Insect Pest Control

By Al Mitlehner

2006 Pest Control  - CT Dahlia Society Display Gardens

The Connecticut Dahlia Society (CDS) conducts its annual Dahlia Display Garden in Elizabeth Park, West Hartford in cooperation with the Friends of Elizabeth Park. The dahlia gardens are planted and maintained by CDS members. Two beds approximately 40x6 feet are planted with 66 different varieties chosen to provide a wide variety of colors, sizes and shapes.

The 2006 gardens got off to slow start as a result of some excessively wet weather during the month of June, However as the season progressed the dahlia garden turned into a spectacular success raising a chorus of praise from the many visitors to Elizabeth Park. The success of the gardens was due in no small part to the effort of many CDS members taking care of planting, fertilizing, watering, tying, deadheading and the control of weeds, insects and diseases. A garden log is used to record any activity conducted by the CDS members at the Display Garden.  For the 2006 season the log showed the following pest control activities.

Prior to mid July hand weeding was routinely done. By mid July the plants had achieved enough size to shade out most would be problem weeds. The beds are raised beds surrounded by gravel walks. Weeds emerging through the gravel were controlled by Roundup sprayed at a rate of 0.5% active ingredient The spray was applied on a windless day to insure that no drift got into the beds. Two sprays were applied, 7/6 and 8/10. This was adequate to keep the aisles relatively clean throughout the season. Some hand weeding was done to remove any weeds missed by the spray.

The primary insect pest noted early in the season (June and early July) was white flies. Isotox (Formula IV, active ingredients Acephate-8.0% and Fenbutatin-oxide-0.5%) was applied at a rate of 4tablespoons per gal as a complete coverage foliar spray on 7/10, 7/16, 8/6, 8/12. Shortly after the 7/10 spray there was a very heavy rain and by 7/13 the whiteflies were very noticeable. The garden log noted that one-day after the 7/16 spraying the white flies were gone. Throughout July and August no damage from leaf chewing or stem borer insects was noted.

In late August two spotted spider mites made their grand appearance on the variety Santa Claus. Within a week the lower leaves were heavily infested and some adjacent varieties showed signs of mite damage. On 9/6 the badly infested leaves of the variety Santa Claus were removed and discarded. On 9/11 all plants were sprayed with Floramite (active ingredient  Bifenazate 50% )  at a rate of ½ teaspoon per gallon. Any plant with noticeable mite damage was sprayed with complete coverage, i.e. both the underside and topside of the foliage was sprayed. Those plants not showing any damage were sprayed only to obtain underside coverage of the foliage. Because most plants in early September were well branched and 5 to 6 feet tall, 2 gallons of spray mix would be needed to provide complete coverage of the 72 plants. By 9/21, 10 days after applying the Floramite, the plants were virtually free of mites. The badly infested Santa Claus variety had put out new clean foliage and was flowering. Because the season was coming to an end and the nights were getting cool, no additional mite sprays were applied or needed.

Because powdery mildew had been a problem in previous years a preventative spray of Terraguard 50W (active ingredient triflumazole) was applied at a rate of 3 teaspoons per gallon on 9/6. The beds were sprayed for complete coverage of the foliage. The garden log indicated no incidence of powdery mildew on 9/28. By the time the beds were dug in mid October a few plants did show some minor powdery mildew infection sites, but there was no need for any additional powdery mildew sprays at that late date.

As was previously noted the 2006 CDS Dahlia Display Garden was an unqualified success. The indicated pest control program was completely adequate to deal with all weed, insect and disease issues that developed during the 2006 season.