164 DeGomez et al.: Protecting Cypress and Juniper from Bark Beetles study tested the efficacy of the following four preventive spray formulations: 0.19% permethrin with cellulose additive (Permethrin Plus C), 0.03% and 0.06% bifenthrin (Onyx), and 1.0% carbaryl (Sevin SL). Bolts 1.25 m (4.13 ft) in length and 7 to 20 cm (2.8 to 8 in) in diameter were cut from freshly felled pole-sized juniper trees. Bolts were arranged in the same randomized block design previously described for the Arizona Cypress Experiment. The 24 treatment blocks were located next to existing roads with 50 to 100 m (165 to 330 ft) between blocks. The stand contained evidence of elevated levels of Phloeosinus beetles but not high tree mortality. Beetles were identified as P. scopulorum neomexicanus. Insecticides were applied as in the Arizona Cypress Ex- periment described previously. Bolts were checked for at- tacks biweekly for ≈15 weeks through 20 July 2004. Attacks by P. scopulorum neomexicanus had stopped by this time, most likely as a result of excessive phloem desiccation. All the bolts were brought back to the NAU greenhouse at this point for peeling and evaluation of brood production like in the Arizona Cypress Experiment. When the logs were peeled, we discovered that they did not have completely developed P. scopulorum neomexicanus galleries. Instead, the galleries were composed of nuptial chambers, egg galleries (including egg notches), and occasional short, undeveloped larval tun- nels. Because this was observed throughout all of the bolts, we assumed that successful larval development was pre- cluded as a result of phloem desiccation. Therefore, we counted a fully developed nuptual chamber accompanied by an egg gallery as a successful colonization. Determination of Insecticide Efficacy We assumed that bolts treated with insecticides had sufficient attack pressure if 60% of the untreated control bolts had evidence of successful beetle colonization (i.e., Phloeosinus galleries were present) (Shea et al. 1984; Haverty et al. 1998). However, because bolts were used as surrogates for live trees, our measure of failure or success was based on the presence or absence of Phloeosinus galleries (i.e., successful defense absence of Phloeosinus galleries) rather than the tree being dead or alive at the end of the experiment. We used one-sample proportion (i.e., binomial) tests (Ana- lytical Software 2000) to determine if each of the insecticide treatments (and the untreated control) provided a protection rate of 90% (i.e., H0: p [proportion successes] 0.90, HA: P < 0.90, 0.05). The data used for the tests were the number of independent trials (i.e., the number of cypress or juniper bolts tested for each treatment), the number of bolts that were successes (i.e., there were no Phloeosinus galleries present), and the probability of success per trial (between 0 and 1). If we failed to accept the null hypothesis, H0, that the protection rate was 90% (i.e., the P value for the binomial test was <0.05), then we conducted another test to decide if the treatment provided a protection rate80%. If the P value ©2007 International Society of Arboriculture for the 80% protection rate test was also <0.05, we con- ducted one more test to see if the protection rate was 70%. We also analyzed data on the number of Phloeosinus gal- leries present per 1000 cm2 (160 in2) of bark surface area on each bolt. First, we used a Kruskal-Wallis analysis of vari- Figure 1. Variation in density of Phloeosinus bark beetle galleries per 1000 cm2 (160 in2 ) of bark surface area per Arizona cypress (A) or one-seed juniper (B) bolt for spray formulations of four insecticide treatments plus an un- treated control. Bars with different letters indicate signifi- cant differences (analysis of variance on ranks, Dunn’s method, = 0.05).
May 2007
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