WSU Nooksack Watershed IPM Mentoring Project in Apples
April thru September, 1997
WSU Nooksack Watershed IPM Project with several grower collaborators/mentors:
Funded by Environmental Protection Agency, Clean Water Act, Section 319 grant; administered by Washington State Department of Ecology.
This mentoring project exposed growers to regular and systematic scouting for key insect, mite, and disease pests in apples during the 1997 growing season. Cooperating growers have and will continue to communicate this scouting experience to other growers in various forums.
Three orchards were scouted on an as-needed basis beginning in late April and continuing through late September up to within a week of harvest. Jonagold is the dominant variety in these blocks interspersed with some Galas. Growers participated in scouting and record keeping activities. Specific scouting methods varied slightly depending on the time of the season and the pests being evaluated. The key pests addressed in this program included codling moth, white apple leafhopper, hemipteran bugs, spider mites, rust mites, and apple scab. Beating trays (described below), field examination, and mite brushing were used to evaluate beneficial insects and predatory mites. Temperature loggers (Optic StowAway, Onset Computer) combined with pheromone trap catch was used to model codling moth development and determine spray needs and timing. This methodology is based on WSU Extension Bulletin 1072 -"Codling Moth Control - A New Tool For Timing Sprays" and decision making guidelines from "Orchard Pest Management" published by Good Fruit Grower. Traps and temperature loggers were checked weekly. First generation white apple leafhoppers were evaluated by examining 25 leaves per site (5 leaves/tree on 5 trees) from five sites distributed throughout the orchard in late May and mid-June after some "stippling" damage became apparent. Beating trays (18" X 18"), designed by WSU Cooperative Extension, and based on the pear psylla tray, were used to monitor beneficial insects and primarily hemipteran pests from late April (bloom) through mid-to late August. 10-25 trays, or limb taps were usually taken from each of five sites throughout the orchard. Field sampling for spider mites using the binomial sampling procedure described in "Orchard Pest Management" was initiated in late May and June. Where spider mite populations increased to potentially damaging levels, leaf samples were returned to the lab and brushed in order to accurately measure spider mite, rust mite, and predator mite densities. Both leaves and fruit were examined for scab lesions periodically for the entire sampling period. Leaf infection was reported on a scale of 0-5 and fruit infection was based on examination of 50 -100 apples per site from five sites per orchard. A thorough fruit examination was conducted before harvest to measure damage from scab, codling moth, and dock sawfly. Results from each visit were recorded on a single page report, which then serves as a snapshot of pest incidence and activity. This information was then used by growers in their decision making process. Each field visit takes approximately one hour, followed by 5-10 minutes to record the findings. Orchards were sampled on five to seven occasions throughout the growing season.
Thiodan and B.t. were applied prior to bloom to control sucking type insects and worms as a preventative treatment. Codling moth BIOFIX (first flight) was set on May 12, based on trap catch in nearby orchards and the degree day model was reset to 200 on that date. First generation codling moth was controlled with a single Guthion application on June 9 at approximately 525-degree days (DD). This orchard has a history of low codling moth pressure. Due to excessive damage to fruit from hail and low second generation trap catch, this orchard was not sprayed again for codling moth. Provado was applied during the first week of July to control a building population of white apple leafhoppers. Beating tray samples taken throughout the season showed very low pest and beneficial insect populations compared to other orchards. Fruit was virtually free of codling moth at the last sample on September 23. Dock sawfly entries ranged from 0-8% at different sites in late September averaging 2.2% across 5 sites.
Spider mites never increased to threatening levels in this orchard. It was treated with Apollo on 4/17 as a preventative. Two species of predatory mites were detected in this orchard in June and July.
Primary scab infection of foliage was present at all sites in late May. Scab pressure was severe this season and this initial infection probably resulted from reduced fungicide coverage and infection that occurred due to a missed spray which should have been applied in early May. In spite of a rigorous fungicide program in late May and early June using a combination of eradicant and protectant materials, secondary infection primarily of foliage took place in early to mid June. Fruit scab infection, first noticed in mid-June ranged from 10-80% at different sites, averaging 40% by late July. Most of the fruit infection was probably from overwintering ascospores (primary infection) rather than due to secondary infection. Pre-harvest fruit evaluation in late September showed similar results regarding scab infection. Unfortunately, this orchard also suffered severe damage from a hailstorm on June 21 which affected 90% of the fruit.
