Thrips palmi | Pest Rating Proposals and Final Ratings

California Pest Rating for

Thrips palmi (Karny): Melon Thrips

Thysanoptera: Thripidae

Pest Rating: A

PEST RATING PROFILE

Initiating Event:

March 5, 2015 the United States Department of Agriculture announced that it is considering a change in the status of Thrips palmi, melon thrips, to non-actionable and may therefore stop taking action on the pest when it is intercepted at U.S. ports¹. A pest rating proposal is required to determine a permanent pest rating.

History & Status:

Background: Thrips palmi is a highly polyphagous insect that breeds on the flowers, stems, leaves and fruit of many species of plants and causes serious damage to food crops²,⁴. Crops that are often severely damaged include: Solanaceae: eggplant (Solanum melongena⁴), pepper (Capsicum spp.⁴), potato (Solanum tuberosum⁴), tobacco (Nicotiana tabacum⁴), ground cherry (Physalis spp.⁴); Cucurbitaceae: bittermelon (Momordica charantia⁴), cucumber (Cucumis sativus⁴), watermelon (Citrullus lanatus⁴), muskmelon (Cucumis melo⁴), cantaloupe (Cucumis melo subsp. melo⁴), pumpkin (Cucurbita pepo⁴), squash (Cucurbita spp.⁴), zucchini (Cucurbita pepo⁴), edible gourds (Cucurbita spp.⁴); hyotan (Lagenaria siceraria⁴); Leguminosae: kidney bean (Phaseolus vulgaris⁴), broad bean (Vicia faba⁴), cowpea (Vigna unguiculata⁴), green bean (Phaseolus vulgaris⁴), soybean (Glycine max⁴), togan (Benincasa hispida⁴); Amaranthaceae: chinese spinach and amaranth spinach (Amaranthus dubius⁴); Benincaseae: Chinese wax gourd (Benincasa hispida⁴); Asteraceae: Chrysanthemum spp.⁴, Dahlia spp.⁴; Malvaceae: cotton (Gossypium spp.⁴); Myrsinaceae: Cyclamen spp.⁴; Convolvulaceae: morning glory⁴, sweet potato (Ipomoea batatas⁴); Orchidaceae: orchids⁴; Apocynaceae: Plumeria spp.⁴; Pedaliaceae: sesame (Sesamum indicum⁴). Other reported hosts include: Lauraceae: avocado (Persea americana⁵); Rutaceae: Citrus spp.⁵; Anacardiaceae: mango (Mangifera indica⁵); Rosaceae: peach (Prunus persica⁵), plum (Prunus spp.⁵). Thrips palmi may be transported long distances when infested nursery stock or fresh plant parts are moved.

Worldwide Distribution: Thrips palmi is native to South-East Asia and has spread to many tropical locations throughout the world². It is established in Hawaii and Florida.

Official Control: Thrips palmi is listed as a harmful organism by 73 nations including: Albania, Antigua and Barbuda, Argentina, Armenia, Austria, Azerbaijan, Belarus, Belgium, Bermuda, Brazil, Bulgaria, Chile, Colombia, Costa Rica, Croatia, Cuba, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, French Polynesia, Georgia, Germany, Greece, Guatemala, Holy See (Vatican City State), Honduras, Hungary, Iceland, Ireland, Israel, Italy, Jamaica, Japan, Kazakhstan, Latvia, Lithuania, Luxembourg, Malta, Mexico, Moldova, Republic of Monaco, Montenegro, Morocco, Netherlands, New Zealand, Norway, Panama, Paraguay, Peru, Poland, Portugal, Romania, Russian Federation, San Marino, Serbia, Slovakia, Slovenia, South Africa, Spain, Svalbard and Jan Mayen, Sweden, Switzerland, Tajikistan, Tunisia, Turkey, Turkmenistan, Ukraine, United Kingdom, Uruguay, and Uzbekistan³.

California Distribution: Thrips palmi has never been found in the environment of California.

California Interceptions: CDFA’s high risk programs, dog teams, and border stations have intercepted Thrips palmi 64 times on consignments from Hawaii and Florida. Most interceptions have been on orchids imported from Hawaii.

The risk Thrips palmi (melon thrips) would pose to California is evaluated below.

