ENY618

Broad Mite1

J.E. Pena and C.W. Campbell2

1. This document is Fact Sheet ENY-618, a series of the Entomology and Nematology Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Publication date: June 1992. Revised: September 2005.

2. J.E. Pena, Associate Professor, Tropical Fruit Entomologist, Entomology and Nematology Department; C.W. Campbell, Retired Professor, Tropical Fruit Specialist, Tropical Research and Education Center, Institute of Food and Agricultural Sciences, University of Florida, Homestead, Florida.

Trade names, where used, are given for the purpose of providing specific information. They do not constitute an endorsement or guarantee of products named, nor does it imply criticism of products not named.

The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. U.S. Department of Agriculture, Cooperative Extension Service, University of Florida, IFAS, Florida A. & M. University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Larry Arrington, Dean

The broad mite, Polyphagotarsonemus latus (Banks), is a very important pest of "Tahiti" lime in Florida. Infestations apparently are confined to spring and summer, except under greenhouse conditions. The species had been found only in the southern half of the citrus belt and is most common during the spring.

Physical Description

Female mites (Figure 1) are about 1/141 inch in length, oval in outline, swollen in profile and light yellow, amber or green with an indistinct light median stripe that forks near the back end of the body. Males are similar in color to females, but lack the stripe, (Figure 2). The two hind legs of the female are reduced to whip-like appendages.

Figure 1. Female mites.

The ovate, flattened eggs (Figure 3) are translucent, with scattered white tufts on the upper surface. Mites move jerkily but rapidly for their size when disturbed, but they normally move deliberately.

The broad mite can be easily confused with closely related nonpestiferous tarsonemid mites that occur on citrus. The broad mite and its eggs are readily visible with a 10X hand lens.

Life History

The broad mite has four life stages: egg, larva, nymph, and adult. Eggs, laid on the underside of new leaves and in the depressions of small fruit, hatch within two days to become six-legged, slow-moving white larvae 0.1 mm long. After one day, the larva becomes a quiescent nymph that is clear and pointed at both ends. The nymphal stage lasts about a day; nymphs are usually found in depressions on the fruit, although female nymphs are often carried about by males.

Archival copy: for current recommendations see http://edis.ifas.ufl.edu or your local extension office.

Broad Mite 2

Figure 2. 1, 2) female, 3) male carrying a female 'chrysalis,' 4) egg. Credits: Ochoa and Erbe.

Figure 3. Egg of a broad mite on a citrus fruit.

Under laboratory conditions, the adult female has a preoviposition period about a day and then begins laying an average of five eggs per day for her ten day life span. Generation time, from newly laid eggs to egg-laying female is approximately four to five days.

The adult male is smaller (0.11 mm) and faster-moving than the female. The greatly enlarged hind legs are used to pick up the female nymph and

place her at right angles to his body for later mating. Since other tarsonemid species found on citrus do the same, this is not a good field identification character for the broad mite.

Behavior and Population Dynamics

Broad mites are usually seen only on the newest leaves and small fruit. Low levels of the broad mite can be detected by examining the shaded side of small fruit (2 to 3 cm in diameter) on the interior of trees with the thickest canopies. This preference for the shaded side of the fruit often results in only one side of the fruit being damaged. In some cases one can walk through a grove without seeing damage, but on closer examination find that the shaded side of almost every fruit is silvered.

Generally, it has not been necessary to spray in the spring, but if the broad mite is found in the summer, especially July and August, it is almost certain to reach damaging levels within a very short time. Populations requiring control can occur in September or later in the fall.

Damage

Broad mites damage young leaves (Figure 4) and young fruit by their feeding. Heavy infestations cause distortion or stunting of leaves, and, at times, defoliation of young shoots (Figure 5). The most important damage is to the fruit. Injury at feeding sites causes a russeting or scurfing of the fruit surface (Figure 6) which varies from whitish or silvery to tan or brown in color. In severe cases premature fruit drop may occur. Severely damaged fruit is not saleable in the fresh market, but the fruit can be used for processing because its internal quality is not affected. The greatest infestations occur in the summer, but some damage is done throughout the year. Most growers use control measures at some time during every year.

The damage caused by the broad mite is easily confused with that caused by the citrus rust mite, Phyllocoptruta oleivora (Ashmead).

Archival copy: for current recommendations see http://edis.ifas.ufl.edu or your local extension office.

Broad Mite 3

Figure 4. Young leaves.

Figure 5. Shoots.

Figure 6. Fruit surface.

Host Range

Broad mites have a wide host range in tropical areas. It attacks greenhouse plants in temperate and subtropical regions. Reported hosts other than citrus are shown in Table 1.

Control Recommendations

Biological Control

Biological control of broad mites is basically dependent upon a predator complex. Within this complex the following predators (Table 2) have been found to be most abundant within citrus groves.

Field experiments have shown that if predators are excluded from the grove, broad mite populations can be 4.39 times higher than if predators are present.

Unfortunately, the number of predators present in commercial groves is low. As a result, chemical controls are needed. However, growers should select chemical pest management practices that have as little effect upon predator populations as possible.

Chemical Control

Recommended miticides for broad mite are included in Table 3.

READ THE LABEL.

Archival copy: for current recommendations see http://edis.ifas.ufl.edu or your local extension office.

Broad Mite 4

Table 1. Reported hosts, other than citrus.

Apple Grape Papaya

Avocado Guava Passion Fruit

Azalea Hollyhock Pear

Begonia Jute Potato

Castor Lemon Sesame

Chili Lime String Bean

Coffee Mango Tangerine

Cotton Marigold Tea

Eggplant Mulberry Tomato

Table 2. Predators within citrus groves.

Scientific Name Common Name

Typhlodromalus peregrinus yellow mite

Galendromus helveolus no common name

Typlodromips dentilis no common name

Amblyseius aerialis long haired mite

Bdella disticta citrus snout mite

Table 3. Recommended miticides.

Miticide Minimum Rate Per Acre

Agri-mek 0.15 EC + Petroleum oil 97+% (FC 435-66, FC 455-88 or FC 470-01)

10 fl oz + min 3 gal

Kelthane MF1 6 pts

Sulfur, Thiolux 80 DF 15 lbs

1May increase citrus snow scale populations if applied in 500 or more gallons of water per acre. Do not use in spray solutions above pH 7.

Archival copy: for current recommendations see http://edis.ifas.ufl.edu or your local extension office.