Thiodan was applied prior to bloom in this orchard as a preventative to control sucking insects. Syneta beetles were detected with beating trays in late April averaging .04/tray. By mid May, counts increased to an average of .3/tray coinciding with the end of bloom. This insect, which has been historically a pest in this orchard was treated on 5/14 with a mix of malathion and methoxychlor. Subsequent sampling revealed that good control resulted and that a building population of predatory minute pirate bugs were temporarily reduced in density.
Mid-June beating tray samples found significant populations of a hemipteran at densities averaging 3 nymphs/tray. This white, long-legged nymph was tentatively identified by Booth as Phytocoris spp., which is in the Miridae family and a likely predator. It was not identified to the species level. Several Phytocoris species have been reported in this area; some of which feed on plants, insects and mites, or both. One species, P.populi, which has been reported in Bellingham, feeds on small arthropods including psocids (bark lice) which were also found in this orchard on beating trays. This insect was still present at slightly lower density in mid-August (2.2 /tray) in both adult and nymph stages. Minute pirate bugs rebounded in mid-June and were numerous by early August, found at a density of 8/tray. Beating tray sampling did not continue after this date.
Codling moth (CM) was managed effectively in this orchard with 2 sprays targeting the first generation and a single spray for the second. Guthion sprays were applied at approximately 500 DD, 770 DD, and 1650 DD. Heat accumulation was based on a May 12 BIOFIX when temperature model was reset to 200 DD. Trap catches for the first generation warranted two sprays, but catches never exceeded the threshold of 4 moths/trap during any 21 day period during the second generation flight. This third spray was more preventative in nature. Fruit examination at harvest detected 1st generation CM stings in 3% of fruit at two sites and in 0% fruit in three sites. Overall, 6 stings were detected in 500 apples throughout the orchard (1%). Sawfly damage was not seen in this final survey.
European Red Mites (ERM) were detected on 1-80% of the leaves examined in mid-June. Using the binomial sampling procedure, estimated density was 5 mites/leaf at the most, which is well below threshold. Leaves were collected from each site, brushed, and counted under a microscope in early July. ERM ranged from .3 to 8 mites/leaf, averaging 3.4/leaf. Stigmaeid predator mites were found at all sites ranging from .1 to .5/leaf. Apple rust mite populations ranged from 500 to 1000/leaf. This orchard has a history of high rust mite populations. They were treated with a low rate of Thiodan in mid-July. Populations declined by early August to 50 rust mites/leaf. Mite brushing was repeated in late July and early August. ERM never increased significantly above early July levels, and predator mites were detected at densities up to 1.6 mites/leaf in early August in a Gala portion of the block, which harbored 6 ERM/leaf at the time. The Thiodan application in July did not significantly disrupt the predator mite and spider mite balance.
Primary scab was well controlled in this orchard. Secondary foliage or fruit infections were not observed at any significant level through the entire season.
Thiodan, occasionally used prior to bloom to control sucking insects which can damage fruit, was not applied prior to bloom in this orchard. Beating tray samples in late April (king bloom) detected 1 adult lygus bug in 90 samples throughout the orchard. Lygus was detected again at a similar low density in mid-May. Syneta beetles were detected at low density (l -2/100 trays) in mid to late May. Beating tray samples detected three different bugs in the Miridae family in the early summer. The dominant one was Phytocoris spp. (also found at the Copeland orchard) at an average density of .4/tray in mid-May. The adult stage of this insect began to appear in July. The other bug detected in mid-May was a small whitish nymph with red and white barred antennae. This insect took on a reddish color in late May. It was tentatively identified by Booth as either Dicyphus, which is not that predaceous or Diaphnocoris, which is. A third bug, detected in June has distinctive flattened antennae. It is in the genus Heteratoma, and is most likely H. planicorne. It has been reported in British Columbia on Scotch broom and apple. In England it is reported to attack ERM and sometimes feeds on apple foliage and fruit. It is also a known aphid predator.
