Host preference and effect of different population levels of Helicotylenchus digitiformis on some field crops

Host preference of Helicotylenchus digitiformis Ivanova, 1967 on 10 common field crops including cantaloupe (Samsuri), canola (Golden), clover, corn (704-Hybrid), cotton (Deltapine 16), lucerne (Hamedani), sugar beet (Pb8), tomato (Rutgers), turf grass (Sport) and wheat (Shiraz) was studied in two separate trials. Tests were performed in randomized complete block designs, with initial field populations of 1.49 and 4.33 nematodes/g of soil, under greenhouse conditions. The results showed that all plants are hosts for the nematode but the highest final population and reproduction factor were happened on the cotton (Deltapine 16) and corn (hybrid 704). In addition, to determine the damaging levels of the nematode on corn (hybrid 704) and cotton (Deltapine 16), two tests were conducted in randomized complete block designs with initial field population, ½ field population and control (4.33, 2.16 and Zero nematodes/g of soil, respectively) and six replicates, under greenhouse and microplot conditions. The results showed that all of the field populations under greenhouse conditions and treatments with nematode under microplot conditions caused significantly decreases in most of growth indices of corn plants. Nevertheless, the nematode population has not any significant effect on the growth indices of cotton, although the nematode multiplied on it and reproduction factor was more than one. Also, similar tests were carried out on two local wheat cultivars (Shiraz and Pishtaz), with field population, ½ field population, 1/3 field population and control (1.49, 0.75, 0.50 and Zero nematodes/g of soil, respectively) in a randomized complete block design with five replicates, under microplot conditions. Results showed that only the field population significantly caused decreases in most of growth indices of wheat (Pishtaz).