Prey consumption by the mealybug predator <Emphasis Type="Italic">Spalgis epius</Emphasis> on pink hibiscus mealybug (<Emphasis Type="Italic">Maconellicoccus hirsutus</Emphasis>)

The pink hibiscus mealybug Maconellicoccus hirsutus (Green) (Hemiptera: Pseudococcidae) is a major pest of economically important crops. The apefly Spalgis epius (Westwood) (Lepidoptera: Lycaenidae) is a potential predator of various species of mealybugs. Studies of its preying potential and preference for prey stages on M. hirsutus are incomplete. An investigation was undertaken to determine the daily prey consumption and preference for prey stages by different larval instars of S. epius reared on M. hirsutus in the laboratory. During the 8-day larval development period with four larval instars of S. epius, the daily prey consumption increased from the first to the seventh day and decreased on the eighth day prior to the prepupal stage. Generally, there was a significant difference in the prey consumption on different days. The 1st to 4th instar larvae of S. epius consumed, respectively, a mean of 181.3, 679.1, 1770.4 and 4333.0 eggs or 19.1, 67.7, 153.0 and 639.0 nymphs or 2.72, 6.26, 13.8 and 32.1 adults of M. hirsutus. When an S. epius larva was fed on M. hirsutus eggs, nymphs and adults separately, it consumed a mean of 6952.6 eggs, 878.8 nymphs or 53.9 adults during its entire development. A single larva of S. epius consumed 2358.3 eggs, 151.2 nymphs and 34.3 adults of M. hirsutus during its entire development when the prey stages were offered all together. The study revealed that S. epius is a voracious predator of M. hirsutus and thus could be utilized as a potential biological control agent.     

Spiromesifen toxicity to the spider mite <Emphasis Type="Italic">Tetranychus urticae</Emphasis> and selectivity to the predator <Emphasis Type="Italic">Neoseiulus californicus</Emphasis>

Tetranychus urticae Koch (Acari: Tetranychidae) is a major pest of several agricultural crops and Neoseiulus californicus (McGregor) (Acari: Phytoseiidae) is an important natural enemy of this pest mite. The objective of the study was to evaluate the effect of spiromesifen on the development and reproduction of T. urticae, and to assess the influence of spiromesifen and other acaricides on the population growth rates of the spider mite and its predator, N. californicus. Toxicity tests with spiromesifen at different life stages of T. urticae indicated that eggs less than 72 h old were more sensitive than other development stages. The oviposition rate of T. urticae was significantly affected by spiromesifen. Experiments on the effects of spiromesifen on the growth rates of T. urticae and N. californicus indicated that spiromesifen is innocuous to the predaceous mite but highly toxic to the spider mite, leading to population suppression in 10 days. Fenpropathrin, acephate and neem oil were not harmful to N. californicus, but were not so efficient as spiromesifen in controlling T. urticae, and had significantly less influence on the population growth rates of the spider mite. Among these three products, only neem oil caused significant reduction in the growth rate of T. urticae. Chlorfenapyr, abamectin, milbemectin and diafenthiuron significantly affected the population growth rates of T. urticae and N. californicus. Spiromesifen was the most promising acaricide for managing the two-spotted spider mite, when used in combination with N. californicus.     

Fumigant toxicity of<Emphasis Type="Italic">Eucalyptus blakelyi</Emphasis> and<Emphasis Type="Italic">Melaleuca fulgens</Emphasis> essential oils and 1,8-cineole against different development stages of the rice weevil<Emphasis Type="Italic">Sitophilus oryzae</Emphasis>

Essential oils extracted fromEucalyptus blakelyi (1,8-cineole, 77.5%),Melaleuca fulgens (1,8-cineole, 56.9%) and 1,8-cineole were shown to have fumigant toxicity against different development stages ofSitophilus oryzae. The eggs ofS. oryzae were the most tolerant, followed by pupae, larvae and adults in that order.M. fulgens oil,E. blakelyi oil and 1,8-cineole at 100 μl per liter of air gave, respectively, LT₅₀ values of 16.2, 17.4 and 9.1 h for adults, 31.1, 19.3 and 17.5 h for larvae, 55.6, 75.2 and 39.7 h for pupae, and required >7 days for eggs. Only 1,8-cineole (200 μl ⁻¹ air) gave a significant egg kill by 7 days and the LT₉₅ was 134.5 h. 1,8-Cineole could be a useful new fumigant. http://www.phytoparasitica.org posting Oct. 3, 2004.     

