Final Report for FNE08-637
Note to readers, attached is the complete final report for FNE08-637
This experiment was conducted to determine if the addition of internal trap crops to a perimeter trap crop system would be an improved organic technique for control of cucumber beetle in organic winter squash. We planted experimental plots with Buttercup plants as both perimeter and internal trap crops in a main crop of Butternut squash. Plots with only a perimeter trap crop were planted as a control. We found that while the internal trap crops did not act as a source for cucumber beetle and increase numbers in the main crop they did not act as a sink either. The effect was in fact neutral. Based on these results, we cannot recommend the use of internal trap crops at this time. We do, however, recommend repeating this experiment with larger plot sizes
As the manager of the Hampshire College Community Supported Agriculture Program, I grow 15 acres of mixed vegetables using organic methods. The CSA is located at Hampshire College in Amherst MA. Crops are distributed to 210 shareholder households from September through November. The majority of shares are sold to students, staff and faculty of the Five colleges (Hampshire, Smith, Mt Holyoke, Amherst Colleges and the University of Massachusetts).
Hampshire College CSA
Role: Assistance with experimental development and design. Supplied information about previous experiments. Visited experiment several times to help with sampling techniques and results interpretation.
Professor of Entomology
Role: Assistance with sampling, experimental design and plot layout. Conducted statistical analysis.
Our objective for this project was to continue research in the development of an effective trap cropping system in winter squash using organic methods. We proposed using Buttercup squash as a perimeter and internal trap crop for the control of cucumber beetles in a Butternut squash main crop. Our goal was to determine if the addition of internal trap crop rows to plots with perimeter trap crops would have one of the following effects:
• act as additional sinks for cucumber beetles and further reduce their numbers in main crops
• act as a source and increase cucumber beetles in the main crop
• have no net effect.
On 5/24 /08 Buttercup and Butternut squash seeds were started in the greenhouse in plastic flats.
On 6/15/08 transplants were set out into the field in eight plots of squash with 60 plants (6 rows of 10 plants) in each plot, and the plots arrayed as four sets or blocks of two treatments. One treatment was a standard perimeter trap crop (PTC) arrangement as a control, with outside single rows of Buttercup in each plot, and Butternut as the main crop inside of the perimeter. The second, or experimental, treatment was like the control perimeter trap crop except that the eight innermost plants in each plot were not Butternut but instead were Buttercup plants as an internal trap crop (P+ITC) (see Figure 1- missing).
We examined every plant in the experiment and counted any live cucumber beetles (CB) on each plant, starting right after planting transplants (the same day, 6/15) and then on 12 subsequent dates: 16, 18, 19, 21, 23, 24, 26, 27, 30 June; 1,3, and 7 July. All internal (non-trap) Butternut squash transplants were treated with Surround only before planting and not subsequently. All perimeter and internal Buttercup trap plants, but not the main, non-trap Butternut plants, were sprayed with Entrust on 6/25 and 6/30 (after insect sampling on that day), when perimeter traps generally exceeded economic thresholds for CB. Entrust was applied to Buttercup plants with a backpack sprayer at the rate of 2.5 oz/ acre.
The results were that the numbers of CB were significantly greater in the Buttercup trap crops than in the Butternut main squash plants, and treating the trap crops with Entrust seemed to succeed in the purpose of reducing CB numbers reaching or persisting on the non-trap plants (at times with some delay in its effect). However, there were no differences in CB numbers compared among only the Buttercup plants by treatment or location, nor were there any significant differences compared among any of the Buttercup traps, regardless of treatment or location as perimeter traps or internal traps (see Figure 2). In short, the main experimental results, on the effect of an internal trap, were neutral — since main Butternut (non-trap) CB numbers were similar regardless of treatment and location, the internal trap crops added to perimeter trap crops acted as neither a source nor an additional sink of CB for the non-trap plants.
[Figure 1 & Figure 2 and captions are missing)]
Although it is good that the internal traps did not act as a source of CB, we had hoped that they would further reduce CB numbers, or act as a sink above and beyond the perimeter traps (by drawing more CB from the Butternut main crop onto sprayed internal traps). One possible additional factor and limitation of this experiment is that our plots were small and CB could thus move easily among all plants and plots alike; this is especially suggested by the result that internal trap CB numbers are comparable to those on the perimeter traps. It would be good to try the experiment in bigger and/or more widely separated plots, or otherwise in an experimental design that allows greater distances between internal and perimeter traps.