Biological Control of Pear Psylla

Transcription

1 Biological Control of Pear Psylla In Areawide Organic Insect Pest Management Tara M. Madsen and John E. Dunley WSU-TFREC

2 Introduction The role of predatory arthropods in Organic orchard pest control: the assumptions Less disruptive pesticides; beneficial insects more common Natural enemies assist softer, less effective chemicals Pest control is achieved by NEs No direct documentation of levels of biological control in pear orchards Areawide organic pest management An opportunity to study predation where biological control is most likely to be observed

3 Methods Pests and predators monitored at a large scale in Peshastin Creek Areawide Organic Project since 22 Narrow valley in central WA, ~ 3 ac. pear, surrounded by native veg. Three treatments: Organic, Soft, Conventional Beating tray samples from 41 plots, 2-1 acres each NEs monitored on 75 m transects since 23 Nine sites, three in each management type (originally) Perpendicular to orchard edge, extend 25 m into surrounding vegetation Beating tray samples, five locations per transect Levels of predation monitored with sentinel prey on some transects Flash-frozen Ephestia eggs on 1.5 x.75 in. cards Monitored for mortality at 24, 48 and 72 h

4 Large Scale Sampling Natural enemy densities in Peshastin Project NE densities in Organic and Soft > than Conventional orchards Mean total NEs / 25 trays * + Mean total NEs / 25 trays * conv soft org conv soft org

5 Large Scale Sampling Pear psylla densities in Peshastin project 2 4 Mean number of adult pear psylla per tray sample Pear psylla Org 3 Soft 3 Conv 3 Org 4 Soft 4 Conv 4-2 3/2/4 5/9/4 6/28/4 8/17/4 Date

6 Large Scale Sampling Natural enemy densities in Peshastin Project Mean number of predators per tray sample Predators /2/4 5/9/4 6/28/4 8/17/4 Date Org 3 Soft 3 Conv 3 Org 4 Soft 4 Conv 4

7 Large Scale Sampling Spiders, Dereaocorids, most numerous NEs Org, 23 (ave total = 4.74 NEs per 25 trays) Trechnites,.31 Spider,.94 Deraeocorid, 1.87 Campylomm a,.47 Lacewing,.44

8 Org, 23 (ave total = 4.74 NEs per 25 trays) Trechnites,.31 Org, 24 (ave total = 4.98 NEs per 25 trays) Wasp,.22 Spider,.94 Deraeocorid, 1.87 Ant,.5 Dereaocorid, 1.57 Campylomm a,.47 Lacewing,.44 Soft, 23 (ave total = 2.62 NEs per 25 trays) Less than Org, 2.9 Deraeocorid,.6 Spider,.8 Conv, 23 (ave total = 1.4 NEs per 25 trays) Anthacorid Dereaocorid Lacewing Lady Beetle Campylomma Spider Ant Earwig Trechnites Wasp Snakefly Lady Beetle,.3 Soft, 24 (ave total = 4.28 NEs per 25 trays) Trechnites,.88 Less than Org,.71 Dereaocorid,.82 Ant,.51 Campylomma,.39 Spider,.74 Conv, 24 (ave total = 1.61 NEs per 25 trays) Dereaocorid,.4 Spider,.52 Spider,.28 Less than Org, 3.31 Less than Org, 3.38

9 Large Scale Sampling Predator composition changed only marginally between years NE density increased in Soft in 24

10 Ave. density of NEs, 23 Org Soft Conv Mean per 25 trays Lacewing Campylomma Trechnites Spider Deraeocorid Snakefly Earwig Anthocorid Ladybird Wasp Ave. density of NEs, 24 Org Soft Conv Mean p er 25 tray s Lacewing C am pylomma Trechnites S pider D ereaocorid A nt A nthacorid Lady B e etle W a sp S nakefly E a rw ig

11 Large Scale Sampling NE densities in Organic and Soft > than Conventional orchards Spiders, Dereaocorids, most numerous NEs Predator composition changed only marginally between years NEs increased noticeably in Soft in 24 Soft and Organic pest control means more predators Or maybe slightly higher pear psylla density means > NEs Or maybe low economic threshold for control of PP limits NEs Or maybe decades of chemical control have reduced the potential diversity of NEs permanently