Feeding potential of <Emphasis Type="Italic">Cryptolaemus montrouzieri</Emphasis> against the mealybug <Emphasis Type="Italic">Phenacoccus solenopsis</Emphasis>

Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae) is an exotic species native to the USA, damaging cotton and other plant families. The feeding potential of different development stages of Cryptolaemus montrouzieri Mulsant, a biological control agent against mealybugs, was investigated on different development stages of P. solenopsis. Fourth instar grubs and adults of C. montrouzieri were the most voracious feeders on different instars of mealybug. The number of 1^st instar nymphs of mealybug consumed by 1^st, 2^nd, 3^rd and 4^th instar larvae and adult beetles of C. montrouzieri was 15.56, 41.01, 125.38, 162.69 and 1613.81, respectively. The respective numbers of 2^nd and 3^rd instar nymphs of mealybug consumed were 11.15 and 1.80, 26.35 and 6.36, 73.66 and 13.32, 76.04 and 21.16, 787.95 and 114.66. The corresponding figures for adult female mealybugs were 0.94, 3.23, 8.47, 12.71 and 73.40, respectively. The results indicate that C. montrouzieri has the potential to be exploited as a biocontrol agent in North India; inoculative releases of 4^th instar larvae and adults may provide instant control of P. solenopsis. Field experiments should be conducted to determine the efficiency of the ladybird on this mealybug.     

Insecticidal activity of crude seed extracts of<Emphasis Type="Italic">Annona</Emphasis> spp.,<Emphasis Type="Italic">Lansium domesticum</Emphasis> and<Emphasis Type="Italic">Sandoricum koetjape</Emphasis> against lepidopteran larvae

Crude ethanolic seed extracts ofAnnona muricata, A. squamosa (Annonaceae),Lansium domesticum andSandoricum koetjape (Meliaceae) collected from different locations and years in Maluku, Indonesia, were screened for inhibition of larval growth against the polyphagous lepidopteranSpodoptera litura (Noctuidae). Extracts ofA. squamosa were significantly more active (20-fold) than those ofA. muricata. A. squamosa collected from Namlea yielded the extracts with the greatest inhibitory activity. There were significant differences among locations for bothA. squamosa andA. muricata but not forL. domesticum andS. koetjape. Extracts ofA. squamosa, collected from Namlea, inhibited larval growth in a dose-dependent manner, with a dietary EC₅₀ (effective concentration to inhibit growth by 50% relative to controls) of 191.7 ppm fresh weight. Extracts ofA. squamosa collected from individual trees in Namlea also varied in growth inhibitory effect againstS. litura andTrichoplusia ni larvae. This species is a candidate for development of a botanical insecticide for local use in Indonesia. http://www.phytoparasitica.org posting Dec. 1, 2003.     

Laboratory evaluation of a botanical natural product (<Emphasis Type="Italic">AkseBio2</Emphasis>) against the pear psylla<Emphasis Type="Italic">Cacopsylla pyri</Emphasis>

A botanical natural product,AkseBio2, was evaluated under laboratory conditions for its oviposition deterrent, ovicidal and larvicidal (nymphicidal) effects against the pear psyllaCacopsylla pyri (L.) (Hemiptera: Psyllidae). The product exhibited a strong oviposition deterrent effect for winterform and summerform females and caused a reduction in the total number of eggs laid in both choice and no-choice assays. Significant mortalities in freshly laid eggs (0–48 h) and various nymphal stages of the pest were recorded in toxicity assays. At a concentration of 0.1% (formulation), the highest biological activity of the product was recorded against the young (1st and 2nd) nymphal stages (up to 87.4% mortality) in comparison with the other biological stages of the pest. It was less active against the older (3rd-5th) nymphs, causing 62.1% mortality at the same concentration. In assays with non-target organisms, a significant negative effect was not observed. There were no significant changes on treated plants up to 7 days after treatment in any trial, nor was there any phytotoxicity on plant tissue as a result ofAkseBio2 treatments. The results suggest that the product can be used in psylla control instead of synthetic insecticides and may serve as an integrated pest management (IPM) component in pear orchards. http://www.phytoparasitica.org posting July 14, 2004.     

