March 11, 2003
Vol. 5 No. 1
By Mike Doerr, WSU-TFREC, Wenatchee, WA
Welcome to 2003!
We have had big changes in the Areawide II (AWII) program at Washington State University Tree Fruit Research and Extension Center. Ted Alway, coordinator for 2001-2002, has moved on to begin restoring native vegetation in the Wenatchee National Forest one plant at a time; well, more like 10,000 plants at a time. I, Mike Doerr, have moved in to oversee the final year(s) of the project. It is my goal in the newsletter series to highlight some of the exciting research being conducted throughout the fruit growing regions of the western United States and funded by IFAFS/RAMP. This issue will focus on the California implementation project as well as some new stink bug research by Drs. Jocelyn Millar and Heather McBrien.
Review of California's implementation project
The California Implementation Project is coordinated by Drs. Bob Van Steenwyk and Steve Welter (UC Berkeley). Van Steenwyk established six demonstration pear orchards (4-Sacramento Delta, 2-Mendocino County) to participate in the IFAFS/RAMP program. Each orchard was divided into 6 treatments:
- OP insecticide + postbloom Agri-Mek
- OP insecticide - postbloom Agri-Mek
- Avaunt + postbloom Agri-Mek
- Intrepid + postbloom Agri-Mek
- Intrepid - postbloom Agri-Mek
- Untreated control
Mating disruption (Isomate C+ at 400 d/a) was applied to all treatments. The general treatment protocol called for Avaunt or Intrepid to be applied two or three times, while Imidan or Guthion was applied only once to the OP treatments. The objective of the AWII pear program was to determine whether eliminating certain insecticides known to be disruptive of many natural enemies in pear orchards could improve the biological control of several key pear pests, including pear psylla, spider mites and grape mealybug.
Preliminary findings indicate that CM populations were maintained at commercially acceptable levels in most orchards (one exception) by the pheromone disruption. One orchard in the Sacramento delta had unacceptable CM infestation and was treated out after the first generation evaluations. In Mendocino County, all programs (both "standard" and "OP-free") that did not receive a post-bloom Agri-Mek application had increased levels of spider mites and required a mid-season application of Apollo. Also increased spider mite populations were observed in the "standard" and Agri-Mek program, but spider mite populations were not high enough to require an application of Apollo. No increased pear psylla populations have been observed as of the first of August, although increased pear psylla populations are expected towards the later part of August. In the Sacramento delta studies, the elimination of Agri-Mek in the "standard" caused increased levels of pear psylla and required an application of Provado in one orchard. No increased spider mite populations have been observed as of the first of August, although increased spider mite populations are expected towards the later part of August.
Dr. Welter is evaluating alternative pheromone delivery technologies for mating disruption including microencapsulated sprayable pheromones and puffer systems (Suterra, Inc, 3M and Pacific Biocontrol) as well as standard hand-applied dispensers (Isomate C+). The most exciting results have been noted in Walnuts. Drs. Welter and Van Steenwyk will focus a portion of California's implementation project for 2003 and beyond to expanding codling moth mating disruption into Walnuts.
Stink bugs making beautiful music
Drs. Jocelyn Millar (UC Riverside) and Heather McBrien are committed to developing better stink bug traps and improving trapping protocols. Of particular interest to me is their study of vibrational cues or songs, which adults use for mate location over short distances once the insects are on the same plant. The songs are created deep within the stink bug's body and as their body shakes to the beat of their favorite love song the vibrations are carried through their legs and into the plant substrate.
To study these songs two virgin, sexually mature bugs were placed on a membrane of a low-range loudspeaker. The bugs were trapped on the drum and the beat played onÖSignals from the loudspeaker were amplified, digitized and recorded for our pleasure. Digitized recordings were burned onto compact discs and are currently available at Amazon.com/popular bug music. Signals were followed in real time with headphones. The duration, repetition and frequencies of pulses were determined from recordings for a variety of species. The researchers also categorized which songs each sex was performing in the absence of their significant other. Mating behavior was linked to bug songs by simultaneously observing and recording positions and behaviors on bean plants.
A simple prototype of a playback device was constructed by Dr. Mike Delwiche (Dept of Agricultural Engineering, UC Davis) for incorporation into pheromone traps. This device consisted of a battery power source, a simple amplifier, and an electronic chip for storage of the bug vibrational songs. The quality of the resulting played back signal was tested by making recordings of the signal using the recording equipment described above.
The male and females stink bug use these songs to locate each other over short distances (<2m) and once they are on the same plant. These songs may be critically important in attracting bugs all the way into traps, thus improving the efficiency of the monitoring tools currently available. Researchers often observe stink bugs clustered around pheromone traps, with few or no bugs actually in the trap. Drs. Millar and McBrien believe the pheromone produced by the male bugs attracts females to their general vicinity, but once close by, the vibrational signals are used as directional beacons to guide the walking bugs to each other. Drs. Millar and McBrien think incorporating these signals into pheromone-baited traps may considerably increase the trap catches. The songs of many of California's economically important stink bugs have been recorded, including Nezara viridula, Acrosternum hilare (Green soldier bug), Euschistus conspersus (Consperse stink bug), Thyanta spp. (Red shouldered stink bug), Murgantia histrionica, and two Chlorochroa spp. (C. uhleri and C. sayi). Several of these are important stink bug pests in Washington state as well.
Stink bugs are pretty clever creatures. A keen biologist might think that a predator or parasite could eavesdrop on these love songs and breakup this tryst. But these songs are vibrational and the airborne sound component is limited. Therefore, biological control agents could only "hear" the songs if they were on the same plant as the singing stink bug. Dr. Millar has begun the development of incorporating this library of songs into playback devices that could be incorporated into the currently available traps. Initial screening of the recorded songs was tested on soft-stemmed plants, but Dr. Millar is currently working on an efficient method of sending these signals through a more solid substrate such as a wooden post or tree branch that would support a trap.
Dr. Millar is also working on improving the now commercially available stink bug traps and lures. He found no advantage to adding a Vapona kill-strip inside the traps as a method of retaining bugs. Further, he found that the red shouldered stink bug was attracted to a technical grade pheromone easily obtained from ginger oil, and expensive pure pheromone is not necessary to attract this species. Dr. Millar also found that the 85% pure consperse stink bug pheromone works as well as the more expensive, highly purified pheromone.
Mike Doerr, Coordinator Areawide II
Phone: 509-663-8181 x248