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.

Pears

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).

PEARS
Sample data
Pear psylla: Psylla is the major pest for most pear growers, and was controlled well at all AWII sites. Psylla populations varied considerably and were consistently higher in the North Central Washington (NCW) sites (P4-P6) than in the Yakima sites (P1-P3) (Table 15). Two of the NCW orchards (P5 and P6) had consistently lower psylla populations post-bloom in the SOFT treatment-blocks.

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.

Leafrollers:
Pandemis leafroller was caught in all orchards and was the dominant species in five. Obliquebanded leafroller was caught in all orchards in NCW, but was the dominant species only in P6 (Table 17). Catches of both species of leafrollers were higher in almost every orchard in 2002 compared to 2001 catch totals, the sole exception being OBLR in P6. Total pandemis catches on average were nearly four times greater in 2002; OBLR catch totals were double the 2001 amounts.

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.

Fruit damage:
All treatment-blocks had 2500 pears examined during harvest for pest damage (Table 19). Russet caused by pear psylla was detected in 10 of 12 treatment-blocks but in only one block (P3 SOFT) did marked fruit exceed 0.4. In the NCW orchards, psylla marking was consistently lower in the SOFT blocks, in line with the lower psylla adult and nymph counts found there. Fruit was considered marked if the cumulative area of psylla-caused russet exceeded the area of a nickel. Grape mealybug counts reflect fruits infested with nymphs, and these infestations were only found in NCW. Fruit infestation was a particular concern in orchard P4, especially in the SOFT treatment block. Codling moth damage was low; the damaged fruit found was mostly on block edges. Leafroller damage was quite low, if it was found at all. Pear rust mite damage was noted on the fruit in two orchards (P1 and P3) and was particularly prevalent in the SOFT block of P3; additional controls will be needed in 2003 to reduce this potentially serious pest. Other pest damage was found at low and variable amounts and appeared unrelated to the treatment program.

Pesticide Use
There was no significant difference in either the number of sprays or cost/acre between the conventional and soft blocks (Table 20). The soft blocks applied none of the more disruptive insecticides (chloronicotinyls, organophosphates, abamectin, pyridaben), while the conventional blocks averaged 2.6 applications/acre of these materials. The Yakima pear orchards applied significantly fewer sprays and at less cost.

SUMMARY

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.

Updated January 21, 2003

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