With this precipitation, the ordinarily challenging management of codling moth and oriental fruit moth has become a more significant issue in many orchards.
It is common to assume none of the insecticides used will retain enough residual activity after more than 2 inches of rain. The summary of results of insecticide rainfastness studies conducted by Dr. John Wise and his team at Michigan State University are presented in Tables 1 and 2. Although insecticides vary in their rainfastness properties, at the moment, it is necessary to accept there is not too much residue of the products left to protect fruit until harvest.
Table 1. Rainfastness Rating Chart
General Characteristics for Insecticide Chemical Classes
Source: Dr. John Wise, Michigan State University
|Insecticide Class||Fruit ≤ 0.5 inch (P)||Leaves ≤ 0.5 inch (P)||Fruit ≤ 1.0 inch (P)||Leaves ≤ 1.0 inch (P)||Fruit ≤ 2.0 inches (P)||Leaves ≤ 2.0 inches (P)|
|Neonicotinoids||M, S||H, S||L, S||L, S||L, S||L, S|
|Avermectins||M, S||H, S||L, S||M, S||L||L|
Key: (P) = Precipitation, H = Highly rainfast (≤30% residue wash-off), M = Moderately rainfast (≤50% residue wash-off), L = Low rainfast (≤70% residue wash-off), S = Systemic residues remain within plant tissue
Table 2. Apple Insecticide Precipitation
Wash-off Re-Application Decision Chart
Expected codling moth control in apples, based on each compound’s inherent toxicity to CM larvae, maximum residual, and wash-off potential from rainfall. Source: Dr. John Wise, Michigan State University
|Insecticides||*1 day/0.5 inch||*7 days/0.5 inch||*1 day/1.0 inch||*7 days/1.0 inch||*1 day/2.0 inch||*7 days/2.0 inch|
Key: * = Number of days after insecticide application that the precipitation event occurred. X = Insufficient insecticide residue remains to provide significant activity on the target pest, and thus re-application is recommended. Empty cell = suggests that there is sufficient insecticide residue remaining to provide significant activity on the target pest, although residual activity may be reduced.
At the same time, it is important to remember pests such as codling moth (CM), oriental fruit moth (OFM), brown marmorated stink bug (BMSB) or leafhoppers (LH) are still active and capable of causing serious fruit injury in the orchards. Under Pennsylvania conditions, the third generation codling moth adults will keep depositing eggs until at least the mid-September, while OFM larvae can infest fruit as late as in the mid-October.
If the pheromone traps located in orchards are still detecting the activity of CM and OFM moths, additional application of insecticide may be necessary to avoid worms in fruit at harvest. With the harvest in mind, only products with a short Pre-Harvest Interval (PHI) should be considered. Most products recommended for the late season control of BMSB (see the list under the BMSB update), are also active against CM/OFM complex. However, the CM/OFM specific products such as Altacor ®, Delegate® or Exirel® will not control BMSB. If only CM/OFM need to be controlled, an organically approved product Madex HP (Cydia pomonella granulosis virus, CpGV) also offers effective option against CM and OFM, while Cyd-X HP will control only CM. Also, although it is still somehow experimental use, sprayable mating disruption products Checkmate OFM-F and Checkmate CM-F should disrupt the mating of both pest species and reduce the potential for finding CM and OFM larvae in fruit at harvest.
Photo 2. Codling moth injured apple fruit. Photo: G. Krawczyk, Penn State
Photo 3. Codling moth adult in a pheromone trap. Photo: G. Krawczyk, Penn State
Brown Marmorated Stink Bug
During the last week, we started to observe increased numbers of brown marmorated stink bug adults and nymphs collected in the standard BMSB monitoring traps, and BMSB ghost traps utilizing insecticide-treated nets placed around commercial orchards.
Despite generally very low BMSB numbers observed earlier this season, traps located on the border of woods, which rarely collected stink bugs for most parts of this season, currently started to collect many BMSB nymphs and adults. Since not every orchard will experience the same pressure from BMSB, cautious scouting and monitoring of the orchard surrounding vegetation should be very helpful in deciding if any special stink bug control treatment(s) is necessary. It is important to remember that the absence of stink bugs during the season, does not guarantee that they will not become abundant in the orchard just before harvest. BMSB is not an orchard resident pest and whatever management tactics were utilized to control BMSB during the season in any particular block, cannot guarantee or prevent new individuals from infesting/re-infesting the site just before the harvest.
It is not too late to deploy BMSB monitoring traps into your orchard, at least in the areas of possible highest BMSB pressure. The BMSB monitoring lures and traps from AgBio Inc., Sterling International, and Trece Inc. are commercially available either directly from the manufacturer, specialty stores, or stores like Walmart, Lowe’s, and Home Depot.
The incessant feeding of nymphs and adults can potentially cause significant injury, especially to later maturing apple cultivars. Fresh injuries from stink bug feeding are initially almost undetectable, but after 10 to 14 days, the injury (i.e., corking) should become very apparent. If BMSB feeding occurs just before harvest, at the harvest time affected fruit will exhibit no visible signs of injury, but the characteristic depression on the fruit surface will develop later, during the storage time. Late-season feeding can be very intensive, as adult stink bugs are trying to accumulate enough resources to survive the winter.
The most effective products will control only the individuals present in the orchard at the time of the application (i.e., direct contact activity), but they will not stop newcomer BMSB adults from at least initially probing the fruit and causing injury. Most effective insecticides provide only a few days of residual control. The results of our residual bioassays revealed that most of the recommended insecticides provide sufficient residual control of BMSB nymphs for at least 7 or even 12 days after the application (higher rates of product usually provide longer residual activity.)
