Washington State University Cooperative Extension
The Newsletter of Pheromone-based Orchard Pest Management
Vol. 2, No. 8 -- July 1, 1997
Cooperating agencies: Washington State University, Oregon State University, University of California, U.S. Department of Agriculture, and Chelan County.
Cooperative Extension programs and employment are available to all without discrimination.
Potential for monitoring campylomma with pheromone traps
By Larry J. Gut & Jay F. Brunner
Campylomma is a true bug that damages apple fruitlets during a relatively short period around bloom. This early season feeding causes a reaction in the fruit, producing a raised wart usually surrounded by a shallow depression. The level of damage in a particular apple orchard depends on pest pressure and the sensitivity of the cultivar.
Most growers have learned how to avoid crop losses caused by campylomma feeding. Monitoring populations from pink through bloom is the key component of a pest management program for campylomma. The most widely used sampling method is a beating tray sample. Action thresholds based on the number of nymphs found per tray have been established. Treatments are suggested if 4 nymphs per tray are found on Delicious, or 0.3 nymphs per tray on susceptible cultivars such as Golden Delicious. Decisions based on beating tray samples are effective, but two factors set some limits on their usefulness. The distribution of campylomma is often clustered, thus a fairly high number of trays is required to accurately sample a population. Additionally, because factors such as weather during the pre-bloom period can influence campylomma hatch and activity, multiple samples throughout the pink to petal fall period are often required to establish that an orchard is clean.
A brief review of the life history of campylomma is needed to help explain how pheromone traps might be used to improve monitoring and management programs for this pest. Campylomma overwinters as an egg on a woody host such as apple. Nymphs from the overwintering eggs are present from mid-April to mid-June in Central Washington. Most adults leave the orchard and complete 1 or 2 generations on herbaceous hosts, especially mullein. Adults return to orchards in late summer to mate and lay overwintering eggs. Within the orchard, female campylomma release a sex pheromone to attract potential mates. Thus, it is during this migration back to apple orchards that pheromone traps can be used as a monitoring tool.
The sex pheromone of campylomma has been identified and researchers have determined that adult males are highly attracted to a trap baited with a synthetic copy of this pheromone. For the past two years, we have been assessing the utility of pheromone traps for monitoring the return of campylomma to apple orchards in late summer. Previous studies indicated that a wing-type trap with spacers between the trap top and bottom was an effective trap (Reding and Beers, pers. comm.). Our studies suggest that a single wing trap baited with campylomma pheromone provides a good assessment of campylomma movement into about a 10 acre apple block. Moreover, adult captures in traps in September appear to be a good indicator of the relative risk of campylomma damage during bloom of the following year. Campylomma nymphs have consistently been absent or in very low densities in orchards where less than 40 adults/week were captured in traps the previous summer. Higher captures in pheromone traps, especially those above 80 trap/week, often have indicated a higher campylomma risk the following year. However, sometimes very low campylomma nymph densities are found, despite high adult captures in traps. This situation occurs primarily when hatching nymphs are controlled by the residual effect of the delayed dormant chlorpyriphos treatment.
Our objective is to develop a tool that will compliment, rather than replace, the very effective monitoring program currently in use, i.e. sampling with a beating tray. Treatment thresholds based on beating tray counts have been very reliable. In contrast, thresholds based on adult catch in pheromone traps have not been developed. Several factors, such as the effect of chlorpyriphos, make it difficult to correlate adult catch in the summer with nymph densities during bloom the following year. A more realistic role for campylomma pheromone traps is to identify orchards that are at risk from this pest and should be the focus of a beating tray sampling program. The major benefits of using campylomma traps would be (1) to eliminate the need for time-consuming beating tray counts in as many orchards as possible, and (2) to free up time that could be used to increase the accuracy of monitoring in high risk orchards (by taking extra beating tray samples). In our studies, adult captures in pheromone traps identified over 60% of the orchards as very low risk, requiring no beating tray counts in the spring.
