Prevalence of a trypanosomatid in the southern green stink bug, Nezara viridula.

The southern green stink bug, Nezara viridula (L.), and certain of its host plants were examined to determine the prevalence and biological characteristics of an intestinal trypanosomatid. Promastigotes with short (< or = 17.5 microm excluding flagellum) and long forms (> or = 25.0 microm) usually infected < 50% of the bugs before August and > 50% (maximum 95%) during August-October, but prevalence was not host-density dependent. The flagellate was detected in adults and in all nymphal instars, at all sampling sites where at least 10 bugs were captured, and in bugs from all host plants sampled (soybean, red clover, vetch). Of bugs with flagellates, 27% were heavily infected (> 20 flagellates per 160X microscope field). Weights of infected and uninfected adults did not differ. Live flagellates were detected in bug feces and in one stem of red clover. When bugs were fed soybean pods, tomatoes, or snap beans in the laboratory, only once were flagellates detected in plant tissue (snap beans). The flagellate was cultured in modified Medium 199. This flagellate is prevalent in N. viridula populations in Louisiana and apparently does not cause significant pathological effects in N. viridula or its host plants, including soybean.

Stressors and rearing diseases of Trichoplusia ni: evidence of vertical transmission of NPV and CPV.

Inability to consistently rear healthy Trichoplusia ni led to a study of its rearing diseases. Four diseases were designated after preliminary research which included electron microscopy: cytoplasmic polyhedrosis (due to cytoplasmic polyhedrosis virus, or CPV), nuclear polyhedrosis (due to nucleopolyhedrovirus, or NPV), "neonate death" syndrome (mortality in first or second instars), and "late-instar" syndrome (death in late instars accompanied by bacterial decomposition). Infectious agents were not detected by electron microscopy in insects with the latter two diseases. Prevalence of CPV and NPV, but not the neonate-death or late-instar diseases, in progeny was significantly associated with pairs of mating adults. In conjunction with egg-surface decontamination, this indicated that both viruses may be transmitted transovarially. Pupae killed by CPV had virions in the cytoplasm of infected cells, but polyhedra were empty, not occluding virions. None of the diseases had a consistent pattern of prevalence associated with the date on which eggs were laid after oviposition began. Prevalence rates of cytoplasmic polyhedrosis, nuclear polyhedrosis, and the late-instar disease were significantly greater at 95-100% relative humidity (RH) than at RH levels of 75% or below. These same three diseases killed significantly more insects in crowded rearing conditions (four or five larvae per cup with 10.2-cm(2) diet surface) than in uncrowded conditions (one to three larvae per cup). As a result of these experiments, healthy T. ni have been reared for 10 generations by use of a modified Pasteur method and rearing cups containing no more than two larvae.

Survey for blood parasites in redheads (Aythya americana) wintering at the Chandeleur Islands, Louisiana.

We detected no infections with species of Plasmodium, Haemoproteus, Leucocytozoon, Sarcocystis or Trypanosoma in blood smears, liver and spleen impressions, and muscle tissue from 136 redheads (Aythya americana) collected or captured at the Chandeleur Islands, Louisiana (USA), during three winters (1987 to 1990). One bird, a juvenile male, was infected with an unidentified species of microfilaria. Thus, we found no evidence that hematozoa had an effect on redheads during the course of the study.