Almond and Stone Fruit Growers Reduce OP, Increase Pyrethroid Use in Dormant Sprays

Instead of applying an organophosphate dormant-season spray, almond growers can monitor and treat only when pests are present. For the peach twig borer, one alternative is a bloomtime spray of the microbial agent Bacillus thuringiensis. Almond and stone fruit growers reduce OP, increase pyrethroid use in dormant sprays

Lynn Epstein u Susan Bassein -I Frank G. Zalom

Growers and pesticide applicators face water contamination and the ore than 750,000 acres of in California are legally required Federal Clean Water Act man- M almonds, nectarines, peaches, to file pesticide use reports with dates a reduction in movement of plums and prunes are grown in the details about every application to OPs into surface water. However, Sacramento and San Joaquin valleys (fig. 1). During the 1970s and 1980s, a commercial crops. We used the the decline in use of OPs has suggested component of an integrated individual applicator records to been accompanied by an increase pest management (IPM) program for document a decline in the use of in use of pyrethroid pesticides, these tree crops was to apply an orga- organophosphatepesticides (OP) particularly in stone fruit orchards. nophosphate (OP) insecticide (e.g., on almond and stone fruit orchards Additional implementation of diazinon, naled [Dibrom], phosmet during the rainy season in Califor- “reduced-risk” integrated pest [Imidan], methidathion [Supracide] or nia, a time period in which the management practices could fur- chlorpyrifos [Lorsban]), generally with trees are dormant. The decline is ther reduce use of dormant appli- oil, during the dormant season. Dor- important because dormant applications of OPs and pyrethroids on mant sprays effectively control a com- cations are a major source of sur- almonds and stone fruit orchards. plex of significant pests, pariicularly

14 CALIFORNIA AGRICULTURE, VOLUME 54. NUMBER 6 the peach twig borer (Anarsia lineatella) and the San Jose scale (Quadraspidiotus perniciosus). The application also controls two important aphids on plums and prunes: the leaf curl plum aphid (Brachycaudus helichysi) and the mealy plum aphid (Hyalopterus pruni). The oil component of the application controls the European red mite (Panonychus ulmi) and the brown mite (Byobia rubrioculus) on all of the orchard crops. When the application of an OP during the dormant season was first intro- duced in the early 1970s, it was viewed as an environmentally sound practice, because one application during the dormant season potentially re- places multiple applications during the growing season (Rice et al. 1972). Also, an application of an OP during the dormant season has other environmental advantages over an in-season application: fewer adverse affects on beneficial arthropods, less exposure to field workers, and no exposure of fruit to potential residues. However, during the 1990s, in response to food safety concerns, regulators took a critical look at use of OPs. Carbamates (e.g., carbaryl [Sevin])and OPs are targeted under the Food Quality Protection Act of 1996. In addition, federal and state regulatory agencies are particularly concerned about OP contamination of surface waters, such as streams and spinosad (Success);or in-season use of Fig. 1. Counties In the Sacramento and rivers. The OPs originate in part from pheromones for mating disruption San Joaquln valleys with at least 6,175 acres of elther almond, nectarine, peach, dormant-season applications that are (Bentley et al. 1999; Zalom et al. 1998). plum or prune orchards. Regulators are washed from almond and stone fruit To control San Jose scale, the reduced- concerned about the contamination of ma- orchards during winter rainstorms risk treatment is a high rate of oil jor rivers by dormant-season appllcatlons (Domagalski et al. 1997). without another insecticide. Alterna- of organophosphates (OP). Research to determine alternatives tive practices for aphids on plums and to dormant-season OPs for almond prunes are currently being researched. throids, with some observed field fail- and stone fruit orchards was initiated To control these pests, growers also ures. Also, residues of the pyrethroid in 1990 (Barnett et al. 1993; Hendricks can use either dormant or in-season insecticides permethrin and esfen- 1995). Use of the research results was applications of conventional pesticides valerate persist on bark, and may im- promoted by UC Cooperative Exten- that have a broad range of activity and pact beneficial arthropods for an ex- sion advisors and specialists, and also are somewhat effective: either pyre- tended period of time (Zalom et al. in by the Biologically Integrated Orchard throids (e.g., permethrin [Ambush or press). Systems (BIOS) demonstration project. Pounce] or esfenvalerate [Asana]) or in To comply with the Federal Clean The first recommended alternative to some instances carbamates. However, Water Act, the California State Water dormant-season OPs is to monitor for there are environmental risks associ- Resources Control Board and the Cali- pests, and treat only when the pest is ated with these materials. Dormant fornia Department of Pesticide Regula- present. For the peach twig borer, en- applications of pyrethroids and car- tion (CDPR) are required to prevent vironmentally reduced-risk treatments bamates might also contribute to con- and to respond to movement of OPs may include any of the following: tamination of surface water. Further- into surface water (Bennett et al. 1998). bloomtime sprays of the biocontrol more, in areas of the Sacramento Toward this goal, the Regional Water agent Bacillus thuringiensis; a dormant, Valley, there is greatly increased toler- Quality Control Boards instituted en- bloom or in-season application of ance of the peach twig borer to pyre- vironmental monitoring and devel-

