[Control effects of Mikania micrantha alcohol extract on citrus red mite Panonychus citri].

This study showed that spraying 0.2 and 0.4 g x L(-1) Mikania micrantha alcohol extracts on Panonychus citri could significantly decrease the survival rates of P. citri eggs, larvae and nymphs, and 0.1 g x L(-1) M. micrantha alcohol extract could also significantly decrease the survival rates of larvae and nymphs. In a no-choice test, both the fecundity and the longevity of female P. citri fed on the leaves treated with all three test concentrations 0.1, 0.2 and 0.4 g x L(-1) of M. micrantha alcohol extracts were significantly reduced, compared with those fed on alcohol-treated leaves. In a field experiment, the efficacy of M. micrantha alcohol extracts at three test concentrations was compared with water, alcohol, and 15% Pyridaben, an acaricide widely used in commercial control of red mite in sweet orange orchards. The survival rates of P. citri eggs, larvae and nymphs in all three M. micrantha treatments were lower than the control, and the interference index of population control (IIPC) was 0.518, 0.292 and 0.277, respectively, while the IIPC for the Pyridaben treatment was 0.945, with a control efficacy of only 5.52%. M. micrantha extract had an increased control effect with its increasing concentration, and was safer to natural enemies than 15% Pyridaben. The leaves in the three M. micrantha treatments were less damaged, and their color was much deeper than that of the other three treatments. Therefore, M. micrantha alcohol extract provided a better control of citrus red mite populations than Pyridaben.

[Suppressive effects of non-preferable plant alcohol extracts on diamondback moth Plutella xylostella population].

In this paper, a life table and an interference index of population control (IIPC) were used to evaluate the effects of spraying the alcohol extracts of non-preferable plants on the dynamics of diamondback moth Plutella xylostella) population. The results showed that the alcohol extracts of Eupatorium odoratum, Lantana camara and Wedelia chinensis were available to protect kidney bean from Plutella xylostella infestation. Their IIPC were 0.110, 0.136 and 0.165, and the efficacies of controlling P. xylostella were 89.0%, 86.4% and 83.5%, respectively, compared with control.

[Bioactivity of Myoporum bontioides extracts to Plutella xylostella].

The bioactivity of Myoporum bontioides extracts to Plutella xylostella was studied with IIPC as evaluated index. The results showed that petroleum ether and chloroform extracts had a higher activity than ethyl acetate and alcohol extracts. At 0.01 gDW x ml(-1), the ODR of petroleum ether and chloroform extracts was 84.69% and 79.90%, and 76.47% and 45.70% after treated 1d and 3d, while the IIPC was 0.1565 and 0.2055, respectively. Provided with a higher concentration of 0.05 gDW x ml(-1), the ODR was 88.52% and 72.25%, and 87.33%, 58.37%, while the IIPC was 0.1125 and 0.2620, respectively. From the chloroform extract of Myopdrum Bontioides, three flavonoids, 2, 3-dihydro-5, 7-dihydroxy-2-phenyl-4H-1-Benzopyran-4-one (I), 3, 5, 7-trihydroxy-2-phenyl-4H-1-Benzopyran-4-one (II) and 5, 7-dihydroxy-3-methoxy-2-(4-methoxyphenyl)-4H-1-Benzopyran-4-one (III), were isolated, and their structure were identified based on the analyses of physical and spectrum data. Among these compounds, (II) had a better bioactivity to Plutella xylostella.

[Bioassay on oviposition repellency of non-preferable plant extracts against citrus red mite Panonychus citri].

The oviposition repellency of the alcohol extracts from 50 species of non-preferable plants and azadirachtin against citrus red mite (Panonychus citri) was determined using laboratory bioassays. In choice tests, the extracts from 42 of the 50 plant species and 1% azadirachtin (2000 x) significantly reduced oviposition 1d after treatment. The repellency effect of the extracts from the 42 plant species was better than that of azadirachtin. Mikania micrantha extract had the best result, with an Interference Index of Population Control (IIPC) of 0.087 1 d after treatment, and significantly reduced oviposition for 9 d, while the extracts from Sesbania cannabina, Allium tuberosum, Paederia scandens, Duranta erecta and Dicranopteris pedata also had good effects, with an oviposition repellency of over 70% 1 d after treatment, and significantly reduced oviposition for 4-6 d. The effect became weaker as time went on. None of the extracts showed significant oviposition attraction.

[Chemical components of volatile oil from Mikania micrantha and its biological activity on insects].

The chemical components of volatile oil from Mikania micrantha were analyzed by GC/MS. Twenty-two compounds were identified, and monoterpenes and sesquiterpenes as well as alcohol and ketone with their derivatives were major components. Biological activity of volatile oil on insect was investigated. The results showed that the volatile oil had significant deterrent effect on oviposition of Plutella xylostella, Phyllotreta striolata and Phaedon brassicae at dose of 5-10 microliters.plant-1. They also possessed established contracting toxicity, and their rectifying reduce rates for Lipaphis erysimi were 50.0%, 59.86%, 62.51% at concentration of 500, 750, and 1000 mg.L-1, respectively. However, they had not fumigating toxicity for virginogeniae, L. erysimi, 2nd instar larvae of P. xylostella, and adult of P. striolata at concentration of 500 mg.L-1.

[Suppressive effect of secondary substances on Liriomyza sativae population].

Life table and interference index of population control (IIPC) were used to evaluate the effects of spraying alcohol extracts of plant secondary substances on the population of Liriomyza sativae. Field experiment results showed that alcohol extracts derived from Lantana camara, Eupatorium odoratum, and Wedelia chinensis, and one kind of commercial petroleum spray oil were positive to protect kidney bean from infestation of L. sativae. The IIPC of these repelling substance compared with control were 0.136, 0.163, 0.213, and 0.222, and the control effects on L. sativae were 86.4%, 83.7%, 78.7%, and 77.8%, respectively. At the same time, the parasitism of vegetable leafminer was increased compared with control, indicated that the effects of parasitism were increased. The results indicated that these substances had strong effects in controlling the population of L. sativae.

[Allelopathic potential of volatile oil from Mikania micrantha].

Mikania micrantha, an exotic plant species, is an important weed in south China. The volatile oil of the weed species had significant biological activities on plants and their pathogens, particularly Pyricularia grisea. The results showed that the seeding growth of 6 plant species decreased obviously when exposed to increasing concentration (200, 400, 800, 1600 mg.L-1) of the volatile oil. The fresh weight of all test plants decreased, and the emergence of all test plants delayed for 1-2 days under soil treatment (2500 g.hm-2). The inhibitory effect of volatile oil of M. micrantha at its medium concentration was the most strong on Pyricularia grisea; secondary on Fusarium oxysporum; but weak on Phytophthora nicotianae. The inhibitory rate was 53.38%, 28.66% and 18.69% for the three plant pathogens, respectively.