Areawide II - 2002 Pear Annual Report
By Ted Alway, Jay Brunner, Elizabeth Beers, John Dunley and Vince Jones
Washington State Univeristy Tree Fruit Research and Extension Center
The Areawide II (AWII) program is investigating the use of new pest control and pest monitoring methods in Washington apple and pear orchards. With funding provided by the Washington State Tree Fruit Research Commission and two federal government grants, 15 apple and 6 pear sites were established in the spring of 2001 in major fruit growing districts of Washington (Fig. 1). The acreage and cultivar at each site is shown in Table 1. Seven tree fruit pest management consultants, with assistance by Washington State University Tree Fruit Research and Extension Center (WSU-TFREC) and the United States Department of Agriculture Yakima Agricultural Research Laboratory (USDA-YARL) personnel, collected the data on pests and natural enemies at all sites. The consultants recorded the data in the field with a PDA (hand held computer) and sent it electronically to the WSU-TFREC, where it was entered in the database from which weekly reports were generated.
Fig. 1. Location of the apple and pear AWII sites in Washington, 2002.
PearsThe objective of the AWII pear program is to determine whether eliminating insecticides known to be disruptive of many natural enemies in pear orchards can improve the biological control of several key pear pests, including pear psylla, spider mites and grape mealybug.
Six pear orchards (each from 15 to 20 acres in size) participated in the AWII program. Each orchard was divided into two treatments: conventional (CONV), in which organophosphates and any other registered pesticides can be used, and selective (SOFT), in which pesticides disruptive to biological control are avoided, including organophosphates, pyrethroids, chloronicotinyls, abamectin and pyridaben.
Each orchard was monitored with both pheromone (BB) and DA traps for CM at a density of one trap per 2.5 acres. Leafrollers were monitored with low-load pheromone lures, as described above, with one trap for each species in each treatment-block. All traps were checked weekly and the number of moths recorded. Every two weeks, each treatment-block in each pear orchard was monitored separately for pear pests and natural enemies by taking a 20 beat-tray sample. Leaf samples were collected at two-week intervals from each treatment-block from fruiting spurs (mid May through August) and top shoots (mid-June through August). These leaf samples were brushed and counted at the WSU-TFREC. Field assessments of CM damage were conducted in all treatments in each pear orchard, and the consultants conducted harvest time examinations of fruit in each orchard (2500 fruits/treatment-block).
Spider mites: Twospotted spider mite was the most common mite species found, but occurred only at low levels (Table 15). Counts were above 0.5 mites/leaf in only five of the 98 samples examined and never exceeded 1.0/leaf.
Grape mealybug: This pest was found in all three NCW pear orchards, but in none of the Yakima orchards (Table 15). Mealybug was found in tray samples and August timed tree searches in all 12 treatment-blocks in NCW. There was a trend for lower counts in the SOFT treatment-blocks.
Pear rust mite: Rust mites were rarely detected in leaf samples but fruit russetting caused by this pest was found in two blocks at harvest (P1 and P3) (Table 20). Nearly 9 of the fruit had rust mite damage in the SOFT treatment of P3; this block had pear rust mites counted in leaf samples several times in 2001 and additional controls will be needed in 2003 to prevent further damage.
Codling moth: There was a wide range in codling moth (CM) populations among the six sites (Table 16). Sites P1 and P2 had the total catch in pheromone traps for the season average 2 months per trap or less, while sites P3, P4 and P6 averaged over 10 months/trap/season. Second generaton CM catches increased significantly in P3 and P4, and fell drmatically in P6. DA lure-baited traps caught few moths in these pear orchards, never exceeding an average of 2.0 moths/trap season. The CM catches in DA traps showed little correlation with the catch in pheromone traps in these orchards.
Natural enemies: Ten types of predators and parasites were counted in this project: deraeocoris, campylomma, anthocorids, lacewings, lady beetles, stethorus beetles, spiders, Trechnites sp. (a key psylla parasitoid), other predators and parasitic hymenoptera in general. The most common, and most significant in terms of potential biological control of pear psylla, were deraeocoris, campylomma, lacewings, Trechnites sp. and spiders (Table 18). Natural enemy counts were higher on average in the NCW orchards. This may be a result of more suitable nearby habitats (wooded and riparian areas that served as natural enemy reservoirs), more food (psylla) to attract and retain them, and, in several blocks, less use of disruptive insecticides. There were few differences in natural enemy counts between treatments in the Yakima orchards, but the NCW orchards had consistently more natural enemies in the soft treatment blocks.
Pears: Effecting changes in pest and natural enemy populations, by shifting to a selective, less disruptive pest control program, can take one, two or more years until the new populations are established. 2002 can be considered Year 1 in this process, as new treatment protocols were adopted. The NCW pear orchards show reduced psylla numbers and increased natural enemy numbers in the SOFT blocks; no such trend is evident in the Yakima orchards. Good control was obtained of most pests in the SOFT blocks, including codling moth and leafrollers. However, potential pest problems are posed by grape mealybug and pear rust mite, particularly in SOFT blocks, and leafrollers, based on greatly increased catches in pheromone traps. The AWII pear orchards should be followed for at least two more years to clearly establish changes in pest and natural enemy populations with the use of selective insecticides.