CALIFORNIA AGRICULTURE, NOVEMBER-DECEMBER 2000 15 ware, the 1990 and 1991 data were too unreliable to use (Epstein et al. in press). Consequently, we used 1992 as the first year of our study, except for two county-crops (Butte County almonds and Stanislaus County peaches) in which the data were not of suffi- cient quality until 1993. For this study, pyrethroids, carbam- The pile of frass at the entrance of a peach ates and endosulfan twig borer hibernaculum indicates the pest‘s presence. To reduce peach twig were classified as “other chemicals.” B. borer populations during the season, thuringiensis, spinosad and oil applied 5 growers can use pheromones for mating without an insecticide were classified -2 disruption. Ym as “reduced-risk” alternatives. Phero- * mones were not included here as a tive IPM practices. There may be ad- reduced-risk material because it is To control San Jose scale in the dormant vantages to growers in switching to al- generally used in-season. In addition, season, a reduced-risk treatment is a high ternative control methods, particularly although there may be underreporting rate of oil without another insecticide. in parts of the San Joaquin Valley of pheromone use in the PURs, the where the San Jose scale is becoming overall use of pheromones for peach oped regional plans. The Region 5 Wa- resistant to OPs. Also, to the extent twig borer mating disruption at any ter Quality Control Plan is focused on that growers can monitor and then time of year was very low during the the Sacramento and San Joaquin river treat only in the years when it is indi- study period. watersheds, including the land drain- cated, reduced use of OPs may lower In this paper, the “rainy season” co- ing into the Sacramento, Feather, San production costs if monitoring is less incides with the ”dormant season,“ Joaquin, Merced, Stanislaus and expensive than pesticide application. that is, the dormant period in which Tuolumne rivers and their associated chemical treatments are applied plus creeks and drains. This area includes Applicator records the bloom period in which either B. the Sacramento Valley and the north- In California, growers and pesticide thiiringiensis or spinosad are applied. ern and central portions of the San applicators are legally required to file We considered the “rainy season” to Joaquin Valley (fig. 1). Pesticide Use Reports (PUR) with de- be from Dec. 10 to March 20. Although The State Water Quality Plans have tails about every application to com- the actual rainy season starts during three tiers of implementation. In tier I, mercial crops. We analyzed the or- the autumn in California, treatments growers are asked to voluntarily use chard crops on which the largest with OPs on the dormant plants do best management practices to reduce quantity of OPs are applied on dor- not commence until mid-December be- movement of OPs into surface water. mant orchards (almond, peach, prune, cause leaves typically remain on the If the Regional Water Quality Control plum and nectarine) and the counties trees at least until this date. Boards deem it necessary, they have with at least 6,175 acres of these tree We computed the relative percentage the authority to invoke the more crops (fig. 1).When indicated, we have of planted acres that were treated with stringent tiers. In tier 11, regulators presented data only for selected coun- either OPs, other chemicals, reduced- set water-quality goals and encour- ties in the Sacramento Valley (figs. 2 risk materials, or were untreated dur- age use of best management practices. and 3) and in the northern and central ing the dormant season. Data also was In tier 111, regulators control effluent San Joaquin Valley because use of examined on a per-grower basis. Re- release. To date (October 2000), CDPR dormant-season OPs in the southern sults on a per-grower basis were com- has asked growers to voluntarily take San Joaquin Valley is of less immedi- parable to the data shown here that are measures to reduce water contamina- ate concern to regulators. on a per-area basis. tion from OPs during the rainy season We retrieved all individual applica- We calculated the total pounds ac- (Bennett et al. 1998). These measures tion records from CDPR from 1990 to tive ingredient of OPs applied per acre include using best management prac- 1998 on the selected crops. Data were of crop for each year in each county tices for applying pesticides and pre- processed with SAS (Cary, NC) soft- using two methods. In the first venting runoff, and adopting alterna- ware. Despite using data-cleaning soft- method, we summed all records. Be-