12 Transect Sampling Surrounding vegetation 1 Orchard 2 Mean number of NEs / tray Org 23 Soft 23 Conv 23 Org 24 Soft 24 Conv Location on transect

13 Transect Sampling Transect sampling reveals an uneven distribution of predators Consistently higher average densities in surrounding vegetation than within orchards Surrounding vegetation 1 Orchard 2 Mean number of NEs / tray Org 23 Soft 23 Conv 23 Org 24 Soft 24 Conv Location on transect

14 Transect Sampling In 23, NE densities in management types not significantly different from each other overall 23 NE density.4 Mean number of NEs per tray sample Conv Soft Org

15 Transect Sampling In 23, NE densities in management types not significantly different from each other overall In the surrounding vegetation levels were highest in Organic treatments and lowest in Conventional In the orchard, Soft treatments had higher levels than Conventional treatments, with Organic intermediate 23 NE density in Surrounding Vegetation 23 NE density in Orchard.7.25 Mean NEs per tray sample Mean NEs per tray sample Conv Soft Org Conv Soft Org

16 Transect Sampling In 23, NE densities not significantly different from each other overall In 24, Soft treatments had more NEs overall than Conventional, with Organic intermediate 24 NE density Mean number of NEs per tray sample * + * Conv Soft Org

17 Transect Sampling In 23, NE densities not significantly different from each other overall In 24, Soft treatments had more NEs overall than Conventional, with Organic intermediate The vegetation showed no differences between treatments In the orchard, levels in Soft treatments were significantly higher than in other treatments 24 NE density in Surrounding Vegetation 24 NE density in Orchard.6.45 * Mean NEs per tray sample Conv Soft Org Mean NEs per tray sample Conv Soft Org

18 Transect Sampling The predators tend to vary by habitat type Spiders were the most common NEs in both habitats Dominant NEs in the Orchard were Green lacewings Deraeocoris Trechnites The Surrounding Vegetation supported more ants Ladybird beetles Snakeflies Geocoris Nabidae

19 Transect Sampling Two orders with consistent differences in density between surrounding vegetation and orchard Arachnida Hymenoptera Higher in the surrounding vegetation in all treatments Orch 23 Veg Orch 24 Veg Conv Soft Org Conv Soft Org Conv Soft Org Conv Soft Org Conv Soft Org Madsen and Dunley, January Arachnida 25. Coleoptera WSU-TFREC Hemiptera Hymenoptera Neuroptera

20 Transect Sampling Two orders with consistent differences in density between surrounding vegetation and orchard Arachnida Hymenoptera Higher in the surrounding vegetation in all treatments Orchard Orchard Vegetation Orch Org Orch Soft Orch Conv Veg Org Veg Soft Veg Conv Vegetation Orch Org Orch Soft Orch Conv Veg Org Veg Soft Veg Conv Arachnida Coleoptera Hemiptera Hymenoptera Neuroptera -.7 Arachnida Coleoptera Hemiptera Hymenoptera Neuroptera

21 Transect Sampling In 23, the management types not significantly different overall In 24, Soft treatments had more NEs overall than Conventional, with Organic intermediate An uneven distribution of predators Predators differ by habitat type Soft and Organic programs have more NEs Increase is due to extended use of Soft/Org chemicals Increase is a seasonal anomaly

22 Sentinel Prey

23 Sentinel Prey.8 Sentinel prey mortality Location on transect (m)

24 Sentinel Prey Results from the sentinel prey predation and exclusion cage study consistent with results from transect monitoring Predation tended to be greater in surrounding vegetation

25 Sentinel Prey Results from the sentinel prey predation and exclusion cage study consistent with results from transect monitoring Predation tended to be greater in surrounding vegetation Levels of potential predation, based on mortality of sentinel prey over 24 to 96h, tended to be Higher in surrounding vegetation than in orchard habitat Did not vary consistently by distance within a habitat type Predation levels were relatively low in general

26 Conclusions Soft and Organic programs do tend to lead to increased numbers of NEs Differences vary with the season, and might be slight or negligible Increased NE density might reflect PP density as much as selectivity of program Upper limit of NE density is determined by PP density Economic threshold for control of PP is quite low The use of even cert. Organic sprays, including oils, may limit density and diversity of NEs

27 All results are preliminary, and research will continue in 25. Thanks to: The Peshastin Creek Growers Association Washington Tree Fruit Research Commission