H. N. Nigg

Phytochemical resources for medicine and agriculture.

An Historical Perspective of Ancient Poison (Cutler). Plants and Plant Products Used im Mummification (David). Plants Used Medically by Indigenous Peoples (Lewis). Plants as Sources of Medicinally and Pharmaceutically Important Compounds (Kinghorn). SocioEconomic Poisons (Brenneisen, ElSohly). Antiparasitic Agents from Plants (Borris, Schaeffer). Antifungal Compounds in Plants (Kuc). Nematicidal Compounds from Plants (Chitwood). Herbicidal Compounds from Higher Plants (Cutler). Insecticidal Compounds from Plants (Bowers). Natural Medicines Are Natural Pesticides? (Duke). Sources, Levels, and Toxicology (Beier, Nigg). Future for Natural Products (Nigg, Seigler). Index.

Dicofol exposure to Florida citrus applicators: Effects of protective clothing

Mixer-loaders and applicators of the pesticide dicofol in Florida citrus groves were monitored for exposure. Alpha-cellulose pads were placed inside and outside regular work clothing. When protective suits were in use, pads were also placed outside the suit. Dicofol accumulation rates were measured when gloves and/or facemasks were worn. Hand rinses were collected. Results showed that an ungloved, normally attired applicator reduced his total dermal exposure 38% by wearing a disposable Tyvek® protective suit, 27% by wearing gloves, and 65% by wearing both. Suits reduced total dermal exposure by 40% for mixer-loaders, but the use of gloves led to an exposure increase, probably because the inside of the gloves became contaminated.

The Development and Use of a Universal Model to Predict Tree Crop Harvester Pesticide Exposure

A simple regression model is presented for predicting the transfer of residual foliar applied pesticide to the body of a Florida citrus harvester. This model is dependent on work rate and residue concentration and agrees with an earlier model derived from similar data taken from a California study. This suggests that observed regional differences in the morbidity of harvesters in treated fields may be due to regional differences in foliar pesticide residue levels rather than regional differences in transport mechanisms of pesticide from foliage to worker. Eventual metabolite output in worker urine is also predicted.

Caribbean fruit fly,Anastrepha suspensa (Loew), attraction to host fruit and host kairomones

Extracts of 22 fruits were tested for their attractancy toAnastrepha suspensa (Loew), the Caribbean fruit fly. Box-orange, calamondin, carambola, cattley guava, loquat, and Surinam-cherry were about equal in attractiveness to males and females. Nine synthetic chemicals, including four found in box-orange ripe seed, were attractive to females. Five synthetic chemicals, including two in box-orange ripe seed, were attractive to males. Farnesol,α-phellandrene, and 3-carene were highest in attractiveness to both males and females. Females were more attracted than males to 12 synthetic chemicals. These data suggest that host chemicals serve as attractants and that female and male specific attractants and traps could be developed from host kairomone data. These data also suggest that the volatilization of chemicals from water may play an important role in kairomone biology.

SEASONAL LIFE STAGE ABUNDANCE OF DIAPREPES ABBREVIATUS IN IRRIGATED AND NON-IRRIGATED CITRUS PLANTINGS IN CENTRAL FLORIDA

Abstract The seasonal abundance of various life stages of Diaprepes abbreviatus (L.), was monitored in separate years in adjacent irrigated and non-irrigated citrus plantings, as well as thickets of Brazilian-pepper located near Poinciana, FL in Osceola County. Adult emergence, estimated by weekly catches in cone-shaped ground traps, occurred throughout the year with a peak in mid-June in both citrus and Brazilian-pepper plantings. Onset of adult emergence coincided with an increase in soil moisture and temperature. Trap counts were highest when soil water potential increased to 3-5 centibars at a depth of 15-30 cm and soil temperature averaged 22-24EC. In the non-irrigated citrus planting, the adult emergence peak was of shorter duration, but of greater magnitude, compared to the irrigated planting. Although the alternate host, Brazilian-pepper, produced fewer weevils than did citrus, the seasonal emergence pattern was virtually the same. Adult abundance within the citrus plantings was also monitored weekly using modified Tedders traps. The number of adults captured approximated the number caught in ground traps. Adult number caught weekly changed seasonally, particularly in the fall when adult populations were the highest. Ground traps caught a larger number of adults in the spring. The number of egg masses collected weekly in the tree canopy and the number of neonates caught weekly beneath the tree canopy were both correlated with the number of adults captured weekly in modified Tedders traps. These data suggest that adults caught in modified Tedders traps provide a reliable indicator for estimating the seasonal abundance of all life stages within a citrus planting. Larvae of different instars, pupae, and teneral adults were recovered from the soil rhizosphere after periodic tree removal. No diseased or parasitized life stages were observed in the study. Most life stages were present in the soil at each sample date, but the proportion of larvae in various instars changed seasonally. The implications of this study for understanding the population dynamics of D. abbreviatus are discussed in relation to current and future IPM strategies.

