Use of high-pressure water spray to dislodge spider mites, aphids, small caterpillars and others from host plants has long been suggested as a non-chemical method of pest control (Meyer and Stone 1989).
Giving infested plants a good, hard hosing down will dislodge many insect pests, particularly aphids, thrips and various worms. Plants should first be inspected to confirm the target pest (p. 69).
Accomplishing this method of pest suppression, however, has not received much attention from research entomologists. The efforts described in this report were undertaken to provide some information about the various commercially-available devices designed to produce pressurized water sprays as hose-end attachments. The practice to produce a high pressure spray by using ones' thumb on the end of the hose was not tested because of the lack of control using this technique.
I. Determination of spray characteristics.
The water pressure in College Station
(pressure of water coming out of the end of a
hose) is 90 to 100 pounds per square inch
(College Station Water Dept., pers. comm.).
Devices tested that are marketed for spider mite suppression were:
1994): This device attaches to hose with
Gilmour metal on-off valve adaptor and has a
3/8 inch diameter tape-wrapped metal tube,
52.5 inches long, with a rubber handle. The
Spraying Systems Co. D-7 cone-type nozzle is
directed at a 90 angle from the tube.
Other devices evaluated which are not marketed for mite or insect suppression included:
Dramm Fogg-it Nozzle Model C-610 Fine Volume 1 GPM manufactured by Fogg-it Nozzle Co. (P.O. Box 16053. San Francisco, California 94116)($8.99, 1993) is sold as an accessory to the Dram 30 inch Rain Wand.
Twist Nozzle manufactured by Gilmour Manufacturing Co. (Somerset, Pennsylvania 15501)($3.99, 1993) is a solid brass adjustable hose-end nozzle. This attachment was tested when attached to the Dram 30 inch Rain Wand.
All devices were attached to a conventional hose. Attachments were then mounted on a test stand with the nozzle as close to the ground as possible with the nozzles pointing straight up. Water was then turned on to full force and the spray pattern and height noted for each attachment. Thereafter, a 1 gallon plastic water jug with a 6 by 6 inch piece of 3/8 inch thick plywood glued to the bottom was hung 12 inches above the end of the nozzle. The jug was hung from a "Put It On Right Calibration Scale" (Dow Chemical Company 1984 134-814-83), a plastic scale which weighs objects ranging from 12 to 2 ounces. The jug was filled with water to weigh a total of 10 ounces. The water was then turned on to full force and the displacement of weigh of the suspended 6 by 6 inch, 10 ounce plate was recorded for each nozzle type and device.
Results and Discussion. Notes on the characteristics of the devices evaluated are presented below and in Table 1. Only the Water Wand for Spider Mites and the Jet-All Water Wand were found to be useful for spraying small soft bodied insects and spider mites from plant surfaces. A very important requirement for these devices is the ability to spray from at or near ground level. All attachments to the Rain Wand® were not capable of spraying upwards from less than about two feet from the ground because of the 135 angle in the tubing. The Fogg-it Nozzle did not provide sufficient force to be capable of dislodging insects or mites. The cone spray provided by the Twist Nozzle produced a spray that was too hard and a spray void in the middle, making this device hard to direct, even if it could be positioned low to the ground to spray upwards. However, the hard stream adjustment may prove to be useful for spraying tent caterpillar webs or wasp nests from a distance.
Water Wand for Spider Mites - This device allows spraying directly upwards from 1 3/8 inches from the ground (the height of the nozzle). The spray is a course, hard spray from a single cone-type nozzle. The device is easily controlled.
Jet-All Water Wand - Due to the curved PVC pipe at the nozzle end of this device, spraying directly upwards can not be accomplished less that 3.5 inches from the ground. However, holding the device at an angle does allow spraying from close to ground level. The three nozzles put out more spray volume than the Water Wand, but was found to be harder to control and carefully direct the spray.
