A Blast from the Past: 17-Year Cicada Control in Pennsylvania Apple Orchards 2021

Oviposition injury from this pest is significant even on large, standard apple trees when population pressure is high enough and can be devastating on small, young semi-dwarf trees. They are sometimes referred to as “Nature’s Pruners”, but in nursery stock, direct tree mortality is most often the outcome when the adults are not controlled over the 6-week oviposition period. Even trees that survive the infestation have large open wounds that are ideal for fire blight to establish in a manner similar to that from heavy hail damage.

Photo 1. Injuries on apple branch caused by the ovipositional activity of female periodical cicada Photo: G. Krawczyk, Penn State

Population pressure by 17-year cicada (Magicicada septendecim) is generally highest next to wooded areas or in older orchards that had been around during the previous emergence 17 years earlier. In the latter case, we have seen cast skins of the ground-dwelling nymphs that climb to the surface that could easily be gathered up to fill most of a bushel basket under only a few trees. The noise in heavily infested orchards can be so loud that conversations are impossible. Since these adults are mostly causing injury with their thick needle-like ovipositor while laying eggs and not through feeding injury, the most effective insecticidal control is through direct contact of the adults while spraying or residual contact of dried residues. Unfortunately, we have little data on residual activity, however, this residual activity is very important because of the continuous emergence of adults and their dispersal by flight to new areas.

Photo 2. Periodical cicada adults on apple branches. Photo: G. Krawczyk, Penn State

It is difficult to control a pest whose lifecycle is longer than the life of some insecticides, but previous control work has demonstrated pyrethroid insecticides and carbamates (such as methomyl and carbaryl) to be the most effective with residual control varying by product, rate, and spray coverage.

In 2004, for many growers, cicada pressure was low enough not to warrant chemical control or only border applications to areas adjacent to woods or the older apple orchards from which they were emerging. For other growers, however, control was accomplished with multiple applications of pyrethroid insecticides (i.e. Asana, Warrior, or Danitol) or the carbamates (Lannate or Sevin XLR). All of these products were potentially devastating to many beneficial insects such as the coccinellid mite predator Stethorus punctum and predatory mite populations. Pyrethroids are also known to have a stimulatory effect on the physiology of pest mites (i.e., European red mite & two-spotted spider mite) in which fecundity is increased and developmental times are shortened (i.e., more generations and more eggs than normal).

These well-documented effects are what cause mite ‘flareups’ following pyrethroid applications. Flares of scale insect and woolly apple aphid populations are also seen after pyrethroid sprays due to the elimination of biological control. Unfortunately, organophosphates such as Imidan and most neonicotinoid insecticides which are generally safe to predatory mites and many biological control agents were mostly ineffective in controlling the 17-year cicada.

Photo 3. Periodical cicada empty pupal cases on apple branches. Photo: G. Krawczyk, Penn State

In 2004 to conserve the predatory mite, T. pyri, we conducted a series of bioassays on field collected adults of 17-year cicadas. We collected these adults from an unsprayed block of apples and the adjacent woodlot to ensure they had not previously contacted pesticide residues. We conducted two direct contact tests and one dry residue bioassays with several neonicotinoid insecticides that were considered safe to predatory mites and were expected to be effective on cicadas. Be aware that in some cases the rates tested were lower than what is currently recommended because we wanted to both conserve our biological mite control which was much more sensitive to some of these recently introduced insecticides that we had relatively little experience with back in 2004. Also note that: a) the neonicotinoid Calypso is no longer available; b) Assail 70WP was the only formulation available in 2004, not the Assail 30DG currently used; and c) Warrior 1CS was the only formulation available in 2004, not the Warrior II currently used.

Periodical Cicada Control Results from 2004 Season

Direct contact spray to the adults

Both Assail 70WP and Calypso are similar neonicotinoid insecticides known to be less plant systemic than others such as Actara, but leave longer surface residues that provide better and longer residual control than those of Actara, Provado, Sivanto or Closer. This can be seen in the first bioassay (Table 1) where Actara was less effective than either Assail 70WP or Calypso used at low rates but comparable to that of the pyrethroid Warrior. That Warrior was only moderately effective was something of a surprise, but we have seen similar results in our contact bioassays over the last 3 years to control Spotted Lanternfly which is similar in size to the 17-Year cicada.

The effectiveness and especially residual activity of various pyrethroids tested on spotted lanternfly have proven to be quite variable. Brigade® and Bifenture® (both containing active ingredient bifenthrin) are significantly more effective and have longer residual activity against spotted lanternfly than Warrior or Mustang Maxx, but were not tested against periodical cicada. Danitol has proven to be just as effective on spotted lanternfly but has had shorter residual activity on that pest. In the second contact trial (Table 2), it can be seen that an even lower rate of Assail 70WP (1.7 oz/A) was just as effective and a higher rate of Calypso did not improve control.

