Spidermites, broadmites and whiteflies are the principle pests of eggplant in southwest Florida.
The mite Neoseiulus californicus is a voracious predator of spidermites and also feeds on broadmites.
Amblyseius swirskii feeds on all three pests but does best on whiteflies and broadmites. It also will control thrips.
Both mites can survive on pollen when live prey is not available.
Both are commercially available and come packed in bran together with a supply of their food mite.
In our experiments, we’ve used mites from Koppert Biological Systems of Howell, Mich.
Our objective last fall was to evaluate each species alone, in combination and in rotation.
Eggplants (variety Zebra) were transplanted Sept. 13 in four rows at 2-foot spacings. Each row was divided into six plots containing 18 plants separated by a buffer plot of 18 plants.
Each of the six plots in each row was designated in a randomized complete block design for one of six treatments.
1. A. swirskii alone,
2. N. californicus alone,
3. A mixture of A. swirskii and N. californicus,
4. A. swirskii released first followed by N. californicus one week later,
5. The same but in reverse order and
6. Control (no release).
Thirty mites of each species were released per plant, with the first release being made Oct. 3, three weeks after transplanting.
Buffer plots received an application of an insecticide/ miticide (Movento at 5 ounces per acre in a volume of 60 gallons per acre) on Oct. 3 and a second two weeks later.
Mites were monitored weekly, beginning Sept. 26, by sampling six leaves—three top and three basal—from six randomly selected plants per plot.
Leaves were examined under a stereoscopic microscope to count eggs, nymphs and adults of each mite species as well as whitefly eggs and nymphs.
Spidermites built up quickly, reaching an average of 205 per leaf on untreated plants by Oct. 10, compared with 7.1 on plants receiving N. californicus followed by A. swirskii.
In contrast, 34.7 spidermites per leaf were seen on plants sprayed with Movento.
Spidermite numbers fell subsequently in all treatments, with best results obtained with treatments that include N. californicus with the first release.
Whitefly nymphs averaged 25.8 per leaf Oct. 10 in the check and initially were lowest on plants treated with Movento (1.6) and A. swirskii alone (5.6), with the other treatments being intermediate.
By Nov. 1, there were no more than two whitefly nymphs per leaf, regardless of treatment.
Broadmite numbers reached a maximum of 3.3 per leaf in the check Oct. 26 and 2.4 per leaf on plants treated with Movento.
There were virtually no whitefly nymphs on plants receiving A. swirskii and N. californicus alone, mixed or in sequence.
Both species of predaceous mite were still found on the plants through Dec. 12, presumably feeding on pollen as all three pests were virtually absent.
Thus, one application of the mixture or of each species in succession controlled all three pests for one full season as well or better than the standard insecticide treatment.
Phil Stansly is an entomology professor at the Southwest Florida Research and Education Center. He can be reached at firstname.lastname@example.org. José Castillo is a research assistant at the center. He can be reached at email@example.com.