Dramm 30 Inch Rain Wand - This device sprays like a fountain. The wand can not be positioned to allow the nozzle to be pointed directly upward less than two feet from the ground.
Dramm Fogg-it Nozzle Model C-610 - This device produces fine mist and air currents carrying small drops; no force.
Twist Nozzle - This device has a variable adjustment from low (hollow cone spray) to high (hard stream, 30-40 ft. height).
II. Evaluation of effectiveness.
Trial 1. Two of the devices, the Water Wand for Spider Mites and the Jet-All Water Wand were used in a trial to remove aphids from spinach in a home vegetable garden. The garden contained two 12 ft. long rows of 7 to 9 inch tall (and 3 inches or less apart) spinach, 12 inches apart. The planting was divided in two 6 ft. long sections. Twenty randomly-selected spinach leaves were removed and the number of aphids counted on each leaf. The two sections were then sprayed with one of the devices by spraying along each side of each row twice from different directions, with the nozzle placed as close to the ground and bases of the plants as possible and spraying upwards at a 45 or greater angle from the ground. One day later (30 March 1994), aphids were monitored as before. Resulting data were analyzed using the Student's t test (P < 0.05).
Trial 2. Four Orange Sunblaze® 'Meijikatar' (P.P. 4682) roses, roughly 6 inches tall and planted in 4 inch pots were used for this trial. Prior to treatment (7 Aug. 1994) andperiodically thereafter (8, 15 and 18 Aug.), 5 compound leaves were removed from each plant at random. The three apical leaflets were examined using a 10x hand lens for the presence of aphids (melon and green peach) and spider mites. Two of the plants were then sprayed using the Jet-All Water Wand. Treated plants were sprayed again on 15 Aug. after mites and aphids were counted.
Resulting data were analyzed using the Student's t test (P < 0.05).
Results and Discussion
Trial 1. Both pressurized water spray devices worked similarly (Table 2). A single spray resulted in both a significant reduction of aphids (56 to 69 percent) and a reduction in the number of aphid infested leaves (28 to 30%), with a significant reduction of aphid infested leaves resulting from use of the Jet-All Water Wand. The structure of spinach plants is one of the more difficult to spray. These plants are low to the ground and the growing point (crown) is on the ground, producing large overlapping leaves. When sprayed, outer leaves tend to protect younger inner leaves. Even with insecticidal sprays, coverage of inner leaves with non-systemic insecticides would be difficult.
Multiple sprays using pressurized water sprays would undoubtedly increase percent suppression of aphids. On other plants tested for crape myrtle aphid suppression (Drees, 1991) and two spotted spider mite suppression on snap peas (Drees, 1991) using the Water Wand for Spider Mites, percent reduction was better (88.9 percent for crape myrtle aphids two days after application and 88.2 percent reduction of spider mites one day after application). These plants have a more open structure allowing the pressurized water spray to reach target areas (undersides) of the leaves.
Trial 2. Treatment using the Jet-All Water Wand significantly reduced spider mite (98 percent) and aphid (93 percent) numbers relative to densities found on untreated plants within 24 hours (Table 3). Numerous predatory Phytoseiulus mites were present on 7 and 8 Aug. These natural enemies of spider mites apparently caused their numbers to decline by 15 Aug. Aphid numbers increased as did populations of Scymnodes lady beetle larvae by 15 Aug. A second treatment with the Jet-All Water Wand again resulted in a significant (97 percent) reduction of aphids relative to untreated control plants.
Conclusion and Limitations
The Water Wand devices evaluated were found to effectively reduce small arthropods from plants sprayed. They provided maximum suppression on open canopy type plants. Use of these devices would be compatible with biological control programs to dislodge pests before natural enemies are released. There are some limitations. When dislodging non-host specific arthropods like spider mites, dislodged mites may land on neighboring plants which are suitable food sources. This was observed in the trial where spider mites were removed from snap peas in a home garden and later found infesting tomatoes (Drees, 1991). This does not occur, however, when treating host-specific arthropods like crape myrtle aphids or where care is taken to direct the spray away from other suitable host plants as was the case in the miniature rose trial.