Consequences of Introduction:

1) Climate/Host Interaction: Thrips palmi is polyphagous and suitable hosts are grown throughout the state. However, melon thrips is only known to be established in tropical climates and greenhouses; some of the colder parts of California may be unsuitable for establishment. Thrips palmi receives a Medium (2) in this category.

Evaluate if the pest would have suitable hosts and climate to establish in California. Score:

– Low (1) Not likely to establish in California; or likely to establish in very limited areas.
– Medium (2) may be able to establish in a larger but limited part of California.
– High (3) likely to establish a widespread distribution in California.

2) Known Pest Host Range: Thrips palmi feeds on more than 50 species of plants in at least 20 families. It receives a High (3) in this category.

Evaluate the host range of the pest. Score:

– Low (1) has a very limited host range.
– Medium (2) has a moderate host range.
– High (3) has a wide host range.

3) Pest Dispersal Potential: Under favorable conditions, Thrips palmi can complete a generation in less than two weeks and each female can lay 100-200+ eggs. This indicates a high reproductive rate. Thrips palmi are small and are frequently hidden in pockets, cracks, and crevices on host material⁴. This enables them to elude inspections and facilities long distance dispersal through the movement of infested consignments. Thrips palmi receives a High (3) in this category.

Evaluate the natural and artificial dispersal potential of the pest. Score:

– Low (1) does not have high reproductive or dispersal potential.
– Medium (2) has either high reproductive or dispersal potential.
– High (3) has both high reproduction and dispersal potential.

4) Economic Impact: Thrips palmi is a primary pest of some crops and can be expected to reduce crop yields and increase crop production costs if it were to establish in California. The species is of quarantine significance to at least 73 nations and can be expected to disrupt markets for Californian agricultural commodities. Thrips palmi is also known to be an efficient vector of multiple plant pathogens including tomato spotted wilt virus⁵, bud necrosis virus⁵, and at least two other plant pathogens². Melon thrips receives a High (3) in this category.

Evaluate the economic impact of the pest to California using the criteria below. Score:

A. The pest could lower crop yield.
B. The pest could lower crop value (includes increasing crop production costs).
C. The pest could trigger the loss of markets (includes quarantines).
D. The pest could negatively change normal cultural practices.
E. The pest can vector, or is vectored, by another pestiferous organism.
F. The organism is injurious or poisonous to agriculturally important animals.
G. The organism can interfere with the delivery or supply of water for agricultural uses.

– Low (1) causes 0 or 1 of these impacts.
– Medium (2) causes 2 of these impacts.
– High (3) causes 3 or more of these impacts.

5) Environmental Impact: If Thrips palmi were to establish in California it could be expected to trigger additional treatment programs at farms, orchards, nurseries, and by residents. Melon thrips would also have significant impacts to home/urban gardening and ornamental plantings. Thrips palmi receives a High (3) in this category.

Evaluate the environmental impact of the pest on California using the criteria below.

A. The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.
B. The pest could directly affect threatened or endangered species.
C. The pest could impact threatened or endangered species by disrupting critical habitats.
D. The pest could trigger additional official or private treatment programs.
E. The pest significantly impacts cultural practices, home/urban gardening or ornamental plantings.

Score the pest for Environmental Impact. Score:

– Low (1) causes none of the above to occur.
– Medium (2) causes one of the above to occur.
– High (3) causes two or more of the above to occur.

Consequences of Introduction to California for Thrips palmi (Melon Thrips): High (14)

Add up the total score and include it here.

– Low = 5-8 points
– Medium = 9-12 points
– High = 13-15 points

6) Post Entry Distribution and Survey Information: Thrips palmi has never been found in California and receives a Not established (0) in this category.

Evaluate the known distribution in California. Only official records identified by a taxonomic expert and supported by voucher specimens deposited in natural history collections should be considered. Pest incursions that have been eradicated, are under eradication, or have been delimited with no further detections should not be included.

– Not established (0) Pest never detected in California, or known only from incursions.
– Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).
– Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.
– High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.

Final Score:

The final score is the consequences of introduction score minus the post entry distribution and survey information score: High (14)

Uncertainty:

The climate of California may be less suitable to the establishment of Thrips palmi.

Conclusion and Rating Justification:

Thrips palmi has not been found in California and would have significant economic and environmental impacts if it were to enter the state. An “A” rating is justified.