Biological Characteristics of Fusarium oxysporum f. sp.niveum Isolated from Watermelon Cultivated in Plastic Greenhouse and Indoor Toxicity Determination of Different Fungicides in Hainan Province of China

[ Objective] The paper was to study biological characteristics of Fusarium oxysporum f. sp. niveum in watermelon cultivated in plastic greenhouse in Hainan Province of China and to determine indoor toxicity of fungicides. [ Method] Effects of various factors on mycelial growth and spore germination were stud- ied, and the lethal temperature of spores and indoor toxicity of fungicides were also determined. [Result] The fungal mycelium had a better growth rate on water- melon juice medium than the others. The optimum temperature for mycelial growth and spore germination were 28 ℃ and 30 ℃, and the optimum pH values were 7 - 8 and 7 - 9, respectively. Light-dark alternation was conducive for mycelial growth. The lethal temperature of spore was 60 ℃ for 5 min. The fungal mycelium grew better while taking fructose and glucose as carbon sources and yeast extract and peptone as nitrogen sources. Toxicity determination showed that 50% pro- chloraz-manganese chloride complex WP had the greatest inhibition effect on mycelial growth, with the ECso value of 0.730 9 μg/mL; followed by 32.5% benzoic azoxystrobin SC, 30% benzoylate· propieanazol EC, 10% difenoconazole WG, 25% bromothalonil · carbendazim WP and 25% bromothalonil WP, with the ECso values from 1.884 7μg/mL to 8. 161 0μg/mL. [Conclusion] The study provided basic data for field control against F. oxysporum f. sp. niveum on watermelon cultivated in plastic greenhouse in Hainan Province.

Study on Biological Characteristics and Toxicity Determination of Colletotrichum orbiculare Causing Anthracnose of Watermelon in Hainan Province

[Objective] This paper was aimed to study the biological characteristics of Colletotrichum orbiculare（Berk.et Mont.） Arx, and accomplish the preliminary screening the test of fungicides. [Method]The pathogen was isolated from the infected leaves of watermelon collected from greenhouse in Hainan Province. The biological characteristics of C. orbiculare and indoor toxicity of fungicides were studied. [Results] The mycelium grew fastest on the medium with leaf extract of watermelon. The optimum temperature for mycelial growth and spore germination was 28 and 30 ℃, and the optimum pH was 7-9 and 6-8, respectively. The continuous darkness condition was most suitable for mycelial growth. The lethal temperature of spore was 55 ℃ water bath for 10 min in water bath. The suitable carbon sources were maltose, L-arabinose and glucose, and the suitable nitrogen sources were yeast extract, beef extract and peptone. In the indoor toxicity determination, 32.5% Benzoic azoxystrobin SC, 50% Dichlorotetrakis WP and 10% Difenoconazole WG showed better inhibition effects against the mycelial growth of C. orbiculare, with the EC50 values of 0.018 0, 0.060 2 and 0.471 5 μg/ml, respectively. [Conclusion]The research provided theoretical basis for the control of watermelon anthracnose in watermelon fields.

Indoor Toxicity Determination of Several Pesticides to Ceratovacuna lanigera( Zehntner)

Toxicity of 96% chlorpyrifos TC, 98% imidacloprid TC, 93% thiamethoxam TC and mixed pesticides of chlorpyrifos with other two agents （D ＋ B, D ＋ S） to C. lanigera （Zehntner） were determined under laboratory conditions by leaf dipping method. The results showed that all of the pesticides had high toxicity with the order of thiamethoxam TC 〉 imidacloprid TC 〉 D ＋ B 〉 chlorpyrifos TC 〉 D ＋ S. The results provided theoretic basis for selecting suitable insecti- cides to control the C. lanigera （Zehntner）.