Dried residue contact bioassay

Pyrethroids are generally known for their long residual effectiveness, so it was surprising to see that an application of Warrior to apple shoots allowed to dry before being challenged with adult cicadas, was not effective. We have seen similar results with our Spotted Lanternfly trials over the last 3 years. During the 2004 cicada trials, only Assail 70WP at the 2.5 oz/A rate gave significant control as a dried residue (Table 3), but 46% control by a freshly dried residue is still not very encouraging. Higher rates of Assail would probably increase residual activity and a 2(ee) label expansion to include 17-year cicada has been submitted. Daily sprays against cicada adults are rather not cost-effective, but at least it appears that Assail 70WP at the rate of 1.7 oz/A should give excellent knockdown control if contacted directly. This means high water volume for the best coverage and the hope that the normally skittish cicada adults will not just fly away from the sprayers.

Table 1. 17-Year cicada direct contact bioassay number 1: 180 adult cicadas tested per treatment in 6 replicates of 30 individuals. (Biddinger & Hull, 2004)

**Note that these rates are for older formulations of Assail and Warrior and are converted to their equivalents in the modern Assail 30SG and Warrior II in Table 4 containing the recommendation table.

Table 2. 17-Year cicada direct contact bioassay number 2: 180 adult cicadas tested per treatment in 6 replicates of 30 individuals (Biddinger & Hull, 2004).

**Note that these rates are for older formulations of Assail and Warrior and are converted to their equivalents in the modern Assail 30SG and Warrior II in Table 4 containing the recommendation table.

Table 3. 17-Year cicada dried residue contact bioassay number 1: 90 adults tested in 3 replicates of 30. (Biddinger & Hull, 2004)

*Means separated by the same letter were not significantly different at P=0.05, Fisher’s Protected LSD.

**Note that these rates are for older formulations of Assail and Warrior and are converted to their equivalents in the modern Assail 30SG and Warrior II in Table 4 containing the recommendation table.

West Virginia trials by Hogmire & Winfield 2004

Insecticide treatments were applied dilute to young trees 3 times on a weekly interval and evaluated for injury at the end of emergence. Of the 11 products tested, Danitol at 16 fl oz/acre was the most effective in preventing oviposition scars, but also Assail 70WP at 3.4 oz, Asana at 10 fl oz, and Warrior at 5 fl oz prevented heavy damage after 3 weeks. Actara (5.5 oz), Lannate LV (3 pt), Calypso (8 fl oz), Avaunt (6 oz), Aza-Direct (1.3 qt), and Surround (50 lb) were not effective in preventing injuries by periodical cicadas.

Virginia trials by Bergh & Engelman 2004

Insecticides were applied to larger trees 3 times on a weekly interval as well and evaluated at the end of emergence. Of the 9 insecticides tested, only Asana at the rate (14.5 fl oz/acre) and Danitol at 21 fl oz/acre rate prevented damage caused by periodical cicada. Assail 70WP at the 3.4 oz/acre gave slightly less, but still good control, but Lannate LV (3 pt), Calypso (8 fl oz), Warrior (5.1 fl oz), Actara (5.5 oz), Avaunt (6 oz), and Aza-Direct (1qt) were also not effective in preventing injury by periodical cicada.

Spotted Lanternfly Experience on Potted Trees

Spotted Lanternfly (SLF) is approximately the same size as 17-Year Cicada, so we feel that some of our experience over the last 3 years with potted trials looking at the residual activity and contact activity should carry over from the over 50 insecticides we have tested. SLF is different in that it feeds on the sap of the trees so that neonicotinoids which systemically move into the sap are obviously more effective on that pest. 17-year cicada is mostly ovipositing eggs into the trees and not feeding, so direct spray contact and residual activity after sprays will be most important for control of that pest.

With products that work purely by contact such as pyrethroids, organophosphates, and carbamates, we think control performance should be similar. So, from those specific SLF trials, we have found the pyrethroids such as Bifenture 2EC and Brigade 10WSP to have the best contact and residual activity of up to 2 weeks when used at the pear label rates of 6.4 fl oz and 16 oz/acre, respectively. We have worked to get special registrations for both products on non-bearing apple and stone fruits, but currently, these products are only registered for use on pear. Both Danitol and Malathion 8F have also been effective on SLF for more than a week at the higher label rates, but Warrior and Asana were less effective and lack residual activity.

Table 4. Recommendations for 17-year cicada control based on trials from the 2004 season and current experience with SLF control on tree fruit

*Based on Spotted Lanternfly Trials by Biddinger (2018-2020).

**Rates mentioned in the text are for Assail 70WG, as Assail 30SG was not available during the 2004 trials. The full rate of 3.4 oz of Assail 70WD equals 8.0 oz of Assail 30SG. Only the rate in the table above is converted for the equivalent rate of Assail 30SG.

***Sevin XLR is a potent fruit thinner on pome fruits and should probably be used mostly on non-bearing trees.

****Rates mentioned in the text are for the Warrior I CS not the currently available Warrior II formulation. Only the rate in the above table is converted for recommended Warrior II rate on pome fruits.