San Jose Scale Management on Peach, 2016

The experiment was conducted to evaluate San Jose scale control treatments at the Rutgers Agricultural Research and Extension Center in Bridgeton, NJ. The experiment was blocked according to over-wintering scale density and was replicated four times, in a RCB. Trees were spaced 20 × 20 ft. The first San Jose scale crawler was observed on 2 Jun. Treatments were applied to 19-year-old “Blushing Star” peach trees using a Rears airblast sprayer (28 inch fan, 180 psi) delivering 100 gpa and pulled through the orchard at 2.6 mph. All trees received regular sprays for disease management. The Damoil treatment was applied at delayed dormant on March 7. Movento (9.0 oz) + LI 700 (1qt), Sivanto (10.5 oz, 14.0 oz), Closer (5.75 oz) + Induce (1 qt) were applied on 7 Jun (5 days after first crawler), Venerate (64.0 oz) and Grandevo (32.o oz) were applied on 7 Jun (5 days after first crawler) and again on 14 Jun (plus 7 days). Crawler stage scale was monitored with a piece of double-sided sticky tape positioned over a strip of black electrical tape and wrapped around an infested branch. Two monitoring tapes were placed per test tree. SJS were monitored weekly. Tape was removed from each branch, returned to the laboratory, and the number of SJS crawlers on a 5 cm section of tape were counted using a stereomicroscope. The first monitoring tapes were applied 2 Jun. SJS fruit damage at harvest was evaluated on 29 Jul by examining total amount of fruit on the tree (up to 25 fruit/tree). When data did not meet assumptions of normality, data were transformed or log(x + 1) before analysis of variance (ANOVA) and means separation with Tukey’s LSD test among treatment means. Damage was determined by examining each fruit for aggregate scale densities and total injury. Data did not meet assumptions of normality and percent scale density category and totally injury were transformed using arcsin squareroot.

Summation of all observed crawlers per experimental unit was analyzed by one-way ANOVA after log(x + 1) transformation and means separation with Tukey’s HSD. There was significant treatment differences (F = 7.64, df = 7, 31, P < 0.0001) and no effect of replicate. Trees treated with Damoil, Movento and Sivanto (10.5 and 14.0 oz) and Grandevo had significantly lower crawler numbers than the UTC. At harvest, only Sivanto (at both rates) was significantly different than the UTC for the ≤1/4″ category (F = 2.78, df = 7, 31, P = 0.029). All treatments except Grandevo, were significantly different than the UTC for the > 1/4 ≤ 1/2″ category (F = 3.47, df = 7, 31, P = 0.010). All treatments were significantly different than the UTC for the > 1/2″ category (F = 5.60, df = 7, 31, P = 0.0006) (Table 1). Overall, there was a significant impact of treatment on the proportion of fruit with SJS injury (F = 4.51, df = 7, 31, P = 0.002). Sivanto had the fewest crawlers and clean fruit at harvest. Interestingly, while Closer, Venerate, and Grandevo did not appear to reduce crawler populations, a Dunnett’s test comparing fruit injury at harvest indicates that they provided control similar to that of Damoil application at DD.

Author notes