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Open access

Robert W. Benortham, Richard H. Mattson, and H. L. Mitchell

Abstract

Total chlorophyll and β-carotene were found to be highest during pre- and intermediate-color stages and decreased during flower developmental stages in bracts of 8 poinsettia (Euphorbia pulcherrima Willd.) cultivars (‘Annette Hegg’‘Paul Mikkelsen’ and their pink, white, and variegated sports). From preanthesis to postanthesis, cyanidin increased in ‘Annette Hegg’ but decreased in ‘Paul Mikkelsen’ bracts. Pelargonidin levels and cyanidin pelargonidin ratios were similar in the two cultivars.

Open access

Brent K. Harbaugh and Richard H. Mattson

Abstract

Nicotine sulfate and resmethrin, applied at recommended rates, were less toxic to adults and larvae of Encarsia formosa than were endosulfan, malathion, or naled. Adult parasites were killed by contact with any of the 5 chemicals. Endosulfan and malathion left residues toxic to adult E. formosa for 2 to 3 weeks; malathion and naled killed many 10- to 15-day-old parasite larvae. The potential uses of nicotine sulfate and resmethrin were shown in theoretical models for integrated control of greenhouse whitefly.

Open access

Theodore E. Bilderback and Richard H. Mattson

Abstract

Selected biochemical, physical, and anatomical characteristics of 9 cultivars of poinsettia (Euphorbia pulcherrima Willd) were measured and compared with adult and nymph whitefly, Trialeurodes vaporariorum (Westwood), distribution. Whiteflies were most numerous on cultivars with less chlorophyll/unit area (µg/cm2) and lighter colored bracts. Neither total sugar content nor plant growth habit was associated with whitefly distribution. Discrimination of parental groups in cultivars can be done on the basis of trichome length, type, or number. Long spike-like trichomes occur on ‘Rochford’, while ‘Eckespoint C-l’ has significantly more trichomes/unit area. Long trichomes with hooked ends, observed on ‘Annette Hegg’ may provide protection to whitefly eggs or nymphs by preventing their physical removal from underleaf surfaces. Significantly more whitefly adults and nymphs were counted on ‘Annette Hegg’ than on ‘Eckespoint C-l’ or ‘Rochford’ cultivars.

Open access

Brent K. Harbaugh and Richard H. Mattson

Abstract

Distribution of the greenhouse whitefly and its wasp parasite, were measured on 12 cultivars of tomato, Lycopersicon esculentum Mill., by counting populations of parasitized and nonparasitized whitefly nymphs per leaflet. Parasitism percentages· were similar on all cultivars despite large differences in whitefly populations. Second generation parasite populations correlated significantly with whitefly numbers (r=0.71**). “Pocketing” behavior significantly influenced whitefly distribution with minimal cultivar preference. However, distribution gradients showed that ‘Floradel’ was the center of 2 large pockets, indicating preference for it.

Free access

Richard H. Mattson*, Eunhee Kim, Gary E. Marlowe, and Jimmy D. Nicholson

At the Lamar County Adult Probation Program in Paris, Texas, a three-year study (Spring 2001-Fall 2003) involving 376 probationers was conducted to investigate the rehabilitative effects on probationers of a horticulture vocational training program. Data were collected on 189 adults who were randomly assigned to a horticulture group doing greenhouse plant production and vegetable gardening activities. The horticulture group was compared with 187 adults who were in a non-horticulture community service group doing trash clean-up and janitorial work. Within the horticulture group, significant improvement occurred in horticultural knowledge (KSU General and Specific Horticulture Exams), self-esteem (Rosenberg Self-Esteem Scale), and environmental awareness (Environmental Response Inventory). These changes did not occur within the non-horticulture community service group. Future research will examine recidivism rates and vocational placements of probationers from both groups.

Open access

Lynn Ellen Doxon, Richard H. Mattson, and Anthony P. Jurich

Abstract

Five physiological measures of stress were made of 20 developmentally disabled adults working in a greenhouse or training center. Systolic and diastolic blood pressure, electrodermal response, and finger skin temperature were significantly lower for adults in the greenhouse as compared to the training center. Pulse rates were significantly lower after training had occurred. Vocational training of mentally retarded adults in a greenhouse environment could lead to healthier, more productive workers.