You may be wondering about the extra effort required to use the pheromone traps. We have tried to develop a campylomma trapping program that is user-friendly. Trap density and placement do not appear to substantially influence the performance of campylomma traps. When multiple traps are placed in a 10-acre block, they all catch similar numbers of individuals. Thus, 1 trap per 10 acres is probably sufficient. Campylomma adults are readily captured in a trap that is placed at a height easily reached from the ground. There is very little variation in adult captures throughout September, i.e., no peak period that needs to be targeted. Thus, traps can be placed in the orchard any time in September the user finds convenient. One count of adult catch over a 1-2 week period is all that is needed. Traps can be removed after the count is taken and stored for use the following year.
We plan to evaluate this trapping program in many commercial orchards this year. If you would like to participate in the study, please contact Ted Alway (509-664-5540). Your commitment for participating is to place traps in orchards in September and monitor campylomma flight for at least a one-week period (two weeks would be great) and provide us with the counts. Then, next year, monitor the same orchards with a beating tray, taking at least two samples of 10-20 trays, and again provide us with the information. Give it a try youll like it!
Summer apple aphid management
Green aphids are among the most common insects found in apple orchards during the summer months. There are actually two species of aphids, indistinguishable in the field, that are found feeding on terminal growth at this time: the apple aphid (Aphis pomi), and the spirea aphid (Aphis spireacola). These aphids can cause damage in the summer in one of two ways. First, their feeding on growing shoots can reduce or stop growth, a particular concern with young trees where maximum growth is desired. Secondly, they excrete honeydew which, when it falls on the fruit, is often colonized by a black, sooty fungus. This "sooty mold" cannot be removed from the stem cavity of apples and will result in downgrading and cullage, particularly of light-skinned varieties like Golden Delicious. With the ongoing changes in apple varieties, training systems and pest control programs, I interviewed a number of consultants to learn about their current aphid monitoring and management programs.
The consultants interviewed use a fair amount of qualitative assessment of aphid populations, trying to get a "feel" for the risk they posed. A few quantified aphid numbers by noting the percent of infested terminals together with a measurement of colony size, expressed as either "infested leaves/terminal" or "inches of aphids/terminal." This was generally done to establish a trend, or when aphids appeared to be close to a treatment threshold. Most biased their samples toward more infested blocks, more susceptible cultivars (e.g., Golden Delicious), and blocks of young trees (5th to 6th leaf or less) where growth reduction was the concern.
Dr. Elizabeth Beers of the WSU-TFREC in Wenatchee conducted several years of research into the correlation of aphid numbers with fruit damage. She was unable to find a good relationship between quantified populations (determined by several sampling methods) and damage. This relationship is greatly influenced by a number of factors, including tree shape, age, cultivar and vigor. She did find that spur-type apples, with more fruit in close proximity to leaves, have a tendency toward more honeydew on the fruit with a given population size. Dr. Beers is presently undertaking a long-term study of the effect of aphid population size upon growth in newly planted trees.
Several consultants recommend treatment in mature blocks when more than 50% of terminals are infested with aphids on an average of 4-5 leaves/terminal, or 4-5 inches of shoot growth. Most consultants dont rely strongly upon a certain numerical threshold because of the many modifying factors they consider in their decision. They are more likely to treat with cultivars like Golden, Gala and Granny Smith, with high vigor trees, with young trees, when honeydew is beginning to accumulate on the fruit, when aphid colonies are close to fruit, and when natural enemies (mostly predators like lady beetles and lacewings) are rare.
Natural enemies are noted in surveys by most consultants, and are often counted in terms of number per terminal or percent of terminals with predators. Those most frequently found are coccinellids (lady beetles), lacewings, syrphid fly larvae, and campylomma. Although several types of predators occur in apple orchards, generally one type of predator predominates in a particular orchard at a given time. Several consultants have seen potential problem aphid populations cleaned up nicely by predators, particularly cecidomyiid larvae (predatory larvae of a small fly), and campylomma, especially later in the summer. Aphid parasitism by parasitic wasps is common, particularly early in the season. The main wasp species, however, dont complete development on apple aphid, so the biological control they provide is limited.
Imidacloprid (Provado∆) is the material of choice, according to these consultants. It controls aphids quickly, and is less toxic to most predators than the organophosphate and carbamate insecticides available. It has also indirectly encouraged better biological control by allowing growers to hold off on treatment and give the natural enemies a chance to work; if control is eventually needed, imidacloprid can "rescue" the situation. Higher rates of this insecticide (6 oz./acre) are recommended with high aphid populations and cool weather, with rates as low as 1 to 2 oz./acre used with hot temperatures and the addition of an organosilicone spreader. Some consultants try not to completely eliminate the aphids, adjusting rates to leave a small residual population for aphid predators to feed upon.