Natural Toxicants in Foods

The purpose of exploring the potential naturally occurring toxic hazards of food plants is not to suggest an irrational avoidance of these common foods. However, it is important to identify, define, and investigate the natural toxicants in our foods and to provide some perspective on these chemicals and to show clearly that their toxicology is unknown in most cases. Many natural toxicants have functions in a manner similar to synthetic pesticides or other biohazardous chemicals. Humans apply synthetic pesticides to food and ornamental plants to prevent insect, fungal, and other pest damage. However, plants produce natural toxicants to protect themselves from pathogens and pests. The natural pesticide concentration in our foods may be as much as 10,000 times higher than that of synthetic pesticide residues (Ames, 1983). Because of the protection they provide to plants, these natural chemicals are prime candidates to be bred into plants by plant producers and plant breeders (Barz et al., 1990).

HPLC identification of allelopathic compounds fromLantana camara.

Aqueous extracts ofLantana camara L. leaves inhibited ryegrass (Lolium multiflorum Lam.) germination and seedling growth. Phytotoxic compounds were fractionated from crude aqueous extracts and fractions were evaluated for their phytotoxicity. Inhibition was most pronounced with the alkaline and acid hydrolysates. Plant inhibition by the crude extract reflected a complex interaction of numerous individual components of diverse chemical compositions and potencies. Presumptive identification of the individual components was accomplished with high-performance liquid chromatography (HPLC). Thirteen phenolic compounds were identified, and most of these compounds were phytotoxic to ryegrass seedlings. Radicle elongation was more sensitive to the toxins than shoot elongation.

Worker exposure to ethion in florida citrus

Dermal and respiratory exposure to ethion was determined for 17 men in eight spray crews in Florida citrus spray operations. Respiratory exposure was less than 1% of the total exposure. Hands represented 42% of the total body exposure for applicators and 76% for suppliers. At one location, suppliers exhibited a larger decrease in ChE activity than applicators. This difference appeared related to the higher mean dermal ethion exposure to suppliers. Acute symptoms of organophosphorous poisoning were not observed. The total percent/hr of the probable human dermal LD50 was very low in all cases. These data indicate a relatively low potential acute hazard to workers applying ethion with air blast equipment under the conditions of this study.

Pesticide exposure to greenhouse handgunners

The exposure of pesticide applicators in a commercial greenhouse facility was assessed. Data were collected from four handgunners who applied fluvalinate (insecticide), chlorpyrifos (insecticide), ethazol (fungicide), and dicofol (miticide). Potential exposure was measured with exposure pads placed outside all clothing of the applicator. Handwashes and air samples were also collected, as were pre- and post-exposure tank mixture samples. Pesticide penetration was measured with exposure pads placed inside protective clothing.When all exposure assessments were normalized for spray rate, it was determined that applicators were at significantly greater potential dermal risk (excluding hands) from fluvalinate. The normalized air samples showed significantly more exposure to the applicator from ethazol. Exposure to outside pads was primarily (84%) to the legs of the applicators. Ethazol penetrated Tyvek® coveralls more readily than the other compounds. Tank mixture analyses suggested that the wettable powder formulations were not well-mixed.

Isolation and partial characterization of phytotoxic compounds from lantana (Lantana camara L.).

Phytotoxic compounds obtained from methanol extracts of field-grown lantana (Lantana camara L.) were quantified in terms of their inhibition of ryegrass (Lolium multiflorum Lam.) seed germination and/or seedling growth. Subsequent partition of the aqueous fraction (derived from drying the MeOH extract in vacuo and redissolving in distilled water) at various pHs with solvents of differing polarity indicated the phytotoxic compounds were both polar and slightly acidic. Thin-layer Chromatographic separation of the acidic butanol fraction in a solvent mixture of butanol, acetic acid, water (4∶1∶5, by volume) yielded an active fraction with anRfvalue of 0.89–1.0 that was inhibitory to both root and shoot growth of ryegrass. Two other fractions withRfvalues of 0.04–0.23 and 0.41–0.57 were inhibitory only to root but not shoot growth.