Abstract
AbstractA gall midge, Pinyonia edulicola Gagné (Diptera: Cecidomyiidae) causes serious damage to pinyon, Pinus edulis Engelm., in urban areas of Colorado. The gall midges infest developing needles, causing them to grow abnormally into spindle‐shaped structures and to drop from the tree at the end of the first year, some five to seven years prematurely. Heavy infestations may result in substantial defoliation. Tests to determine efficacy of several insecticidal materials for control of P. edulicola were conducted in a residential area of Fort Collins during 1981 and 1982. Observations were also made on the population levels of the parasitoid Platygaster sp. (Hymenoptera: Platygasteridae). Sticky traps, plastic collection bags, and periodic observations were used to determine the onset of adult emergence to facilitate timing of application of treatments. The materials tested included acephate, carbofuran, oxydemetonmethyl, dimethoate, and two soap products reported to have insecticidal properties. Results indicate that effectiveness of treatments is dependent upon proper rate, timing, and method of application. None of the materials tested in 1981 reduced the number of midge infested needles. Carborufan, dimethoate and oxydemetonmethyl reduced infestation levels significantly in 1982 trials but differences among those treatments were not significant. Infestation levels on trees treated with acephate and insecticidal soap were not different from the check plots. About 1.7 percent of the midge population was parasitized by Platygaster sp.ZusammenfassungUntersuchungen über Schlüpfen, Parasitierung und Bekämpfung der Nadelgallmücke Pinyonia edulicola Gagné an Pinus edulis in ColoradoIn den Siedlungen von Colorado verursacht die Gallmücke P. edulicola an Pinus edulis erhebliche Schäden, indem sie an den Nadeln spiralförmige Verkrümmungen und Gallen hervorruft, durch welche die Nadeln 5–7 Jahre zu früh abfallen. Der Befall kann bis zum völligen Entnadeln gehen. Versuche über die Wirksamkeit verschiedener Insektizide zur Bekämpfung der Gallmücke wurden 1981 und 1982 in Fort Collins durchgeführt. Gleichzeitig erfolgten Beobachtungen über den Parasitoiden Platygaster sp. Zur zeitlichen Festlegung der Bekämpfungsaktion wurden Lichtfallen, Plastikbeuten und periodische Beobachtungen über das Erscheinen der Gallmücke verwendet. Die getesteten Insektizide waren Acephate, Carbofuran, Oxydemetonmethyl, Dimethoate sowie 2 Seifenverbindungen. Die Ergebnisse zeigten, daß die Wirksamkeit von der Dosierung, der Methode und dem Zeitpunkt abhing. 1981 konnten die Insektizide die Zahl der befallenen Nadeln nicht verringern. Dagegen reduzierten 1982 Corbofuran, Dimethoate und Oxydemetonmethyl den Befall signifikant. Die zwischen diesen Wirkstoffen bestehenden Unterschiede waren nicht gesichert. Dagegen zeigten die 2 Seifenverbindungen keine Wirkung. Etwa 1,7% der Gallmücken‐Population wurde von der Schlupfwespe Platygaster sp. parasitiert.
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