Natural pest management in New York high tunnel and greenhouse vegetables

Natural pest management in New York high tunnel and greenhouse vegetables

Summary

High tunnels and greenhouses are an important tool for cutting-edge Northeast fresh market vegetable farmers. These structures extend the growing season and help farmers deliver locally grown product to their customers in the ‘off-season’. Produce quality is generally improved over its outdoor field grown equivalent.

However, the enclosed environment can favor the development of some pest populations. Alternatives to chemical control are important in these settings. Many farmers using this technology are certified organic, others do not want to apply inseciticides in an enclosed environment, many chemicals do not fit well with the frequent harvests and mixed crop environment common on these farms.

Biological control is a great fit for greenhouse/high tunnel vegetable production.
Biological control includes the introduction of beneficial arthropods (generally insects and mites, as well microbial fungicides and plant resistance.

The use of biological control in protected culture has a long history and widespread adoption in areas such as Europe, Canada and the Mediterranean. Large-scale U.S. vegetable greenhouses also now use biological control. However, adoption by small-scale operations in the Northeast is currently low.

This project promtoes biological pest management among greenhouse and high tunnel vegetable growers in New York. By working on-farm we help farmers indentify pests and the collaborate on biological control techniques. Other farmers then visit our cooperating sites.

This year we worked with nine different growers, at a total of twelve different on-farm demonstration sites. Out of the twelve sites that we scouted, nine locations had pest populations significant enough to release a biological control agent. The other three locations were scouted on a weekly basis until it was evident that damaging levels of pests would not interfere with the crop. We also had an on-site grower meeting, and one University sponsored meeting that were solely focused on the use of biological control practices. Here individuals (growers, researchers, industry representatives, etc) were able to interact and share successes, concerns, and opinions with each other.

Again this year we were able to hire a part-time technician to monitor the pest populations, on a weekly basis, document the impact of biological control measures, input data, and attend informational sessions. These results have been shared throughout the season and again at our winter meetings.

Throughout the second season of the project the primary pest problems that we encountered included aphids, spider mites and white flies. The crops we worked in were cucumbers, tomatoes, melons, lettuce and eggplant. Success rates at each site and with each pest were variable due to many different factors. Some factors include populations being too large to control, not enough releases, or temperature barriers. However we were able to accomplish many positive milestones towards the goal of increased adoption of biological control.

Objectives/Performance Targets

Technician scouted 11 sites.

8 farms cooperated on regular data collection.

Technician made 109 on-farm scouting visits during the 2008 season.

40 growers attended a 1 on-farm demonstration meeting in August 2008.

Nearly 100 growers attended a winter meeting (January 2008) that included industry, farmer and university speakers. At this meeting the bascis of pest and biocontrol biology were covered. Also the results from the year 1 on-farm demonstration trial were presented.

Accomplishments/Milestones

Each site was rated on a scale of 0 to 5 (0= biological control release failure, 3= pests were suppressed but not controlled and 5=good pest control). Two sites were rated with a perfect 5, both for excellent control of aphid populations, one site was rated 4, three sites were rated 3, one site was rated 2 and one site was rated 1. Brief summaries of each of the eleven locations are included below:

Location: Phelps, New York (1)

High Tunnel/Greenhouse Crop: High Tunnel Eggplant
Problematic Pest: Two-spotted Spider Mites
Biological Control Used: Phytoseiulus persimilis
Dates on Farm: Weekly from April 29 to October 6, 2008
Success Rating (0=failure to 5=control): 3
Scouting at the Phelps farm (1) began on April 29; however plots were not setup until June 9 when the row covers were taken off of the high tunnel eggplant. At this time the only pests present were flea beetles and a few aphids. Scouting continued weekly. Two spotted spider mites first started to show up on June 30. At this time four replicas of four plants each were set up and damage ratings (1=clean, 10=dead) were conducted, pressure was low (damage ratings below 1.5). The following week, July 7, numbers had increased enough to require a treatment (average damage rating greater than 1.5). At this point it was decided to order the biological control agent Phytoseiulus persimilis, which was released July 11. Spider mite populations continued to rise, slow and steady, over the next eight weeks (maxing out at a damage rating of just under 7). However, plants were still producing quality fruit and growing at an excellent rate. Starting on September 9th there were very few live mites found, but the damage on the plants was still very visible. Over the next four weeks the live mites were almost completely eradicated, leaving behind only their silvery markings on the eggplant leaves. The biological control agent Phytoseiulus persimilis did a good job at holding the population to a manageable level but did not completely control the spider mite pests. We have learned that spider mite populations can multiply rapidly and in subsequent years we would be more prepared to release at the very first sign of this particular pest. Other strategies may include a second release, higher rates, or combination releases with generalist predators.