Olfactory response of the ladybird beetle <Emphasis Type="Italic">Stethorus gilvifrons</Emphasis> to two preys and herbivore-induced plant volatiles

The spider mites Tetranychus urticae Koch and Panonychus ulmi (Koch) (Tetranychidae) cause severe economic losses to vegetable farms and deciduous fruit orchards in Turkey. One of their predators, the ladybird beetle Stethorus gilvifrons (Muls.) (Col., Coccinellidae), aggregates on mite-infested patches of plants. The present study assessed whether there is a role for herbivore-induced plant volatiles (HIPVs) and/or odors emitted directly from these two mite species in the aggregative response of ladybird beetles. The olfactory responses of the predator females to volatiles from T. urticae- and/or P. ulmi-infested sweet pepper (four cultivars, viz. ‘Demre’, ‘Yalova Carliston’, ‘Kandil Dolma’ and ‘Yag Biberi’), kidney bean (cv. ‘Barbunya’) and apple (M9 rootstock) were investigated using a two-choice olfactometer. Our results showed that HIPVs emitted from both T. urticae- and P. ulmi-infested plants significantly attracted S. gilvifrons adults for all plants except the sweet pepper cv. Yag Biberi. In addition, it was found that volatiles from apple plants infested by T. urticae and, especially, P. ulmi are more attractive for S. gilvifrons females than those emitted by other infested plants. The results also suggest that the odors of T. urticae adults and their products might influence the attraction of S. gilvifrons females.     

Toxicity of selected insecticides to the two-spot ladybird <Emphasis Type="Italic">Adalia bipunctata</Emphasis>

The toxicity of pirimicarb, imidacloprid, dimethoate, lambda-cyhalothrin, flonicamid and spinosad to the two-spot ladybird, Adalia bipunctata, was evaluated in a laboratory study. Susceptibility of fourth instars and female adults was assessed by measuring toxicity via residual contact and ingestion through feeding on contaminated green peach aphids (Myzus persicae). Flonicamid and spinosad had no lethal effects on larvae and female adults. Pirimicarb was harmless to the predator by ingestion exposure but showed some residual toxicity at high concentrations to both larval and adult stages. Imidacloprid was highly toxic to the larval stage by residual and ingestion exposure but caused very low adult mortality when ingested through contaminated prey. Dimethoate and lambda-cyhalothrin were highly toxic to both the larval and adult stages of the ladybird. Our findings indicate that pest management programs in agricultural crops using dimethoate, lambda-cyhalothrin and, to a lesser degree, imidacloprid, are detrimental to A. bipunctata, whereas pirimicarb, flonicamid and spinosad are more compatible with the use of this predator.     

Biological traits and prey consumption of <Emphasis Type="Italic">Anthocoris minki</Emphasis> fed on <Emphasis Type="Italic">Agonoscena pistaciae</Emphasis> and <Emphasis Type="Italic">Brachycaudus (Thuleaphis) amygdalinus</Emphasis>

