Effects of juvenile hormone analogue and ecdysteroid on adult eclosion of the fruit fly Bactrocera minax (Diptera: Tephritidae).

The univoltine Bactrocera minax (Enderlein) is a devastating pest of citrus in Nepal, India, Bhutan, and China. To better understand the overwintering pupal diapause, we investigated the juvenile hormone III (JH III) and ecdysteroid 20-hydroxyecdysone (20E) titers across the developmental stages, and the effects of juvenile hormone analog (JHA) and 20E treatments on adult emergence patterns. The results showed that both JH III and 20E levels fluctuated from the late larval stage to the late pupal stage. JHA and 20E treatments at the late larval stage had marginal effect on the adult emergence patterns, with slightly faster adult eclosion and higher eclosion rate. Similarly, JHA treatment at the early pupal stage did not affect the adult emergence. However, 20E treatment at the early pupal stage remarkably shortened the duration of diapause, but lowered the eclosion rate, especially with relatively high dose. These findings demonstrated that 20E treatment at the early pupal stage is a suitable method to hasten the diapause termination of B. minax, which will contribute to the rearing of B. minax in the laboratory as needed for routine experiments.

Infection by Wolbachia bacteria and its influence on the reproduction of the stored-product psocid, Liposcelis tricolor.

Wolbachia are maternally inherited intracellular bacteria that infect a wide range of arthropods and nematodes and are associated with various reproductive abnormalities in their hosts. The infection by Wolbachia of the psocid, Liposcelis tricolor (Psocoptera: Liposcelididae), was investigated using long PCR amplification of the wsp gene that codes for a Wolbachia surface protein. The results showed that L. tricolor was positive for Wolbachia . Phylogenetic analysis showed that the Wolbachia found in L. tricolor was related to the B-group. Wolbachia infection in L. tricolor could be removed through antibiotic treatment. The results of crosses including female(W+) x male(W+), female(W-) x male(W+), female(W+) x male(W-), and female(W-) x male(W-), suggested that the removal of Wolbachia resulted in lower egg production by L. tricolor . The mean embryonic mortality of offspring produced by L. tricolor without Wolbachia was significantly higher than that of control.

Influence of long-term exposure to simulated acid rain on development, reproduction and acaricide susceptibility of the carmine spider mite, Tetranychus cinnabarinus.

Development, reproduction and acaricide susceptibility of Tetranychus cinnabarinus (Boisduvals) (Acari: Tetranychidae) were investigated after long-term (about 40 generations) exposure to various levels of acid rain; pH 2.5, 3.0, 4.0, and 5.6. Deionized water (pH 6.8) served as a control. The mites were reared on eggplant leaves at 28 degrees C, 80%RH and a photoperiod of 14:10 (L:D) in the laboratory. The results showed that the duration of the immature stage was significantly affected by acid rain exposure. The shortest duration (8.90 days) was recorded for populations exposed to pH 5.6 acid rain, while the longest duration (9.37 days) occurred after exposure to pH 2.5 acid rain. Compared with the control population, adult longevity was shortened with an increase in acidity. Similarly, the oviposition duration was also shortened by an increase in acidity. Statistically, female fecundity did not differ significantly between pH 5.6, pH 4.0 and control populations, but did differ significantly between the control population and those exposed to pH 2.5 and pH 3.0 acid rain. This suggested that the mite suffered reproductive defects after long-term exposure to acid rain with higher acidity (pH 2.5 and 3.0). The intrinsic rate of increase among different populations was not significantly affected, but the net reproductive rate of populations exposed to pH 2.5 and 3.0 acid rain was significantly less than pH 4.0, 5.6, and control populations. Bioassay results showed that after long-term exposure to acid rain, susceptibility of the mites to two acaricides, dichlorvos and fenpropathrin, did not change significantly.

Effect of six insecticides on three populations of Bactrocera (Tetradacus) minax (Diptera: Tephritidae).

The Chinese citrus fruit fly, Bactrocera minax is one of the most economically important and aggressive pests threatening the Chinese citrus industry. In order to provide some recommendations for the improvement of integrated pest management of this species, the authors evaluated the toxicity of 6 insecticides on the second stage larvae, fourth stage larvae, and adult flies from multiple geographical B. minax populations. In addition, the influences of each pesticide on pupation and emergence were examined for one population, from Hanzhong. The 6 reagents displayed a wide range of toxicity on various stages of B. minax. Abamectin and Dichlorphos displayed the highest and lowest toxicities, respectively. All of the insecticides had negative effects on pupation and emergence of B. minax from Hanzhong, while Chlorpvrifos had the strongest impact on pupation, and Phoxim had the strongest influence on emergence. Though Phoxim and Chlorpvrifos were both effective, these insecticides belong to the class of organophosphorus pesticides, and their use should be reduced in orchards because of their high toxicity and long residual period.

The effect of the insecticide dichlorvos on esterase activity extracted from the psocids, Liposcelis bostrychophila and L. entomophila.

