Leistungsfähigkeit der aphidophagen Gallmücke Aphidoletes aphidimyza (Rond.) (Diptera, Cecidomyiidae) in Abhängigkeit von verschiedenen Einflußfaktoren

Abstract

Factors influencing the efficiency of the aphidophagous gall midge, Aphidoletes aphidimyza (Rond.) (Diptera, Cecidomyiidae) Experiments on the efficiency of Aphidoletes aphidimyza (Rond.) were carried out in the laboratory at 21 °C and 75 % rel. humidity with its natural prey, the green peach aphid, Myzus persicae (Sulz.) reared either on brussel sprouts (Brassica oleracea var. gemmifera) or on artificial diet. When preying on 1–2 day‐old green peach aphids the total food consumption of the female larvae of A. aphidimyza was higher than that of the males. Larvae of both sexes, however, consumed about 50 % of their total food requirements in the last day—fourth day—of their development. Three‐day‐old larvae were inclined to pupate prematurely, if they were exposed to a period of starvation as short as only a few hours. The percentage of premature larvae inclined to pupate increased with extended period of starvation. Newly emerged females transfered reserve substances accumulated during larval development into egg production within the first two days of the adult life. The number of eggs thus produced was independent on the presence or absence of honeydew and males. The number of eggs produced did not change with increasing aging of the females, if they were supplied with only water. Adult midges of A. aphidimyza take in honeydew of the aphids, which is essential for the maintainance of their life. The life span of the males was, however, always shorter than that of the females. Also the total egg production of the females was significantly increased when honeydew was supplied. Under optimal nutritive conditions in both larvae and adult stage the honeydew intake of the famales made out 50–60 % of the total egg production, if the single females were kept together with only one male. Another 40–50 % could be realized through larval food without honeydew intake of the adults. These percentages varied, however, with the quality of the larval food and the proportion of ovipositing females. Insufficient feeding in the larvae stage due to starvation or less nutritiv quality of the supplied prey aphids (for instance, dead aphids killed with insecticides or through deep‐freezing) led to a reduction in egg production initially effected by larval reserve substances. Such a reduction could not be compensated through later intake of honeydew by adults. Mating is an absolute prerequisite for oviposition. This did not affect the number of eggs produced from the larval reserve substances in the first two days of adult life, if no honeydew was supplied. In the presence of honeydew, however, the weight of the females was significantly increased with a slight rise in egg production. During the whole adult life oviposition stimulated significantly the maturing of the eggs, and the total egg production was correspondingly increased significantly. The nutritive quality as well as the stimulating effect of honeydew on egg production, adult life span and oviposition was not significantly changed when fresh and 15 days'‐old honey...

Optimizing aphid biocontrol with the predator Aphidoletes aphidimyza, based on biology and ecology

“…As mentioned above, prey availability is crucial for the survival of early larval instars. The last instar is the most voracious, responsible for >75% of total aphid consumption during larval development; the larvae consume about 50% of their total food requirement in the last day of development (fourth day) …”

“…A mere few hours of starvation causes 3‐day‐old larvae to prematurely initiate pupation . However, survival and posterior adult emergence from premature pupa are seriously compromised (Boulanger FX, unpublished).…”

“…Newly emerged females transfer the reserves accumulated during larval development into egg production within the first 2 days of adult life . Female fecundity depends on the food quality (aphid species) and quantity (aphid availability) during larval development .…”

Prey Density Dependent Life Table of Aphidoletes Aphidomyza Rondani (Dip., Cecidomyiidae) Feeding on Aphis Craccivora Koch (Hem., Aphididae) under Laboratory Conditions

“…In addition, in previous studies it has been discussed that the variation in fecundity of A. aphidimyza might be related to variation in aphid density, host plant, genetic makeup, larval nutrition, and honeydew intake by females (El-Titi 1973;Mansour 1975;Kuo 1982;Havelka and Ruzicka 1984;Sell and Kuo 1987). The lowest fecundity was observed at 5 prey/ day, but a rapid increase was found at higher density levels with no significant difference between 20 and 40 prey per day and 60 and 80 prey per day during the larval stage.…”

Improved methods of testing and release of Aphidoletes aphidimyza (Diptera: Cecidomyiidae) for aphid control in glasshouses

“…They have also been observed mating on the edges of leaves. Sell & Kuo-Sell (1987) recorded that between 40 and 60% of the females were fertile, but did not give an explanation for this low percentage. Havelka & Zemek (1999) showed that there are large differences in fecundity between females from different geographical populations.…”