The predatory insect Anthocoris minki Dohrn (Heteroptera: Anthocoridae) is an indigenous Anthocoris species for the biological control of pests in pistachio orchards. The pistachio psylla Agonoscena pistaciae Burckhardt and Lauterer (Homoptera: Psyllidae) is an important insect pest in pistachio trees in Turkey. Similarly, Brachycaudus (Thuleaphis) amygdalinus (Schouteden) (Hemiptera: Aphididae) is a pest of almond trees that is considered as alternative prey for A. minki when pistachio psylla are not available in early spring on pistachio trees. The development time, survival percentage of immature stages, longevity, fecundity, prey consumption, and life table parameters of A. minki fed on A. pistaciae and B. amygdalinus nymphs were determined at 25 ± 1°C, 70 ± 5% r.h., and a 16 h:8 h (L:D) photoperiod under laboratory conditions. The nymphal survival rate was significantly higher when nymphs were fed on A. pistaciae (an average of 96.7%) than on B. amygdalinus (an average of 71.4%). The development time of A. minki was significantly shorter when nymphs were fed on B. amygdalinus (10.3 days) as opposed to A. pistaciae (11.0 days). No significant differences among prey species were found for longevity and fecundity. The total female longevity and fecundity of A. minki was 38.0 days and 247.2 eggs, respectively, when nymphs were fed on A. pistaciae; and 35.4 days and 233.0 eggs, respectively, when nymphs were fed on B. amygdalinus. On average, 104.4 A. pistaciae and 77.7 B. amygdalinus nymphs were consumed during the nymphal development time for A. minki. Adults of A. minki consumed significantly more psyllids than aphids throughout their life span. The greater difference did not significantly inpact the longevity and fecundity of A. minki. Females of A. minki consumed an average of 631.0 A. pistaciae and an average of 273.3 B. amygdalinus nymphs, while female predators consumed significantly more prey than males. The intrinsic rate of increase (r _m ) of A. minki fed on A. pistaciae (0.174) was significantly greater than those fed on B. amygdalinus (0.148). The successful development and reproduction of both A. pistaciae and B. amygdalinus indicates that they are suitable prey for A. minki.     

Note: Life history of<Emphasis Type="Italic">Lixus bardanae</Emphasis> on curly dock (<Emphasis Type="Italic">Rumex crispus</Emphasis>) in Turkey

The biology ofLixus bardanae (F.) (Coleoptera: Curculionidae) on curly dock (Rumex crispus L.) in northeastern Anatolia (Bayburt, Erzurum and Kars Provinces), Turkey, was studied during the years 2000 and 2001.L. bardanae completes one generation in a year, overwintering as an adult. It feeds on leaves of the host plant. Females lay eggs individually into stems and the young larvae create galleries in stems while feeding. Pupation occurs inside stems in cells fashioned from frass. In late September, adults move into soil and overwinter in an upright position around the roots of the host plant. Infestation levels were found to range between 34% and 84%. Two parasitoids,Exeristes roborator F. andEndromopoda phragmitidis Perve (Hymenoptera: Ichneumonidae), were reared fromL. bardanae. http://www.phytoparasitica.org posting Dec. 21, 2003.     

Seasonal abundance and spatial distribution of the predator<Emphasis Type="Italic">Macrolophus costalis</Emphasis> and its prey<Emphasis Type="Italic">Myzus persicae</Emphasis> on tobacco

Field studies were conducted to assess the population and the spatial dynamics of the predatory bugMacrolophus costalis Fieber (Hemiptera: Miridae) and of its prey, the aphidMyzus persicae (Sulzer) (Hemiptera: Aphidoidea), on tobacco. From an untreated tobacco field in Tithorea (central Greece), tobacco leaves were collected from the upper and the lower half of the plants from June until September, in 1999 and 2000. The numbers ofM. costalis andM. persicae individuals per leaf were counted. Most aphids were observed during July and August (early and mid season), with densities dropping markedly in September. In contrast,M. costalis population densities increased late in the season (September). Significantly higher numbers of aphids were found on the upper half of the plants than on the lower half. In contrast, significantly moreM. costalis individuals were observed on the lower half. Iwao’s Regression Analysis was used in order to characterize the spatial pattern of the two species. According to this model, in both sampling seasons, aphids andM. costalis nymphs displayed an aggregated spatial pattern, whileM. costalis adults were found to be randomly distributed among sampling units. Although moreM. costalis individuals were recorded on leaves with relatively high aphid densities, this species did not react numerically to changes in prey density. In addition, a significant number of bugs were found on leaves with low aphid densities or no aphids at all. http://www.phytoparasitica.org posting Dec. 18, 2002.     

