Pear psylla adults feeding on pear shoot. Photo G. Krawczyk, Penn State
In our Penn State Fruit Research and Extension Center (FREC) orchards the biofix for redbanded leafroller (RBLR) was established on March 30, for the tentiform leafminer (TFLM) on April 12 and for the Oriental fruit moth OFM) on April 22. This year's date for the OFM biofix is one of the latest for the twenty years we've monitored this pest. No other biofixes are established, although the bloom time on apple usually coincides with biofixes for codling moth, tufted apple bud moth, and lesser peach tree borer. The biofix, which is defined as the beginning of sustained adult moth activity, is established based on adult male moths captures in pheromone traps. A correctly established biofix will help to better predict the development of pest populations in the field and helps to perform the future pest management practices at the best timings.
Early season control of insect pests on apples
The timing of an insecticide application after the petal fall stage on apples is usually well synchronized with the best period for the control of European apple sawfly (EAS), rosy apple aphid (RAA), Oriental fruit moth and plum curculio (PC). If other pests such as European red mites (ERM), scale insects (SJS) and other aphids were not controlled before the bloom, the same application timing also adds the opportunity to manage this group of pests. The choice of used insecticide should be determined by the pest(s) needed to be controlled. Some broad-spectrum products such as Assail® or combination of Avaunt® plus neonicotinoid insecticide such as products containing imidacloprid (e.g., Provado®) should provide good control of all pests listed above. If only selected pest species requires special attention, specific selective insecticides should be considered. Older neonicotinoids (Admire® Pro, Actara®) applied at the petal fall timing will provide good control of aphids and leafminers, but they will not be effective against many other pests. However, both products provide good contact activity against brown marmorated stink bug and plum curculio (if present in the orchard).
If only leafrollers (OBLR larvae), OFM, and leafminers are the intended target(s) of the treatment, then an application of Intrepid®, Proclaim®, Rimon® will be sufficiently effective. If no dormant oil was applied during the pre-bloom period, European red mite populations can be reduced with an application of Agri-Mek® (or other formulations of abamectin) plus a penetrant (i.e., oil) at the petal fall stage. Abamectin still offers good control of ERM and spotted tentiform leafminers (STLM), and fair to good control of WALH. Agri-Mek should be applied before the leaves harden off, generally no later than within 10-14 days of petal fall. The ovicidal acaricides Apollo® or Savey® can be applied during the petal fall to first cover period. Other acaricides such as Acramite®, Envidor®, Portal®, Kanemite®, Nealta®, Nexter® or Zeal® are registered mainly for the summer mite control.
Due to valid concerns about the possible pesticide direct and sub-lethal effects on honey bee and other native pollinator populations, it is strongly recommended that growers avoid using insecticides until honey bees are completely removed from orchards.
Peach shoot injured by Oriental fruit moth larvae. Photo G. Krawczyk, Penn State
Young apple fruit injured by plum curculio adult. Photo G. Krawczyk, Penn State
European apple sawfly larva inside young apple fruit. Photo G. Krawczyk, Penn State
Protection of honey bees and wild pollinators
To maximize the protection of wild pollinators and honey bees, we continue to recommend avoidance of insecticide applications before the bloom. Although numerous insecticides are registered for use just before bloom, some up to the pink stage of apple trees, we recommend to eliminate (or at least limit) the usage of insecticides in the time between delayed dormant period and until after the bloom.
Most pest insects present in the orchard before the bloom period can also be effectively managed by the insecticide application(s) at the petal fall timing, which remains one of the most important treatments, setting the tone for the rest of the season. The insect pest complex present in orchards around bloom time such as obliquebanded leafroller (OBLR), European apple sawfly (EAS), rosy apple aphid (RAA), Oriental fruit moth or plum curculio (PC) can be controlled at and after petal fall.
Due to valid concerns about the possible pesticide direct and sub-lethal effects on the population of honey bees and other native pollinators it is strongly recommended that growers refrain from using insecticides until bees are completely removed from orchards.
Wild native pollinators on apricot trees. Photo G. Krawczyk, Penn State
Honeybee and wild native pollinator on an apple blossom. Photo G. Krawczyk, Penn State
Pear psylla update
The petal fall timing on pears represents one of the most important timings for the control of pear psylla. Although similarly as with other pests, this year development of pear psylla is very slow (currently the pear trees are at the white bud stage), at the petal fall pear tree foliage will support pear psylla adults, all nymphal stages, and eggs. At this time the majority of nymphs will be feeding mostly along the main vein on the. For proper monitoring during the petal fall period, at least ten leaves per tree (5 spur and five recently expanded shoot leaves) on a minimum of five trees per block should be examined. The action threshold for an insecticide application is reached when on average 0.5 nymphs per leaf is found.
The application of Agri-Mek® SC (4.25 fl oz/acre) or one of the generic products such as Abacus®, Abba®, Reaper® or Zoro® containing abamectin (IRAC Group 6) remains one of the best PP control options at the petal fall to PF + 10 days timing. Various formulations of available abamectin products contain a different percentage of active ingredient. Therefore it is always recommended to use the material at the high end of recommended rate listed on the label for each product. A penetrating surfactant such as a summer oil at 0.5-1.0 percent concentration is a necessary addition to Agri-Mek to provide the best residual control. For good coverage of trees, this spray should always be applied with at least 100 gals of water per acre. Due to hardening of the foliage and decrease in absorption of the active ingredient, after this petal fall application window, the abamectin containing products will provide less effective PP control.
Products such as Actara®, Centaur®, Delegate®, Exirel®, Movento®, Sivanto®, Portal®, Admire Pro or Nexter® can also be used at this time if additional control options are needed. Another option for PP control is the use of kaolin clay Surround®. If a good coverage is achieved, Surround (applied at 25-50 lb/acre) can represent a very effective additional tool for the PP control and possible repellent for BMSB. Surround is registered for use in organically managed orchards.
Pheromone traps for monitoring lepidopteran pests in orchards
Sex pheromone traps are the simplest tools to accurately establish biofix for various pest species and to precisely monitor the trends in population development throughout the entire season. Establishing the biofix for most important pests will help in better timing of management practices and help to decide if these activities are even needed. At least two pheromone traps per species should be placed in the orchard before the expected start of the insect flight. And although the exact dates fluctuate from year to year, the overall rule is to have OFM traps in the orchard by early April, traps for monitoring CM, lesser peach tree borer, and tufted apple bud moth should be placed around pink stage on apples, while traps for peach tree borer, dogwood borer and obliquebanded leafroller no later than two weeks after apple bloom.
Our newest 2018-2019 Penn State Tree Fruit Production Guideprovides all necessary information about insect trap placement, maintenance and sources for the lure and trap purchases.
Pheromone traps for Oriental fruit moth in peach orchard. Photo G. Krawczyk, Penn State
Seasonal Activity of Fruit Pests
2018 season weekly average captures of adult moths in pheromone traps located at the Penn State Fruit Research and Extension Center, Biglerville, PA (Adams County)
Accumulated degree-days base 43°F from Jan 01 for each reported year (courtesy of SkyBit, Inc.) The accumulated degree-days for the last date of the current year (April 28th) mentioned in the table are based on the weather forecast.