| China has the largest bamboo species in the world. Phyllostachys praecox is the most popular bamboo in Zhejiang province for its earlier shoot harvest, higher output and higher economic benefits. Due to these reasons, the planting areas of Phyllostachys praecox have been increasing at 15% for recent years. However, irrational cultivation causes the decreasing of the output of bamboo shoots, wireworm should be responsible for the crisis. The famers can not use pesticide because its toxicity and residue, which increasingly needs an effective, green and non-pollution bio-control way. The larvar of Melanotus cribricollis—wireworm is the study object in this paper. We isolated the parasitic fungus from dead worm and studied its biology characteristic. The bioassay was carried out as well.1. The species of the fungus was identified by morphology and molecular biology. The fungus was the Metarhizium anisopliae var. anisopliae's. The tissue of the dead wireworm was purified in PPDA medium, the mycelium was light yellow and spores were dark green. The spore production area was concentric circle around the centre, spores'arrangement was like chain. The single spore was colorless with tip end and another round end. The ITS sequence was compared with data of Genebank, we judged the fungi was Metarhizium anisopliae var. anisopliae's.2. The strain WP08 expanded faster in PPDA medium and had largest sporulation quantity. the spore production was 2.1×105spores/mm2 ,in SMAY medium,the spore production was 1.5×105 spores/mm2 and 0.9×105 spores/mm2 in PDA.In 25℃, the strain expanded fastest and the sporulation quantity was largest, the spore production was 9.05×108, the production in 30℃was 1.50×108, in addition, the expand speed in 30℃was similar with that in 25℃,but the sporulation quantity was lower. The strain was sensitive with the UV light, different time UV light could reduce the generation rate, and the longer UV light caused the lower generation rate. After 5min UV light, the generation rate after 12h and 24h was 60.2% and 76.2%, after 30min UV light, the the generation rate after 12h and 24h was 28% and 37.8%. The spore generation rate was lower when treated in 40℃, and longer heated time caused lower generation.After 30min heated, the the generation rate after 12h and 24h was 76.2% and 62.5%. With the time ?of heating increasing, the generation rate was lower, after 3h heated, the 12h and 24h generation rate was down to 28% and 37.8% .When pH was 7, the spore generation rate was highest, acidic and basic environment caused decrease of generation rate.3. We carried out bioassays of Metarhizium anisopliae var. anisopliae's pathogenicity on the larvae of Melanotus cribricollis (Faldermann), and studied the external environment condition for M. anisopliae var.anisopliae's pathogenicity. The results showed: In a conidia concentration gradient (104, 5×104, 105,5×105 106 ,5×106 ,107 condia/g dry soil), the higher conidia concentration resulted in more mortality ,which is 20%, 30%, 56.7%, 66.7%, 80%, 93.3% and 100%, respectively. Under four trial temperature ranges, 15℃, 20℃, 25℃, 30℃, increasing temperature caused higher mortality. No wireworm mycosis were observed in 15℃. In three other temperatures, the higher caused more mycosis. In soil with three moisture contents, 6%, 12%, 18%, mortality was higher when soil was moister. In 6% moisture soil, no wireworm was killed. We compared the two methods of fungus application, the result showed spores with soil caused higher death rate. |
PDF Full Text Request