Note: Tachinid parasitoids of<Emphasis Type="Italic">Ancyrosoma leucogrammes</Emphasis> and notes on parasitization rates of<Emphasis Type="Italic">Clytiomya dupuisi</Emphasis>

The study deals with the tachinid parasitoids ofAncyrosoma leucogrammes (Gmelin) (Heteroptera: Pentatomidae):Clytiomya dupuisi Kugler,Clytiomya sola (Rondani) andGymnosoma clavatum (Rohdendorf) (Diptera: Tachinidae). All species are recorded for the first time as parasitoids ofA. leucogrammes, andC. dupuisi was reared for the first time from a host. The parasitization rates ofC. dupuisi on adults ofA. leucogrammes varied from 7% to 9% between 1994 and 1999.C. sola andG. clavatum were reared in only small numbers. http://www.phytoparasitica.org posting July 10, 2003.     

Prey density-dependent feeding activity and life history of <Emphasis Type="Italic">Scymnus subvillosus</Emphasis>

The functional response, development time, survival and reproduction of the lady beetle Scymnus subvillosus (Goeze) (Coleoptera: Coccinellidae) were evaluated at different densities of the mealy plum aphid Hyalopterus pruni (Geoffroy) (Homoptera: Aphididae). Treatments were carried out at 25 ± 1°C, 60 ± 10% r.h. and 16L:8D photoperiod in a controlled temperature room. The larvae and adults of S. subvillosus were fed with different densities (5, 10, 20, 40 and 80) of H. pruni in petri dishes. The shape of the functional response was determined by logistic regression, and the values of the coefficient of attack rates (α) and handling times (T _h) were estimated by using nonlinear least-squares regression. Behavior of each larval stage and adults matched Holling’s type II functional response. Estimates of α for all stages of S. subvillosus tested were similar, but estimates of T _h varied; it was the shortest for adult females and the longest for third instar larva. Larvae were able to complete their development at each of the five prey densities, but increased prey densities reduced development time and mortality rate. Increased prey consumption did not change longevity, but resulted in a higher intrinsic rate of increase (r), the finite rate of increase (λ), net reproduction rate (R ₀ ), gross reproductive rates (GRR), and shorter mean generation time (T) and doubling time (DT). This research was funded by the Yuzuncu Yil University/foundation of scientific research projects (No. 2002-ZF 044)     

Rhyzobius lophanthae prey consumption and fecundity

The daily and total prey consumption and the fecundity of the predatorRhyzobius lophanthae Blaisdell (Coleoptera: Coccinellidae) fed on the scaleAspidiotus nerii Bouché (Homoptera: Diaspididae) were studied under controlled laboratory conditions. The prey consumption ofR. lophanthae was studied on larvae and on virgin adults, and the fecundity on mated females. For the development of the 1 st instar larvae ofR. lophanthae at 25° C, 1.2 adult femaleA. nerii were consumed; for the development of the 2nd, 3rd and 4th instar larvae, prey consumption was 2.7, 7.5 and 24.6 adult females, respectively. The duration of the larval development of the 1st, 2nd, 3rd and 4th instars was 3, 2.2, 2.7 and 6.2 days, respectively,R. lophanthae male and female adults consumed in their lifetime 390.6 and 672.3 adult femaleA. nerii, respectively. Thus, the male’s daily prey consumption came to 7 and the female’s to 12 adult femaleA. nerii. The average fecundity ofR. lophanthae was calculated to be 633.7 eggs per female and the daily fecundity to be 18–25 eggs. The average longevity was 63.4 days for mated adult females and 119.4 days for unmated.     

