Papaya tree leaves falling off

common name: papaya fruit fly (suggested common name)
scientific name: Toxotrypana curvicauda Gerstaecker (Insecta: Diptera: Tephritidae)

The papaya fruit fly, Toxotrypana curvicauda Gerstaecker, is the principal insect pest of papaya (Carica papaya L.) throughout the tropical and subtropical areas of the New World. The insect was introduced into Florida in 1905, most likely from the West Indies on papaya shipments. It first became established in the Florida Keys and Miami, then spread throughout the state wherever papayas are grown. Papaya fruit fly larvae and adults have been found in Florida in every month of the year. Although originally considered to be monophagous, infesting only wild and cultivated papaya, the insect has also been reported on mango and milkweed in Florida, and other plant species in Mexico.

Figure 1. Adult female papaya fruit fly, Toxotrypana curvicauda Gerstaecker. Photograph by Doug Caldwell, University of Florida.

Synonymy (Back to Top)

Mikimyia furcifera Bigot.

Distribution (Back to Top)

The papaya fruit fly is distributed throughout the Caribbean, particularly in Puerto Rico, the Dominican Republic, Trinidad, Cuba and the Bahamas. It is also found in Central America (Belize, Costa Rica, Guatemala, Honduras, Mexico, Panama) and South America (Columbia, Venezuela).

In the United States, the fly is found in southern Texas and southern Florida.

Figure 2. Florida distribution of the papaya fruit fly, Toxotrypana curvicauda Gerstaecker, in 2004. Drawing by G. J. Steck and B. D. Sutton, Division of Plant Industry.

Description (Back to Top)

Adult: Commonly mistaken for a vespid wasp due to its size, form, coloration, and behavior, the papaya fruit fly is predominantly yellow marked with black. The female has a very long, slender abdomen with a greatly elongated, curved ovipositor which exceeds the length of its body (body length: 8.5-12.5 mm; ovipositor length: 9-14 mm). The male fly resembles the female with a hairy, but less markedly banded, stalked abdomen and without the ovipositor (body length: 11-13.5 mm; wing width: 8.5-11 mm).

Figure 3. Adult female. Drawing by Division of Plant Industry.

Figure 4. Adult male papaya fruit flies, Toxotrypana curvicauda Gerstaecker, dorsal view (lower left) and ventral view (upper right). Photograph by James L. Nation, University of Florida.

Egg: The egg is long, slender, and yellow with a long cylindrical stalk. The average length is approximately 2.5 mm, and the largest diameter is 0.2 mm.

Larvae: Larvae are white and the typical fruit fly shape (cylindrical-maggot-shape, elongate, with the anterior end narrowed and somewhat recurved ventrally, with anterior mouth hooks, ventral fusiform areas and flattened caudal end). The last instar is large compared to other species at 13-15 mm in length. Other features include the venter with fusiform areas on segments 4 through 11, anterior buccal carinae narrow, long and usually 13 to 15 in number, anterior spiracles nearly straight on dorsal edge but with noticeable depression centrally, with tubules numerous, varying from 22 to 28 and usually with some tubules in a somewhat secondary dorsal row.

Figure 5. Larvae of the papaya fruit fly, Toxotrypana curvicauda Gerstaecker, in papaya. Photograph by Scott Bauer, USDA.


Figure 6. Head and buccal carinae of larva. Drawing by Division of Plant Industry.

The primary diagnostic characters for papaya fruit fly larvae involve the large anterior spiracles, the number of narrow buccal carinae (13 to 15), the lack of prominent tubercles on the caudal end of the larva, and a bifid anal elevation. The anterior spiracles are longer than in most other known fruit fly larvae. The caudal end of the body is particularly distinctive in lacking any prominent tubercles or papillules and has only the spiracular region as a depressed plate, but some indistinct and small tubercles and papillules are present. However, relative to other tephritid larvae, the species has the appearance of a smooth caudal end. The pharyngeal skeleton is particularly distinctive due to the sclerotization along the dorsal margin of the pharyngeal plate.


Figure 7. Anterior spiracles of larva. Drawing by Division of Plant Industry.

Cephalo-pharyngeal skeleton with large convex mouth hook (approx. 2× hypostome length), having a large bulbous lower muscle attachment; hypostomium long, with bulbous subhypostomium; post-hypostomial plates curved dorsally to dorsal bridge sclerotizations; parastomium prominent, pointed; anterior of dorsal bridge with a slightly sclerotized point, more extensive internally towards dorsal wing plate; pharyngeal plate somewhat shorter than dorsal wing plate, both with relatively extensive sclerotizations, especially distinctive along the mid-dorsal margin of the pharyngeal plate beneath median hood.


