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Brent Rowell, Sue Nokes, Annete Meyer, Ric Bessin, and William Nesmith

Farmers' field trials conducted in western Kentucky counties in 1995 and 1996 showed that dramatic reductions in insecticide usage are possible using scouting and action thresholds. Five-acre plots were scouted and treated according to action thresholds while adjacent 5-acre plots were treated weekly with insecticides. Seven out of 10 insecticide sprays were eliminated, saving $65/acre for the 1995 season. There were no differences in yield, insect damage, or fruit quality between the scouted plots and the plots that were treated weekly. Assuming similar low pest populations in all 885 acres of the company's contracted fields, savings could have amounted to nearly $31,000 for 1995 after deducting scouting costs. There were no yield or quality differences from three test plots treated according to regularly scheduled applications and three plots treated according to action thresholds for insect pests and according to Tomcast predictions for fungal disease control in 1996. We have demonstrated the value of using Tomcast as an aid in making fungicide spray scheduling decisions for processing tomatoes in Kentucky. Although we were able to greatly simplify the Tomcast-CR10 datalogger interface program in 1996, there were still difficulties in getting information from the university-based computer to the company making spray applications. The company will be able to access the datalogger and obtain the information directly in 1997. The further analyses of “Skybit” satellite data collected in 1996 should also tell us whether this type of information might be used instead of a remote datalogger thus simplifying the process even further. We plan to build on the quick adoption of the Tomcast system and to make it sustainable by transferring “ownership” to the growers and processing company in 1997.

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Raymond A. Cloyd and Clifford S. Sadof

A 2-year greenhouse study was conducted to evaluate the seasonal population dynamics and use of an action threshold for western fl ower thrips (Frankliniella occidentalis) in cut carnation (Dianthus caryophyllus). An action threshold of 20 thrips/card/week was adopted to time insecticide applications. The highest numbers of thrips were caught on blue-colored sticky cards from May through September whereas the lowest thrips numbers were present from November through March 1994 and 1995. Thrips numbers based on sticky card counts, from December through March for both years were below the action threshold and as a result, no insecticides were applied. Thrips abundance on blue sticky cards was significantly correlated with both numbers of thrips in fl owers and a subjective ranking of fl ower quality. Seasonal patterns of both insecticide use and numbers of damaged fl ow- ers closely followed patterns of thrips abundance found on blue sticky cards. Our findings are the first to demonstrate, based on a case study over a 2-year period, that routinely scouting for thrips throughout the year can lead to fewer insecticide applications and thus possible cost savings in labor and insecticide purchases. This study suggests that sticky cards can be an effective tool for reducing insecticide applications in regions of the U.S. where there are seasonal fl uctuations of thrips abundance.

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George P. Opit, Yan Chen, Kimberly A. Williams, James R. Nechols, and David C. Margolies

In three experiments, damage caused by twospotted spider mite (TSSM; Tetranychus urticae Koch) was correlated with the quality of ivy geranium [Pelargonium peltatum (L.) L'Her ex Aiton], and the action threshold for TSSM on ivy geranium was developed. Ivy geranium quality was measured as overall plant quality—plant size and form, and leaf greenness and glossiness—leaf browning, and leaf distortion. Young plants with high initial TSSM numbers (30 TSSM/plant) exhibited the greatest damage, suggesting that monitoring for TSSM early in the plant production cycle is necessary to prevent extensive damage. The leaf distortion index and overall plant quality were correlated with cumulative TSSM density and marketability in 4-week-old plants infested with 30 TSSM, whereas leaf browning was not correlated with either. Thus, either leaf distortion or overall plant quality can be used to measure economic damage resulting from TSSM. The action threshold for TSSM on ivy geranium was determined using overall plant quality. When the predatory mite, Phytoseiulus persimilis Athias-Henriot, is used to control TSSM, the action threshold was found to be 2 TSSM/leaf. Results also showed that fertilizer combinations of 8 or 24 mm nitrogen and 0.32, 0.64, or 1.28 mm phosphorus had no effect on cumulative TSSM density. When P. persimilis was released at predator: prey ratios of 1:60, 1:20, and 1:4, TSSM damage, measured as both leaf distortion and overall plant quality, was significantly reduced at 1:4 and 1:20, but not at 1:60. A 1:4 rate resulted in the most marketable plants. These results suggest that P. persimilis should be released at a rate of 1:4 when the TSSM action threshold is reached.

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David J. Schuster

The silverleaf whitefly (Bemisia argentifolii Bellows & Perring) is an important pest of tomatoes in Florida and elsewhere. Associated with populations of the whitefly is an irregular ripening disorder of fruit characterized by inhibited or incomplete ripening of longitudinal sections of fruit and by an increase in the amount of interior white tissue. Experiments were conducted during the spring and fall tomato production seasons of 1995 and 1996 to elucidate the relationship of nymphal and pupal density with severity of the disorder. Insecticides or insecticide combinations were applied at predetermined densities of whitefly nymphs and pupae and the subsequent severity of the disorder was rated separately for external and internal symptoms on red ripe fruit harvested weekly. Expression of irregular ripening symptoms, especially external symptoms, were correlated positively to the density of whitefly nymphs and pupae (number·10-1 terminal leaflets on the seventh to eighth leaf from the top of a main or lateral stem) increased. Expression of external symptoms tended to be better correlated with whitefly density when symptom severity was rated 1 and 3 weeks after estimating whitefly density for the spring and fall seasons, respectively. Expression of internal symptoms tended to be more consistently correlated with whitefly density when symptom severity was rated 2 and 3 weeks after estimating whitefly density for the spring and fall seasons, respectively.

