Petal Fall Insect Management Review
Andres Antolinez Delgado, Cornell AgriTech HVRL; and Mike Basedow, CCE-ENYCHP
As we will soon approach petal fall in portions of the Capital Region, we want to share a reminder of the key pests we are targeting during this critical pest management timing.
Woolly Apple Aphid
This pest has been creeping into more blocks in ENY over the past few years. It is critical to do the best possible job on getting the timing right for this spray—especially if choosing a softer insecticide like Movento. If selecting Movento early in the season, it’s essential to incorporate a penetrant such as horticultural oil and utilize high-volume application (>100 GPA) to obtain complete coverage. To get the correct timing, check a hot spot in your orchard weekly regularly from king bloom/petal fall and into early June. However, this year, populations have emerged earlier in several regions across the state. During scouting activities, prioritize examination of the lower sections of the tree and areas adjacent to the trunk, as infestations commonly initiate in these regions. As the infestation advances, colonies may also manifest in the upper canopy and outer branches. When you start to find populations colonizing, this is the time to treat. Once you start to see well-established, fluffy white colonies, it is getting a bit too late and then, it would be best to consider using Diazinon. The use of diazinon will depend on the severity of the infestation and the crop’s history. Reserve it for special cases due to its toxicity to humans, pollinators, and natural enemies. Other soft options for control and suppression are: Sivanto and Versys (Sefina). Make sure to follow the label instruction for adjuvants for the soft insecticides—they often will be significantly less effective without adjuvants.
Plum Curculio
Adults move into orchards from overwintering sites in hedgerows or the edges of woods and adults are active when temperatures exceed 60°F. Adult females oviposit in fruit during both day and night, but feed mostly at night. Depending on temperature, overwintering adults remain active for 2–6 weeks after petal fall. Because adults are not highly mobile, orchards near overwintering sites, woodlands, and hedgerows are most susceptible to attack. Fruit damage is usually most common in border rows next to sites where adults overwinter. Although initial postbloom sprays for plum curculio control should begin at petal fall, growers are often unsure how many additional sprays will be necessary to maintain protective chemical residues to prevent subsequent damage throughout the PC oviposition cycle, which varies according to temperatures and weather patterns after petal fall. A fact sheet with photos and descriptions of this insect’s life stages can be found at: https://hdl.handle.net/1813/43118
Following from the fact that PC activity and oviposition are largely determined by temperature, we are able to use an oviposition model to estimate when control sprays after petal fall are no longer necessary to protect fruit from PC damage. This model is based on the assumption that residues from sprays applied after petal fall need to be maintained on fruit and foliage only until PC adults stop immigrating into orchards, which happens to correspond to the time when about 40% of the oviposition cycle is complete. The model predicts this to occur at 308 DD (base 50°F) after petal fall of McIntosh. This strategy most likely works because, after 40% of PC oviposition is complete, adults usually do not move into the orchard from outside sources, or within orchards from tree to tree. Therefore, by this time, adults residing in treated trees have already been killed by insecticide residues and are unable to complete the remainder of their normal oviposition cycle.
Understanding an orchard’s historical damage is important for the management of plum curculio. If there has been significant damage in the previous years, it is helpful to pinpoint the hotspots of damage within the orchard and to place pyramid traps at the end of where hotspots occur. This can help early detection and confirmation of their movement into the orchard.
In order to use this strategy: (1) Treat the entire orchard at petal fall with an effective insecticide (e.g., Imidan, Actara, Avaunt, Verdepryn). (2) Start calculating the accumulation of DD after petal fall of Macs (base 50°F); this is easily done from the NEWA Apple Insect Models page (https://newa.cornell.edu/crop-and-pest-management) by entering the petal fall date for your area. (3) No additional sprays are necessary whenever the date of accumulation of 308 DD falls within 10–14 days after a previous spray.
In cherries and other stone fruits that are already at shuck fall, sprays should start (or should have started, as appropriate) at the first opportunity.