Figure 8. Cephalo-pharyngeal skeleton of larva. Drawing by Division of Plant Industry.

The sclerotizations of the cephalo-pharyngeal skeleton vary to some extent (see Figure 35 in Phillips 1946), but the prominent sclerotization of the dorsal margin of the pharyngeal plate, the strong central sclerotizations and the large mouth hooks are distinctive for the species. The anterior spiracles usually have a large number of tubules when there is an apparent secondary row of tubules. Illustrations and descriptions of the caudal end of the larva of this species have been incorrect in past works (Berg 1979, Phillips 1946) in not noting the small D1-2 and triangle of L1-3 papillules. Compared to other fruit fly larvae these papillules, as well as the small tubercle for papillule V1, are not readily evident; thus, the larvae appear to have a nondescript smooth caudal end. Careful examination, however, reveals the papillules, tubercles and raised plates as illustrated herein. Published keys to larvae (e.g., Berg 1979) are not compromised, however, since routine identification efforts will not generally make note of the small papillules and tubercles. Larvae examined came from verified samples from Florida in the larval collection of the Florida State Collection of Arthropods.

Caudal end lacking any prominent tubercles or papillules but with several small papillules; the caudal end generally convex, with depressed subquadratic spiracular plate; all papillules not easily seen, with paired dorsal papillules (D1 and D2) angled dorsally, an obtuse triangle of three intermediate papillules (I1-3) ventral to spiracular plate, and a single small V1; all tubercles or raised plates very slightly elevated to maintain an overall impression of a relatively smooth caudal end; L1 papillule not evident; I1 somewhat more prominent than all other papillules; posterior spiracles elongate (approx. 4× to 5× width), with central spiracles nearly straight, dorsal pair slightly angled, and ventral pair angled ventrally; interspiracular processes (hairs) in small tufts with needle-like extensions; spiracular wall thick and internal bars prominent; anal elevation with lobes bifid, rounded.

Figure 9. Caudal end of larva. Drawing by Division of Plant Industry.

Figure 10. Posterior spiracles (left side) of larva. Drawing by Division of Plant Industry.

Figure 11. Anal lobes of larva. Drawing by Division of Plant Industry.

Pupa: The puparia are stout and cylindrical with rounded ends and vary in length from 8.5–12 mm. They are yellow to almost black. The color does not indicate age, as some remain light colored until the adults emerge.

Life Cycle (Back to Top)

The female is capable of producing 100 or more eggs. The female fruit fly oviposits in the green immature fruit by thrusting her ovipositor through the flesh of the fruit. She then deposits a group of 10 or more long, slender eggs in the papaya’s central cavity where the young larvae feed on developing seeds and the interior parts of the fruit. As the larvae mature, they eat their way out of the fruit, drop to the ground beneath the plant, and pupate just below the soil surface. Flies emerge in about two to six weeks, depending upon humidity and temperature of the soil.

Eggs are usually laid in small fruit, about two to three inches in diameter, but they may be deposited in smaller or larger fruit. However, unripe papaya juice is fatal to the larvae so the fruit must be ripe before the larvae begin to eat their way out of the inner cavity. Eggs hatch approximately 12 days after oviposition and larval development in the fruit lasts about 15 to 16 days.

Damage (Back to Top)

Fruit infected with papaya fruit fly larvae will turn yellow and drop from the tree prematurely. Damage levels in Florida fluctuate between 2 and 30% of fruits infested during the spring-summer season.

Management (Back to Top)

Prevention of egg-laying is the key to controlling papaya fruit fly. It is necessary to kill the adult female before she deposits eggs in the fruit.

Florida Crop/Pest Management Profile: Papaya

Bagging can be an effective control measure for the fruit fly in small plantings (one to 25 plants or less than 1/10 hectare). Bagging should begin when the fruit is small, shortly after the flowers have fallen off. Each fruit should be enclosed in a paper bag or rolled tube of newspaper and tied around the stem. This method can be very practical and successful if enough labor is available. Attention to covering new fruit and increasing the covering as the fruits increase in size is necessary.

Sanitation is also important in the control of the papaya fruit fly. All dropped and prematurely ripe fruit, as well as infested young fruit, must be destroyed in order to prevent the larvae from developing into adults.

Very little research has been done on the biological control of papaya fruit fly, considering its economic importance. One parasitic wasp, in particular, Doryctobracon toxotrypanae Marsh (Hymenoptera: Braconidae), from southern Mexico and Costa Rica, may have potential for control.

