. Bulletin. Insekten; Schädlinge; Entomologie; Insekten; Schädlinge; Entomologie. 14 laubwechselnden Frucht Insekten und Insektizide. Thripse sind im Boden alle tMs-Zeit, und in den meisten Fällen innerhalb der Reichweite der Grubber, aber sie reifen und kommen auf die Bäume im März und April, vor dem Frühjahr Pflege begonnen wird. Natürliche Feinde. Die Birne thripse ist weitgehend von den gewöhnlichen preaaceous und parasitäre Insekten geschützt, denn es gibt eine so lange Zeit in der Erde versteckt. Eine successfid Parasit muss in einer Art parallel das Leben Ihrer Gastgeber, und wir haben keine Insekten, also auch das p folgt gefunden

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. Bulletin. Insects; Insect pests; Entomology; Insects; Insect pests; Entomology. 14 DECIDUOUS FRUIT INSECTS AND INSECTICIDES. Thrips are in the ground all of tMs time, and for the most part within reach of the cultivator, but they mature and arrive on the trees in March and April, before spring cultivating is begun. NATURAL ENEMIES. The pear thrips is largely protected from ordinary preaaceous and parasitic insects, because it spends so long a time hidden away in the ground. A successfid parasite must in a way parallel the life of its host, and we have found no insect which thus follows the pear thrips. Raphidians, or snake flies, their commonest enemies in the vSanta Clara Valley, feed rather on the younger forms than on the fully developed insects, and they do not appear early enough in the spring to constitute an effective check to the pest. To be competent thrips killers they would have to feed on other insects for perhaps ten months in the year and then, when thrips appear, suddenly change their diet and later, after tlu"ips have gone into the ground, as suddenly change back again to aphides or to something else. Such feeding habits are not to be expected in a nredaceous species. Ants were at one time thought to be doing much good as an enemy of the thrips. A certain orchardist brought in an ant with a thrips impaled in its jaws—the evidence complete. After a careful investi- gation, however, it was found that only a very small percentage of ants were actually killing thrips. Four hundred ants were examined as they descended a thrips-infested tree. Twelve of these carried something in their jaws and only 4 of these objects were thrips. Thus only 1 per cent of the ants on the tree were actually killing thrips aiul carrying them down. It has been a common observation among orchardists, however, that tlmps are not common where ants are unusually abundant. Spiders and mites are active enemies of thrips. In some of our breeding cages almost all of the thrips

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• bookcentury1900
• bookdecade1900
• booksubje
• booksubjectentomology