Effects Of Different Temperatures And Light Conditions On The Growth, Development And Fecundity Of Bradysia Difformis Frey

Bradysia difformis is a Dipteran in the family Sciaridae(fungus gnats)(Frey,1948). Bradysia difformis is one of the most common types of fungus gnats occurring in edible mushrooms, medicinal fungus and other greenhouse plants. Bradysia difformis Frey is the most main types of insect pests occurring in not only edible mushrooms but also Chinese chives. What is more, the black fungus gnat has became the dominant species in leek planting regions in Tianshui city, Gansu province, and occurring with Bradysia odoriphaga Yang et Zhang.This study aimed to provide reference material of forecasting and prevention about Bradysia difformis Frey by rearing it with leek and researching effects of different temperatures, photoperiods,light intensities and sex ratios on the growth, development and fecundity of the insect.1 Effects of different temperatures on the growth, development and fecundity of Bradysia difformis FreyRearing Bradysia difformis Frey with leek, under 10, 15, 20, 25 and 30 ℃ constant temperature conditions. The results showed that the developmental duration of Bradysia difformis Frey were progressively shorter with the increase of temperature under 10 ℃, and the developmental duration from egg to pupa was the longest, with an average of 71.96 d, while under 30 ℃, the average developmental duration from egg to pupa shorten to 16.28 d. Developmental threshold temperature of eggs, larvae, pupae and eggs- pupae were respectively 4.04, 5.79, 8.38 and 4.97 ℃, the effective temperature were respectively 102.36, 218.03, 48.57 and 395.79 degree-days. Adult life were gradually shorter with the increase of temperature, and female life expectancy was longer than males. Fecundity up to the highest 117.25 under 25 ℃, but under 10 ℃, it reach to the lowest 43.87. At 10 ℃ to 25 ℃, as the temperature rises gradually, its intrinsic rate of increase also improved, under 25 ℃ reaches to 0.2072. There are significant differences between 4 temperatures.2 Effects of different light conditions on the growth, development and fecundity of Bradysia difformis FreyRearing Bradysia difformis Frey with leek, under 0, 8, 12, 16 and 24 h/d different photoperiods and 588, 1275, 1575, 2072 and 3323 Lx light intensities, respectively. The results showed that net reproductive rate and intrinsic of increase rate of Bradysia difformis Frey were 42.28 and 0.2032 at 16 h/d, in addition, they were both higher than other 4 photoperiods significantly. Fecundity also up to the highest 101.54 under 16 h/d. At 16 h/d, the developmental duration from egg to pupa was the shortest, with an average of 16.86 d, while under 12 h/d, the average developmental duration from egg to pupa extended to 21.50 d. In 588 Lx, its intrinsic of increase rate was 0.2032, higher than other 4 light intensity conditions significantly. So, under 16 h/d and 588 Lx conditions, the growth, development and fecundity of Bradysia difformis Frey reach to a good state.3 Effects of different ratios on the fecundity and hatching rate of Bradysia difformis FreyRearing Bradysia difformis Frey with leek, under five different temperature conditions(10, 15, 20, 25 and 30 ℃) and five different sex ratios(1:1, 1:2, 1:3, 2:1 and 3:1). Experiment results showed that temperatures had significant influence on adult life, but sex ratios effect on adult life were not remarkable. The average number of eggs and hatching rate decreased with the increase of proportion of females of sex ratio structure. The hatching rate up to the highest 94% under 25 ℃ with the sex ratio 1:1. And fecundity of female up to the highest 117.30 under the same condition.