Pheromone lures and traps are critical for monitoring fruit fly populations, measuring distribution, and acquiring control or eradication. Research in Miami and Gainesville, Florida has resulted in the development of a pheromone lure and functional trap for this species. Studies are presently being performed to test female pheromone lures with the addition of host odor chemicals in order to increase the attraction of flies and to improve its performance in competition with males.

Other possible control measures have been suggested for future research, such as papaya fruit without seeds. Due to the strong dependence of larval feeding on the seeds as an early food source, a seedless papaya variety could be explored. For similar reasons, thicker pulp could possibly provide enough resistance to hinder the ovipositor from successfully depositing eggs. Another suggestion has been to look for varieties of papaya with higher levels of chemicals that are toxic to the larvae.

Selected References (Back to Top)

  • Benjamin FH. 1934. Descriptions of some native trypetid flies with notes on their habits. U.S. Department of Agriculture Technical Bulletin 401: 1-95.
  • Berg GH. 1979. Pictorial key to fruit fly larvae of the family Tephritidae. San Salvador: Organ. Internac. Region. Sanidad Agropec. 36 pp.
  • Castrejon-Ayala F, Camino-Lavin M. 1991. New host plant record for Toxotrypana curvicauda (Diptera: Tephritidae). Florida Entomologist 74: 466.
  • Greene CT. 1929. Characters of the larvae and pupae of certain fruit flies. Journal of Agricultural Research 38: 489-504.
  • Ibrahim RB. 1980. Fruit Flies of Florida (Diptera: Tephritidae). Ph. D. Dissertation: University of Florida. Toxotrypana curvicauda Gerstaecker. p. 188-190.
  • Knab F, Yothers WW. 1914. Papaya fruit fly. Journal of Agricultural Research 2: 447-453.
  • Landolt PJ. 1994. Fruit of Morrenia odorata (Asclepiadaceae) as a host for the papaya fruit fly, Toxotrypana curvicauda (Diptera: Tephritidae). Florida Entomologist 77: 287-288.
  • Landolt PJ. 1990. Behavior of the papaya fruit fly (Diptera: Tephritidae): host finding and oviposition. Environmental Entomology 19: 1305-1310.
  • Landolt PJ. 1984. Behavior of the papaya fruit fly, Toxotrypana curvicauda Gerstaecker, (Diptera: Tephritidae). Folia Entomologica Mexicana 61: 215-224.
  • Landolt PJ, Heath RR. 1996. Development of phermone-based trapping systems for monitoring and controlling tephritid fruit flies in Florida. pp. 197-207. In Rosen D, Bennett FD, Capinera JL. (editors)., Pest Management in the Subtropics. Intercept Limited, United Kingdom.
  • Mason AC. 1922. Biology of the papaya fruit fly, Toxotrypana curvicauda, in Florida. U.S. Department of Agriculture Technical Bulletin 1081. 10 pp.
  • Peña JE. 1988. Effectiveness of pesticides against two tropical fruit pests. Proceedings of the Florida State Horticultural Society 101: 249-251.
  • Peña JE, Howard DF, Litz RE. 1986. Feeding behavior of Toxotrypana curvicauda (Diptera: Tephritidae) on young papaya seeds. Florida Entomologist 69: 427-428.
  • Phillips VT. 1946. The biology and identification of trypetid larvae (Diptera: Trypetidae). Memoirs of the American Entomological Society 12: 1-161.
  • White IM, Elson-Harris MM. 1994. Fruit Flies of Economic Significance: Their Identification and Bionomics. CAB International. Oxon, UK. 601 pp.
  • Wolfenbarger DO, Walker SD. 1974. Two major pest problems of papayas. Proceedings of the Florida State Horticultural Society 87: 384-385.

Question: I have maggots in my papayas. What are they, and what can I do to prevent them from eating my fruit?

Carl

New smyrna Beach

A: When papaya fruit develops, Caribbean fruit flies lay eggs on your fruit. Its offspring, maggots, use the fruit to feed before they pupate and form into a fly again.

To prevent them from laying eggs, protect the fruit as it ripens. Use paper bags or my favorite, knee-high stockings, to cover each fruit when young. You will have to throw away your infected fruit, but protect the ones that don’t have maggots and start covering the fruit earlier next year.

Q: I am trying to start mandevillas from seed, but I have not had any luck. I get the seed from the base of the spent bloom. I let the bloom dry out, and then I remove the seed and dust it with rooting powder. I plant it in “seed-start soil” and wet it, then cover it with clear plastic in which I have poked a few holes. I placed it in bright light, but not sunlight. Can you give me any advice as to what I should be doing? Any pointers will be appreciated.

