IR-4 Ornamental Horticulture Program Research Report over Sheet Researcher(s) Richard owles Affiliation: onnecticut Agricultural Experiment St 153 ook Hill Road P.O. Box 248 Windsor T 06095 PhoneNumber: 860-683-4983 Email: richard.cowles@po.state.ct.us Trial: 2008 T ProjectTitle: Scale Efficacy Protocol #: 00-000 PR# Research Target rop/plant Product EPA Reg. # Production Site Status 28386 Elongate Hemlock Scale Botanigard 22WP - Beauveria bassian Laverlam Inter 28384 Elongate Hemlock Scale Judo 2S 432-1280 Spiromesifen OHP 28385 Elongate Hemlock Scale Onyx Bifenthrin 279-3177 FM 25315 Elongate Hemlock Scale Safari 20SG 33657-16-5963 Dinotefuran Valent
Efficacy of insecticides for armored scale management on hristmas trees Richard S. owles onnecticut Agricultural Experiment Station, Valley Lab 153 ook Hill Road P. O. Box 248 Windsor, T 06095-0248 (860)683-4983 fax (860)683-4987 Richard.owles@po.state.ct.us Elongate hemlock scale () and cryptomeria scale (Aspidiotus cryptomeriae) are armored scales of increasing importance in hristmas tree plantations in New England. Populations of these species of scales have been in outbreak condition for the last 6-7 years. In previous work, I have determined that horticultural oil does not provide adequate suppression for these scales, furthermore, the potential for injury or surface wax discoloration on balsam fir, Douglas-fir and olorado blue spruce necessitates finding alternatives to horticultural oil. There is a pressing need for insecticides that are selective at killing scales rather than their natural enemies. In 2007, the two products that are effectively used in foliar sprays to manage armored scales, Onyx Pro and Safari, were found to completely exclude the parasitoid Encarsia citrina in trials conducted. Other products that were expected to be selective were found to either be ineffective (buprofezin) or, when moderately effective at suppressing scale populations were detrimental to their parasitoids (pyriproxifen). This trial compared the Onyx Pro chemical control standard and an untreated check with various options that were anticipated to have a good likelihood of selective suppression of scale populations. Methods This trial took place among 4 7 foot tall Fraser fir (), planted in a 6 8 foot spacing in Berlin, T, of which nearly all trees had some branches heavily infested with both elongate hemlock and cryptomeria scales. The grower in the previous year had applied Onyx Pro with a tractor driven hydraulic boom sprayer. The observed poor degree of control demonstrated that this sprayer provided very little spray penetration and poor under-needle spray deposition. I have repeatedly observed across onnecticut that poor spray coverage with Onyx Pro sprays exacerbates scale problems. The trees were randomized into a complete block design with 5 replicates of 16 treatments; each block contained space for 12 trees in four rows of three trees each. Foliar sprays were applied with a Stihl backpack mist blower sprayer calibrated to deliver 25 gallons per acre of spray (103 ml per tree). The product was applied in 2 minutes per plot with the #2 setting and operating the engine at full throttle. The sprayer s tank and hose were rinsed between treatments. The first foliar spray timing (Movento pre-bud
break timing) was 19 May 2008. onditions were 13 º and winds gusting to 15 mph; spraying was timed for calmer intervals. The remaining foliar treatment sprays were applied 3 June 2008. onditions on this date were 15-28º, winds 0 5 mph. The soil application and the trunk spray treatments of Safari were also applied on 3 June 2008, with a O 2 -pressurized research sprayer, equipped with a Spraying Systems 8002V nozzle and operated at 22 psi, for an application volume of 26.4 ml per tree, or 6.3 gal/ac. The soil application distributed the product over the herbicide strip area within the row, for approximately a 5 foot banded application. The trunk spray involved wetting the lower 10 inches of bark. Previous experience indicated that considerable time is required between the time of spraying and when full treatment effects can be observed. Because the intent of this experiment was to evaluate both efficacy and the impacts on parasitism, the treatments were not evaluated until mid-october, when crawlers from the second generation should also have settled. Ten branches of 20 cm length with encrustations of scale populations present on the previous year's growth were cut from each plot on 6 October 2008 and carried back to the laboratory, where they were held at 10 until counted. Branches were chosen in a biased manner in an attempt to find the most heavily infested foliage within treated trees. Three measurements were taken from each plot. A sample biased towards sensitive detection of successful colonization by scales of the current season's growth was collected by removing 5 needles from each subsampled branch, from the proximal portion of new growth, to obtain a 50 needle composite sample. All visible scales were counted from this sample, or from a subsample sufficient to obtain a count of at least 100 scales. For heavily infested samples, the number of scales per 100 