The inhibition kinetics of dichlorvos on carboxylesterase and acetylcholinesterase (AChE) activity extracted from Liposcelis bostrychophila and L. entomophila (Psocoptera: Liposcelididae) were compared. The results showed that L. entomophila had significantly greater specific activity of carboxylesterase than L. bostrychophila (0.045 versus 0.012 micromoles/mg/min). Moreover, the carboxylexterase of L. entomophila showed higher affinity (i.e. lower Km value) to the substrate 1-naphthyl acetate than L. bostrychophila (0.29 versus 0.67 mM). The specific activity and affinity of AChE of the two species were not significantly different. The carboxylesterase of L. bostrychophila was more sensitive to the insecticide dichlorvos than that of L. entomophila. The I50s values of dichlorvos to carboxylesterase for L. bostrychophila and L. entomophila were 1.43 and 3.28 microM, respectively, and to AChE were 324 and 612 nM, respectively. Inhibition kinetics revealed that AChE from L. bostrychophila was 5.8-fold more sensitive to inhibition than AChE from L. entomophila.

[Resistance realized heritability and risk assessment of Panonychus citri to avermectin and fenpropathrin].

On the basis of resistance breeding and selection in laboratory, and by using the threshold trait analysis in quantitative genetics, this paper studied the realized resistance heritability of Panonychus citri (McGregor) collected from Beibei of Chongqing to avermectin and fenpropathrin, and predicted the resistance risk of P. citri to these two acaricides. After 11- and 16-generations of selection with avermectin and fenpropathrin, the resistance of P. citri to the two acaricides increased by 3.8- and 29.9-fold, and the realized resistance heritability was 0.0475 and 0.1544, respectively. Under laboratory condition, to develop a 10-fold increase of resistance required 12-26 generations of selection for avermectin, and 7-16 generations of selection for fenpropathrin under the selection pressure of 50%-90% mortality for each generation. Under field condition, it would require more generations to develop the same resistance level. Comparing with bioacaricide avermectin, pyrethroid fenpropathrin had obviously higher resistance risk to P. citri. The results provided references for the resistance management of P. citri to acaricides.

Population forecasting model of Nilaparvata lugens and Sogatella furcifera (Homoptera: Delphacidae) based on Markov chain theory.

Nilaparvata lugens (Stål) and Sogatella furcifera (Horváth) are the two most important long-distance migratory insect pests that cause great yield losses to rice in China. Accurate long-term population forecast is needed to implement effective management strategies for these two rice pests. In this paper, a transition probability matrix of 5-yr steps of Markov chain theory was constructed based on 31-yr light-trapping data of the two pests from 1977 to 2007 in Jiangkou County, Guizhou, China. The weight of each step for the transition probability matrix was calculated according to its prediction accuracy. Insect occurrence levels in the sixth year were predicted based on the occurrences of the previous 5 yr. Nonparametric Wilcoxon paired sample tests showed that there were no significant differences between the actual and predicted occurrences for both N. lugens and S. furcifera. In addition, the models accurately forecasted field occurrence in 2008 in Jinangkou County for both species. The results showed that the Markov models developed in this study offer an effective method for long-term population forecasting of N. lugens and S. furcifera and thus provide plant protection agencies and organizations with valuable information in implementing appropriate management strategies for these two devastating rice pests in Jiangkou and neighboring areas.

[Relative fitness of Tetranychus cinnabarinus resistant strains at different temperatures].

Based on resistance selection, the life tables of abameetin-resistant (AbR), fenpropathrin-resistant (FeR), and susceptible (S) strains of Tetranychus cinnabarinus at 15 degrees C, 20 degrees C, 25 C, 28 degrees C, 31 degrees C, 34 degrees C, and 36 degrees C were constructed, and the development duration, fertility, and intrinsic rate of increase (r(m)) of the strains were compared, aimed to understand the relative fitness of T. cinnabarinus resistant strains at different temperatures. The results indicated that compared with S strain, AbR and FeR strains had longer development duration at 15 degrees C but lower fertility at 20 degrees C-28 degrees C, and their relative fitness (represented by r(m)) was smaller at 15 degrees C but similar at 20 degrees C - 31 degrees C. For AbR and FeR strains, the fitness cost was moderate at 15 degrees C but lower at 20 degrees C - 31 degrees C. However, at high temperatures ( > or =34 degrees C), FeR strain possessed remarkable fitness cost while AbR strain showed better fitness.

[Seed population dynamics and germination characteristics of Eupatorium adenophorum].

With bare land, farmland, and masson pine forestland in the Eupatorium adenophorum- invaded area of Dechang County, Sichuan Province as test habitats, this paper studied the seed population dynamics of E. adenophorum at the levels of seed rain and seed bank, and its seed germination characteristics under effects of light and soil medium. The results showed that in the three habitats, the seed population of E. adenophorum only existed from March to June, and reached its peak by the end of April. The annual seed rainfall in bare land habitat amounted to 2.4 x 10(5) individuals per square meter, and all the seeds were distributed in the soil layer above 2 cm. The thousand seed weight and seed activity of E. adenophorum in bare land habitat were significantly higher than those in another two habitats. No active seed was found in the three habitats by the first ten days of July. Under artificial light condition, full light had some inhibitory effects on seed germination, while 28% of full light gave the highest germination rate. Sandy loam soil was more favorable for the seed germination, while in un-reclaimed red soil, both the germination velocity and germination rate were the lowest.

