Written by Louis Nottingham, WSU Entomology. June 3, 2021
Pear Psylla’s Current Status: Old nymphs (hardshells) from the first generation are still present but declining. Summerform adults and eggs are rapidly building in cooler locations (Cashmere) and nearing peak at 1500DD in warmer ones (Medford). Early instar nymphs of the second generation are building in all locations, and will peak at 1750DD. Hardshells of the second generation are just starting in all locations.
Pear psylla IPM Recommendations (by Category):
A particle film should have been applied at 800DD, but if not, do so ASAP to help deter further egg-lay. Our experiments have shown that spraying particle films after egg-lay provides some control of nymphs, however, it is less effective than spraying before egg-lay. It is still early enough that particle films will not leave problematic lasting residues on fruit; however, past the first week in June there could be issues, especially for early harvested red pear varieties.
Conventional IPM Insecticides
Two Ultor sprays should occur after petal fall, one at 1000DD and a second 14 days later. If your populations are consistently above 1 psylla adult per tray, you can apply Ultor + Esteem together. Neither Ultor or Esteem will reduce adult numbers but will prevent nymph development. While it may not be immediately gratifying, this slow kill is much better for promoting natural enemies.
*Both Ultor and Esteem can only be used twice per season, and consecutive sprays cannot be applied less than 14 days apart.
Cinnerate and/or neem products (but no neem on Comice) are effective on psylla, but may need to be sprayed as tank mixes and repeatedly from 1000 to 2200DD (around July 1) to keep populations suppressed. Monitor populations to determine spray frequency and tank mixing needs. The goal is to keep your population at or below one psylla per tray. Stop spraying after 2220DD, because these products will not control hardshell nymphs.
Two main cultural strategies can be used for pear psylla: 1. Summer pruning and 2. Honeydew washing.
Summer Pruning: The removal of vegetative shoots (water sprouts) from trees. This not only improves spray penetration, it can reduce the psylla population and amount of honeydew in trees if timed correctly. Aim for 2000–2200DD to maximize psylla removal. Summer pruning can occur later in the season at 3100DD as well, however, there is a greater a risk of sunburned fruit.
Honeydew Washing: The process of washing honeydew from trees by overhead sprinklers or airblast sprayer. This method is different from overhead irrigation because it is only used to remove honeydew (we highly recommend performing general irrigating with under tree sprinklers to reduce the risk of diseases). Because washing too often and for too long can cause disease issues, it is important to only wash when there is enough honeydew to cause injury. Wash near the end of the hardshell stage for each generation, around 1400, 3000, and pre harvest if honeydew is high. These timings are not exact, but research to determine thresholds and timings for washing is currently underway. If using overheads to wash, we recommend about 6 hours of runtime for a system delivering ~70 gallons of water per acre per minute. A nonionic surfactant like Regulaid can be mixed in halfway through the cycle to improve honeydew removal. For airblast sprayer washes, use at least 800 GPA for smaller trees, and increase gallonage with tree size; the goal is to make water run off all leaves.
Remember, a soft codling moth program is critical to conserve natural enemies that control pear psylla. Mating disruption and first sprays should have already occurred by this point. Soft codling moth spray materials include: oil, granulosis virus, Intrepid (methoxyfenozide), Esteem (pyriproxyfen) and Altacor (chlorantraniliprole).
All the methods suggested above will have low impacts on natural enemies. Natural enemies like lady beetles (Fig. 2A), predatory bugs (Fig. 2B), and parasitoid wasps (Fig. 2C) are critical to prevent psylla and mite population explosions closer to harvest, and they do it for free! So avoid broad spectrum materials, especially multiple products at a time.
Louis Nottingham, Ph.D.
Research Assistant Professor
Dept. of Entomology, WSU TFREC, Wenatchee WA
Funding and Acknowledgements: This project to develop psylla model recommendations is funded by the Fresh and Processed Pear Committees of Washington and Oregon and a WSDA Specialty Crop Block Grant. The psylla model was developed by Dr. Vince Jones. Model visualization graphics are being performed by Dr. Robert Orpet. Recommendations are based on research from various research and extension groups, primarily L. Nottingham and T. DuPont.
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