Location: Phelps, New York (2)
High Tunnel/Greenhouse Crop: High Tunnel Winter Greens
Problematic Pest: Aphids
Biological Control Used: Aphidius colemani and Aphidius ervi
Dates on Farm: Bi-weekly from September 22 to November 5, 2008
Success Rating (0=failure to 5=control): 1
The Phelps Farm (2) has a long history of aphids on their farm and especially in their winter greens. This is a valuable crop on an organic farm that the grower would like to be able to save and sell for a late season market. The greens were planted into a high tunnel, during the week of September 15, after the spring/summer greens crop was removed. There were already aphids in the greenhouse earlier in the year so we kept close track of the population to try and catch them as soon as possible. However, immediately after planting the crop was covered with row covers which made scouting difficult. The crop was checked every week (9/16, 9/22) and then every other week (10/6, 10/13, 10/21, 11/5). The first sign of aphids started to show up on October 6, at very low levels (an average of 1.3 aphids per plant). Prior to this scouting date we had decided to be proactive and order and release before significant populations were reached in hopes of stopping incoming pests in their tracks. Therefore the biological control agents Aphidius colemani and A. ervi were released on October 7. The combination of A. colemani and A. ervi was selected to cover the broadest range of aphid species. On the next scouting day (10/13) the population was already on the rise with an average of 24.4 aphids per plant (approximately five leaves per plant). By the next visit the population had completely exploded, only on certain types of greens (mainly the mustards), with numbers being, on average, over 63 aphids per leaf.
Unfortunately there were many factors that made this site difficult to monitor. Due to the placement of the row covers it is possible that the aphid populations were higher on the center rows allowing populations to increase without being detected. Another problem that we faced was the temperature. As we got later into October nighttime temperatures were falling below freezing. This leads us to a question worth addressing; what types of biological control agents would work best in cooler temperatures, or even hotter temperatures?

Location: Keuka Park, New York
High Tunnel/Greenhouse Crop: High Tunnel Tomatoes
Problematic Pest: White Flies
Biological Control Used: Encarsia Formosa (Nile Delta strain)
Dates on Farm: Weekly from July 18 to September 9, 2008
Success Rating (0=failure to 5=control): 3
We visited this farm at the end of April because of a long standing history of whiteflies, figuring it would be a good site to monitor. However, the grower informed us that he had moved the high tunnel and it was sitting on all fresh soil. We all figured these factors would be a cure to the white fly problem and decided not to concentrate on weekly scouting at this site. However, in mid-July the grower contacted us regarding a white fly infestation in his high tunnel tomatoes. At this point initial counts were taken showing approximately 5.5 white flies per leaflet. The biological control agent Encarsia formosa (Nile Delta strain) was ordered immediately and released on July 19. Over the next month averages dropped below the initial counts, ranging from 2.9 to 5.4 whiteflies per leaflet. However on August 25 the population had jumped to 13.5 white flies per leaflet, on average and did not descend for the remainder of the season. This is a case where a second release may have helped. However the initial population was quite large and established when scouting began, which also make it difficult for the beneficial insects to work to their best ability. According to other researchers, there were questions about the viability and quality of E. formosa during the 2008 season.

Location: Dundee, New York (West)
High Tunnel/Greenhouse Crop: Greenhouse Tomatoes
Problematic Pest: Two Spotted Spider Mites
Biological Control Used: Amblyseius californicus
Dates on Farm: Weekly from June 2 to October 13, 2008
Success Rating (0=failure to 5=control): 3
This tomato crop was grown in plastic growing bags and struggled with nutrient deficiencies throughout the growing season making spider mite evaluations difficult. However, there was positively an infestation of mites that was recorded. When scouting began on June 2 the mites already had an established population (average rating of 3.4). Predators were released on July 13 when mite ratings were an average of 6 across the plot (four reps of eight plants each). The spider mite damage rating decreased every week by about one point, ending the season with a 3.5 rating, right about where we started. We have clearly learned that spider mites are a difficult pest to control, however at this site we were able to sustain a manageable level of pests without dramatic damage.

Location: Dundee, New York (East)
High Tunnel/Greenhouse Crop: Greenhouse Tomatoes
Problematic Pest: Two Spotted Spider Mites and Aphids
Biological Control Used: Amblyseius californicus and Aphidius colemani
Dates on Farm: Weekly from April 28 to October 13, 2008
Success Rating (0=failure to 5=control): 4
Scouting at this site began on April 28, at this time we detected extremely low levels of two-spotted spider mites. Scouting continued weekly throughout the season. Spider mite levels remained fairly low within the trial for the remainer of the season. Aphids were first detected on May 19. The grower decided to go ahead with one of their own biological control releases, a fungus AphidStop, on May 23. By the next week numbers had increased to almost 2 aphids per leaf. We released an Aphid and Spider Mite biological control on June 6. Aphid numbers dropped to zero over the next four weeks and spider mites remained in check.

