Meloidogyne hapla in Organic Soil: Effects of Environment on Hatch, Movement and Root Invasion

Abstract

Using new techniques, hatch and movement of Meloidogyne hapla and nematode invasion o f lettuce roots growing in organic soil were studied under controlled soil conditions of temperature, moisture, O[sub2] and CO[sub2]. When O[sub2] levels of 2.7, 5, 10, 21 and 40% with CO[sub2] maintained at 0.03% were used, O[sub2] below 21% or at 40% reduced nematode activities compared with those at 2 l%. When CO[sub2] levels of 0.03, 0.33, 2.8, 10 and 30% with O[sub2] maintained at 21% were used, all levels above 0.03% CO[sub2] resulted in less activity than at 0.03% except for more invasion at 0.33% than at 0.03%. Results suggested M. hapla was tolerant of CO[sub2] below 10% but adversely affected by 30% CO[sub2]. Effect of O[sub2] was influenced by the level of CO[sub2] present. No larvae invaded roots at 3.2% O[sub2] and 18.6% CO[sub2] but hatch and movement occurred. Night and day temperatures of 21.1 and 26.7 C were more favorable for movement and invasion than 15.5 and 21.1 C, 26.7 and 32.2 C or 26.7 and 32.2 C. Optimum moisture for movement was 80 cm suction and for invasion was 100 cm. Key Words. Soil atmosphere, soil moisture, soil temperature, lettuce.