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A.H.D. Francesconi, A.N. Lakso, J.P. Nyrop, J. Barnard, and S.S. Denning

The hypothesis that carbon balance is the basis for differences in responses by lightly and normally cropped apple trees to European red mite (ERM) [Panonychus ulmi (Koch)] damage was tested. Mature `Starkrimson Delicious' (Malus domestica Borkh.)/M.26 apple trees were hand-thinned to light (125 fruit/tree, about 20 t/ha) or normal (300 fruit/tree, about 40 t/ha) target crop levels and infested with low [<100 cumulative mite-days (CMD)], medium (400 to 1000 CMD) or high (>1000 CMD) target levels of ERM. A range of crop loads and CMD was obtained. Mite population density, fruit growth, leaf and whole-canopy net CO2 exchange rates (NCER) were measured throughout the growing season of 1994. Leaf area and vegetative growth per tree were also measured. Yield and final mean fruit size were determined at harvest. Return bloom and fruiting were determined the following year. Total shoot length per tree was not affected by crop load or mite damage. ERM reduced leaf and whole-canopy NCER. Normally cropped trees showed fruit weight reduction earlier and more severely than lightly cropped trees with high mite injury. Variation in final fruit weight, return bloom and return fruiting was much better related to whole-canopy NCER per fruit than to CMD.

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Elsa S. Sánchez, Ermita Hernández, Mark L. Gleason, Jean C. Batzer, Mark A. Williams, Timothy Coolong, and Ricardo Bessin

were removed at the action threshold for a 2-week-long period during which pollinators could access flowers and insecticides were applied late in the evening after pollinators returned to their hives, then rowcovers were replaced until harvest began and

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Ronald C. Stephenson, Christine E.H. Coker, Benedict C. Posadas, Gary R. Bachman, Richard L. Harkess, John J. Adamczyk, and Patricia R. Knight

value. Because of unpredictability and variability of markets, economic thresholds can be difficult to apply. As a result, action thresholds have been developed as levels of pest density that result in loss of crop quantity or quality ( Schuster and

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E.R. Mitchell, Guangye Hu, and Denise Johanowicz

Collard greens (Brassica oleracea var. acephala L.) were planted in the peripheries of cabbage (Brassica oleracea var. capitata L.) fields in the spring growing seasons of 1997 and 1998 to evaluate their effectiveness as a trap crop to manage the diamondback moth (DBM) [Plutella xylostella (L.)]. The numbers of DBM never exceeded the action threshold for application of insecticides in any of thefields that were completely surrounded by collards, but did exceed the action threshold in three of the fields without collards on four sampling dates in 1998. In both years, the numbers of DBM larvae in the collards exceeded the action threshold of 0.3 total larvae/plant in eight of nine fields. Larval counts in cabbage surrounded with collards were not significantly higher than in the conventionally planted cabbage, even though the number of pesticide applications was reduced in the former. The few pesticide applications in fields surrounded by collards probably targeted the cabbage looper [Trichoplusia ni (Hübner)], which was not impeded by the collards from infesting the interior cabbage. There was no significant reduction in marketability, and damage to cabbage was similar to that in fields where collards were planted and in fields where only conventional pesticides were used. The reduced number of pesticide sprays, as well as the high concentration of host larvae in the collards, may help maintain populations of natural enemies of DBM in the agroecosystem. Planting collards in field peripheries is a potentially effective tactic to manage DBM in cabbage.

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E.R. Mitchell, Guangye Hu, and Denise Johanowicz

Collard greens (Brassica oleracea var. acephala L.) were planted in the peripheries of cabbage (Brassica oleracea var. capitata L.) fields in the spring growing seasons of 1997 and 1998 to evaluate their effectiveness as a trap crop to manage the diamondback moth (DBM) [Plutella xylostella (L.)]. The numbers of DBM never exceeded the action threshold for application of insecticides in any of the fields that were completely surrounded by collards, but did exceed the action threshold in three of the fields without collards on four sampling dates in 1998. In both years, the numbers of DBM larvae in the collards exceeded the action threshold of 0.3 total larvae/plant in eight of nine fields. Larval counts in cabbage surrounded with collards were not significantly higher than in the conventionally planted cabbage, even though the number of pesticide applications was reduced in the former. The few pesticide applications in fields surrounded by collards probably targeted the cabbage looper [Trichoplusia ni (Hübner)], which was not impeded by the collards from infesting the interior cabbage. There was no significant reduction in marketability, and damage to cabbage was similar to that in fields where collards were planted and in fields where only conventional pesticides were used. The reduced number of pesticide sprays, as well as the high concentration of host larvae in the collards, may help maintain populations of natural enemies of DBM in the agroecosystem. Planting collards in field peripheries is a potentially effective tactic to manage DBM in cabbage.

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J. Kabashima, T.D. Paine, and R. Redak

Pesticide use in the landscape has been reduced through the implementation of integrated pest management (IPM) (Holmes and Davidson, 1984, Olkowski et al., 1978; Smith and Raupp, 1986). IPM emphasizes prevention, identifying pests and their symptoms, regular surveying for pests, determining action thresholds and guidelines, and using sound management methods. Monitoring techniques such as pheromone traps, degree-day models, and ELISA kits, in addition to traditional methods, have enabled pest managers to determine accurately when to apply IPM techniques. Examples of serious California landscape insect pests successfully controlled through IPM include the ash whitefly [Siphoninus phillyreae (Halliday)], the Nantucket pine tip moth [Rhyacionia frustrana (Comstock)], and the eucalyptus longhorned borer (Phoracantha semipunctata F.).