16 CALIFORNIA AGRICULTURE, VOLUME 54, NUMBER 6 100 - ~-~ ~~ Organophospate. stone fruit -m- Organophosphate. almond 8o 4 t- Pyrethrold,aimond

~ + Pyrethroid. stone fruit -1 3 60 4 (II g!’ c. 01 ag! 401 I I 20-1 I 0 i 1992 1993 1994 1995 1996 1997 1998 Year

Fig. 2. Percentage of area treated during the dormant season with OPs and pyrethroids in almond and stone fruit orchards, 1992 to 1998, including orchards in counties in the Sacramento Valley and northern and central San Joaquln Valley with at least 6,175 acres of almond, peach, prune, plum or nectarine.

cause a sum is vulnerable to a few gross errors in a small number of records, we also computed a somewhat biased but very robust estimate of the total pounds of OPs based on a median application rate. We first computed the median application rate per county for each of the OPs. Then for all sites in each county, we multiplied (acres treated) by (median application rate in pounds of active ingredient per acre in that county in that year). Then the calculated pounds of all the active ingredients was summed. The values obtained using the median application rates were reasonably close (within 12%) of the values obtained by sum- ming in 53 of the 54 (98%) county- crop-period combinations. The calcu- Fig. 3. Relative amounts of planted area in almond and stone fruit orchards that were treated during the dormant season or at bloom, for counties with largest planted areas. lated sums are cited in this paper. “Other chemicals” are nearly ail pyrethroids, but also include carbamates and endosui- To minimize the impact of annual fan. “Reduced-risk’’ products include Bacillus thurlngiensis, spinosad and dormant oil fluctuations in OP use due to weather without another insecticide. conditions or changes in pest densi- ties, we averaged the data in the early years of the study (1992 to 1994) and stone fruit and almond orchards, the the final 3 years of the study (1996 to Current OP use and reductions percentage of area treated with OPs 1998). For each of the selected county- In each year from 1992 to 1998, a declined between 1992 and 1998. crops, the percent change in annual .larger percentage of the area of stone For selected counties and crops, fig- OP use during the later period in fruit orchards was treated with dor- ure 3 shows a pest management per- comparison to the earlier period was mant applications of OPs than almond spective of the relative amount of calculated. orchards (fig. 2). However, in both planted area that was treated with ei-

