R. K. Lindquist

RESISTANCE OF SELECTED INTERSPECIFIC LYCOPERSICON HYBRIDS TO GREENHOUSE WHITEFLY (HOMOPTERA: ALEURODIDAE)

Lycopersicon interspecific hybrids and species inbreds were examined for resistance to the greenhouse whitefly, Trialeurodes vaporariorum (Westwood) (Homoptera: Aleurodidae), in four separate greenhouse studies. The two L. pennellii Correll interspecific hybrids (ICR. 13 X LA1735 and ICR. 13 X LA716) were the most toxic and/or repellent to adult whiteflies. ICR.13 X LA1735 exhibited the most adult and nymphal antibiosis and adult antixenosis, supported the lowest number of eggs and nymphs and developed the smallest second generation of adults. The L. esculentum Miller entry (ICR. 13) was usually intermediate in all characteristics examined. All the entries in the study were able to support all the whitefly developmental stages which suggests selective pressure could possibly overcome a resistance mechanism based solely on adult antibiosis. This study provides evidence for adult and nymphal antibiosis mediated by trichome exudates and the possibility that a second nymphal antibiosis mechanism is present within the leaves of LA1735.

Use of an air-assisted electrostatic sprayer to increase pesticide efficiency in greenhouses

The spraying system described in this paper uses air and electrostatics to deliver small drops (20 um Dv 0 . 5 ) to the target. The use of this system in greenhouses is especially attractive since air movement can be controlled and drift is contained. It has been found that charged drops are collected more efficiently by, and distributed more evenly upon plant targets than uncharged drops. Evaluation of spray distribution on cucumbers and poinsettias confirmed that the theoretical advantages of small, charged drops may be exploited in greenhouses. Although the lower spray volume necessitated a correspondingly high concentration of active ingredient, no phytotoxic damage was observed.

Application, Distribution and Efficacy of Electrostatically Charged Sprays on Chrysanthemums

A hand-held sprayer, producing an electrostatically charged air-atomized spray, was used apply small droplets D v 0 . 5 : 25um), in low volumes (-30 1/ha) of aqueous sprays, to bench grown, potted chrysanthemums. Spray distribution was assessed using water-sensitive paper clipped to leaves, and microscopic examination of fluorescent tracer deposits. The biological efficacy of the deposits was determined from bioassays in which bifenthrin was applied against aphids (Aphis gossypii). These data were compared with results obtained in the laboratory using a uniform droplet generator. Particular emphasis was placed on the proportion of the spray deposits on leaf undersides, since this is where most pests occur, and upon behavioural responses of A. gossypii to sub-lethal residues of this pyrethroid. Positioning a hot-wire probe within the plant canopy showed how changes in droplet size, number of droplets available and air velocity may have influenced spray distribution at specific localities. Spray penetration of the canopy, and upper : lower leaf surface deposition on the plants had its greatest biological efficiency when the nozzle was aimed into the row, horizontally, with an air pressure of 138KPa. Comparing numbers of droplets per second, measured by the probe at different locations, with the corresponding deposits, showed that deposition and distribution were most uniform towards the center of the row, and this is attributed to still air allowing electrostatic forces to influence deposition.