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Research and IPM

Almond Production in California: A Study of Pest Management Practices, Issues, and Concerns

The role of PCAs in pest management decision making in California almond production

By Sonja Brodt1, Frank Zalom2, Rose Krebill-Prather3, Walt Bentley1, Carolyn Pickel1, Joseph Connell4, and Larry Wilhoit5

State-licensed Pest Control Advisers, or PCAs, have come to play an important role in shaping almond growers' pest management practices. But how do growers interact with them and what is their role in growers' decisions to use integrated pest management practices? A recent survey of almond growers conducted by the University of California Integrated Pest Management Program (UC IPM) is beginning to answer these questions.

The survey, conducted in 2000, asked growers to report on practices they used during the 1999 growing season. The sample was drawn equally from California's three major production regions, the Central and South San Joaquin Valley, the North San Joaquin Valley, and the Sacramento Valley. Results presented here focus on growers reporting more than 20 bearing acres and include data for up to 316 responding growers. Due to length considerations, only half of the sample was asked questions on insect and mite monitoring and control practices, while the other half was asked questions about weeds, diseases, and nematodes. Consequently, only for those particular questions dealing with insect and mite management, which will be discussed below, the completed responses are reduced to approximately 125 growers.

About 73 percent of responding growers involve one PCA in pest management, while an additional 21 percent involve two PCAs and 3 percent involve three or more PCAs. Taken together, these figures show that use of PCA services is almost a universal practice (97 percent of responding growers). Only 3 percent of responding growers did not use any PCA. The degree of PCA influence on decision-making, however, varies with different pest types. When those growers who use PCAs were asked what percent of time they follow their primary PCA's recommendations for pest management actions, 80 percent reported following their primary PCA's recommendation 80 percent or more of the time for insect and mite pest management actions and 78 percent follow recommendations 80 percent or more of the time for disease management. On the other hand, only 60 percent indicated they follow the primary PCA's recommendations 80 percent or more of the time for weed management. In fact, more than a quarter of respondents, 28 percent, reported that they follow the primary PCA's recommendations for weeds only half or less than half of the time. These differences are likely due to the fact that insect, mite, and disease management in almonds typically involves more complexity in monitoring techniques, more variability in treatment thresholds (especially for insects) and treatment timings, and more strategic decision-making to balance pest and beneficial populations. These are all factors for which expert input can make a substantial difference in effectiveness and cost of control measures.

The issue of PCA affiliation with agricultural product suppliers has received much attention recently. Affiliated PCAs provide pest monitoring and consulting services for free, but stay in business by selling pest control products. Independent PCAs, on the other hand, are not on the payroll of a supply company and must charge a per acre fee for their services. In the 2000 survey, nearly two-thirds (64 percent) of responding growers who use a PCA work most closely with a supplier-affiliated PCA, while just under one-third, or 31 percent, work with an independent PCA as their primary PCA. An additional 5 percent reported having an in-house PCA, or a PCA who is one of their own employees.

Growers who reported consulting an independent PCA as their primary PCA also reported a significantly greater tendency to follow the PCA's recommendations for insect/mite and disease management (Kruskal-Wallis p= 0.0013 and p=0.042 respectively), in comparison to those who use a supplier-affiliated PCA as their primary PCA. The growers with independent PCAs also indicated that their PCAs made more frequent orchard visits in the peak season (Figure 1) and tended to give more frequent written and verbal status reports (Figures 2 and 3) in comparison to growers using affiliated PCAs as their primary PCAs (Chi square p=0.001).

Figure 1. Frequencies of Orchard Inspections by Primary PCA During
Peak Season as Reported by Surveyed Growers.
Frequencies of Orchard Inspections by Primary PCA

Only one-third of growers using supplier-affiliated PCAs (34 percent) reported receiving any written status reports at all (Figure 2). In contrast, the majority of growers with independent PCAs, 61 percent, indicated receiving written reports as often as once per week or more during the peak season. A statistically significant lower percentage of growers with affiliated PCAs, only 8 percent, received written reports once per week or more (Chi square p=0.001).

Figure 2. Frequency of Written Reports from PCA to Grower, as Reported
by Surveyed Growers.
Frequency of Written Reports from PCA to Grower

In contrast, grower responses suggest that supplier-affiliated PCAs favor verbal reports, with the overwhelming majority of growers using these PCAs, or 87 percent, receiving verbal reports from once per month to once per week (Figure 3). Even so, a significantly higher percentage, or 53 percent, of growers with independent PCAs received verbal reports at the more frequent rate of once per week compared to 31 percent of growers with supplier-affiliated PCAs (Chi square p=0.001). The higher levels of verbal and written communication and more frequent field visits provided by independent PCAs may be partly responsible for the greater reported influence independent PCAs have over growers' decisions, described earlier. The greater direct costs to growers in terms of fees may also positively affect their tendency to follow the independent PCAs' recommendations more closely.

