Effects of four chemosterilants on Bactrocera tau.

Bactrocera tau (Walker) is a fly pest species mainly distributed in Southeast Asia and the South Pacific; it causes substantial ecological and economic issues because of its destructiveness and rapid reproduction. Chemical sterilization technology can reduce the use of insecticides and is widely applied for insect pest control. In this study, the sterilization efficacy of varying concentrations of four chemosterilants, namely, hexamethylphosphoramide (HMPA), CSII Aqua, 5-fluorouracil (5-FU), and colchicine, on adult pumpkin flies was investigated. The results indicated that a solution of 0.03% HMPA had the highest sterilization efficacy. When the number of sterile males was equal to or exceeded 20 times that of untreated males, the hatching rate of offspring eggs was less than 10%. Chemosterilant treatment significantly altered the levels of acid phosphatase (ACP), alkaline phosphatase (AKP), and B. tau vitellogenin (BtVg); these substances have an important impact on reproductive development. The treatment also decreased the size of the reproductive organs (i.e., testes and ovaries). Our results suggest that 0.03% HMPA has unique sterilization properties and may represent a new chemical agent for the control of B. tau populations in agricultural settings.

Insecticidal activity of pogostone against Spodoptera litura and Spodoptera exigua (Lepidoptera: Noctuidae).

BACKGROUND: Essential oil of Pogostemon cablin (Blanco) Benth. has been reported to exhibit strong insecticidal activities, but few studies have focused on the insecticidal activity of its main individual constituent, pogostone (PO). The goal of this research was to investigate the insecticidal activity of PO against two harmful noctuid insects, Spodoptera litura (Fabricius) and Spodoptera exigua (Hübner). RESULTS: In a no-choice assay, PO exhibited strong antifeedant activity against S. litura and S. exigua. PO showed pronounced larvicidal activities, including oral toxicity (LC50 986.88 mg L(-1) and 545.61 mg L(-1) respectively) and contact toxicity (LC50 1041.42 mg L(-1) and 519.48 mg L(-1) respectively) against these two noctuid insects. Additionally, PO treatment significantly increased the larval and pupal developmental period. Furthermore, PO showed moderate ovicidal activities and influenced the emergence and deformity of the moth. However, PO failed to exert a potent effect on adult development. These tested parameters proved to be dose dependent for both insect species. CONCLUSION: PO possesses strong insecticidal activities, especially antifeedant, larvicidal, growth inhibitory and pupicidal activities, against S. litura and S. exigua. PO may partly account for the insecticidal activity of patchouli oil and may be a promising candidate for the control of agricultural insects.

[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.

[Bioactivity of volatile oils from Myoporum bontioides on Plutella xylostella].

This study showed that the volatile oils from Myoporum bontioides had a significant repellent action on Plutella xylostella. When Plutella xylostella adults entered into the 4-arm selective olfactometer, the preferred times and average staying duration, in the order from more to less, were 3, 1, 4, and 2 arms, which showed a tendency of keeping away from the treatment arms. The males were more sensitive to the volatile oils than the females, when the velocity of flow was 200 ml.min-1. On the first day of the 3rd bioassay, the oviposition deterrent rate and IIPC of the volatile oils on Plutella xylostella adults was 94.48% and 0.0552, respectively. A liquid component of the volatile oils from Myoporum bontioides was isolated, purified, and identified as myoporone.

[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.

[Suppressive effect of plant secondary substances and ecological measures on Liriomyza sativae population].

A state-space population model was used to evaluate the effect of plant secondary substances and ecological measures on the population dynamics of the vegetable leafminer, Liriomyza sativae. In the vegetable field, by spraying alcohol extracts of Lantana camara (1 g.100 ml-1), or spraying the petroleum spray oil (300 x), or releasing the parasitoids, the indices of population control(IIPC) of L. sativae compared with control were 0.136, 0.222 and 0.292, respectively, but the index of population trend of vegetable leafminer in control was as high as 11.15, the population of vegetable leafminer still increased by control each one of the methods. Based on the state space analysis, the controlling effects of the alcohol extracts combining with other methods on vegetable leafminer were stimulated, which showed that the alcohol extracts from Lantana camara (1 g.100 ml-1) plus horticultural spray oils(300 x) used once at the period of adult summit, and the parasitoids released 1000 to 2000 per 100 m2 gave the index of population of vegetable leafminer below 1, means that vegetable leafminer would be controlled sustainably.