Department
of Agriculture
_{State of Hawaii}

Financial Assistance
Agriculture Development
Importing(Quarantine)
Exporting
Quality Assurance
Statistics
Pest Control
Pesticides
Aquaculture
Land and Water
Admin Rules
Forms
Who We Are
Job Opportunities
What's New

Many long-standing pest problems in Hawaii are under less than complete biological control:

WEEDS

Koster's curse (Clidemia hirta): Of pestiferous weeds in Hawaii, this melastome has continued to be a major pest in Hawaiian forests since its detection on Oahu in 1941. Since then, the weed has spread to the islands of Hawaii (1972), Molokai (1973), Maui (1977), and Kauai (1982). First alarms about the threat posed by this weed were sounded around 1968; by 1989, approximately 40,500 ha were infested on Oahu alone. Clidemia hirta, the natural range of which extends throughout the humid tropics of Central and South America from southern Mexico to northern Argentina and the islands of the West Indies, is a densely branching melastomataceous shrub, growing up to four m in height and covered with dense hairs. Plants flower and fruit prolifically throughout the year, producing sweet, pulpy, dark-blue berries filled with minute seeds. Berries are avidly eaten by birds, which serve to spread the plant over wide areas. On a good soil, this weed can produce an impenetrable stand. It thrives both in open grassland and in deep shade, and can result in greatly increased weeding costs in commercial plantations. A pioneering species after disturbance, in forests it tends to displace native plants.

The Hawaii Department of Agriculture(HDOA) has continued to evaluate biological control of clidemia since 1952. In 1953, after testing, review, and approval for introduction by entomologists of the pineapple and sugar industries and the University of Hawaii, Liothrips urichi Karny was imported from Fiji and released. Within eight days of release, thrips were found breeding on clidemia plants, and were considered established. Liothrips urichi, when at high densities, can cause complete die-back of all young growth, as well as reduce seed production. It has proven to be effective in preventing spread of clidemia into open pastures and cultivated land; however, it was not effective in shaded areas, such as those covered by forest, female thrips ovipositing significantly less in shady than in sunny areas. Predation also may have reduced effectiveness of the thrips. A leaf-rolling pyralid caterpillar, Ategumia matutinalis (Guenee), obtained from Puerto Rico and Trinidad in 1969, was released on Oahu and Hawaii in 1970. First recovery was made in 1974. Parasitoids are thought to be reducing the effectiveness of this moth. Lius poseidon Napp, a leaf-feeding buprestid beetle from Trinidad, was introduced on Oahu and Kauai in 1988. Adults feed on clidemia leaves, producing a ragged feeding strip, whereas larvae are leaf miners. This beetle favors plants in light, never heavy, shade, and rarely in open fields. An isolate of the fungus, Colletotrichum gloeosporioides, discovered in Panama and recently introduced into Hawaii, has been shown to be an effective control agent under conditions of moderate to high humidity, conditions that prevail in infested zones in Hawaii for much of the day. Recently, three additional moth species, Antiblemma acclinalis Hubner (Noctuidae), Carposina bullata Meyrick (Carposinidae), and Mompha trithalama Meyrick (Momphidae), have been approved for release against clidemia. Based on studies made thus far with the fungus and the phytophagous insects, the outlook for eventual management of clidemia in Hawaiian forests appears promising.

Lantana camara: This weed is a perennial, spreading, thicket-forming, aromatic shrub, native to subtropical and tropical Central America. The races or subspecies found in Hawaii have stems with sharp spines. Flowers are multicolored, arranged in masses in flat-topped heads. The weed thrives on margins of rainforest, in forest clearings, along roadsides and streambanks, and in neglected pastures and plantations. Lantana can form impenetrable thickets, up to several meters in height. It is poisonous to cattle and sheep. Spread is accomplished mainly by means of the fruits, which are avidly eaten by some birds. The weed was purposely introduced into Hawaii in 1858 from Mexico as an ornamental. By 1902, it had spread to occupy large areas, aided by two introduced birds, the Chinese dove, Streptopelia chinensis, and common myna, Acridotheres tristis. That year, 23 insects were introduced from Mexico for its control, eight of which became established. Lantana was the first weed to be studied for the purpose of biological control in what is now the U.S. Beginning in the 1950s, exploration in the U.S., Latin America, and Africa resulted in the introduction of 13 additional control agents, six of which became established; a final introduction was made from material collected in Peru in 1969. The most effective control agents are the lace bug Teleonemia scrupulosa Stal. (Tingidae); the chrysomelid beetles Octotoma scabripennis Guerin-Meneville and Uroplata girardi Pic; and the moths Hypena strigata F. and Neogalea sunia (Guen‚e) (Noctuidae), and Salbia haemorrhoidalis Guen‚e (Pyralidae). While biological control of lantana by most of the established insects appeared to have reached an equilibrium by 1969, the overall impact of the phytophage complex has been a steady and considerable reduction in abundance of the weed, particularly in drought-prone areas. Although lantana is considered generally to be under partial to substantial control in drier areas, it still remains a pest in some other environments, such as national parks.