Photo 4. Container type BMSB monitoring traps from Ag-Bio Inc. (A) and Sterling International (B), and sticky traps for BMSB monitoring from AlphaScent Inc. (C) and Trece Inc. (D). Photos: G. Krawczyk, Penn State
The following list includes insecticides with good activity against BMSB adults and nymphs, as well as the pre-harvest (PHI) information for each product. The BMSB adult efficacy rating is based on our laboratory and field bioassay results conducted at the Penn State Fruit Research and Extension Center in Biglerville, PA.
Acetamiprid (IRAC Group 4A) (Assail 30 SG); 7-day PHI on pome and stone fruit, no more than 32.0 oz of formulated product per acre per season, BMSB adult direct contact mortality at 72 hours - about 87%.
Bifenthrin (IRAC Group 3) (Brigade WSB, Bifenture EC, Bifenture 10DF); products are registered under Special Section 18 Emergency Exception Registration for the 2018 season – 14-day PHI on apples, peaches, and nectarines. BMSB adults direct contact mortality and BMSB nymphal residual mortality (at seven days) were at 100 percent.
Clothianidin (IRAC Group 4A) (Belay); 7-day PHI on apples and pears; 21-day PHI on peach, no more than 0.2 lb AI per acre/per season is allowed, BMSB adult direct contact mortality at 72 hours - 100%.
Dinotefuran (IRAC Group 4A) (Scorpion, Venom,); products are registered under Special Section 18 emergency registration until Oct 15, 2018; 3 days PHI on pome and stone fruit, no more than 2 applications of this active ingredient per season, BMSB adult direct contact mortality at 72 hours – about 98%.
Fenpropathrin (IRAC Group 3) (Danitol); 14-day PHI on apples and pears; 3 days on stone fruit. No more than 0.8 pounds of AI is allowed per acre/season, BMSB adult direct contact mortality at 72 hours) – about 82%.
Imidacloprid (IRAC Group 4A) (Admire Pro, Leverage (imidacloprid mix with beta-cyfluthrin)); Admire Pro has 7-day PHI on pome fruit, no more than 0.5 lb AI per season; Leverage SC 360 has 7 day PHI on pome fruit, no more than 0.044 lb AI per acre of beta-cyfluthrin and/or 0.088 lb AI per acre of imidacloprid. Admire Pro BMSB adult direct contact mortality at 72 hours – about 87%; while for Leverage the BMSB adult direct contact mortality at 72 hours – about 93%.
Lambda-cyhalothrin (IRAC Group 3) (Warrior II with Zeon Technology, Taiga Z); 21-day PHI on pome fruit, 14-day PHI on stone fruit, BMSB adult direct contact mortality at 72 hours – about 72%.
Methomyl (IRAC Group 1A) (Lannate); 14-day PHI on apples; 7 days on pears; 4 days on peaches; 1 day on nectarines (PA only). On apples no more than 4.5 pounds of AI/acre is allowed, on peaches no more than 5.4 pounds of AI per acre/season; on pears no more than 1.8 pounds of AI per acre/season, BMSB adult direct contact mortality at 72 hours – about 90%.
Thiametoxam (IRAC Group 4A) (Actara, Endigo); 35-day PHI for both products on pome fruit, no more than 0.2 lb AI lambda-cyhalothrin containing products or 0.172 lb AI (stone fruit) or 0.258 lb AI (pome fruit) of thiamethoxam containing products per season. For Actara the BMSB adult direct contact mortality at 72 hours – about 95%, for Endigo the BMSB adult direct contact mortality at 72 hours - 100%.
Spotted Lanternfly Update
While most of Pennsylvania is still spared from the invasion of the spotted lanternfly (SLF), the residents of the 13 counties located in the south-east corner of the state are experiencing very high numbers of this relatively new, invasive insect species. The spotted lanternfly adults started to appear about four weeks ago on ornamental trees in woods, but just today (Aug 28) I received the first call from a fruit grower in Lancaster County reporting a high number of SLF adults swarming in his apple orchard.
It is still unclear how severe the SLF impact will be on fruit, but the examples of serious losses coming from vineyards and the severe nuisance impact on homeowners from the quarantine area warrant full attention to this insect in orchards. Based on the efficacy studies conducted this summer by Dr. David Biddinger on SLF nymphs, it appears most of the products registered for the control of BMSB should also provide effective management of SLF. The most current updates on the effectiveness of insecticides against SLF are provided in the article Updated Insecticide Recommendations for Spotted Lanternfly on Tree Fruit .
While tremendous effort to prevent the spread of this insect to new areas is directed by specialized teams from Pennsylvania Department of Agriculture (PDA) and the United States Department of Agriculture - Animal and Plant Health Inspection Service (USDA APHIS), it is very important that each fruit grower pay special attention to this pest and if observed, immediately notify PDA about the SLF presence.
For more information about the SLF biology, surveillance, and reporting, please visit the Penn State Extension Spotted Lanternfly web site and the PDA Spotted Lanternfly web site.
Photo 5. Spotted lanternfly adult. Photo: G. Krawczyk, Penn State
Photo 6. Spotted lanternfly nymph. Photo: G. Krawczyk, Penn State
Photo 7. Spotted lanternfly adult and nymph. Photo: G. Krawczyk, Penn State