Pesticide Use and Grower Perceptions of Pest Problems on Ornamental Crops in Hawaii

Ornamental crops produced in Hawaii generated $68.2 million in wholesale value in 1997, the most recent year for which statistics are available (Hawaii Agricultural Statistics Service, 1999). The three commodities responsible for most of this income were cut flowers (excluding orchids), $14.7 million; orchids (cut and uncut), $15.5 million; and foliage crops (cut and uncut), $17.8 million. The Big Island of Hawaii, with 312 producers of ornamental crops, generates more than half of the state's wholesale value of flower and nursery products.

The majority of the production is exported to the mainland United States. According to current quarantine laws, most ornamental crops can be exported without treatment as long as the crop is free of all pests of quarantine concern. Several different certification procedures are used to ensure that the export shipments are free of pests. The general procedure is that a shipper must present the commodity to USDA-APHIS (Animal and Plant Health Inspection Service) inspectors or their state counterparts to obtain a phytosanitary certificate for each shipment. Certain growers are qualified to carry out self-inspection for specified commodities, based on a previous history of presenting pest-free consignments to inspectors.

If pests are found, quarantine inspectors will not allow shipment. If the pest is found by state inspectors after it arrives on the mainland, the entire shipment, or part of it, may be rejected (returned) or destroyed, depending on the situation. Further, if this shipper or grower/shipper has a permit for self-certification, this permit may be revoked as a penalty. Most post-shipment rejections come from the California Department of Food and Agriculture, which has a vigorous inspection program.

Given the high value of ornamental crops per unit area, and the high cost of shipping to the mainland, grower/shippers are strongly motivated to exclude pests from the commodity prior to shipment. Methods currently used to exclude pests on shipments of export ornamentals include intensive use of pesticides in the field, and/or post-harvest dip treatments (hot water, soap solution, or soap mixed with an insecticide) which are often combined with hand removal, using brushes.

The specific goals for this survey were:

• to collect data on current pesticide use, in order to document progress associated with future pest management programs
• to collect data on grower perceptions of pest problems
• to find out what decision criteria growers use before applying pesticides
• to find out which types of post-harvest treatments are being used, and whether growers are satisfied with their options in this regard, and
• to find out what areas relating to pest control growers need more information, and in which areas they would like to see more research.

Survey forms were mailed to 400 growers of ornamental crops in Hawaii in October 1998. Self-addressed, stamped return envelopes were provided with survey forms. The survey included questions about pest problems (excluding plant pathogens) and pesticide use. For the question regarding which pests growers considered to be the most serious, 4 blanks were provided on the form. Growers were asked to list the most serious pests first, and so forth, in order. Pests listed first, second and third were assigned scores of 4, 3 and 2, respectively. Any pest listed after the first three was assigned a score of 1.

For the question regarding how spray decisions are made, growers were given a choice between 1) spraying on a "calendar basis," 2) spraying only "when pests are present" and 3) "other method." If the grower chose 1), he/she was asked to record the interval in weeks. If the grower chose 2), he/she was asked to indicate if the criteria for spraying was based on "scouting," "information from pickers/other workers," or "other source of information".For the purposes of analysis, "information from pickers/other workers" was considered a form of "scouting." To find out about pesticide use, growers were asked to list which insecticides, miticides and nematicides they used on their main crop in the previous year. Space was provided for listing 6 different pesticides. Growers were asked to estimate how many applications they had made during the past year for each material listed.

Altogether, 95 survey forms were received, for a response rate of 23.8%. Valid survey responses were provided on 92 forms. Answers for questions were either missing or incomplete in some cases. Therefore, the total number of responses for any particular question was generally less than 92.

Eighty-four of the respondents have their farms on the Big Island (Hawaii Island), mostly along the eastern side. The islands of Oahu and Maui were represented by 6 and 2 respondents, respectively.

Thrips were considered the most serious pest by anthurium growers, followed by nematodes, mites and slugs/snails (Table 1). Other pests were much less significant by comparison. Growers of cut orchids considered slugs and snails to be their most serious pests, followed by thrips, mites, aphids, orchid weevils, and mealybugs. Other pests were listed much less frequently.

Growers of potted orchids had pest problems similar to growers of cut orchids, except that growers of potted orchids did not mention orchid weevils as pests (Table 1). The most serious pests listed by growers of tropical exotics (ginger, heliconia, calathea flowers and cut tropical foliage) included ants and slugs/snails (Table 1). Ants are a problem because they tend the homopteran insects (such as aphids, scales and mealybugs) that feed in flowers and in leaf bracts. Also, certain species of ants are quarantine pests, and their presence in the commodity can lead to shipment rejections.

Pesticide use was heavy by orchid and anthurium growers. The average number of pesticide applications (excluding fungicides) made per year for growers of cut orchids, potted orchids, and anthurium was 35.8, 29.3, and 27.7, respectively; organophosphates and pyrethroids were the most common types of pesticides applied (Table 2). Applications of organophosphates comprised 43.6, 45.5 and 50.2% of total pesticide applications for anthurium, cut orchids and potted orchids, respectively. Applications of pyrethroid pesticides comprised 17.3, 21.5 and 23.2% of total applications for these same three crop types. Use of abamectin ranged from 8.6 to 13.7% for these three crop types.