Insects

Four species of tephritid fruit flies have become major agricultural pests in Hawaii over the last century:

Melon fly (Bactrocera cucurbitae [Coquillett]): This fruit fly was introduced into Hawaii from Japan in 1895. It also has been reported from southern China, Taiwan, Okinawa, the Philippines, Malaysia, Cambodia, Laos, Vietnam, Thailand, Burma, India, Sri Lanka, Mauritius, North and East Africa, Guam, parts of Melanesia, Indonesia, and northern Australia. This pest has been recorded from more than 80 different host plants, including tomato, peppers, watermelons, cantaloupe, pumpkin, beans, eggplant, cucumber, squashes, and other cucurbits, and in Hawaii, in addition to these, passion fruit. Damage is caused by the larvae feeding in fruits. Fruit develops a water-soaked appearance; introduced saprophytic organisms cause the fruit to rot. Adult females may also oviposit in stems of cucurbits of various ages. Seedlings may be killed in this way. Biological control explorations by the Hawaii Board of Agriculture and Forestry were undertaken during 1915-1916 in India, Sri Lanka, the Malayan peninsula, Java, and the Philippines. Of all potential control agents found, the most effective was a larval parasitoid, Psyttalia fletcheri (Silvestri) (Braconidae), which was introduced from India in 1916, released, and quickly became established. Studies have shown that P. fletcheri often destroys considerable numbers of melon fly larvae infesting wild host fruits. Average parasitization rates have ranged from 5-44%, depending on season. However, the parasitoid is less effective in attacking larvae in cultivated crops. The value of P. fletcheri therefore lies in reducing melon fly populations in reservoir hosts.

Mediterranean fruit fly or Medfly (Ceratitis capitata [Wiedemann]): Medfly became established in Hawaii in 1910. This species is distributed throughout the subtropical regions of the world, excluding Southeast Asia, and has been recorded from more than 200 host plants, including citrus, mango, coffee, guava, and peach, as well as many wild fruits. Damage to fruit is similar to that caused by melon fly. Importation of natural enemies of C. capitata was undertaken by the Hawaii Board of Agriculture and Forestry in 1912 in West and South Africa and Australia. Five species of hymenopterous parasitoid were introduced into Hawaii, three of which became permanently established: Psyttalia humilis (Silvestri) (Braconidae) from South Africa, Dirhinus giffardii Silvestri (Chalcididae) from West Africa, and Diachasmimorpha tryoni (Cameron) (Braconidae) from Australia. In 1914, another expedition to West Africa by Hawaii Board of Agriculture and Forestry entomologists resulted in introduction and establishment of Biosteres fullawayi (Silvestri) (Braconidae) and Tetrasticus giffardianus Silvestri (Eulophidae). A third program of importation of natural enemies by the U.S. Department of Agriculture in 1935-1936 conducted explorations in East and West Africa, Brazil, Malaysia, India, Sri Lanka, and Mexico. Of the resulting species of Opiinae introduced into Hawaii, none became established. Parasitization of the Medfly has varied among host plants: up to 94.4% in coffee, 23.1% in guava, 24.8% in mango, and 12.8% in orange.

Oriental fruit fly (Bactrocera dorsalis [Hendel]): This species was first found in Hawaii in 1946, and quickly spread throughout the islands. It is reported as a major fruit pest from India, Japan, China, and Taiwan, being native, apparently, to the Indo-Malayan region. Over 90 plants, both cultivated and wild, have been recorded as hosts. In Hawaii, citrus, mango, papaya, guava, banana, and avocado are among the more important commercial crops attacked. Damage to fruits is similar to that caused by the other fruit fly species. From 1947 through 1951, a search for fruit fly parasitoids (not restricted to those specific to B. dorsalis) was conducted in the major tropical and subtropical regions of the world, including the Philippines, Malaysia, Australia, New Britain, New Caledonia, Fiji, Saipan, India, South China, Taiwan, Thailand, Indonesia, Sri Lanka, Africa, and Brazil. Puparia from more than 60 species of Tephritidae were collected from a wide range of host plants and shipped to Hawaii for emergence of parasitoids. (All of the known fruit fly parasitoids of consequence complete their development in, and emerge from, host puparia, regardless of the stage in which oviposition occurs.) The majority of these were B. dorsalis. During 1947 through 1953, inclusive, field releases were made of 29 species and subspecies of parasitoids and one predator (a staphylinid beetle). Of these, the following five hymenopterous species have become permanently established: Diachasmimorpha longicaudata (Ashmead), Biosteres arisanus (Sonan) (= Opius oophilus Fullaway), B. vandenboschi (Fullaway), Psyttalia incisi (Silvestri) (all Braconidae), and Aceratoneuromyia indica (Silvestri) (Eulophidae).