[Predation of Typhlodromus bambusae Ehara on Sehizotetranychus bambsae].

The simulation study under laboratory condition showed that the functional responses of Typhlodromus bambuse to Schizotetranychus bambuse at different development stages could be expressed by the curve of Holling Type II. The number of prey consumed by predator quickly increased with initial prey density, but soon leveled off. At 25 +/- 0.5 degrees C, the handling time (Th) of T. bambuse to S. bambusae at the stages of egg, larva, protonymph, deurtonymph and female was in order of egg

[Effects of simulated acid rain on physiological and biochemical characters of eggplant, the host plant of Tetranychus cinnabarinus].

In a series of laboratory trials, this paper studied the responses of eggplant (Solanum melongena), the host plant of carmine spider mite Tetranychus cinnabarinus, to different pH values simulated acid rain. The results showed that with the increasing acidity of simulated acid rain, the CAT activity and the contents of P and soluble protein in egg plant leaves increased significantly first, reaching the highest at pH 4.0 or 3.0, and then decreased; while the POD activity and soluble sugar content were in adverse. The reduced sugar content and SOD activity of eggplant leaves increased, but the pH value decreased with increasing acidity of acid rain. Acid rain had no effect on leaf water content. Among the test indices, leaf POD was most insensitive to the acid rain, followed by leaf pH, SOD and CAT, while the others were very sensitive. Weak acid rain (pH > 4.0) promoted the protective ability of eggplant leaf and its growth, and the growth of T. cinnabarinus was also promoted because of the changed contents of soluble sugar, P and soluble protein in eggplant leaves being more favorable to its eating; while strong acid rain (pH < 3.0) inhibited the growth of both host plant and mite.

[Niches analysis of three aphid populations on spring sowing maize].

Systematic analysis of aphid populations and niches patterns on spring sowing maize was carried out during 1998-1999 in the suburbs of Chongqing. The results indicated that there were three aphid populations Rhopalosiphum maidis Fitch., Rhopalosiphum padi Linn. and Sitobion avenae Fabricius distributed on the spring sowing maize. The mixed aphid populations traded off during the growth period of spring sowing maize, and two peaks of quantitative counts were shown at the mid and last ten days of May and the last ten days of June. In addition, the niches of aphid population were also discussed from one dimension (i.e., temporal or spatial) to two dimensions (i.e., temporal and spatial). Through the quantitative analysis of niche breadth and niche overlap, the highly temporal differentiation of M. avenae and the highly gathering character of R. maidis were all indicated. R. padi showed an indistinct differentiation, while R. maidi was a dominated population on the spring sowing maize.

[Acute lethal and behavioral response of Liposcelis bostrychophila (Psocoptera: Liposcelididae) to DDVP].

Book louse Liposcelis bostrychophila is a minor pest in stored products, and may seriously infest the stored products when its population outbreaks. This study was conducted to evaluate the toxic effect of DDVP on various development stages of L. bostrychophila. The results showed that at 28 +/- 0.5 degrees C and 24 h exposure under 75%-80% RH, the LC50 of the eggs, larvae of 1st to 4th stadium, and adults was 16.83, 0.22, 0.22, 0.23, 0.26 and 0.25 micrograms.L-1, respectively. The lethal effect of DDVP on the adults at different exposure periods showed that their mortality was linearly related to the treated time, implying that the test colony of L. bostrychophila was susceptible to DDVP. In the practical fumigation, DDVP as a fumigant had a good effect on the pest control if the development stage, time and periods of treatment were appropriate.

[Host plant suitability and reproductive isolation of two Schizotetranychus bambusae populations from the bamboo species Phyllostachys pubescens and Neosinocalamus affini].

Development, survivorship, reproduction and procreation isolation of Schizotetranychus bambusae from the bamboo species Phyllostachys pubescens and Neosinocalamus affinis reared on different host plants were evaluated in laboratory. The results showed that the population of S. bambusae from Phyllostachys pubescens (PhS) failed to complete its life cycle when reared on the leaf of N. affinis. When the population of S. bambusae from N. affinis (NeS) was reared on the leaf of P. pubescens, the survivorship and fecundity decreased. The rm, lambda and Ro were 0.0391, 1.0399 and 2.5542, respectively. At 27 degrees C, when the PhS was reared on P. pubescens, rm, lambda and Ro were 0.1415, 1.1520, and 15.6298, respectively, whereas NeS was reared on N. affinis, rm, lambda, and Ro were 0.0993, 1.1044, and 10.0622, respectively. Reciprocal cross test between PhS and NeS showed tht the two populations could mate, but laid unfertilized eggs that produced male only, indicating the existence of reproductive isolation.