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Influence of Pistia stratiotes Plant Quality on Fecundity and Egg Distribution of the Biological Control Agent Spodoptera pectinicornis.

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The potential fecundity of an insect may be influenced by the quality of the larval diet. Moreover, the distribution of eggs on the leaf surface may determine the success of that species colonizing the plant. This study determined the influence of larval host quality of the aquatic weed Pistia stratiotes on the fecundity and egg distribution of the biological control agent Spodoptera pectinicornis. Plants were grown with relatively low and high levels of NPK fertilizer. The results indicated that all three elements were higher overall in the high treatment and that nitrogen and potassium levels decreased in the high treatments from the inner to the outer leaves. The phosphorus and potassium levels increased in the low fertilizer treatment from the inner to the outer leaves. Female and male pupal biomass was significantly greater in the high fertilized treatments. Adult females that emerged from larvae fed the low fertilizer treatment lived 4.6 days or about one day longer than those from the high treatment. Most of the eggs were laid in egg masses, while overall about 12 percent were laid as solitary eggs. A significantly greater percentage of solitary eggs were laid by females from the low fertilizer treatment 17.3 - 3.4 percent compared with those from the high fertilizer treatment 8.3 - 2.3 percent. Total fecundity was greater P0.15 in the high fertilizer treatment. Females that emerged from larger pupae, regardless of larval diet, produced significantly more eggs. Most of the egg masses were laid on the lower surface of leaves, on leaf positions 5-8 counting from the young inner to the outer leaves and on days 1 and 2. Leaf position and day significantly influenced solitary egg position, where more eggs were found on leaves 1-8 during days 1-4.

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  • Biology
  • Chemical, Biological and Radiological Warfare

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