Entomology Update for June 2017

The 2017 biofix for the first brood tufted apple bud moth (TABM) at the Penn State orchards in Biglerville was established on May 1st while for the obliquebanded leafroller (OBLR) on May 20th.
Entomology Update for June 2017 - News


Growing apple terminal injured by Obliquebanded leafroller (June). Photo: Greg Krawczyk

Despite almost three weeks difference between the biofix dates for these two species, based on the egg hatch models (SkyBit, Inc) the 10 percent egg hatch for both species should happen sometime between June 5th and June 10th.

Codling moth and leafrollers update

In the majority of PA orchards where leafrollers are present, TABM is the dominant leafroller species responsible for most of the fruit injuries. During last few years, the TABM sex pheromone traps located in many orchards consistently captured very high numbers of TABM males. Although we still do not see severe damage caused by this pest, the observed TABM numbers are similar to the numbers of TABM captured in the 1990, when the TABM was the most important pest in apple orchards. Due to this increase in the numbers of observed TABM adults, special attention needs to be directed toward monitoring and management of this pest.

If Altacor®, Delegate®, Exirel®, Voliam Flexi®, or Intrepid® are to be used for TABM control, 1-2 complete, precisely timed applications of any one of these products per brood are recommended. Application(s) of Altacor, Delegate and Voliam Flexi in the early part of June and later (corresponding with the second codling moth (CM) control timing) should not only provide excellent control of both leafroller species, but also of codling moth. If applying two complete sprays exclusively targeting only TABM, the first application should be applied at about 10-30 percent egg hatch (500-600 DD base 45) followed by a second application (if necessary) at about 60-70 percent egg hatch (800-850 DD). The low rate of Intrepid (10-12 oz/acre) should provide excellent control of TABM larvae but this low rate of Intrepid will not control codling moth or Oriental fruit moth. If applying only one complete application of above mentioned compounds against TABM, this spray should be done at 30-40 percent egg hatch (640-695 DD).

Insecticides that are effective against TABM should also provide good control of OBLR larvae, especially during this season when the egg hatch for both species is occurring during a very similar time period. Two sprays are usually needed for higher OBLR populations. Since young OBLR larvae prefer to feed inside the growing terminals, the insecticide coverage of fresh growth plays a critical role in the control of OBLR larvae. Only complete sprays are recommended against this pest. The better the coverage, the better level of larval control will be achieved. The insecticides recommended for the OBLR control during this time of the season include: Altacor, Bacillus thuringiensis (BT) products, Delegate, Intrepid, Voliam Flexi or Exirel.

As the first treatment for the control of CM should already been applied in most orchards, the timings for the second and possibly third CM applications should coincide well with the expected timings for effective control of TABM and OBLR. Based on the egg hatch models it appears the June 5-10 period should provide a good timing for the second CM and first TABM and OBLR treatments (the actual exact timing may vary by location of the orchard). Then, about two weeks later, if necessary, all three pests can be controlled again at the same time (second against TABM and OBLR and the third CM treatment). Except for the BT based products and Intrepid which are effective only against leafrollers, all other insecticides mentioned above should be very effective in controlling both leafrollers species and codling moth. In organically managed orchards, if needed, weekly applications of codling moth granulosis virus (CpGv) as in Cyd-X® or Madex HP® will provide good control of codling moth while applications of BT based products or Entrust® should effectively manage leafrollers.

Pear psylla update

So far, in most pear orchards the management of pear psylla (PP) during the 2017 season seems to be quite effective. The early season fluctuations of temperatures provided a well deserved break in the conundrum of challenges related to control of pear psylla. In our pear block at the Penn State Fruit Research and Extension Center (FREC), the petal fall application of Agrimek ® provided good control of PP first generation nymphs. The next critical period to control the second generation of pear psylla occurs during the first week of hatch of the young PP nymphs and then 12-14 days later. An application of effective insecticide is recommended if the action threshold of 1 live nymph per leaf is reached. If chemical control is required, Admire ® Pro, Actara 25WP or Assail® 30SG (plus a quart of summer oil) are very effective for psylla control. In addition, Nexter ®75WP or Portal ® should also provide good to excellent control of pear psylla as well and excellent control of European red mites.

If application against PP nymphs is needed, all above mentioned products should be used at the high end of the pear psylla recommended rates. Other products such as Delegate, Exirel, Sivanto®, Movento®, or Closer® should also be considered if multiple applications of insecticides will be needed as the season progress. A good coverage of Surround could also help to control pear psylla, although the product residues on fruit may create potential marketing issues. Also, since new shoots are continuously growing, multiple applications may be necessary to maintain good coverage by Surround (see photos below).

Surround application on pear trees to control pear psylla. Photo: Greg Krawczyk

As the tree grows, the new shoots are not protected against pear psylla feeding. Photo: Greg Krawczyk

Leopard Moth Mystery

During last two growing seasons, on multiple occasions, fruit growers reported the presence of large yellow larvae, with dark dots in their young trees, causing long shallow tunnels and killing the growing branch or even a tree leader. The most recent findings of the larvae were reported mostly during the winter pruning, but some larvae were found also in the spring when often the top terminal(s) of young trees become dead. Due to very characteristic injury symptoms and distinctive coloring of the larvae, we were able to identify the larvae as the leopard moth caterpillars.

Leopard moth larvae inside young branch. Photo: H. Morin

Hollow tunnel in branches caused by feeding of leopard moth larvae. Photo: H. Morin

Dead top of the young tree terminal as the result of feeding by the leopard moth caterpillar. Photo: H. Morin

Leopard moth, Zeuzera pyrina (L.) (Lepidoptera: Cossidae) is a wood boring insect attacking more than 150 tree species from up to 20 genera. The species originated in Europe but was introduced to northeastern United Stated in the late nineteenth century. In the US, the known distribution for this species ranges from Maine to Pennsylvania. Unfortunately, apple trees are one of the preferred hosts for the leopard moth larvae.

Fresh feeding by the leopard moth caterpillar. Photo J. Hickerson

Adults moths have furry white thorax marked with six black spots and heavily spotted white wings. The leopard moth wingspan ranges from 35 to 60 mm. Adults are flying from June to September and can be monitored utilizing sex pheromone traps. At a single New Jersey' location back during the 2008 season, at the peak of the flight, more than 60 moths were collected per week. A female leopard moth can deposit several hundreds of clustered eggs.

Leopard moth male. Photo G. Krawczyk, Penn State

Leopard moth male single adults captured in pheromone traps. Photo G. Krawczyk, Penn State

Larvae disperse at dusk, usually attached to silk threads and carried by the wind, and bore into the tips of branches and shoots. Feeding and tunneling of a single larvae normally continues two to three years, with larvae moving to new branches as it increases in size. When fully grown, the caterpillars are about 50 mm (2 inches) long. Larvae like to attack trees in young orchards and trees close to hedges and borders.

Leopard moth pupae. Photo H. Morin

The current management recommendations are mostly based on utilizing insecticides after the peak adult activity, however due to the very extended flight period, the chemical control is not very effective. Although mass trapping employing pheromones and light provided good results in some European studies, the practice is not widely adopted. The list of natural enemies includes a number of pathogens, parasites, and predators--including birds such as woodpeckers.

Although the leopard moth infestations were observed only in a few, mostly young apple orchards, the frequency of the findings during last few years has become intriguing. At this moment, it has not been determined if this is a location-based phenomenon associated with an indigenous population of leopard moth present on the wild hosts surrounding orchards; or some other factors contributing to an increased presence of the larvae. Most of the current findings are associated with young apple trees, but it is possible similar levels of injuries are also present on older trees, but simply not detected.

If any signs of leopard moth caused injuries were observed in your commercial orchards, especially on young trees, please share this information by sending a brief description of the findings and your contact information to Dr. Greg Krawczyk.

To view the insect hatch and trapping data for all major insect pests, please visit the Penn State Fruit Research and Extension Center (FREC) website. For control recommendations, refer to the Insect and Mite Control Toolbox for Apples - timing or efficacy .