Sep 6, 2018

Updated insecticide use for spotted lanternfly on peach, grape

Spotted lanternfly (SLF) is an invasive and important pest for grapes in Southeastern PA. Evaluation of insecticides for managing this insect in the 2018 growing season are ongoing, and we present the most up-to-date data below. Both nymphs and adults of this pest have been reported feeding on grapevines, and there is no current economic threshold for SLF damage. SLF does not feed on the fruit, but instead feeds on the plant sap from the trunk and vines. Most damage has been reported from SLF adults, which have been observed aggregating and feeding heavily on grapevines. In areas with heavy feeding, grape growers have reported yield loss, reduced berry quality, and vines not being able to survive the 2017-2018 winter. For more information about the damage that SLF causes, see ” Spotted Lanternfly on Grapes and Tree Fruit .”

Results from 2018 insecticide trial on SLF nymphs

We tested 20 different insecticides for their efficacy against SLF nymphs on peach trees. In this experiment, we sprayed peach trees (2-year-old in 5-gallon pots) using the maximum labeled rate of the insecticide for peach at a typical spray volume of 50 gallons/acre. Please note that while we are currently carrying out insecticide efficacy trials for spotted lanternfly on grape, the data presented below is on peach. Previous work has shown SLF nymphs and adults to be very susceptible to direct sprays, but the goal of this trial was to assess how long the sprays would last (residual activity) and how often sprays would need to be re-applied to protect the crop. Peach and grape growers typically apply on a 10-14 day schedule, so the goal was not to determine mortality by spraying the nymphs directly on the tree. Some products have long pre-harvest intervals that prevent late season spraying just before harvest, which is often when the adult SLF are most active. Some products also have long re-entry periods that restrict activities in the vineyard for periods of several hours to several days, depending on the product used and the rate of application.

For this evaluation, we placed field collected 3^rd instar nymphs on peach trees in net cages after the spray had dried (about 30 minutes). Mortality was assessed after 48 hours of exposure and all SLF were removed from the tree at that time. Nymphs barely alive, but clearly intoxicated (moribund) were recorded as well, but for the purposes of this analysis were considered dead. Contact insecticides such as pyrethroids, carbamates and organophosphates kill quickly by contact, but others such as neonicotinoids may kill more slowly by interfering with the insect nervous system or feeding.

Products that failed to give 50 percent mortality at this time and were discontinued from this study. Some of these products are being evaluated for longer-term feeding trials, but they were removed from this study, so 17 products are shown in the table. Using the same sprayed peach trees (application was made only once), we placed new nymphs (mostly 3^rd instar nymphs) 7 days after the insecticide application and again assessed mortality after 48 hours of exposure. If products failed to give at least 50 percent control at this time they were considered to have failed and further evaluations were discontinued. Those products that were still performing well were assessed again with new (mostly 4^th instar) nymphs 14 days after the spray application, assessing mortality 48 hours later. All treatments except Brigade failed to give at least 50 percent mortality and the experiment was discontinued at that time. Rain-fastness was not evaluated in this study, but heavy rains did occur prior to the 14-day assessment and some products did not last as long as expected, which could be explained by the rain. The average percent mortality of each of these compounds compared to an untreated control are presented in the table below. Compounds that do not appear in the 7-day and 14-day columns were not evaluated because of low mortality in the preceding assessment.

Insecticide results for control of spotted lanternfly nymphs on peach

Different letters following each percent mortality mean within a column indicate a significant difference at a 95% confidence limit. The letter “a” represents the compounds with the highest mortality level, while the subsequent letters (i.e. “i”) represent lower mortality levels and means followed by the same letter were not significantly different.

Of the insecticides tested on peach in the table above, 14 of the 16 chemicals had excellent knockdown activity. Seven days after the application, the insecticides that still had above 60% mortality were: Closer, Imidan, Actara, Danitol, Carbaryl, Brigade, and Vydate. Note: Control mortality on the 7-day assessment (24.7 percent) was higher than the 0-day and 14-day assessments possibly due to very high temperatures. Only two products had mortality greater than 40 percent at 14 days after the application: Imidan (48 percent mortality) and Brigade (79 percent mortality). The Avaunt 7-day mortality reading was mistakenly not taken at the same time as the other products, but all nymphs when evaluated several days late, were dead indicating this product will at least last for 7 days. Avaunt will be assessed soon against the adults on both peach and grape in the next round of trials.

Please note that most of the chemicals evaluated in this peach trial not are currently labeled specifically for use on SLF. However, many of the insecticides used for other pests in grape, peach, and apple (such as brown marmorated stink bug, Japanese beetle, and grape berry moth) will provide some protection against SLF damage. The control timing of sprays for BMSB adult in apple coincide with the movement of SLF adults into the orchards and two products which have special emergency (section 18) registrations for BMSB in apple are very effective on SLF. Results from this and future trials in the next few weeks are being utilized by several pesticide companies to modify their insecticide labels to specifically include SLF on their labels.

To date, these are the current insecticides that have a registered 2(ee) label modification for spotted lanternfly in Pennsylvania on grape, peach or apple are: Assail 30SG, Imidan 70WP, Brigade 10WSB, Mustang Maxx 0.8EC, Assail 30SG, Avaunt 30DG, and Actara 25WDG (nymphs only). Several other products are pending a 2(ee) label, and this list will be updated regularly. Another excellent website where pesticide label modifications can be found promptly is the Crop Data Management Systems website. Of the above listed products, all have been shown to be effective against SLF. In particular, Imidan and Brigade had the longest residual activity against SLF.

The table below provides a list of insecticides registered for use against SLF in tree fruit and grapes. Selection of insecticides for SLF control should take into account the other pests present, harvest date, the re-entry date, and potential non-target impacts. Always follow the specific label restrictions for your crop and state. The level of control achieved will depend on the SLF population within your farm and in the surrounding landscape, the timeliness of the application, coverage, and the product effectiveness. Remember to rotate classes of insecticides to reduce likelihood of insecticide resistance.

Organic control of SLF

Entrust (spinosad) was the only OMRI-approved insecticide evaluated in this study. It had 58% mortality immediately after the spray and gave no appreciable control 7 days after the application. Direct sprays to the nymphs or adults would most likely increased the efficacy of this product, but the lack of residual control by this product indicates timely applications at shorter intervals are necessary. A request for a 2(ee) label amendment for Entrust was denied until more data could be provided. There are no OMRI-approved products that are currently labeled for use against spotted lanternfly.

Ongoing studies

The data presented here are from a trial done on SLF nymphs on peach at the Peiffer Turf Farm at the Penn State University Berks Campus. We are continuing to test effective insecticides against spotted lanternfly adults on peach and grape in the coming weeks. We are also evaluating slower acting compounds against SLF that may give better long-term control or are safer to pollinators and biological control. Pyrethroids in particular are very disruptive to biological control, and may cause flares of secondary pests such as mites, aphids, scale, or mealybugs. Previous trials on apple for BMSB control with fall applications of neonicotinoids did not cause secondary pest outbreaks and analysis of pollen and nectar samples taken the following spring did not have detectable residues of the insecticide. Products being tested for the longer-term feeding trial include: Esteem 35WP, Exeril 0.83EC, Beleaf 50 SG, and Movento 2SC + LI-700 (a penetrant at 0.25%). Data will be made available as soon as possible. Registrations and recommendations change, so keep informed through our Spotted Lanternfly website and your local extension educator.

Insecticides for control of spotted lanternfly in grape using foliar applications

Please note that registrations and labels change, and human error is always possible. You must check the most current label before applying any pesticide. Note that SLF Activity levels are excellent, good or poor.