Effects of a commercial neem (<Emphasis Type="Italic">Azadirachta indica</Emphasis>) extract on<Emphasis Type="Italic">Streblote panda</Emphasis> larvae

Biological effects of a commercial formulation of azadirachtin, Align^TM, were assessed onStreblote panda Hübner [1820] (Lasiocampidae) first instars by means of choice and nochoice bioassays. Survival, development, and food consumption were recorded. The product tested did not show clear antifeedant effects, but produced dose-dependent larval mortality. All treatments resulted in significant inhibition of growth, presumably through endocrine regulatory effects. At higher doses assayed the product appears to have direct toxic effects. Our results suggest that Align^TM may be used in IPM programs forS. panda and should be evaluated for efficacy under field conditions. http://www.phytoparasitica.org posting July 10, 2003.     

Elucidating resistance in cotton genotypes to whitefly, <Emphasis Type="Italic">Bemisia tabaci,</Emphasis> by population buildup studies

Plant resistance has become an important component of integrated pest management (IPM) for management of whitefly, Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae), an important pest of cotton in India. The present studies were undertaken to standardize the plant stage and identify resistant cotton genotypes against whitefly. Nine plant stages of F846, a susceptible cotton genotype, were exposed to whitefly for 25 days under no-choice conditions. The population buildup (eggs, nymphs, pupae and adults) was recorded. The 12-, 14- and 16-leaf stages were suitable for plant resistance studies against whitefly, and the 14-leaf stage was taken for further studies. Ten cotton genotypes of Gossypium hirsutum and two of G. arboreum were covered with split cages in which five pairs of B. tabaci (F₁) were released. The population buildup was recorded to categorize genotypes as resistant, moderately resistant, moderately susceptible or susceptible. The experiment was repeated with F₂ and F₃ generation whiteflies. Based on overall average score of three experiments, LD694 was rated as resistant; LK861, Supriya, RS2013, CNH911 and PA183 as moderately resistant; IS-376/4/1/20/72, NHH44, TxMaroon2-78, Bt 6304 and RS2098 as moderately susceptible; and F846 as susceptible. LD694 was found to be resistant in three consecutive generations of whitefly.     

Effect of apple cultivar and of temperature on the biology and life table parameters of the twospotted spider mite<Emphasis Type="Italic">Tetranychus urticae</Emphasis>

Development duration and reproduction rate of the twospotted spider miteTetranychus urticae Koch (Acarina: Tetranychidae) were studied on five different apple cultivars (‘Amasya’ (local cultivar), ‘Golden Delicious’, ‘Granny Smith’, ‘Starking Delicious’ and ‘Starkrimson Delicious’) at 25°C, 65±10% r.h. and 16:8 L:D. In addition, the same parameters were determined on Golden Delicious leaves at three constant temperatures (20°, 30° and 35°C, 65±10% r.h. and 16:8 L:D) in the laboratory.T. urticae performed better on Granny Smith than on the other cultivars, due mainly to high daily egg production (4.6 eggs/♀/day) and the intrinsic rate of natural increase (r _m , which was 0.243 ♀/♀/day). The lowestr _m was observed on Amasya variety (0.231 ♀/♀/day). Development periods of immature stages ofT. urticae varied from 6.5 to 15.5 days at 35° and 20°C, respectively, for females, and from 5.9 to 14.5 days at 35° and 20°C, respectively, for males. The development thresholds of the eggs and pre-adult stages, respectively, were 10.78° and 8.43°C, and total effective temperatures were 57.80 and 172.41 degree-days. Mean generation time (T _o ) of the population ranged from 9.94 days at 35°C to 25.99 days at 20°C. The net reproduction rate increased from 66.99 ♀/♀ at 20°C to 92.19 ♀/♀ at 25°C, and decreased to 84.34 ♀/♀ at 30°C and to 12.04 ♀/♀ at 35°C. The highest r _m occurred at 30°C (0.302 ♀/♀/day) and the lowest at 20°C (0.161 ♀/♀/day). http://www.phytoparasitica.org posting Dec. 19, 2003.     