Location: Trumansburg, New York
High Tunnel/Greenhouse Crop: High Tunnel Eggplant
Problematic Pest: aphids
Biological Control Used: Aphidius colemani
Dates on Farm: Weekly from June 9 to August 25, 2008
Success Rating (0=failure to 5=control): 5
Monitoring of the Trumansburg Farm began on June 2 after noticing high levels of aphids (upwards to 100 per leaf) in their High Tunnel Eggplant crop. The following week, June 9, a plot was set up and the aphid population was reported. Initial counts, done on three leaves per plant, ranged from 6 to 22 aphids per leaf, with an average of 12.2 aphids per leaf. With pest levels sky rocketing the decision was made to spray and then release a beneficial insect. The grower sprayed pyganic on June 3 to help knock down the population, followed by the release of a biological control on June 10. The predatory insect selected to control the suspected green peach and potato aphids was Aphidius colemani. The week following the Aphidius release (June 16) the aphid population had nearly been reduced by one third, ranging from 1 to 5 aphids per leaf. Over the next two weeks (June 23 and 30) the population continued to decline to less than one aphid per leaf. Beginning on July 7 the aphid numbers slowly began to increase, however at very low incidence (still less than one per leaf). They remained this low until the crop was finished and removed in late August. Other problematic pests that were identified on the eggplant crop were flea beetles and thrips; however they remained at non-threatening levels.
Location: Hilton, New York (1)
High Tunnel/Greenhouse Crop: Greenhouse Cucumbers
Problematic Pest: Two spotted spider mites
Biological Control Used: Phytoseiulus persimilis
Dates on Farm: Weekly from April 29 to July 15, 2008
Success Rating (0=failure to 5=control): 3
This greenhouse grower has had problems with two-spotted spider mites in his cucumber greenhouse for several years. So much so that he plans on mites ending his production for the season. Scouting began on the vigorous cucumber plants on April 29. Very low incidences of a spider mite population were first detected on May 28. Due to the aggressive nature of this pest the biological control agent Phytoseiulus persimilis was ordered immediately and was released throughout the entire greenhouse one week later (June 3). Over the next four weeks pest pressure increased moderately (from a rating of 1.1 up to a rating of 4.8 over the course of the season) in the experimental plots, however certain areas of the greenhouse were being demolished. After speaking with the grower he reassured us that even though the population did eventually terminate his crop, he was able to gain two to three weeks of additional harvest time than he has in the past. He is confident that P. persimilis did its job in suppressing the spider mite population.

Location: Interlaken, New York
High Tunnel/Greenhouse Crop: High Tunnel Winter Greens
Problematic Pest: Aphids
Biological Control Used: Aphidius colemani and Aphidius ervi
Dates on Farm: Bi-weekly from October 6 to November 3
Success Rating (0=failure to 5=control): 5
This high tunnel had a cover crop in place before the winter greens crop was planted. The grower noticed an aphid population in the cover crop so it was likely that the new crop of winter greens would also be prone to get aphids on them. Scouting began on October 6 with an average of 3.5 aphids per plant. Biological controls Aphidius colemani and A. ervi were released the next day (October 7). Over the next month the population was essentially eradicated.

Location: Hilton, New York (2)
High Tunnel/Greenhouse Crop: Greenhouse Tomatoes
Problematic Pest: none detected
Biological Control Used: na
Dates on Farm: Weekly from April 29 to July 15, 2008
Success Rating (0=failure to 5=control): na
In the past two-spotted spider mites have been problematic pests in this tomato greenhouse. However after a weekly scouting program throughout the 2008 growing season no pest pressure was detected. Therefore biological controls were not necessary.

Location: Dundee, New York
High Tunnel/Greenhouse Crop: High Tunnel Tomatoes
Problematic Pest: not at problematic levels
Biological Control Used: none necessary
Dates on Farm: Weekly from April 28 to August 25, 2008
Success Rating (0=failure to 5=control): na
At this site the high tunnel had been moved to eliminate any reoccurring pest problems. It seems to have worked. Four plots of five plants each were set up in the tomato crop on April 28 and weekly scouting was preformed for sixteen weeks. On the first visit we were concerned about aphids migrating from pepper plug trays that were being stored next to the tomato crop. However once the peppers were removed the aphids went with them. Towards the end of the season (August 18) some two spotted spider mites started to show up. However the crop was almost complete so a biological control would have been impractical.

Location: Manchester, New York
High Tunnel/Greenhouse Crop: High Tunnel Greens
Problematic Pest: none identified
Biological Control Used: none necessary
Dates on Farm: Weekly from April 29 to May 19, 2008
Success Rating (0=failure to 5=control): na
Scouting at this site began on April 29 and continued weekly until May 19. When scouting started spring greens were planted in the high tunnel, however no pests were detected. A summer crop was not planted.

Collaborators: