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Accueil du site → Master → Etats Unis → 1968 → Bionomics of the alfalfa stem nematode, Ditylenchus dipsaci, in Arizona

University of Arizona (1968)

Bionomics of the alfalfa stem nematode, Ditylenchus dipsaci, in Arizona

Ellis, Kenneth Carl

Titre : Bionomics of the alfalfa stem nematode, Ditylenchus dipsaci, in Arizona

Auteur : Ellis, Kenneth Carl

Université de soutenance : University of Arizona

Grade : Master of Science (MS) 1968

Résumé
The bionomics of the alfalfa stem nematode, Pitylenchus dipsaci (Kuhn 1857) Filipjev 1926, attacking alfalfa in Arizona was studied for a period of 11 months. During this time it was found that when the nematodes were inactive, as expressed by lack of symptoms in the host, they were concentrated in the crowns of the alfalfa plants and were almost exclusively pre-adult forms. Observations on nematode activity in relation to temperature and stage of development during this time indicate that the tempera ture range between 76 F and 38 F was the most favorable for nematode activity, reproduction, and development under the conditions of this study. Time vs. temperature studies of dessicated pre adults show that for any interval of time survival was greater at 4 C than at 25 C or 45 C. Survival at 45 C was very low at any time interval, never being higher than .2%. Time vs. temperature studies of D. dipsaci in distilled water showed that after 2 days at 35 C or 45 C all the nematodes were killed. The highest percent of survival was again at 4 C. There is evidence that dessicated D. dipsaci can withstand higher temperatures than D. dipsaci in water. Fresh fecal samples collected from sheep pastured on an alfalfa field heavily infested with stem nematodes were checked for the presence of D. dipsaci. No eggs, larvae, or adults were found and it was concluded that D. dipsaci could not survive digestive action.

Mots clés : Alfalfa — Diseases and pests. ; Nematode diseases of plants.

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