Figure 3. Frequency of Verbal Reports from PCA to Grower, as Reported
by Surveyed Growers.
Frequency of Verbal Reports from PCA to Grower

PCAs in general seem to be important agents for introducing growers to IPM, but independent PCAs seem to be somewhat more so. Half of responding growers (50 percent) who primarily rely on independent PCAs reported that they first heard about IPM from a private consultant or PCA, as opposed to only 19 percent of responding growers with supplier-affiliated PCAs. Those using supplier-affiliated PCAs seem to rely on a greater variety of information sources, as they reported first learning about IPM from UC Cooperative Extension farm advisors and specialists (20 percent), UC publications (11 percent), trade publications (14 percent), and to a lesser extent, other sources such as friends and neighbors (8 percent), farm supply dealers (6 percent), and the BIOS program of the Community Alliance with Family Farmers (8 percent).

Surveyed growers using independent PCAs also responded feeling more knowledgeable about IPM in almonds than their counterparts with supplier-affiliated PCAs (Chi square p=0.009). While the majority of growers in both groups reported feeling either somewhat or moderately knowledgeable about IPM (74 percent of growers with independent PCA and 83 percent of growers with supplier-affiliated PCAs), 19 percent of those with independent PCAs responded feeling very knowledgeable, while only 5 percent of the supplier-affiliated PCA group felt very knowledgeable. While these results show that growers who are more knowledgeable and perhaps more interested in IPM also have a higher tendency to use independent PCAs, more research needs to be done to determine whether consulting with an independent PCA actually leads to greater grower confidence in IPM knowledge.

Whether an independent or supplier-affiliated PCA is used, however, does not have a significant effect on responding growers' use of some of the most common chemical controls for insect and mite pests. Regardless of which type of PCA they use, the same percentages of growers tend to use insecticide sprays during the dormant season (66 percent), in May (22 percent) and at hull split (58 percent) to control peach twig borer, San Jose scale, or navel orangeworm. There is also no difference in use of dormant oil alone (28 percent) or summer oil alone (12 percent) without insecticides to control scale, spider mites, or leafhoppers. The reported use of biopesticides like Bt and spinosad is also similar between these two surveyed groups (47 percent) (N for all above practices ranges from 122 to 125 growers).

On the other hand, growers with different PCAs vary significantly on cultural controls and monitoring techniques. Surveyed growers who consulted with independent PCAs were more likely to perform winter sanitation by poling or shaking (90 percent of respondents) and to count mummy nuts to determine sanitation effectiveness (78 percent of respondents) compared to responding growers with supplier-affiliated PCAs (65 and 40 percent, respectively). Winter sanitation is one of the most important means for controlling navel orangeworm, and effective sanitation can in many cases eliminate the need for in-season insecticide sprays. Responding growers with independent PCAs were also more likely than growers with affiliated PCAs to report the use of various techniques for monitoring peach twig borer, San Jose scale, mites, and navel orangeworm (Table 1).

Table 1. Differences in Monitoring Practices Between Surveyed Growers Using an Independent PCA and Surveyed Growers Using a Supplier-Affiliated PCA (N = 120 to 125; Chi square p < 0.06).
Monitoring Practice Percent of Responding Growers Who Reported
Using the Practice
Growers with
Independent PCA
Growers with
Supplier-Affiliated PCA
Monitor emergence of peach twig borer at overwintering hibernaculae 71 49
Place pheromone traps for peach twig borer 81 51
Use degree days with monitoring 67 43
Place double-sided sticky tape to monitor San Jose scale crawler 36 9
Place pheromone sticky traps for San Jose scale males 24 8
Sample dormant spurs for San Jose scale 55 30
Sample dormant spurs for mite eggs 55 35
Use presence/absence spider mite monitoring 71 59
Brush or count mites per leaf 71 54
Place navel orangeworm egg traps 76 36
Monitor navel orangeworm eggs or larvae on mummy nuts or hull-split nuts 80 51
Count number of ant hills per orchard area 45 28
Monitor for predatory mites and six-spotted thrips 88 66
Monitor sticky traps for San Jose scale parasites 32 10

One factor that will be explored further is the size of the almond acreage and how that might impact pest management decision making. The amount of bearing almond acreage varies significantly with type of PCA consulted, with larger farms in the response sample exhibiting a higher tendency to use an independent PCA than smaller farms. In addition, a majority of the monitoring techniques noted above are also more likely to be practiced on larger farms than on smaller farms in the sample. It is not clear, therefore, whether these differences are solely due to PCA influence or to other economic factors that are affected by farm size, such as the per acre cost of performing some of the more complex monitoring techniques.

Overall, this survey shows that PCAs of all types are important sources of information about IPM practices, especially for insect and mite pests and diseases. Furthermore, some evidence suggests that greater contact between growers and PCAs, in person and through written reports, might help growers to become better informed about IPM practices in general and more specifically about pest problems on their own acreage.


The survey was conducted by the UC IPM Program in support of the Almond Pest Management Alliance. In addition to the authors, Pete Goodell (UC IPM Program), Chris Heintz (Almond Board of California), Marsha Gibb (Community Alliance with Family Farmers), and Gene Beach (Almond Hullers and Processors Association) participated in developing the survey and their contribution to the effort is gratefully acknowledged.

1 University of California Statewide Integrated Pest Management Program
2 Department of Entomology, University of California, Davis
3 Social and Economic Sciences Research Center, Washington State University
4 University of California Cooperative Extension, Butte County
5 California Department of Pesticide Regulation

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