Growers of tropical exotics reported fewer pesticide applications (average number was 9.5). Organophosphate insecticides were used almost exclusively (Table 2).

Regardless of crop type, growers who based pesticide applications on the results of scouting reported using fewer pesticide applications than growers who applied pesticides on a calendar basis. For anthuriums, cut orchids, and potted orchids scouting was associated with 57, 46 and 3% fewer pesticide applications, respectively (Table 3).

Growers were asked where they obtained most of their information on pest control. Government sources were utilized the most (Table 4). The Cooperative Extension Service (CES) and the University of Hawaii (which includes the CES) were by far the government sources most frequently mentioned, with a total of 23 and 15 mentions, respectively. Commercial sources (such as pesticide salespeople and staff at garden stores) received only 19 mentions, which was less than one-half the number for government sources.

When asked if they exported the crop that produced the most income for them, 50 growers reported they did, and 37 responded that they did not export this crop. Export markets were to the mainland USA (48 responses) and to foreign countries (12 responses), principally Japan. Of those who exported, 23 used post-harvest treatment prior to export. Twenty-six exporters used visual inspection as a substitute for post-harvest treatments. Presumably, pest problems encountered during visual inspection were handled by either culling or hand cleaning of the commodity. Of the 37 growers who did not export, only one reported using a post-harvest treatment. However, 7 of these growers used post-harvest inspections to prevent pest-infested commodities from being sold.

Types of post-harvest treatments used (with numbers of responses in parentheses) included pesticide dips (sometimes used in combination with soaps) (9), soap or detergent dips used alone (6), pesticide sprays (2), water rinse (1), alcohol spray (1), hot water dip followed by soap dip/hand washing (1), and hand-cleaning (1). Three respondents reported using dips, but did not specify the kind of dip used. Of those using post-harvest treatments, 11 respondents indicated they were satisfied with the treatment, and 4 respondents indicated they were not.

Growers were asked how many crop shipments were rejected during the previous two years because of pests (insects, mites and slugs). The 42 growers with valid responses to this question reported a total of about 24,500 shipments over the two year period with only 32 shipment rejections. Thirty of the 42 respondents had no shipment rejections during this period.

The survey asked growers to indicate for which topics related to control of insects and mites they wanted more information. The responses show that growers particularly wanted more information about using pesticides. There was also strong interest in scouting for insects, and non-chemical ways of controlling pests. Below is a list of topics growers chose in order of preference, with the number of respondents choosing a particular topic given in parentheses at left:

(72) What new insecticides or miticides are available,

(68) Which insecticides/miticides are most effective,

(61) List of insecticides or miticides which are legal (and available for each crop,

(53) Which pesticides can be tank-mixed together,

(48) How to control pests without using chemicals (e.g. plant variety selection, cultural control),

(44) Which adjuvant chemicals I should use,

(44) Better ways to scout for pests (either to save time or prevent unnecessary sprays),

(31) Pest identification,

(25) Post-harvest treatments, such as pesticide and hot water dips,

(5) I already have enough information relating to control of insects and mites.

The survey also asked growers in which areas they would like to see more research. Consistent with the previous question, respondents showed a strong interest in pesticides and pest control alternatives to conventional pesticides. There was relatively little interest in cost-benefit studies relating to pesticide use and improved post-harvest treatments. The topics they chose are listed in order of preference:

(66) testing of "natural" pesticides (including microbial insecticides, and compounds derived from plants or microbes that are not very poisonous to mammals),

(63) pesticide screening, to find out which insecticides work the best,

(52) reduced pesticide use,

(50) monitoring pesticide resistance levels that might be present in pest populations,

(49) using natural enemies to control pests (e.g. use of predator insects or mites, or insect parasites),

(45) pesticide application methods (including the testing of various adjuvants),

(36) cost/benefit studies relating to pesticide use,

(25) improved post-harvest treatments for insect or mite control.

Most growers and grower/shippers of ornamental crops in Hawaii rely heavily on insecticides and miticides for pre-harvest control of pests in order to produce a commodity acceptable for export. Organophosphate and pyrethroid insecticides were the most common types of pesticides used pre-harvest. Growers who scouted for pests used far fewer pesticide applications than those who did not. This suggests that future research and extension programs should emphasize pest monitoring as the basis for pesticide use.

Growers are concerned about the possibility that pests might be accidentally shipped with the crop; almost all growers who export use post-harvest treatments and/or pest inspections to exclude pests. Pesticide and/or soap dips were the most common type of post-harvest treatment used. The mainland USA is the main market for most of the growers who export, although some ship to foreign countries such as Japan.

The authors thank James Hansen (USDA-ARS, Wapato, WA), Kenneth Leonhardt (University of Hawaii, Honolulu, HI), and James Baker (North Carolina State University, Raleigh, NC) for their constructive reviews of this manuscript.

Hawaii Agricultural Statistics Service. February 1999. Statistics of Hawaii Agriculture 1997. Hawaii Department of Agriculture, Agricultural Development Division, Honolulu. 106pp.