The Zucchini yellow mosaic virus （ZYMV） （Potyvirus） on “zucchini” presents great economic importance for Malagasy farmers. Numerous aphid species （Hemiptera： Aphididae） spread viral particles, which are easil...The Zucchini yellow mosaic virus （ZYMV） （Potyvirus） on “zucchini” presents great economic importance for Malagasy farmers. Numerous aphid species （Hemiptera： Aphididae） spread viral particles, which are easily transmitted mechanically, too. Farmers ignored this disease, therefore, its control became extremely difficult with insecticides. This study aimed to evaluate efficacy of chili pepper extracts. Treatments vary as a function of its initiations and were repeated at weekly intervals until harvest. It was conducted in market gardens around the town of Antananarivo. The study compared four treatments and repeated three times： firstly, plots received a protection as soon as installation of culture （preventive protection）; secondly, plots received treatment with low infestation （about a quarter plants infested） （late protection）; thirdly, plots received treatment with high infestation （about half of plants infested） （latest protection）; lastly, plots without treatment （the control）. As a result, pepper extracts can provide a significant level to control against aphids attack, and permit to delay virus installation on plots, which received treatment as soon as implementation of culture. However, it cannot eradicate and cannot limit extend of virus disease on plots already infested. Economic analysis shows that preventive treatment of pepper extracts to fight virus attack provides an even greater return on its investment than all other terms. Thus, use of pepper extracts can reduce chemical treatment and pollution.展开更多
In this paper the management model a two-species fishery involving impulsesis investigated by using optimal impulsive control theorem. Optimal impulsive harvesting times andthe corresponding optimal harvesting populat...In this paper the management model a two-species fishery involving impulsesis investigated by using optimal impulsive control theorem. Optimal impulsive harvesting times andthe corresponding optimal harvesting population levels in different cases are obtained.展开更多
文摘The Zucchini yellow mosaic virus （ZYMV） （Potyvirus） on “zucchini” presents great economic importance for Malagasy farmers. Numerous aphid species （Hemiptera： Aphididae） spread viral particles, which are easily transmitted mechanically, too. Farmers ignored this disease, therefore, its control became extremely difficult with insecticides. This study aimed to evaluate efficacy of chili pepper extracts. Treatments vary as a function of its initiations and were repeated at weekly intervals until harvest. It was conducted in market gardens around the town of Antananarivo. The study compared four treatments and repeated three times： firstly, plots received a protection as soon as installation of culture （preventive protection）; secondly, plots received treatment with low infestation （about a quarter plants infested） （late protection）; thirdly, plots received treatment with high infestation （about half of plants infested） （latest protection）; lastly, plots without treatment （the control）. As a result, pepper extracts can provide a significant level to control against aphids attack, and permit to delay virus installation on plots, which received treatment as soon as implementation of culture. However, it cannot eradicate and cannot limit extend of virus disease on plots already infested. Economic analysis shows that preventive treatment of pepper extracts to fight virus attack provides an even greater return on its investment than all other terms. Thus, use of pepper extracts can reduce chemical treatment and pollution.
基金This research is supported by the Foundation of Educational Committee of Liaoning Province (No.20331080)
文摘In this paper the management model a two-species fishery involving impulsesis investigated by using optimal impulsive control theorem. Optimal impulsive harvesting times andthe corresponding optimal harvesting population levels in different cases are obtained.
