Abstract
Ten 4,7-methanoisobenzofuran-1(3H)-ones were synthesized and their insecticidal activities against the insect pest Diaphania hyalinata were evaluated. The most active substances have been selected from the initial screening to find the dose to kill 50 (LD50) and 90% (LD90) of the melonworm. Time-mortality curves of the three selected formulations at the LD90 concentration have been made against D. hyalinata. From the time-mortality curves we found that the formulation (3aR,4R,5S,6S,7S,7aS)- and (3aS,4S,5R,6R,7R,7aR)-5,6-dichlorohexahydro-4,7-methanoisobenzofuran-1(3H)-one + (3aR,4R,5R,6R,7S,7aS)- and (3aS,4S,5S,6S,7R,7aR)-5,6-dichlorohexahydro-4,7-methanoisobenzofuran-1(3H)-one has killed 50% of the melonworm after 2 h, presenting the best knockdown effect. Bioassays against Solenopsis saevissima and Tetragonisca angustula were carried out for the lactones selected in the initial screening against D. hyalinata. The formulation (3aS,4R,5S,6S,7S,7aR)- and (3aR,4S,5R,6R,7R,7aS)-5,6-dibromohexahydro-4,7-methanoisobenzofuran-1(3H)-one + (3aS,4R,5R,6R,7S,7aR)- and (3aR,4S,5S,6S,7R,7aS)-5,6-dibromohexahydro-4,7-methanoisobenzofuran-1(3H)-one has killed 31.25 and 68.30% of the pest natural enemy and the pollinator bee, respectively. At the same concentration this formulation killed 90% of D. hyalinata. The selectivity in favor of the non-target organisms has rendered this formulation a position as a promising agrochemical.
Highlights
The melonworm Diaphania hyalinata (Lepidoptera: Crambidae) is an important pest of plants of the family Curcubitaceae and occurs in the Americas.[1,2] The leaves are first attacked by these insects, limiting plant photosynthesis, growth and development
Cycloaddition reaction of furan-2(5H)-one 1 and cyclopentadiene has been employed in first stage of our work for the synthesis of 4,7-methanoisobenzofuran1(3H)-ones
The double bond is confirmed by the multiplet at 6.25-6.33 ppm in the 1H nuclear magnetic resonance (NMR) spectrum
Summary
The melonworm Diaphania hyalinata (Lepidoptera: Crambidae) is an important pest of plants of the family Curcubitaceae and occurs in the Americas.[1,2] The leaves are first attacked by these insects, limiting plant photosynthesis, growth and development. After this the stems and shoots are damaged leading to the plant death. Solenopsis saevissima, an ant widely distributed in South America, is among the natural enemies of D. hyalinata Worker individuals of this species are aggressive and have a painful sting.[4] Predation by S. saevissima contributes significantly to the biological control of agricultural crops.[5] Species of the genus Solenopsis have been considered important predators contributing to insect pest reduction in the tropics and subtropics.[6]
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