Enhancement of Sustainable Pest Management Techniques through Utilization of Banker Plants and Colored Mulches in Commercial Greenhouses
During year two of this project, colored plastic mulches (blue, red, silver, and yellow) trials were conducted in a commercial greenhouse tomato operation to examine their effect on insect development and crop yield over a five-month crop cycle. Black polyethylene plastic was used as a standard. The total marketable yield for each color was determined. Yield increases ranging from 5 to 10% can be expected from plants grown on the colored mulch compared to plants grown on the standard black mulch. This second year study again indicates that insect populations can be manipulated with mulch color.
The “banker plants” that serve as a host for the establishment of insect pests and the appropriate biocontrol is under development. A colony of Encarsia formosa, the Hymenopteran parasitoid used to control greenhouse white fly, was successfully established. A colony of the parasitoid Aphidius colemani was established to control green peach aphid and potato aphid. The banker plants will be used in the future as a distribution method for natural enemies in commercial operations. Better understanding of these two concepts and their integration will augment the effectiveness of other Integrated Pest Management (IPM) strategies, and may serve as a catalyst for increased adoption of IPM in greenhouse operations throughout the nation.
* Evaluate the effect of polyethylene mulch color in a greenhouse environment on crop and pest response.
* Develop a strategy to utilize banker plants as a distribution method for natural enemies in commercial greenhouse production.
Colored polyethylene mulch used on the ground beds in the greenhouse of this experiment included red, yellow, blue, and silver, with black as the control. All polyethylene mulches were non-degradable and one millimeter thick. The highest fruit yield was harvested from plants growing on blue mulch (10.7% yield increase compared to the control) and the lowest yield was from plants growing on the control black mulch. Silver and yellow produced similar yields (10.7% yield increase compared to the control) and red only produced a 3.5% increase in fruit yield from plants grown on this color compared to the control. There was no significant increase in soil temperature from the different mulch colors, and there was no consistent trend in soil temperatures by color over the growing season. Recent field research has demonstrated that a more reflective red mulch has produced higher fruit yields of tomato from plants grown on reflective red compared to either the dull red or standard black mulch.
Insect development on tomato plants varied with mulch color. Results in 1998 were consistent with 1997 findings. The three target pests for this tomato crop included western flower thrips, potato aphid, and greenhouse white fly. Immature stages of western flower thrips were observed first on plants grown with the blue mulch. For ten of the twelve weeks in which the crop was monitored, thrips development was highest on the blue mulch for both adult and larval stages. Results indicate that greenhouse white fly and potato aphid (adults and immature stages) developed first on plants grown with the yellow mulch. Yellow mulch was also an attractant for thrips; however, population development was not as great as it was on the blue mulch. Red, silver and black revealed low levels of all pests. This data indicates that blue and yellow serve as pest reservoirs and can be used to manipulate pest development. When identified, these areas can be used as to make target applications of beneficial insects. Strategic placement of biocontrols near the pest population increases the efficacy of the treatment.
Using colored mulch in commercial tomato production has resulted in elimination of synthetic insecticides; control was obtained by using biological controls with the colored plastic mulch.
The development of the banker plant system was moved from a laboratory situation to a commercial tomato operation. Six-foot-high cages were erected, since it was determined in 1997 that rearing cages needed to be larger. In one cage, greenhouse white fly adults were introduced and allowed to oviposit on tomato plants. Adults were removed from cage and immatures allowed to develop to suitable stages (third instar) for parasitism. The parasitoid Encarsia formosa was then introduced into the cage. Leaves containing parasitized pupae were then distributed in the production houses. These production houses were augmented with Encarsia purchased through a supplier since there were not adequate amounts to control white fly populations.
The same efforts were made to rear the parasitoid, Aphidius colemani to control green peach aphid and potato aphid. Additional introductions of A. colemani were purchased to augment those reared in the cages.
Future efforts will be made to increase the number of parasitoids. Other efforts will be directed at improving air circulation in rearing cages. Slow air movement has increased the incidence of foliar diseases developing, such as powdery mildew and leaf mold. Further development of the banker plant system will offer growers the option of having a sustainable, on site supply of biological controls when an insect pest problem develops during crop production.
All growers involved in the project reduced their dependency on synthetic pesticides. Grower one experienced a 95% reduction and grower two a 75% reduction.
One of the growers has allowed the project to expand to two production houses. The grower talks of using effective colors separately in houses, especially for control of western flower thrips. The grower involved with banker plant study has expressed interest in using the colored mulches so that the biocontrols work more effectively.
One grower reports, “The use of colored plastic mulch in our operation definitely will work. The plastic mulch can be applied easily to the top of the troughs. Anything that will make the biocontrols more effective we are all for. Since we are so limited with registered pesticides, we must be constantly looking for other methods to keep production going. My employees are happy since their exposure to pesticides is greatly reduced.” Another says, “We like the idea of rearing beneficial insects on our operation. The use of the banker plant system will provide us with a steady supply of biocontrols. Since we market our tomatoes as an IPM grown commodity, our participation in these types of projects is crucial to keep the greenhouse vegetable industry strong.”
Dissemination of Findings
The project has been presented and discussed at eight plasticulature and vegetable production workshops and meetings across Pennsylvania during 1998, and the project has been publisher in a professional journal (Orzolek, M. D., W. J. Lamont and L. Otjen. 1998. Day-neutral strawberry production on colored mulch. Proc. Nat. Ag. Plastics Cong. 27:199-202.). Further dissemination is pending.
Reported December 1998. 1999 Northeast Region SARE/ACE Report.