Artificial Diet Influences Population Growth of the Root Maggot Bradysia impatiens (Diptera: Sciaridae)

In order to investigate the effects of artificial diets on the population growth of root maggot Bradysia impatiens, its population growth parameters were assayed on eight artificial diets (Diet 1, D2, D3, D4, D5, D6, D7, and D8). Results showed that developmental duration from egg to pupa was successfully completed on all eight artificial diets. However, the egg to pupal duration was shortest, while the survival rate of four insect stages was lowest when B. impatiens was reared on D1. When B. impatiens was reared on D7 and D8, the survival rate, female longevity, and female oviposition were higher than those reared on other diets. When B. impatiens was reared on D7, the intrinsic rate of increase (rm = 0.19/d), net reproductive rate (R0 = 39.88 offspring per individual), and finite rate of increase (λ = 1.21/d) were higher for its population growth with shorter generation time (T = 19.49 d) and doubling time (Dt = 3.67 d). The findings indicate that the D7 artificial diet is more appropriate for the biological parameters of B. impatiens and can be used an indoor breeding food for population expansion as well as further research. We propose that vitamin C supplement added to the D7 is critical for the improvement of the B. impatiens growth.

Aspectos morfo-fisiológicos del tracto digestivo en larvas de IV estadio de Bradysia impatien (Diptera: Sciaridae)

La morfología, citología y algunos aspectos fisiológicos del tracto digestivo de larvas de cuarto estadio del siárido Bradysia impatiens se estudiaron utilizando microscopía de campo brillante. Se observó la división del tracto digestivo (estomodeo, mesenterón y proctodeo); las células que lo componen son columnares, regenerativas y endocrinas. Las larvas no presentan buche y la digestión del bolo alimenticio se realiza en el intestino medio; tienen dos ciegos gástricos bien desarrollados, que permiten suponer que existe una gran absorción de nutrientes. La membrana peritrófica es del tipo II, con un tamaño de poro que permite el paso de moléculas de hasta 150 kDa y divide el intestino medio en dos regiones, los espacios endo y ecto peritrófico. Tiene cuatro tubos de Malpighi. El intestino medio posee un gradiente de pH que va de alcalino en el intestino anterior a neutro en los ciegos gástricos y el intestino posterior. Tiene un mecanismo de recirculación que mejora la digestión y reutilización de enzimas digestivas, que va del espacio endoperitrófico al ectoperitrófico y viceversa. Las características morfofisiológicas mostradas en las larvas de B. impatiens permiten confirmar que son organismos bien adaptados como detritívoros. Además, la membrana peritrófica protege al intestino medio de agentes patógenos.

Effects of host plants nutrient on the nutrient in Bradysia cellarum and Bradysia impatiens

The chive maggots Bradysia cellarum the fungus gnats Bradysia impatiens are two main root pests of plants. They can coexist on same host plants and have become devastating pests on liliaceous crops and edible fungi. Their growth and development are affected by nutrients of their host plants. We studied the effects of different host plant nutrients on the nutrient contents of these two Bradysia species. We assayed the nutrients in the roots of chive, board bean (B-bean), lettuce, cabbage, wild cabbage (W-cabbage) and pepper, and analysed the nutrient content of the two Bradysia species after three continuous generations of feeding on these different host plants. There chive and B-bean had higher contents of protein, free amino acid and starch than in other host plants. Soluble sugar, fat and protein contents were significantly higher in both Bradysia species when they were reared on chive and B-bean than when reared on cabbage, lettuce, W-cabbage and pepper. Our study provides a reference for further studies on the host range of the two Bradysia species, as well as knowledge for consideration in field crop rotations.

Development of Lycoriella ingenua and Bradysia impatiens on different phases of agaricus composts

Fungus gnats are small, dark colored, mosquito like fragile insects. They can be encountered all around the world, excluding places with extreme climate. Gnats prefer habitats that are damp with high relative humidity and rich in organic debris. Most of the species are not considered to be harmful in agriculture, but some may cause serious damage, especially in forcing of vegetable or ornamental plants. In mushroom production, however, they are considered as the most destructive pests; the damage caused by them alone can result in huge loss for mushroom farmers. In the Hungarian mushroom industry, fungus gnats damage mainly white-button mushroom, oyster mushroom and pioppino productions. Lycoriella ingenua (Dufour, 1839) and Bradysia impatiens (Johannsen, 1912) are the two most commonly found fungus gnat species from the family Sciaridae on Hungarian mushroom farms. We have conducted an experiment with the two aforementioned species, to find out, whether they can fully develop into adults, feeding purely on Agaricus compost diet. We used unspawned white button mushroom compost (phase 2) and spawned compost which has been colonized by the mycelia of Agaricus bisporus (phase 3). We did not conduct any experiment with the first compost phase, as it undergoes pasteurization, which eliminates any pests in it. We recorded emerging gnats only from phase 2 compost. Neither L. ingenua, nor B. impatiens could complete its development on phase 3 compost diet, furthermore not even pupae were observed in these breeding pots. From pots containing phase 2 compost, a total of 1607 adults emerged. The number of B. impatiens adults was 653, and 954 for L. ingenua. Sex ratios for the two species were different. For B. impatiens, the number of females was 1.36 times greater than that of males, in L. ingenua there were 1.7 times more males than females in total. Swarming took approximately 6 days for B. impatiens and 10 days for L. ingenua. From the experiment we can conclude that phase 3 compost, which is well interwoven with Agaricus bisporus mycelia is not suitable for B. impatiens and L. ingenua to complete their whole life cycle.