Effects of pat size, simulated rainfall, and temperature on the mortality of immature face flies (Musca autumnalis degeer); and lateral migration of infective Trichostrongyle nematodes onto vegetation in Eastern Tennessee

The effects of pat size, simulated rainfall, and temperature manipulated by different shading regimes on face fly (Musca autumnalis DeGeer) immatures were studied at the UT-KES Small Grains Unit in Knoxville, Tennessee, from May to August 1998. Pats of 600 grams in size and a density of 24 grams/larva had the highest face fly larval mortality (66.4 %) and the heaviest individual pupal weights (0.029 g). Smaller pats (below 200 grams), regardless of larva/gram density, caused lower mortality (trial #1: 40.8 % and trial #2: 67.2%) and had the lowest pupal weights. First instar face fly larvae suffered the greatest mortality after being exposed to 3 hours and 122.5 mm of simulated rain. Unexpectedly low face fly larval mortality (40.4 - 42.8 %) occurred in pats with high moisture loss (71 - 72 %) and high internal pat temperatures (44 - 47°C). The highest face fly larval mortality (60 - 70 %) was from pats with the lowest moisture loss (53 - 60 %) and the lowest internal pat temperatures (31 - 35°C).

An additional study was carried out to examine the lateral migration from cow pats of Trichostrongyle larvae at the UT-KES Small Grains Unit, Knoxville, Tennessee, from November 1998 to June 1999. Cooperia was the only trichostrongyle nematode recovered throughout the study. Four weeks after the November plot contamination, larvae of Cooperia spp. were recovered 5 cm away from the pat and were still present on the forage 6 months later.