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The effects of tomato, Lycopersicum spp., leaves treated with imidacloprid on probing and settling behavior of Frankliniella fusca (Hinds) and Frankliniella occidentalis (Pergrande) were examined using an electrical penetration graph technique and an intact leaf bioassay. For each experiment, thrips were subjected to nontreated plants and plants treated with either of two rates of imidacloprid: 7.81 and 41.55 microg [(AI)] per plant. F. fusca probed less frequently on plants treated with the high rate of imidacloprid compared with the nontreated plants. The duration of F. fusca noningestion probing waveforms and ingestion was shorter on plants treated with the high rate of imidacloprid compared with that on nontreated plants. In contrast, F. occidentalis probed longer and more frequently on plants treated with either the low or high imidacloprid rates compared with nontreated plants. They also ingested more frequently and for longer durations on plants treated with the high rate compared with nontreated plants. The duration and frequency of noningesting probing waveforms were greater on the imidacloprid-treated plants compared with the nontreated plants. F. occidentalis probed and ingested more frequently and for a longer duration than F. fusca on plants treated with the high rate of imidacloprid. F. fusca ingested more frequently and the duration of ingestion was longer than F. occidentalis in untreated plants. F. fusca and F. occidentalis settling behavior differed within the first 30 min in a choice bioassay. F. fusca preferred settling on leaves of nontreated plants, whereas F. occidentalis showed no preference in an intact leaf choice bioassay.

A 2-yr study was conducted on the effects of tillage and soil insecticide (chlorpyrifos) treatment on peanut arthropod pests. A 3 by 2 split-plot experiment with five replications was subjected to factorial ANOVA. Main plot treatments consisted of three tillage systems: conventional moldboard plow, strip tillage into a killed wheat cover crop, and strip tillage into corn stubble residue. Subplot insecticide treatments were granular chlorpyrifos applied at early pegging (growth stage R2) and untreated. Populations of corn earworn, Helicoverpa zea (Boddie), and velevetbean caterpillar, Anticarsia gemmatalis Hübner, were lower in strip tillage systems. Chlorpyrifos applications caused corn earworm outbreaks in all tillage systems, but these applications were more disruptive in strip tillage. Chlorpyrifos treatment also increased populations of fall armyworm, Spodoptera frugiperda (J.E. Smith), but had no measurable effect on velvetbean caterpillar populations. Pod damage from lesser cornstalk borer, Elasmopalpus lignosellus (Zeller), and wire-worms, Conoderus spp., was lower in strip tillage systems, and chlorpyrifos suppressed pod damage in all systems. Threecornered alfalfa hopper, Spissistilus festinus (Say), damage to peanut was greater in the wheat residue strip tillage system. Chlorpyrifos treatment reduced threecornered alfalfa hopper damage in all systems. Spider mite injury was not affected by tillage, but chlorpyrifos treatments resulted in mite outbreaks in all tillage systems. Burrower bug, Pangaeus bilineatus Say, injury to peanut kernels was greater in the strip tillage systems in 1999; and burrower bug injury was suppressed in the strip tillage systems by chlorpyrifos treatment. There was a significant interaction effect for burrower bug injury between tillage and insecticide treatment. Incidence of tomato spotted wilt virus also was reduced by strip tillage. Use of an effective fungicide program and a 3-yr crop rotation out of peanut production probably obscured any potential tillage effects on fungal diseases (southern stem rot, Rhizoctonia limb rot, and leaf spot). However, chlorpyrifos treatment increased Rhizoctonia limb rot incidence. Weed populations were generally greater in strip tillage systems, but postemergence herbicides effectively eliminated any potential confounding effect on yield and grade. Yield was not affected by tillage in either year, and chlorpyrifos had no effect on yield in 1998. In 1999, however, chlorpyrifos increased yield in both strip tillage systems. Neither tillage nor insecticide treatment affected grade (percentage total mature kernels) in 1998, but in 1999 grade was highest in conventional tillage and grade was improved by chlorpyrifos treatment in strip tillage systems. Crop value losses of $249 and $388/ha were attributed to burrower bug injury in untreated corn and wheat residue strip tillage systems, respectively. This injury may have been an anomaly of drought conditions but, given the potential economic impact, burrower bug merits further study in conservation tillage peanut production.

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The effect of tomato, Solanum lycopersicum L., plant and leaf age on the probing and settling behavior of Frankliniella fusca (Hinds) and F. occidentalis (Pergande) was studied using electrical penetration graph technique and whole plant bioassays. Male and female F. fusca probed and ingested more and for longer periods of time on 3- and 4-wk-old plants compared with 6- and 8-wk-old plants. Female F. fusca probed and ingested more frequently than males in the plant age experiment, but not in the leaf age experiment. F. fusca probed and ingested more frequently on 2- and 4-wk-old leaves compared with 1-wk-old leaves. Plant age did not affect the probing frequency or duration of F. occidentalis; however, males probed and ingested longer than females in the plant age experiment and on the oldest leaf in the leaf age experiment. Both thrips species preferred to settle on 3-wk-old plants. F. fusca preferred to settle on 4-wk-old leaves after settling randomly for an hour. F. occidentalis showed no settling preference relative to leaf age. The preference of F. fusca for young plants suggests that this species could attack tomato plants at a very early stage, which is important for understanding its role as a vector in the transmission of Tospovirus in the field.

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