Suitability of different artificial diets for development and survival of stages of the predaceous ladybird beetle <Emphasis Type="Italic">Eriopis connexa</Emphasis>

The ladybug Eriopis connexa (Germar) (Coleoptera: Coccinellidae) is an important natural enemy of various pests. The potential of rearing it on 17 different diets was evaluated. The percentage of E. connexa adults was higher when its larvae received only eggs of Anagasta kuehniella (Zeller) (Lepidoptera: Pyralidae) after freezing for 1 day (92.5%) or combined in artificial diets with honey and water (82.5% to 100.0%). The viability from larvae to adult was 72.5% with eggs of A. kuehniella (after 1 day’s freezing) plus an artificial diet based on pet food. No adults of E. connexa were obtained with artificial diets as a stand-alone food source. The duration of the larval period to adult of this predator was longer, but with low viability, with only A. kuehniella eggs (after 6 months’ freezing) or with eggs + artificial diets. Eggs of A. kuehniella (after 1 day’s freezing) supplied separately or along with artificial diets were more appropriate to rear E. connexa and both diets can be used for mass rearing of this natural enemy.     

Bioactivity of pyrogallol against melon fruit fly, <Emphasis Type="Italic">Bactrocera cucurbitae</Emphasis>

The insecticidal effects of pyrogallol were studied by treating eggs and larvae of the melon fruit fly, Bactrocera cucurbitae (Coquillett) (Tephritidae: Diptera), with various concentrations (1, 5, 25, 125, 625 and 3125 ppm) of the phenolic compound. Although egg hatching decreased following treatment of 0–8-h old eggs with pyrogallol, the decrease was not significantly different from the control. Larval period and total development period declined significantly in 64–72-h-old and 88–96-h-old B. cucurbitae larvae fed on pyrogallol-treated diet. However, in the 44–48-h-old larvae, the larval period and total development period were not affected by pyrogallol treatment at any of the tested concentrations. None of them survived up to the pupal stage at the highest concentration. Number of pupae formed and adult emergence decreased significantly in all larval instars following feeding on pyrogallol-treated diet. The analysis of enzymes in 64–72-h-old larvae treated with LC₄₀ concentration (16.21 ppm) of pyrogallol at three time intervals, i.e., 24 h, 48 h and 72 h, showed significant induction in the activities of ascorbate peroxidase (APOX) and glutathione S-transferases (GSTs) at 24 h but a decrease was observed following prolonged treatment. On the other hand, superoxide dismutase (SOD) and peroxidases (POX) activity remained suppressed during the initial treatment interval but increased with prolonged treatment in 136–144-h-old larvae. The catalase (CAT) activity was suppressed at all treatment durations whereas glutathione reductase (GR) activity was not affected by pyrogallol treatment. An increase in the activities of ascorbate peroxidase, superoxide dismutase, peroxidases and glutathione S-transferases indicates an induction of defensive response of the melon fruit fly to the toxic effects produced by ingestion of pyrogallol. Although the effects of the compound on enzyme activity were tested on second instar, it would be interesting to see the effects on other instars too.     

Influence of temperature on toxicity of propylene oxide at low pressure against<Emphasis Type="Italic">Tribolium castaneum</Emphasis>

Toxicity of propylene oxide (PPO) at low pressure against the most common stored-product insect,Tribolium castaneum (Herbst), over a short exposure time, was tested at three different temperatures (16°, 22° and 30°C). Toxicities of PPO at 100 mm Hg were strongly influenced by ambient temperature. LD₅₀ and LD₉₉ toxicities ranged from 4.7 to 28.9 mgl ⁻¹ and from 10.5 to 72.6 mgl ⁻¹ respectively, showing that susceptibility was positively correlated to the temperature. The LD₉₉ values for all life stages (except the larval stage) were significantly lower at 30° than those at 16° and 22°C. However, the LD₉₉ values for all life stages (except the pupal stage) at 16° were not significantly different from those at 22°C. A concentration × time (Ct) product of 291, 171 and 98 mg h/l was required to obtain complete mortality (99%) ofT. castaneum at 16°, 22° and 30°C, respectively. Thus, the efficacy of PPO at 100 mm Hg to all life stages ofT. castaneum also decreased as the temperature decreased from 30° to 16°C. http://www.phytoparasitica.org posting Sept. 28, 2004.