Literature Cited
Drees, B. M. and T. R. LeRoy. 1991. Evaluation of alternative methods for suppression of crape myrtle aphids. pp. 21-22 in Upper Coast 1990-1991 Entomological Result Demonstration Handbook, Texas Agricultural Extension Service, Texas A&M University System.
Drees, B. M. 1991. Suppression of two-spotted spider mites with high pressure water sprays. p. 23 in Upper Coast 1990-1991 Entomological Result Demonstration
Handbook, Texas Agricultural Extension Service, Texas A&M University System.
Meyer, A. and P. Stone (Eds.) 1989. The Healthy Garden Handbook. A Fireside Book, Simon & Schuster Inc., New York, 192 pp.
Table 1. Characteristics of commercially available devices used to generate pressurized water sprays, 1993.
| Spray pattern | Spray Height | Weight Displacement | |
|---|---|---|---|
| Water Wand for Spider Mites | 40o cone | 8 ft. | 5.0 oz. |
| Jet-AllTM Water Wand | 80 o x 3=150o by 10o | 8 ft. | 4.0 oz. |
| Dramm 30 Inch Rain WandTM | 75o | 7 ft. | --- |
| Dramm Fogg-it Nozzle Model C-610 | 30o | 1.8 ft. | 0.5 oz. |
| Twist Nozzle -low adjustment (hollow cone spray) high adjustment (hard stream) | 70o 5o | 9 ft. 30 ft. | 1.0 oz. >10.0 oz. |
Table 2. Effectiveness of two pressurized water spray devices for removing aphids from spinach, College Station, 1994.
| Pre-treatment | One day post-treatment | Percent control | |
|---|---|---|---|
| Mean (+ S.D) no. aphids/leaf (n=20) | |||
| Water Wand for Spider Mites | 3.8+3.9* | 1.6+1.8* | 56% |
| Jet-AllTM Water Wand | 5.8+4.0* | 1.8+1.7* | 69% |
| Mean no. aphid infested leaves/5 leafs (n=4) | |||
| Water Wand for Spider Mites | 4.0+0.8 | 3.3+1.3 | 28% |
| Jet-AllTM Water Wand | 5.0+0.0** | 3.5+5.8** | 30% |
* indicates means are significantly different using the Student's t test (P < 0.05, d.f = 38).
** indicates means are significantly different using the Student's t test (P < 0.05, d.f = 6).
Table 3. Average number of spider mites or aphids per compound leaf before and following treatment (Aug. 7 and 15, 1994) with the Jet-All Water Wand, Orange Sunblaze® 'Meijikatar' miniature roses.
| Mean (+ S.D.) no. spider mites or aphids per compound leaf | ||||
| 7 Aug. | 8 Aug. | 15 Aug. | 18 Aug. | |
| Plants | pre-treatment | 24 hr. post | 8 days & retreat | 3 days post |
|---|---|---|---|---|
| Spider mites | ||||
| treated plants | 4.1 + 3.9 | 0.1 + 0.3* | 0.0 | 0.1 + 0.3 |
| untreated plants | 3.6 + 2.8 | 5.4 + 4.3* | 0.1 + 0.3 | 0.2 + 0.4 |
| Aphids | ||||
| treated plants | 4.9 + 4.7 | 0.4 + 0.8* | 4.0 + 5.4 | 0.1 + 0.3* |
| untreated plants | 9.3 + 6.7 | 5.6 + 4.6* | 28.6 + 48.2 | 3.8 + 1.7* |
* Mean pairs are significantly different using the Student's t test (P < 0.05, d.f = 18).
Educational programs conducted by the Texas Agricultural
Extension Service are open to all people without regard to race,
color, sex, disability, religion, age or national origin.
1994
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Last modified: March 18, 1997 by Edgar Cross