Recall that, in addition to the industry standard broad-spectrum materials such as Imidan, some additional options may be considered: Avaunt and Actara are effective for plum curculio in apples and pears, and Avaunt is also labeled in stone fruit as another PC option. Delegate, Assail, and Altacor all have some activity on PC, but should not be considered as the first choices in high-pressure blocks. Another option would be Exirel, a 2nd-generation diamide with better efficacy against this pest.
European Apple Sawfly
This primitive bee and wasp relative prefers early or long-blooming varieties with a heavy set of fruit. While it has historically been more of an issue for eastern New York, it has been gradually becoming more problematic in the western counties, and now frequently reaches as far as Wayne Co. (and beyond). The adult sawfly emerges around bloom and lays eggs in the apple blossoms. Young larvae begin feeding just below the skin of the fruits, creating a spiral path usually around the calyx end. This early larval feeding will persist as a scar that is very visible at harvest, and which some have described as decorative looking, although fruit marketability is obviously affected. The larva usually begins tunneling toward the seed cavity of the fruit or an adjacent fruit, which usually causes it to abort. As the larva feeds internally, it enlarges its exit hole, which is made highly conspicuous by a mass of wet, reddish-brown frass. The frass may drip onto adjacent fruits and leaves, giving them an unsightly appearance. The secondary feeding activity of a single sawfly larva can injure all the fruit in a cluster, causing stress on that fruit to abort during the traditional “June drop” period. A fact sheet with photos and descriptions of this insect’s life stages can be found at: https://hdl.handle.net/1813/43091.
European apple sawfly damage is characterized by its russetted, spiraled scars. Image courtesy OMAFRA.
Certain insecticides that control this pest also adversely affect bees, which can pose a problem at petal fall because certain apple varieties lose their petals before others. In blocks of trees where petal fall has occurred on one variety but not the others, the variety that has lost its petals is likely to sustain some curculio or sawfly injury until an insecticide is applied. Some insecticides with activity against both plum curculio and sawfly — like Avaunt and Actara — may have an advantage over the conventional OP Imidan in this case. Assail represents another option for controlling sawfly; it’s not very active against plum curculio, but will do a good job against rosy apple aphid (and spotted tentiform leafminer, if those still can be found in your orchard), as well as sawfly, at this timing. Altacor and Exirel are both rated high in their control efficacy against sawfly. In regions of eastern New York where this issue has been prominent, it is recommended to deploy white sticky board traps for monitoring purposes. Utilize the threshold of a cumulative capture of 3 adults per trap by 90% of petal fall as a guideline for management decisions. To minimize the hazard to honey bees, make sure any pesticide is applied only when no bees are actively foraging on blooming weeds (evening is better than early morning).
Obliquebanded Leafroller (OBLR)
As your looking through your buds this time of year, it would be prudent to have a quick look for later-stage larvae in problem blocks to determine whether a treatment against the overwintered brood should be included in your petal fall plans. Scout the blossom clusters or foliar terminals for larvae feeding within both the flowers and rolled leaves; a 3% infestation rate could justify an application of a control spray to minimize overwintered fruit damage and help reduce summer populations; there’s a sequential sampling chart to facilitate this process on p. 72 of the 2024 Guidelines). A fact sheet with photos and descriptions of this insect’s life stages can be found at: https://hdl.handle.net/1813/43111. To adjust the timing of your application against the summer generations, monitor adults of the summer generation by deploying pheromone traps. In the Hudson Valley area, first trap captures are typically observed in the first week of June. Following the first trap catch (biofix), eggs will hatch at 350 degree days (base 43F). Apply insecticide at this point to target larvae, and subsequently second spray 10 to 14 days later if there is a history of severe OBLR fruit damage in your area.
Damage caused by overwintering OBLR larvae around the petal fall timing. Image courtesty NYSIPM.
Among the selective insecticides available, Intrepid and Rimon have been successful at this timing, and B.t. products, which can be used while blossoms are still present, include Agree, Biobit, Deliver, Dipel, and Javelin. Additionally, Proclaim has been shown to be very effective at the petal fall timing, and also provides activity against early season mite populations. Delegate, Altacor, Exirel, and Verdepryn all offer very good efficacy against not only OBLR, but also the internal leps. Grandevo is a newer biological that is also effective against this broad group of leps. Pyrethroids such as Asana, Baythroid, Danitol, Warrior II, Proaxis or Leverage may also be effective, depending on past use history, but be aware of their broad-spectrum effects, which can work both for and against you, according to your approach towards conserving beneficial mites and insects.
