1. to identify grower perceptions of key pest problems in onions;
2. to measure use of pest control tactics by commercial onion producers, especially use of pesticides and their alternatives.

• The typical survey respondent farmed approximately 625 acres annually. Average yearly onion production was 50+ acres, virtually all of which was grown under furrow irrigation. On average, survey respondents were middle-aged, well-educated, and reported gross farm sales in the $250,000 to $500,000+ range during 1997. Respondents were evenly represented from Oregon and Idaho (TABLE 1).

• To the extent these respondents represent the "typical" commercial onion grower, survey data here can be interpreted as a snapshot of regional onion production.

Table 1. Demographic characteristics of onion growers participating in the
survey.

• Growers said that insects are their most important pest problem in dry onion production. More than half the respondents ranked insect pests as "serious" problems; no grower ranked insects as "not a problem" (TABLE 2).

• Onion growers perceive diseases, nematodes and weeds as important but slightly less serious pests than insects (TABLE 2); more than 4 in 10 survey respondents ranked these as "serious" problems. A higher percentage (12%) said diseases and nematodes were "not a problem," compared to 2% who said weeds were "not a problem."

• Nearly 9 in 10 onion producers said that rodents are not problems in dry onion production (TABLE 2). No grower said that rodents were serious problems.

Table 2. Pest concerns (% growers responding)

• Growers reported their 3 most important pest problems were thrips, annual broadleaf weeds and yellow nutsedge (TABLE 3); more than half of survey respondents ranked these as "serious."

Table 3. Individual pest concerns
(% growers ranking pests as
"serious")

• Growers generally perceive more individual diseases and weeds as serious problems than individual insects pests. Each disease on the survey questionnaire was ranked by at least 20% of growers as a "serious" problem; most weed problems similarly were ranked as serious by growers (TABLE 3).

• Pests ranked as "not a problem" by a majority of onion growers were
  

  stubby root nematode	76%
  stem & bulb nematode	76%
  wireworms	73%
  bulb mite	61%
  onion maggot	55%
  herbicide resistant weeds	45%

  where values in parentheses are % growers scoring pest as "not a problem."

• Essentially all commercial dry onion growers practice certain elements of Integrated Pest Management. Multiple pest control tactics are the norm.

• "Good farming" cultural practices are widely used to control onion pests (TABLE 4). Nine of 10 onion producers reduce buildup of diseases, nematodes, weeds and insects on more than half their onion acreage by rotating fields out of onions, by cultivating, by destroying cull onions and plant debris after harvest, and by minimizing bulb injury during weeding and harvest. Nearly 75% of growers follow a four-year rotation (onions every 4th year or longer) on at least half their acreage.

• Use of biological controls is limited to modest adoption levels of field scouting for beneficial natural enemies and use of reduced insecticide application rates to reduce harm to beneficial biocontrol agents (TABLE 4). "Biologically-intensive" IPM methods with particularly low levels of use by growers are as follows: 

• Growers rely heavily on programs of field scouting and economic thresholds to determine the need for pesticides (TABLE 4). But "high-tech" methods (infrared photography, aerial monitoring, use of computers to make pest control decisions) are used by fewer than 5% of onion growers.

• Over 90% of the commercial dry onion acreage is checked at least once weekly during the growing season for pest problems (FIGURE 1).

Table 4. Percentage of growers using IPM practice on more
than half their commercial dry onion acreage on average
during the past 5 years.*

Figure 1. Frequency onion fields are checked
during the growing season for disease, insect,
nematode or weed problems (% growers)
[NOT SHOWN: "never check" = 0%, "check once or twice
during growing season" = 0%]

• Pesticides are an integral part of onion production (TABLE 5). Essentially all commercial onion acreage is treated with herbicides, fungicides and insecticides. The majority of fields receive 2 or 3 applications each of herbicides, fungicides and insecticides, generally applied as foliar sprays.

• Nearly 7 in 10 fields also are treated with soil fumigants, while 1 in 3 fields are treated with a nematicide (TABLE 5).

Table 5. Pesticide use patterns reported by commercial onion producers.
Values are grower averages over the past 5 years.

NOTE: data in columns 3, 4 and 5 (% fields receiving 1, 2-3, or 4 or more applications yearly) are valid only for fields treated (example: 83% of the fields were treated with pre-emergence herbicides; of that 83% treated, 78% received 1 pre-emergence application, 20% received 2-3 pre-emergence applications, and 2% received 4 or more pre-emergence applications; by subtraction, 17% of the fields never were treated with a post-emergence herbicide).

• Survey sample size is relatively small, but production system characteristics (PART 1) suggest our sample population of growers is in fact representative of regional onion production.

• Data here is growers subjective perceptions of pest importance and not necessarily an objective measure of actual economic impact; nonetheless, grower beliefs about pest status and attitudes about pest control needs are critical if we are to conduct research and extension programs that fit the way farmers produce onions.

• Surveys suggest 3 priority pests for future research emphasis: thrips, annual broadleaf weeds and yellow nutsedge; more than half the growers surveyed consider these as serious pest problems. Alternatives to insecticides for thrips seems critically urgent. Thrips control currently depends on repeated applications of foliar insecticides. Over 75% of growers surveyed said they make at least 2 applications of foliar insecticides to each onion field every year; 15% make 4 or more applications. Intensive insecticide use pose a risk for pesticide resistance. Further, the organophosphate and carbamate insecticides registered for onion thrips control [diazinon, Guthion, Lannate, malathion, Penncap-M, Vydate] may be subject to reduced uses as the Food Quality Protection Act is implemented.

• Extension outreach is needed to help onion growers make the best use of biological approaches to pest control; adoption rates remain low throughout the region.