Consistently high parasitization of B. dorsalis by B. arisanus since 1950 in Hawaii has resulted in a substantial reduction in fruit infestation. This is particularly seen in cultivated fruits, such as avocado, banana, papaya, loquat, peach, persimmon, and mango, which were heavily infested during the period 1947-1949, but, after the general population build-up of B. arisanus, were substantially free from attack. Some authors have concluded from this that B. dorsalis is now of relatively little economic importance in most kinds of fruits. The lessened impact on commercial fruit production contrasts with the situation in widespread, naturalized hosts, such as guava, which remain heavily infested. However, indications are that B. arisanus consistently effects a parasitization of around 75% of B. dorsalis larvae in guava, the wild host plant that provides the main reservoir for this fruit fly in Hawaii. Substantial control of Medfly has also been effected by the parasitoids from Malaysia introduced against oriental fruit fly. Biosteres arisanus, in particular, has been shown to be an effective parasitoid of the Medfly at higher elevations (to which this fly has been displaced through competition with the oriental fruit fly), with parasitization rates averaging 60% since 1951.

Malaysian or solanaceous fruit fly (Bactrocera latifrons [Hendel]): This recent immigrant was first discovered on Oahu in 1983, thereafter spreading to all of the neighbor islands, except Lanai, by 1991. Bactrocera latifrons has been reported from China, India, Sri Lanka, Taiwan, Malaysia, Thailand, Laos, and the Philippines. The most common host plants are Solanaceae, especially chili pepper; other hosts reported include cucumber, melon, and various wild Solanum species. This fruit fly has been targeted for biological control by the U.S. Department of Agriculture, HDOA cooperating.

Southern green stink bug (Nezara viridula [L.]): This pentatomid is probably native to northern Africa or the Mediterranean region. It has been recorded from a broad range of host plants, including crops, such as legumes (peas, beans, and soybean), sesame, cucurbits, tomato, potato, passion fruit, peanut, sorghum, sunflower, tobacco, maize, crucifers, spinach, alfalfa, grapes, citrus, mango, and macadamia nut; and various ornamentals, such as orchids. It has also been reported as a pest of rice and other grains, guava, cowpea, peppers, and cotton. In Hawaii, wild hosts include cheese weed, castor bean, black nightshade, amaranth, and wild spider flower. Attack is concentrated mainly on fruits and fruiting bodies, which results in discoloration, malformation, stunting, and shriveling. The bug has also been shown to transmit plant pathogens during feeding. Nezara viridula was first discovered in Hawaii on Oahu in 1961; by late 1963, it had spread to all of the neighbor islands. Initial chemical eradication attempts having failed, a biological control program was begun in 1962-1963. At least nine parasitoids were introduced into Hawaii for control purposes. Of these, the wasp Trissolcus basalis (Wollaston) (Scelionidae), an egg parasitoid from Australia, Trichopoda pennipes (F.) from Florida, U.S.A., and T. pilipes (F.) from the West Indies, the latter two both tachinid parasitoids of last-instar nymphs and adults, became established. Populations of the stink bug declined steadily thereafter to subeconomic levels with only sporadic outbreaks, and the pest is generally considered to be under effective biological control, with average parasitization by T. basalis ranging to 95%, that by T. pilipes to 86%. However, N. viridula continues to have a significant negative impact on particular crops, such as macadamia nut.

CHINESE ROSE BEETLE (Adoretus sinicus Burmeister): This polyphagous scarabaeid beetle was introduced into Hawaii sometime before 1896. It is distributed in Southeast and East Asia, including Indonesia, Taiwan, and China; it is also found on Guam. Introduction into Hawaii probably was accomplished by larvae in the soil of plants. Adults feed at night on the leaves of a great variety of plants. At least 255 plant species in 56 families have been recorded as hosts, including rose, grape, cycad, okra, beans, soybean, pigeon pea, sweet potato, eggplant, maize, cucumber, asparagus, taro, banana, and cotton. Damage is caused by the adult. Attacked leaves show numerous small holes, or may become entirely skeletonized. Larvae feed on decaying plant matter in the soil, and only rarely attack live roots. Although parasitoids and predators have been introduced into Hawaii, no satisfactory control measures have been developed for A. sinicus, and it remains a significant pest.