2) behavior observations in tomato field: We had planned to observe stink bugs in a planting of unsprayed tomatoes at OARDC/Fremont to determine the movement patterns of stink bugs within the tomato canopy, to better understand when injury occurs and how bugs might be avoiding contact with insecticides. However, because damage and bugs were detected more readily than usual in the daytime in the threshold study plots, we decided not to make these observations. Sticky tile traps were tested as a tool for monitoring nocturnal activity of stink bugs, but they were found ineffective; they were placed on the ground in late day and checked in the morning.
3) behavior observations on tomato in lab: Observations were made to characterize damage to green and red tomato fruit by the one-spotted stink bug, Euschistus variolarius, in each of its development stages. From lab colonies of E. variolarius, individual young nymphs were placed in a container with an excised green and red tomato fruit, and held at 24oC with 16 h light, 8 h dark. Three to six nymphs from each of six egg masses were used; a total of 31 nymphs were started of which 21 bugs completed development to adults. Bugs were observed once per day until they reached adulthood. Fruit were replaced every 4 days, and held until ripe when damage was characterized by evaluating the percentage of fruit surface injured and the depth of injury into tomato flesh. Data is being analyzed to test the hypothesis that damage is significantly greater on green fruit than on red fruit.
4) field scouting of gourds and butternut squash: To determine the number, type, and timing of squash or gourd samples to take to detect bug infestations, and to determine seasonal trends in insect and disease incidence with emphasis on fruit injury, four commercial fields were scouted once per week. The sample unit was one mid-canopy mature leaf, one stem, one flower, and one fruit, and 50 samples were taken per field. In squash and gourd fields in central Sandusky County, no fruit problems were detected, squash bug was never found on sampled plants although eggs were noted once on a non-sampled plant; only cucumber beetles were found on leaves from 25 June to 18 August and in flowers from 7 July to 7 September. In squash and gourd fields in western Sandusky County, no fruit problems were detected, squash bug was found from 8 July until 25 August; stink bug was found once in gourds (adult on 8 July) and 3 times in squash (adult on 8 July, 28 July; nymph on 12 August); cucumber beetles were found on leaves from 3 June to 5 August and in flowers from 8 July to 25 August. Of 50 samples examined per field per week, squash bug was found on 0 to 9 samples (0 to 18% of samples). During the 8 week period that squash bug was found in the western squash field, the number of positive samples per 50 samples was 1 to 5 for leaf samples, 0 to 5 for stem samples, and 0 to 1 for fruit samples. The range in total number of squash bugs on one sample was: on leaf sample, 0 to 1 adults, 0 to 1 egg masses, 0 to 17 nymphs; on stem sample, 0 to 10 nymphs; on fruit sample, 0 to 1 nymphs. Based on the variability between fields, the sample size of 50 per field seems appropriate as a minimum for large fields. Scouting both leaves and stems is needed for best detection of squash bug. To supplement scouting, one pheromone trap was placed in each field to monitor squash vine borer; adults were found in all 4 fields with a peak catch ranging from 9 to 22 moths per trap per week.
5) field trial with bugs and bacteria on gourds: To determine whether feeding by squash bug or stink bugs predisposes gourd fruit to bacterial diseases, a field experiment was conducted with caged fruit.
Methods: Six replicates of 9 treatments were evaluated. The treatments were combinations of 3 bacteria (Xanthomonas or Pseudomonas or buffer with no bacteria) and 3 injuries (bug or pinprick or none). Seeds of 'Nest Egg' gourds were planted at Waterman Farm in Columbus, after treating seed with Clorox. Plants were trained to climb on a trellis. Gourd fruit were enclosed in fine-mesh bags as soon as the flower petals wilted. Experiments were initiated when fruit had been bagged for an average of one week with range 3 days to 3 weeks. Bacterial leaf spot (Xanthomonas campestris pv cucurbitae) and angular leaf spot (Pseudomonas lacrymans) were obtained from USDA and kept in culture. Bacteria were mixed with buffered water and sprayed on fruit for artificial inoculation. Lab colonies were established using stink bug adults collected from alfalfa in April and squash bug eggs collected from zucchini in early July. The experiment was set up on 26 July with stink bug and on 26 August with squash bug. One adult female bug was used per fruit. Bugs were placed on fruit for 24 hours before bacteria was inoculated.
Results: In the first trial (with stink bug), which was initiated during a period of unusually hot weather, water-soaked lesions typical of bacterial diseases developed on only three of 54 fruit tested: two fruit treated with bug and no bacteria, and one fruit treated with no bug and no bacteria; apparently weather conditions during the trial were not conducive to disease development. In the second trial (with squash bug), water-soaked lesions typical of bacterial diseases developed on only five of 54 fruit tested: two fruit treated with bug and Pseudomonas, one fruit treated with bug and Xanthomonas, one fruit treated with bug and no bacteria, and one fruit treated with Xanthomonas and no bug. Damage from Pseudomonas appeared somewhat more severe when squash bug was present than when a pinprick or no injury was present.
Extension program implementation: The tomato field trial was featured in two field tours on 20 July and 5 August 1999, and conclusions on scouting and thresholds are being incorporated into a stink bug fact sheet that has been drafted. Results from the squash and gourd work will be featured in a talk at the Ohio vegetable growers' congress on 12 February 2000.
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