Most consultants see more consistent biological control of aphids where the use of broad spectrum insecticides has been reduced or eliminated, as in orchards using codling moth mating disruption. This trend also been found in the mating disruption blocks that Dr. Beers is monitoring for secondary pests across Washington, in comparison with conventionally managed blocks.
A consistent relationship exists between tree vigor and aphid populations. Aphids reach higher levels in blocks where terminal growth continues well into the summer. One consultant noted that aphids increase with the application of foliar urea sprays, as is done in some Granny Smith blocks. Conversely, another consultant found that aphids were generally lower year after year in blocks in which the grower had reduced nitrogen levels to improve fruit color on Red and Golden Delicious.
Several tours are planned for this summer featuring developments in tree fruit pest management, including information on new insecticides, mating disruption and other new pest control technologies.
|Thursday, July 10||Chelan, WA||2:00 PM
| ||Apple IPM tour, featuring the Codling Moth Areawide Management Program, Year 3 of the SARE program (producing apples without broad spectrum insecticides), presentations on new traps and lures for monitoring codling moth and leafrollers, and more!
Meet 2:00 PM in the parking area by the office of Naumes, Inc., on Highway 151, just east of Chelan.
|Tuesday, July 29||Wapato, WA||1:30PM
| ||Yakima Valley Tree Fruit IPM Tour, with presentations on new mating disruption technologies, including "the puffer" and sprayable pheromone formulations, areawide management programs (CAMP), and new developments in orchard pest control research (such as the intriguing "M96").
Meet 1:30 PM at the Redman and Sons parking lot, on Kays Road, off of Lateral A.
|Thursday, August 7||Brewster/Bridgeport area, WA
| ||All-day tour of several sites of horticultural and pest management interest, including BAM (Brewster Areawide Management), the largest codling moth mating disruption area in North America (!), and other pest-control developments.
Time and meeting location to follow in next newsletter.
International mating disruption experts to visit Washington
Two of the world leaders in studies of mating disruption of codling moth, leafrollers, and related insects will be visiting Washington this summer. Dr. Max Suckling with New Zealand HortScience and Dr. Gerhard Karg with the University of Kaiserlautern in Germany have published research on the distribution of pheromone in treated orchards and vineyards, the role of the absorption of pheromone by leaves, and the relationships of pheromone point sources, atmospheric pheromone concentration and moth behavior. They will be in Washington for several weeks visiting with scientists and collaborating on research.
While in the state, they will present two seminars open to interested members of the fruit industry. These are scheduled for:
|Tuesday, July 29||USDA Yakima Agricultural Research Lab, Wapato
| ||10:00 AM|| ||Conference Room
|Wednesday, July 30||WSU Tree Fruit Research and Extension Center, Wenatchee
| ||3:00 PM|| ||Conference Room
Pheromone lures for newly identified cutworm
In recent years there have been some increased cutworm infestations of apple trees reported. Larvae have been found feeding on apple foliage and fruit throughout the tree not limited to low limbs and weedy patches, as is common with most cutworm species. Larvae were collected from orchards in the Columbia Basin, Yakima Valley, and Milton-Freewater areas, in both organic and conventionally-managed orchards. The culprit was identified by Dr. Peter Landolt of the UDSA-ARS lab in Wapato as Lacanobia subjuncta.
L. subjuncta has two generations per year in the Yakima Valley. Larvae were found last year in July and again in September and early October. Moth flights occur in June and August. Dr. Landolt and Connie Smithhisler have identified the components and ratios of this noctuid moths pheromone, and this pheromone is now available commercially. Those wishing to monitor for the presence and flight of the moths can buy red rubber septa containing the pheromone from Scenturion, Inc., at 360/341-3989.
Ted Alway, Editor
Phone: (509) 664-5540
Fax: (509) 664-5561
Partial Funding provided by: Washington State Tree Fruit Research Commission, U.S. Department of Agriculture-Agricultural Research Service.
AREAWIDE IPM UPDATE
WSU Cooperative Extension, Chelan County
400 Washington St.
Wenatchee, WA 98801
Wenatchee WA, 2 July 1997