needles was estimated by proportions (e.g., if 161 scales were counted from 10 needles, the value entered for scales per 100 needles was 1,610). The sample was then re-evaluated to determine the number of live and dead scales. Scale viability was determined by flipping the scale cover with an insect pin to see whether a yellow, fleshy scale body was present under the cover. Finally, four replicates of samples were evaluated for the percent parasitism. Only adult scale covers (100 per plot) were considered for evaluating parasitism, these covers were examined for presence or absence of circular emergence holes. If samples of 100 scales could not be obtained the percent was calculated from the available scales. The number of live scales per 100 needles was obtained by multiplying the number of scales per 100 needles by the percentage of live scales. This variable was subjected to analysis of variance with Statistix 9 Software (Analytical Software). Percent parasitism was analyzed with non-transformed data. Non-transformed means are presented in Table 1. Results As in 2007, experimental treatments with spirotetramat proved to be ineffective at suppressing cryptomeria scale: three of the four treatment combinations tested in 2008 ended up with average counts of live scales exceeding the untreated check. Unlike the
2007 results, some of these counts (the high dosages) were not significantly different from the check. The 2 2 factorial comparison for time of application application rate for Movento demonstrated a significant impact with dosage (P = 0.002) but not for timing (P = 0.39) for the number of live scales per 100 needles. There was no evidence in 2008 that the percent parasitism was affected by spirotetramat. Trees treated with BotaniGard had elevated numbers of live scales compared with the untreated check (P = 0.0025). There is no evidence of negative impact of Beauveria bassiana on the parasitoid, but it is possible that the elevated population is mediated by mycoses of coleopteran predators: both ybocephalus nipponicus and hilocorus spp. were found in foliage samples. Safari applied in a broadcast band application to the soil surface was an ineffective method to apply this product. Of the three dosages, only the highest application rate to soil, 2.7 lb of product per acre, resulted in a significant reduction in scale populations. However, application in a spray to the trunk resulted in dramatic reductions in scale populations. Nearly all the scales counted as "live" from these treatments were actually the scale covers remaining from the first generation of scales. They were counted as being alive because they had been able to complete development after the treatment had been applied. Numerous dead crawlers from the second generation were observed in these treatments. There was no evidence of the parasitism of scales having been affected by this trunk spray technique. Because the low dosage with the trunk spray was equivalent (or even better) than the medium or high dosage, there will need to be additional effort to determine how low a dosage can be used to manage armored scales in hristmas trees with this approach. At the lowest dosage, the trunk spray will be similar in cost to the higher labeled dosage of Onyx Pro, the current chemical standard. The disadvantage with the Safari treatment is that some feeding by cryptomeria scales does occur, so there is some aesthetic damage. However, the less expensive application equipment, suitability to small farms, reduced labor to conduct a trunk spray, and minimal impact on natural enemies may make this a preferable approach for scale management.
Table 1. Effect of various insecticides on the populations of elongate hemlock and cryptomeria scale and its parasite (Encarsia citrina). Product Active Rate, form. Application Live scales/ ontrol Parasitism Name Ingredient (per acre) Date Method 100 needles a (%) b (%) Movento 240 S c spirotetramat 5 fl. oz. 19 May foliar 1470 ab 0 14.3 ab Movento 240 S c spirotetramat 10 fl. oz. 19 May foliar 742 def 7 13.2 ab Movento 240 S c spirotetramat 5 fl. oz. 3 June foliar 1090 bcd 0 14.5 ab Movento 240 S c spirotetramat 10 fl. oz. 3 June foliar 857 cde 0 10.9 abcd Safari 20 SG dinotefuran 0.68 lb. 3 June soil 528 efg 34 7.2 cde Safari 20SG dinotefuran 1.35 lb. 3 June soil 810 cde 0 9.6 abcd Safari 20SG dinotefuran 2.70 lb. 3 June soil 328 fg 59 8.9 abcde Safari 20SG dinotefuran 0.68 lb. 3 June trunk 106 g 87 5.6 de Safari 20SG dinotefuran 1.35 lb. 3 June trunk 114 g 86 7.6 cde Safari 20SG dinotefuran 2.70 lb. 3 June trunk 194 g 76 5.3 de BotaniGard ES Beauveria bassiana 64 fl. oz. 3 June foliar 1530 a 0 15.5 a BotaniGard ES Beauveria bassiana 64 fl. oz. 3 June foliar 1230 abc 0 8.5 bcde + Prev-Am 43 fl. oz. Onyx Pro bifenthrin 6.4 fl. oz. 3 June foliar 279 g 65 2.5 e Untreated check - - - - 796 de - 11.8 abcd a Means followed by the same letter in the same column are not significantly different, for non-transformed data, LSD test, P < 0.05. b ontrol is expressed as number of live scales relative to the untreated check. c In all cases, Movento was applied with 0.25% of the carrier volume containing methylated seed oil (Destiny).