Sri Lankan weevil — Myllocerus undecimpustulatus undatus Marshall

Beetroot weevil: common and gray, control methods

Myllocerus undecimpustulatus undatus Marshall, the Sri Lankan weevil, is a plant pest with a wide range of hosts. This weevil spread from Sri Lanka into India and then Pakistan where many subspecies of Myllocerus undecimpustulatus Faust are considered pests of more than 20 crops. In the United States, the Sri Lankan weevil was first identified on Citrus sp. in Pompano Beach a city in Broward County Florida. Three specimens were identified by Dr. Charles W. O’Brien, first as Myllocerus undecimpustulatus, a species native to southern India, and then again as Myllocerus undatus Marshall native to Sri Lanka, finally as Myllocerus undecimpustulatus undatus Marshall to show its status as a subspecies.

Figure 1. Sri Lankan weevil, Myllocerus undecimpustulatus undatus Marshall, adults on Hong Kong orchid tree, Bauhinia blakeana. Photograph by Anita Neal, University of Florida.

Distribution (Back to Top)

The Sri Lankan weevil was first detected in 2000. By May, 2006 it was found in 12 counties in Florida. Michael Thomas of the Florida Division of Plant Industry has obtained data from field agents identifying this weevil in an additional 13 counties since May of 2006. It has not been determined how the Sri Lankan weevil arrived in south Florida.

Figure 2. Distribution of Sri Lankan weevils, Myllocerus undecimpustulatus undatus Marshall, in Florida based on initial collection from 2000 to 2006, and additional data through 2012. Map created by Anita Neal, University of Florida.

Description (Back to Top)

Adults: Adult Sri Lankan weevils vary in length from approximately 6.0 to 8.5 mm; the female weevil is slightly larger than the male by 1.0 to 2.0 mm. Some of the notable features of the Sri Lankan weevil are toothed femora (front and middle bidentate and hind femora tridentate), strongly angled humeri (shoulders, see red arrows in figures 3 and 6) are broader than the prothorax, the yellowish coloration of the head, and the dark-mottled dark elytra. These features help distinguish the Sri Lankan weevil from other weevils of similar size and coloration. Artipus floridanus Horn, the little leaf notcher, is most similar in appearance but the femora lack teeth, the humeri are not angled, and the elytra are grayish to white, with smaller black cuticular marks formed by perforations on the elytra.

Figure 3. Adult Sri Lankan weevil, Myllocerus undecimpustulatus undatus Marshall, with angled humeri and dark mottled elytra. Photograph by Anita Neal, University of Florida.

Figure 4. Adult Sri Lankan weevil, Myllocerus undecimpustulatus undatus Marshall, with yellowish coloration of head. Photograph by Anita Neal, University of Florida.

Figure 5. Adult Sri Lankan weevil, Myllocerus undecimpustulatus undatus Marshall, hind femur with spines. Photograph by Paul Skelley, FDACS-Division of Plant Industry.

Figure 6. Adult Sri Lankan weevil, Myllocerus undecimpustulatus undatus Marshall (left) comparison with the little leaf notcher, Artipus floridanus Horn (right). Photographs by Paul Skelley, FDACS-Division of Plant Industry.

Eggs: Female Myllocerus spp. may lay up to 360 eggs over a 24-day period, and larvae emerge in 3-5 days. Sri Lankan weevil eggs are laid directly on organic material at the soil surface, which is common for most Myllocerus spp. Eggs are less than 0.5 mm, ovoid and usually laid in clusters of 3-5. The eggs are white or cream-colored at first, then gradually turn brown when they are close to hatching.

Larvae: The larvae range in size from 1.09 ± 0.05 mm as first instar larvae to 4.0 ± 0.05 mm as fourth instar larvae and are beige-white with a reddish brown head. They burrow into the soil where they feed on plant roots for approximately one to two months. The larvae pupate in the soil for approximately one week.

Figure 7. Life cycle of the Sri Lankan weevil, Myllocerus undecimpustulatus undatus Marshall, eggs, larva, pupa, and adult life stages. Photographs by Holly Glenn, University of Florida.

Host Plants (Back to Top)

The Sri Lankan weevil has a wide host range of over 150 plant species including native, ornamental, vegetable and fruit species. Some host plant examples include Citrus spp., citrus; Conocarpus erectus, green buttonwood; Bauhinia x blakeana, Hong Kong orchid tree; Chrysobalanus icaco, cocoplum; Phoenix roebellenii, pygmy date palm; Prunus persica, peach; Lagerstroemia indica, crepe myrtle; Capsicum spp., pepper; Litchi chinensis, lychee; Muntingia calabura, strawberry tree; and Solanum melongena, eggplant. It is unclear what the larval host plants are, but they have been reared in the laboratory on pepper, eggplant, cotton, carrot, and sweet potato roots.

Figure 8. Adult Sri Lankan weevil, Myllocerus undecimpustulatus undatus Marshall, feeding damage on Terminalia catappa L., tropical almond. Photograph by Susan Halbert, FDACS — Division of Plant Industry.