Oriental Fruit Moth (OFM)
Use the NEWA Apple Insect Models page to chart current degree day (base 45°F) progress towards the recommended totals of 170 DD (in peaches) and 350 to 375 DD (in apples) after the biofix (first trap capture) as the timing at which to apply a protective spray. To maximize the efficacy of 1st brood control, peach growers should use one of the suggested options from the Guidelines starting at petal fall, backed up 10–14 days later to target the larvae. In apples, in addition to Delegate, Altacor, Exirel, and Verdepryn, a number of the petal fall selection of insecticides will do an acceptable job of controlling this generation, including Imidan, the pyrethroids, Intrepid, Assail, and Avaunt. Between 600 and 700 DD, it is advisable to monitor the terminals for damage to determine if the infestation warrants an additional application. A fact sheet with photos and descriptions of this insect’s life stages can be found at: https://hdl.handle.net/1813/43112
European Red Mite
Where prebloom conditions were so difficult for allowing applications of oil or even ovicides, it would be prudent at petal fall to have a look at your rapidly expanding terminal shoots for evidence of hungry motile mites, and consider an early “summer” application of a suitable material to head off problems before they get out ahead of you; it’s suitable to use the regular June 2.5/leaf threshold (p. 74 in the Guidelines). There are numerous choices of products available at this time, including the traditionally considered ovicides such as Apollo, Savey and Onager (if not already used this season), as well as Agri-Mek, which can still easily get into the tender leaf tissue to do its work, plus a host of moderate- and quicker-acting maintenance/rescue materials such as Zeal, Kanemite, Nexter, Portal, Acramite, Envidor, Nealta, and Banter. Additionally, if you’re planning to apply Proclaim for OBLR, you’ll get some miticidal activity too. Be aware of seasonal use limits and IRAC rotational considerations with anything you use now. A fact sheet with photos and descriptions of this pest’s life stages can be found at: https://hdl.handle.net/1813/43092
San Jose Scale
Minute SJS adult males emerge in the spring from beneath scale covers on the trees, usually following petal fall, and mate. The females produce live crawlers about 4–6 weeks after mating; these make their way to new sites and insert their mouthparts into the tree, secreting a white waxy covering that eventually darkens to black. SJS infestations on the bark contribute to an overall decline in tree vigor, growth, and productivity. Fruit feeding causes distinct red-purple spots that decrease the cosmetic appeal of the fruit. Insecticidal sprays are most effective when directed against the first generation crawlers, specifically timed for the first and peak crawler activity, which are usually 7–10 days apart.
Monitoring for SJS crawler emergence with double sided black tape around tree limbs. Image courtesy netreefruit.org.
In the Hudson Valley, overwintering adults can typically be detected in the second to third week of May. The emergence of first-generation crawlers is observed in June, followed by the appearance of mature adults in July. The second generation typically develops from July to September, with the possibility of a third generation occurring from October to November. In the Geneva area, first crawler emergence has tended to occur sometime around mid-June. To monitor, place a piece of double sided tape on branches to track initiation of crawler movement. If and when a treatment against this stage is needed, Esteem 35WP is one option. It should be applied at 4-5 oz/acre at first crawler emergence; a low rate (0.25% or 1 qt/100) of a highly refined summer oil (see above) has been shown to improve penetration and, therefore, control. Additional products showing control efficacy include Centaur (except Nassau and Suffolk Counties), Movento (most effective when applied at PF-1C, and mix with an organosilicone or nonionic spray adjuvant), Sivanto Prime, and Assail. Other options include Imidan, Admire, or pre-mixes such as Endigo, Leverage, or Besiege. Achieving comprehensive coverage is imperative to target the areas where insects seek refuge. These applications should also effectively combat White Prunicola Scale, which has become increasingly prevalent in our region, affecting both apples and peaches.