Howard

Ormond Beach

A: Mandevillas are relatively easy to start by seed. Given the seeds’ little wispy tails, they naturally fly away and germinate on their own. But if you are having trouble, here are some tips. Make sure you’re using fresh seed. Sow pretty soon after the seeds develop to make sure your seeds are viable. Knowing when the seeds are ready is imperative. Let the plant tell you by allowing the seedpod to open on its own. It should be easy to remove the seeds from the plant when they are fully developed.

Soak them for several hours before planting. Plant just below the surface and barely cover them so they keep moist and warm. Allow the seeds in your starter mix to be in partial sun. Keep them moist by covering with plastic over it, but don’t keep watering them. A common mistake when growing seedlings is overwatering, which can lead to rot or disease. The plastic will keep them moist for a couple of days. After 10 to 14 days, you should see some green growth emerge. Be patient: Seedlings may seem a little slow because they are not an annual vine.

Q: When and how often should I prune poinsettias?

Diana

Port Orange

Answer: It is important to prune poinsettias so the plants don’t get leggy. You don’t want to prune them often, however, because they need to have new growth for the leaves to turn color when the days become shorter in fall or winter. Prune anytime after it flowers, between spring and summer. Pruning in later winter is not recommended because of sensitivity to cold.

INTRODUCTION
LOCATION AND PLANTING
WATERING
CARE AND FROST PROTECTION
FERTILIZING
SOIL
WINDS
SUN AND HEAT
INTRODUCTION
There are two types of papayas, Hawaiian and Mexican. The Hawaiian varieties are the papayas commonly found in supermarkets. These pear-shaped fruit generally weigh about 1 pound and have yellow skin when ripe. The flesh is bright orange or pinkish, depending on variety, with small black seeds clustered in the center. Hawaiian papayas are easier to harvest because the plants seldom grow taller than 8 feet. Mexican papayas are much larger the the Hawaiian types and may weigh up to 10 pounds and be more than 15 inches long. The flesh may be yellow, orange or pink. The flavor is less intense than that the Hawaiian papaya but still is delicious and extremely enjoyable. They are slightly easier to grow than Hawaiian papayas. A properly ripened papaya is juicy, sweetish and somewhat like a cantaloupe in flavor, although musky in some types. The fruit (and leaves) contain papain which helps digestion and is used to tenderize meat. The edible seeds have a spicy flavor somewhat reminiscent of black pepper.
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LOCATION AND PLANTING
Papayas like to be warm with both sunshine and reflected heat, so the hottest place against the house where nothing else seems happy is an ideal location. They also like to be as free from wind as possible, although this is not as critical as their need for sun. Papayas can be grown successfully in shade, but the fruit is rarely sweet. They are best planted in mounds or against the foundation of a building where water can be controlled.
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WATERING
Watering is the most critical aspect in raising papayas. The plants should be kept on to the dry side to avoid root rot, but also need enough water to support their large leaves. In winter the plant prefers to remain as dry as possible. A plant that has been injured by frost is particularly susceptible to root rot. In the summer they can handle all the water you can give them provided the soil drains well.
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CARE AND FROST PROTECTION
Papayas need warmth and a frost-free environment, but can often withstand light freezes with some kind of overhead protection. This can be provided by building a frame around the plants and covering it with bedding, plastic sheeting, etc. when frost threatens. Electric light bulbs can also be used for added warmth. Potted specimens can be moved to a frost-secure area. Prolonged cold, even if it does not freeze, may adversely affect the plants and the fruit. Mexican papayas are more hardy than Hawaiian varieties.
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FERTILIZING
The fast-growing papaya requires regular applications of nitrogen fertilizers but the exact rates have not been established. Feed monthly and adjust according to the plant’s response. They can take fairly hot organic fertilizing such as chicken manure if used with deep irrigation after warm weather has started. Phosphorus deficiency casuses dark green foliage with a reddish-purple discoloration of leaf veins and stalks.
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SOIL
Papayas need a light, well-drained soil. Cactus mix works best.
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WINDS
Protection from wind is best but not crucial. If you have a warm sunny spot with protection from high winds that would be ideal. Otherwise just choose the hottest sunniest spot in your yard.
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SUN AND HEAT
The papaya will take full Arizona sun. If the soil temperature is above 55 degrees and drains well (the basin will empty in less than 30 minutes), it is okay to flood irrigate and the tree will respond with fast growth. You can’t believe how fast. When the temperature rises over 90, use good judgement but water often and deeply.
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How To Ripen A Papaya: Getting Sweet Papaya In 4 Easy Steps

Step 1: Picking The Right Papaya

Before you think about how to ripen a papaya, you need to focus on choosing one that is in good condition. This is because papayas that are too green will not taste good even if you try to hasten its ripening process. If you buy ones that are bruised, you will end up getting a rotten papaya.