Codling moth traps were not placed in this orchard until mid-June, but catch at nearby orchards was used to establish a May 12 BIOFIX. This orchard has a history of moderate CM pressure. Guthion was applied at 500 DD and 850 DD to control first generation CM. Imidan was applied in early July within a week of the second Guthion due to heavy rains following that spray. With second generation trap catch approaching threshold, Imidan was applied on August 11 at 1600 DD. Fruit examinations in late September detected no damage from either codling moth or dock sawfly.
Field sampling for mites from late May through mid-July showed very low spider mite populations in this orchard. Leaves were collected for brushing in early August. This orchard had a mix of ERM and twospot spider mites. Combined spider mite populations were very low in the Jonagold samples (< 2 mites/leaf). Density was greater in the Galas (2 ERM/leaf and 7 twospot/leaf), but still well below treatment level. Rust mites ranged from 19 - 80/leaf across 4 sampling locations in this orchard. Two species of predator mites were present at densities favorable for biological control and were quite evenly distributed throughout the orchard. Typhlodromus occidentalis, the western or orchard predator mite, averaged 1.2 mites/leaf and a Stigmaeid mite (most likely Zetzellia mali) averaged .5/leaf. No miticide sprays were necessary in this orchard.
Infection of both leaves and fruit was first detected under this monitoring program on June 19. Most of the infection was located in the upper portion of the canopy and resulted from spray equipment failure which reduced the fungicide coverage in this zone. This allowed for ongoing secondary infection of leaves primarily from spores that were rain-splashed to lower portions of the trees. Fruit infection in mid-July was estimated at 20 to 40% in the scab infected areas. Late September fruit examination revealed a range of 2% to 20% scabby fruit across 5 sites, averaging 10% in the orchard. The grower had removed lots of cull fruit prior to this visit; much of the cullage due to scab.
The combination of pheromone trapping and using temperature loggers to model coding moth development provides a good system to schedule and determine the need for CM sprays. Most orchards have a favorable ratio of predator mites: spider mites which implies that current pesticide programs are not significantly disruptive to this balance. Mite brushing provides a more accurate assessment of mite populations than field evaluations, but it also requires added expertise and effort which growers may not pursue. Importance of controlling primary apple scab infection. Orchards can be scouted in about one hour. Insect and mite densities vary between orchards.
Incorporate this experience into the IPM scouting manual for apples. Encourage mentors to share this scouting experience with other growers. Investigate the apple scab ascospore maturity model as a tool to help manage the primary infection period of this disease. Pursue identification of hemipterans and determine whether they are beneficial or pestiferous or both. Identify technology and training needs or services that can be transferred to growers to assist them in continuing a similar program. ie: Temperature loggers, mite brushing equipment etc.
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IPM Mentoring Summary 1997
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WSU Nooksack IPM Project | ||||
| Apples | |||||
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Crop Stage and Number
of Scouting Visits
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| Pre-Bloom | Bloom | Early Summer | Late Summer | Pre-Harvest | |
| Scout Period: | Late March | 4/20 - 5/15 | 5/16- 6/15 | July & August | September |
| # Visits | None | 2 | 2 | 2 | 1 |
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Insect and Spider Mite
Spray Requirements
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|||||
| Pest |
# Fields of 3 scouted that were
treated with a pesticide application to control listed insect of mite
pest during these crop stages.
|
||||
| Sucking Insects | 2* | ||||
| Leafrollers | 1 | ||||
| Leafhoppers | 2 | 1 | |||
| Syneta Beetle | 1 | ||||
| Spider Mites | 1 | 0 | 0 | 0 | 0 |
| Rust Mites | 0 | 0 | 1 | 0 | |
| Codling Moth | 3 | 2 | 0 | ||
| Dock Sawfly | 0 | ||||
| indicates key monitoring period for specific pests | |||||
| *preventative spray targeting miscellaneous sucking insects | |||||
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Disease Development
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| Pre-Bloom | Bloom | Early summer | Late Summer | Pre-Harvest | |
| Late March | 4/20 - 5/15 | 5/16 - 6/15 | July & August | September | |
| Disease | |||||
| Apple Scab | Primary | Primary | Secondary | Secondary | Secondary |
| (Key scab fungicidal control period) | |||||
| Anthracnose | Summer Lesions/cankers developing on bark | conidial infection | |||
| begins | |||||
| (Canker removal period) | |||||