CALIFORNIA AGRICULTURE, NOVEMBER-DECEMBER 2000 17 Sacramento Butte erage of 76,000 acres of almond or- Almond Valley chards in the early period and 87,000 Prune acres in the later period (fig. 4). During Colusa Almond the 1992 to 1994 period, 0.63 pounds of Glenn Almond active ingredient were applied per Prune acre, when averaged over the entire Sutter Peach planted area; this figure dropped to Prune 0.17 pounds per acre during the later Tehama Almond Prune period (fig. 4). The amount of OPs ap- Yuba Peach plied to Merced County almonds in Prune the earlier period is therefore approxi- Northern SJV mately 48,000 pounds (0.63 lb/acre x Merced Almond 76,000 acres = 48,000 lb) (fig. 4). Con- tinuing the calculation, in Merced County, dormant-season OPs applica- Peach tions on almond orchards decreased San Joaquin Almond 70% during the study period. On the whole, the total amount of OPs applied during the dormant sea- Stanislaus Almond son in both almond and stone fruit orchards decreased between 12% and TO%, depending on the county-crop, Peach in all but two county-crop combina- Central SJV Fresno Almond tions (prune orchards in Tehama County and almond orchards in Tulare County) (fig. 4). Although fig- Nectarine ure 4 shows modest declines in the Peach pounds of OPs per acre in these two Plum county-crop combinations, the in- creases in acreage resulted in no Madera Almond change in the total pounds of OPs. Somewhat similarly, although there Southern SJV was no decline in the pounds of OPs per acre in peach orchards in Yuba Kern Almond County, there was a decline in the total amount applied because acreage decreased. Tulare Almond Growers treat nonbearing orchards Nectarine less frequently than bearing orchards, Peach Plum presumably because there is no fruit to Prune be damaged. Consequently, in those county-crops with an increase in acreage (nonbearing acres shown in fig. 4 below the dotted line in the white rec- Fig. 4. Amount of OPs applied during dormant season In counties with at least 6,175 tangle), some of the decline in OP acres of almond, peach, prune, plum or nectarine. The 1996-1998 period overlays the use on a per-planted-acre basis was 1992-1994 period, showing reductions In use from the earlier to later period. The portion below the dotted line In the yellow boxes refers to nonbearing acreage for 1996 to 1998. presumably due to new plantings. The area of each rectangle = base x height = “lblacre” x acres = total pounds for that Whether OP use will increase as crop In that county, where “total pounds” is yearly average over a 3-year period of OPs these orchards come into bearing is applied during the dormant season. “Pounds per acre” Is “total pounds” divided by the unknown. yearly average total planted acres. Despite the reductions in use of dormant-season OPs, large quantities ther dormant-season OPs or the alter- County almond orchards, a yearly av- of OPs were still applied in dormant native treatments for each year of the erage of 30% of the planted area was orchards. In the 1996 to 1998 period, study. The three highest years of use treated with OPs during the 1992 to approximately 230,000 pounds of of dormant-season OPs typically oc- 1994 period, whereas only 9% was dormant-season OPs were applied curred in the 1992 to 1994 period, then- treated in the 1996 to 1998 period (fig. yearly on the almond orchards in 11 declined. For example, in Merced 3). In Merced County there was an av- counties. Similarly, in the 16 county-

