A field experiment was conducted, based on the premise that only when a determined economic damage threshold of the cotton bollworm is reached the application of selected chemical insecticides is justified.
The results obtained indicated that the economic threshold of damage for the pink bollworm (Pectinophora gossypiella) was either 17 larvae or 11% infestation/100 green bolls. For the spiny bollworm (Earias insulana) that level was 10 larvae and 8% infestation/100 green bolls (depending on the two years 1972 and 1973 averages).
Zusammenfassung
Zar wirtschaftlichen Schadensschwelle von 2 an Baumwolle schädlichen Lepidopteren‐Arten
In Freilanduntersuchungen sollte die Frage geklärt werden, bei welchem Befall durch Pectinophora gossypiella und Earias insulana jene Schadensschwelle erreicht wird, die den Einsatz chemischer Bekämpfungsmaßnahmen rechtfertigt. Die Ergebnisse aus den Jahren 1972 und 1973 zeigen, daß bei P. gossypiella 17 Raupen oder 11% Befall auf 100 grüne Baumwollkapseln sowie bei E. insulana 10 Raupen oder 8% Befall auf 100 grüne Kapseln jeweils das Erreichen der wirtschafllichen Schadensschwelle bedeuten.
Adults developed from diapause larvae fed on okra pods, cotton bolls and kenaf fruits, the mean longevities of female moths was always significantly longer than males. There are highly significant differences between the longevities of moths of both sexes fed as larvae on different host plants. Moths developed from larvae fed on okra pods or cotton bolls laid more eggs than those reared on kenaf fruits. No ripe eggs were present in the ovarioles of a newly emerged female. Ripe eggs were found after 17–18, 20–21 and 24–25 h in moths when fed as larvae on okra pods, cotton bolls and kenaf fruits, respectively. The number of oocytes did not increase during the first 28–30 h from emergence.
Zusammenfassung
Wirkung der Raupenernährung auf die Lebensdauer, Fruchtbarkeit und Eireifungsquote von Pectinophora gossypiella (Saund.) (Lep., Gelechiidae)
Die mittlere Lebensdauer weiblicher Falter von P. gossypiella, die aus Raupen hervorgingen, die mit Hibiscus esculentus‐Schoten, Baumwollekapseln und Hibiscus cannabinus‐Früchten gefüttert wurden, war stets signifikant größer als die der Männchen. Es bestanden hoch signifikante Unterschiede zwischen der Lebensdauer der Falter beiderlei Geschlechts, die von Raupen unterschiedlicher Ernährung stammten. Falter aus H. esculentus oder Baumwollekapseln fressenden Raupen legten mehr Eier als solche, die aus Raupen hervorgingen, welche H. cannabinus fraßen. Reife Eier wurden nach 17–18, 20–21 bzw. 24–25 h in den Eischläuchen solcher Falter gefunden, die aus Raupen stammten, welche mit H. esculentus, Baumwollekapseln, bzw. H. cannabinus gefüttert wurden. Die Zahl der Oozyten stieg während der ersten 28 bis 30 h nach dem Schlüpfen nicht an.
In Egypt, larvae of the first generation of Pectinophora gossypiella (Saunders) on cotton, which occur in July, do not go into diapause. In August, the larvae which enter diapause remain resting for a longer period than those which undergo diapause in subsequent months. The emergence of the majority of moths the following season from diapausing larvae occurs, therefore, within a short period and coincides with the first appearance of flower buds. There are two types of diapause, a short one lasting for an average of 42 days in 14.7 O/o of the larvae, and a long one lasting for an average of 184 in 85.3 O/o. The main diapausing sites are the dry bolls on cotton sticks stored on houses for fuel purpose, and infested bolls fallen and buried in the ground. If cotton sticks are used before cotton plants of next season start flowering infestation will be very much reduced. The fate of larvae buried in the ground is determined by the kind of crop which follows cotton in the rotation. Under clover, which is irrigated 10-12 times most buried larvae are killed; but under wheat which is irrigated 3 times most buried larvae can survive.
The total sugars, total nitrogen, phosphorus and potassium in the leaves of two castor-bean varieties, and the absolute requirements for these minerals and organic substances as dietary constituants for the larvae of the Eri silk worm, A t t a w s ricini Boisd. had been determined.The leaves of the two varieties showed different concentrations in their dietary constituants, where the red variety attained significantly higher values of total sugars, total nitrogen, phosphorus and potassium than the bloomy green. Similarly, the intake of all tested dietary constituants for larvae fed on the red variety was significantly higher than that of those fed on the green variety. The same trend could be applied to the approximate digestibility.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.