When buying a papaya, look for one that is of the right size and one that is already mostly colored. The papaya should be firm and not hard or too soft. This will help ensure that you will get good results after the fruit has ripened. Ripening this kind of papaya will usually take 2-3 days.

If the papaya already has spots of yellow on its skin, you might just want to put it inside the fridge and allow it to ripen in its own time. Keeping the papaya in the fridge will help protect it from insects who will be attracted to its aroma. Do not freeze the papaya, just keep it in a cool place so that it will not rot.

Step 2: Use The Paper Bag Method

After picking a papaya, you need to put the fruit in a paper bag. This will help keep the humidity down and it will also help keep the papaya away from moisture. Inside the paper bag, the papaya will release ethylene which will trigger the ripening process. The bag will also keep the ethylene from escaping.

This technique is ideal for papayas that have begun to ripen, since the fruit can produce the ethylene on its own. It should not be used on very green papayas. If you are going to use newspaper, you need to wrap the papaya carefully so that the gasses will not escape. Do not wrap the fruit too tightly.

Step 3: Lightly Score The Skin Of The Papaya

If the papaya is still too green, you can score the skin or the peel of the papaya so that it will release ethylene. After scoring, you should put the papaya in a paper bag and allow it to sit in a cool dry place. Check the papaya after a day or two so you will be able to eat it when it has fully ripened.

Keep in mind that scoring the papaya’s skin can cause the fruit to rot, this is why you should keep an eye on the fruit. You should also make sure that you will only score the skin of the papaya and not let the knife go through its flesh so you will allow it to ripen and not rot.

Step 4: Put A Banana With It Inside The Paper Bag

If the papaya is still very green, you should let another ripe fruit release the ethylene gas inside the paper bag. Put the papaya inside the paper bag and add a ripe banana before you close the bag. The banana will release the gas which will help hasten the ripening of the papaya.

papayas.jpg

Papaya fruit will not ripen properly once it gets cold. You can harvest the largest of the fruit and try ripening them indoors. Keep them at room temperature and see what happens. If they are far enough along, they may ripen off the tree.

(Chris Granger, The Times-Picayune/NOLA.com)

QUESTION: On my tree, I have lots of papayas that just will not ripen. Now that it’s getting cold, should I pick them? Will they ripen once they’re picked? I would hate to lose them due to a freeze. Thanks for your help. — Alice

ANSWER: Papaya fruit will not ripen properly once it gets cold. So, it is unlikely any of the green papayas will ripen on the tree from this point on. You can harvest the largest of the fruit and try ripening them inside. Keep them at room temperature and see what happens. If they are far enough along, they may ripen indoors. Green papayas are edible. Do an Internet search for green papaya recipes, and you’ll see many ways to prepare them. If a hard freeze threatens, down in the upper 20s, harvest any fruit you want to use. Subfreezing temperatures can ruin the fruit. If the tree is damaged by cold this winter, cut it back in spring to remove the damage. It should send up new growth from the stump. It likely will produce ripe fruit next year before it gets too cold.

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QUESTION:

This is the first time I have ever had this problem on my mirlitons (see photo at left). How do I control this and are they safe to eat after trimming off the portion that has been affected.

— Warren

ANSWER: These are called pickleworms. There also was a heavy outbreak on our late-summer cucumbers and squash. I guess they have hung around and now are attacking the mirliton crop. I’ve had several gardeners contact me with this problem. The adult is a moth that lays eggs on the developing mirliton. The eggs hatch, and the larvae burrow into the fruit. Treating the plants and fruit regularly with Sevin, Bt (Dipel, Thuricide and other brands) or spinosad might help reduce the damage. Feel free to trim away the bad part of the mirliton and use the rest.

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QUESTION: When should I prune my pentas? They are huge. Also, is it too late to plant some wildflower seeds? Which seeds would you recommend down here? — Stacey Dehmer

ANSWER: I would leave the pentas alone for now. They are more cold tolerant left large. Winter weather may freeze back the plants. In spring, prune off the dead growth and then trim back even farther, if you like. It is not too late to plant wildflower seeds. Choose a mix labeled for the southeastern United States.

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