18 CALIFORNIA AGRICULTURE, VOLUME 54, NUMBER 6 stone fruit combinations, approxi- cosmetic requirements for nectarine, use of reduced-risk alternatives to dor- mately 230,000 pounds of dormant- peach and plum fruits in comparison mant-season chemicals could further season OPs were applied yearly. to almond and prune fruits. Also, reduce use of OPs, as well as pyre- The year-to-year fluctuations in OP there are two additional pests of con- throids and carbamates, and thereby use (fig. 3) are an indication that many cern in plums and prunes: the leaf curl reduce the risk of environmental con- factors affect pesticide use. These fac- plum aphid and the mealy plum tamination and additional regulation. tors include the frequency of rain, aphid, both of which are controlled by which influences whether or not grow- a dormant OP application. Finally, L. Epstein is Associate Professor, Depart- ers can move equipment into their educational outreach was perhaps ment of Plant Pathology, UC Davis; s. fields to apply pesticides; grower's fi- greater for almonds during this time Bassein is Statistician, Data Analysis and nances and relative prices of the crop because this crop covers more primary Presentation, Berkeley; and F.G. Zalom is and pesticides; and environmental areas of concern for OP contamination Director, UC Statewide IPM Project, and conditions that either favor or deter an of surface water. Entomologist, Department of Entomology, increase in the pest population. UC Davis. The authors thank Larry Pesticide use reports Wilhoit and Edward Morgan for provid- Increase in pyrethroids The California pesticide use reports ing the California Department of Pesticide Overall, growers did not replace (PUR) are supposed to be a census of Regulation's Pesticide Use Report com- dormant-season OPs with in-season all pesticide use in production agricul- puterfiles, and Janet C. Broome of UC OPs. For example, there was no in- ture, rather than a sampling. However, SAREPfor helpful discussions. Funding crease in the amount of area treated the extent of underreporting is un- was provided by the UC Statewide IPM with OPs during the growing season known. Nonetheless, it is extremely Project. (data not shown). unlikely that there has been a system- For both stone fruit and almond or- atic decrease in reporting OPs, but not chards, the decline in area treated with other pesticides. The data provide References dormant applications of OPs was ac- overwhelming evidence of a system- Barnett WW, Edstrom JP. Coviello RL. companied by an increase in area atic decrease in use of dormant-season Zalom FG. 1993. Insect pathogen "Bt" con- treated with dormant-season pyre- OPs on almond and stone fruit or- trols peach twig borer on fruits and almonds. Cal Ag 47(5):4-6. throids (fig. 2). However, particularly chards in California (fig. 4). This is Bennett KP, Nordmark CE, Schuette J, et in 1997 and 1998, a higher percentage particularly noteworthy because al. 1998. Occurrence of aquatic toxicity and of planted area with stone fruit or- there are few documented examples dormant-spray pesticide detections in the San chards was treated with pyrethroids Joaquin River Watershed, Winter 1996-1 997. of declines in pesticide use on other Environmental Hazards Assessment Program than in almond orchards. Some pyre- crops. EH 98-02. Department of Pesticide Regula- throids are less expensive than OPs California has the best agricultural tion, Sacramento, CA. 32 p. and the other alternatives. In both al- pesticide use database in the world. Bentley WJ, Rice RE, Zalom FG. 1999. In- sects and mites. In: Flint ML (ed.). Integrated mond and stone fruit orchards, the Although the database contains much Pest Management for Stone Fruits. UC DANR percentage of area treated with dor- information, utilization of the PUR Pub. 3389, Oakland, CA. p 51-109. mant applications of OPs decreased presents challenges. The PUR database Domagalski JL, Dubrovsky NM, Kratzer and the area treated with pyrethroids has errors; the impact of those errors CR. 1997. Pesticides in the San Joaquin River, California-Inputs from dormant increased from 1992 to 1998 (figs. 2 can be minimized by using the indi- sprayed orchards. J Environ Quality 26:454- and 3). Likewise, in almond orchards, vidual applicator records, a data- 65. a substantial area was not treated with cleaning program, and a careful ex- Epstein L, Bassein S, Zalom FG, Wilhoit LR. (In press.) Changes in pest management either OPs or with other conventional amination of the results, as was done practice in almond orchards during the rainy pesticides, and the area of almond or- here. However, use of the individual season in California USA. Ag, Ecosystems chards treated with reduced-risk alter- applicator records requires computer and Envir. natives increased (fig. 3). Use of either expertise. For IPM researchers, the Hendricks LC. 1995. Almond growers reduce pesticide use in Merced County field tri- B. thuringiensis or oil without a con- greatest limitation of the PUR is that it als. Cal Ag 49(1):5-10. ventional insecticide increased in al- does not contain information on the Rice RE, Jones RA, Black JH. 1972. Dor- mond orchards. In contrast, in stone target pest(s), the amount of pest pres- mant sprays with experimental insecticides fruit orchards there was no overall sure, or the susceptibility and in- for control of peach twig borer. Cal Ag 26(1):14. change in the percentage of area tended use of the crop. Nonetheless, Zalom FG, Van Steenwyk RA, Bentley treated with any of the reduced-risk the PUR does provide a wealth of in- WJ, et al. 1998. Insects and mites. In: UC products or in which there was no formation about trends in chemical IPM Pest Management Guidelines for Al- monds. UC DANR Pub. 3339, Oakland, CA. dormant treatment. control programs. p B1-821. In contrast to almonds, we did not Additional information on monitor- Zalom FG, Stimmann MW, Arndt TS. et al. observe a trend toward increasing use ing for insects, and the use and cost of (In press.) Analysis of permethrin (cis-and of reduced-risk alternatives in stone the alternatives, is available an the UC trans-isomers) and esfenvalerate on almond twigs and effects of residues on the western fruit orchards. This may be due to sev- IPM Web page (www.ipm.ucdavis. orchard predator mite, Galendromus eral factors. There are differences in edu/WATER/OPCALC/). Greater occidentalis Nesbitt. Env Entomology.

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