced by an apparent increase in phosphine toxicity.     

Impact of high temperatures on efficacy of cyfluthrin and hydroprene applied to concrete to control Tribolium castaneum (Herbst)

In laboratory trials, concrete was treated with cyfluthrin wettable powder (WP) at 40 mg active ingredient [AI] cyfluthrin WP/m², then heated for 4, 8, or 16 h at either 45°C or 55°C, or treated but not heated (seven treatment combinations). Bioassays were conducted by exposing adult Tribolium castaneum (Herbst) for 0.5, 1, and 2 h. Survival of T. castaneum was generally greater on unheated concrete compared with the heating treatments, and survival appeared to decrease as heating time increased at both 45°C and 55°C. In a second laboratory trial, concrete was treated with hydroprene (Gentrol) at the label rate of 1.9×10⁻³ mg [AI]/cm², and bioassayed by exposing late-instar T. castaneum larvae on the treated surface. There were significant differences between untreated controls and the heat treatment regimes (P<0.05) with respect to the percentage of live emerged adults, the percentage of those adults with deformities, and the percentage of dead adults, but heating did not reduce efficacy of hydroprene. In a field trial, concrete was treated with cyfluthrin at 2 mg [AI] cyfluthrin WP/m², and placed in a flour mill undergoing an experimental heat treatment and in an unheated office. Treated concrete was bioassayed by continually exposing adult T. castaneum for 0.5-120 h. The effect of heating time on insect mortality was not significant (P?0.05). Except for T. castaneum exposed for 0.5 h, the percentage of beetle survival on unheated concrete was greater (P<0.05) than survival on concrete that had been heated in the mill, indicating a possible beneficial effect on cyfluthrin toxicity due to heating. Results of these studies show that short-term exposures to high temperatures may have no appreciable effect on efficacy of either cyfluthrin WP or hydroprene, and combination treatments of heat plus either of these insecticides may be effective alternatives to methyl bromide for disinfesting milling facilities.     

Laboratory toxicity and large-scale commercial validation of the efficacy of ethanedinitrile,a potential alternative fumigant to methyl bromide,to disinfest New Zealand Pinus radiata export logs

We tested the efficacy of ethanedinitrile (EDN), a new fumigant considered as a potential methyl bromide (MB) replacement for the quarantine treatment of New Zealand pine, Pinus radiata D. Don, export logs. Firstly, toxicity trials were conducted in the laboratory with pine logs infested with the larvae, pupae, or adults of pine bark beetles, Hylurgus ligniperda and Hylastes ater, at 10 and 20 °C in 28-L chambers, to identify the most tolerant species and life stages. Then, logs infested with the most tolerant species and life stage were fumigated in 500-L laboratory chambers to determine whether the increase in the volume of the fumigated space and logs that will occur when scaling up from laboratory to commercial fumigations would affect EDN efficacy. Finally, confirmatory fumigation trials using commercial or semi-commercial sized log stacks, were conducted in a deforested commercial plantation area in Tokoroa, New Zealand, to demonstrate the efficacy of EDN in the field.Our results suggest EDN could be an effective alternative fumigant to MB for the phytosanitary treatment of logs exported from New Zealand. A phytosanitary fumigation schedule with EDN for P. radiata export logs that uses a concentration of 100 g/m³ for 20 h across a range of temperatures from 10 to 20 °C is recommended. Future efforts should focus on implementing the recommended schedule, under commercial practices, to provide quarantine security for export logs using EDN as a replacement for MB.     

Effects of spinosad and spinetoram on larval mortality,adult emergence,progeny production and mating in Cadra cautella (Walk.) (Lepidoptera: Pyralidae)

The bacterial formulations, spinosad and spinetoram, were evaluated for their efficacy in suppressing development and mating success in Cadra cautella (Walk.) (Lepidoptera: Pyralidae), the almond moth. A dilution series of spinosad and spinetoram was sprayed on rice flour. Rice flour samples sprayed with water served as the control. Late instar C. cautella larvae were introduced onto spinosad-, spinetoram-, or water-treated rice flour. The first experiment tested the effects of spinosad and spinetoram on larval mortality, as well as emergence of adults and progeny at different insecticide concentrations. In the second experiment, the mating success of C. cautella adults that had emerged from larvae exposed to spinosad was tested inside a cubicle. Both spinosad and spinetoram increased larval mortality, whereas both compounds reduced adult emergence and progeny production. Natural mating was reduced in the presence of the synthetic sex pheromone (Z,E)-9,12-tetradecadienyl acetate. However, exposure of C. cautella larvae to spinosad did not alter mating in adult progeny. Spinosad was more effective than spinetoram at suppressing C. cautella development. The study concludes that both spinosad and spinetoram suppress the development of immatures of C. cautella to the adult stage as well as mating. Thus, the both compounds can be used to protect stored grains from infestation by C. cautella.     

Seasonal variations in chemical composition and fumigant activity of five Eucalyptus essential oils against three moth pests of stored dates in Tunisia

The present work investigates seasonal variation in chemical composition of essential oils isolated from leaves of five Eucalyptus species (Namely: Eucalyptus camaldulensis, Eucalyptus astringens, Eucalyptus leucoxylon, Eucalyptus lehmannii and Eucalyptus rudis) and assesses their fumigant activity against three stored-date moth pests: Ephestia kuehniella, Ephestia cautella and Ectomyelois ceratoniae.GC and GC–MS analyses showed that chemical composition varied with Eucalyptus species and seasons. The five essential oils contained 1,8-cineole, α-pinene, and α-terpineol as major common compounds. Of the other major constituents, β-pinene and p-cymene were only present in E. rudis essential oil. In addition, o-cymene was specific only to E. camaldulensis and E. rudis essential oils. Oil yields were the highest and generally richer in toxic compounds during the summer season.Results demonstrated that fumigant toxicity varied with season, insect species, essential oil concentration and exposure time. E. camaldulensis essential oil was more toxic against E. cautella and E. kuehniella. LC₅₀ values were respectively 11.07 and 26.73 μl/l air while LT₅₀ values were 13.49 and 30.46 h. However, for E. ceratoniae, E. rudis essential oil was more effective, with LC₅₀ and LT₅₀ values of 31.4 μl/l air and 36.1 h respectively. For all pest species, fumigant activity was strongest for the summer season oils. E. cautella was the most sensitive species.