Economic Importance (Back to Top)

Leaf-feeding adults damage the foliage of ornamental plants, fruit trees, and vegetables, whereas the larvae injure root systems. Due to its feeding habits, the Sri Lankan weevil could negatively affect subtropical and tropical fruit, ornamental, and vegetable industries here in Florida. The possible impact to the horticulture industry in nurseries, landscape services, and horticultural retailers could reach billions of dollars based on the value they generate in Florida (Kachatryan and Hodges 2012). Extension agents and Master Gardener volunteers around the state have received requests from homeowners for information on the control of this weevil. Botanical gardens and plant nurseries have reported damage due to chewing injury and require effective control measures.

Damage (Back to Top)

When adult weevils feed on leaves, they feed inward from the leaf margins (or edges), causing the typical leaf notching. There are some instances where the leaf material is almost completely defoliated, where the weevil has fed along the leaf veins. The adults prefer new plant growth. Intense feeding by numerous weevils may cause plant decline or stunting. Young seedlings may not survive a large amount of feeding damage. With healthy plants, however, the feeding damage may be considered cosmetic if the plant recovers.

Figure 9. Adult Sri Lankan weevil, Myllocerus undecimpustulatus undatus Marshall, feeding damage on Conocarpus erectus L., green buttonwood. Photograph by Holly Green, University of Florida.

Management (Back to Top)

Traditional methods of control include pesticides, many of which provide only limited management of this pest. Chemical control of the adults is difficult because of their ability to fly, hide, or feign death and drop to the ground. Chemical control of the eggs, larvae, and pupae is more difficult due to their location on or in the soil.

Adult weevils can be removed from plants by vigorously shaking a branch over an open, inverted umbrella. The collected weevils can then be dumped into a container of soapy water.

As insecticide recommendations and regulations are updated yearly, it is advisable to consult a local Extension Service office or a pesticide reference guide for current information on control methods for this pest.

Selected References (Back to Top)

  • Arevalo HA, Stansly PA. 2009. Suppression of Myllocerus undatus (Coleoptera: Curculionidae) in Valencia orange with chlorpyrifos sprays directed at ground and foliage. Florida Entomologist 92: 150-152.
  • Atwal AS. 1976. Agricultural pests of India and South-East Asia. New Delhi, India: Kalyani Publishers. pp. 295-296.
  • Epsky N, Walker A, Kendra PE. 2009. Sampling methods for Myllocerus undecimpustulatus undatus (Coleoptera: Curculionidae) adults. Florida Entomologist 92: 388-390.
  • Frank JH, Thomas MC. 2012. Invasive insects (adventive pest insects) in Florida. University of Florida/IFAS EDIS. (12 April 2017)
  • Josephrajkumar A, Rajan P, Mohan C, Thomas RJ. 2010. First record of Asian grey weevil (Myllocerus undatus) on coconut from Kerala, India. Phytoparasitica 39: 63-65.
  • Khachatryan H, Hodges AW. 2012. Florida nursery crops and landscape industry economic outlook. University of Florida/IFAS, Food and Resource Economics Department, Gainesville. November 2012. 4-5. (12 April 2017)
  • Mannion C, Hunsberger A, Gabel K, Buss E, Buss L. 2006. Sri Lanka weevil (Myllocerus undatus). University of Florida/IFAS, Tropical Research and Education Center, Homestead. August 2006: pp. 1-2. (23 October 2013)
  • O’Brien CW, Haseeb M, Thomas MC. 2006. Myllocerus undecimpustulatus undatus Marshall (Coleoptera: Curculionidae), a recently discovered pest weevil from the Indian subcontinent. Florida Department of Agriculture and Consumer Services, Entomology Circular No.412. (12 April 2017)
  • Thomas M. 2005. Myllocerus undatus Marshall, a weevil new to the Western Hemisphere. Pest Alert. Florida Department of Agriculture and Consumer Services, Division of Plant Industry. (12 April 2017)

Acknowledgements: Special thanks to Morgan Byron, Dr. Ron Cave, Dr. John Capinera and Dr. Howard Frank for their review of this document.

Author: Anita Neal, University of Florida
Photographs: Anita Neal, University of Florida; Paul Skelley, FDACS — Division of Plant Industry; Holly Glenn, University of Florida; Susan Halbert, FDACS — Division of Plant Industry
Web Design: Don Wasik, Jane Medley
Publication Number: EENY-579
Publication Date: November 2013. Reviewed: April 2017.

An Equal Opportunity Institution
Featured Creatures Editor and Coordinator: Jennifer L. Gillett-Kaufman, University of Florida

entnemdept.ufl.edu

Grain Weevils

Order: Coleoptera (‘sheath-wings’)
Family: Curculionidae.

Grain Weevils:
3.5mm long


CHARACTERISTICS:
Forewings hard and leathery, meeting along mid-line of dorsal surface; hindwings membranous, sometimes lacking; biting mouthparts; well developed thorax; complete metamorphosis with egg, larval, pupal and adult stages. Insects with cylindrical bodies and a pronounced rostrum (snout) equipped with mouthparts which is used by females as a boring tool; elbowed, clubbed antennae set on rostrum; 4-segmented tarsi.

SPECIES CHARACTERISTICS:
Grain Weevil (Granary Weevil) (Sitophilus granarius)
Adults, 3-4mm long; colour: dark brown, nearly black, with shiny appearance; 8-segmented antennae; prothorax with distinct oblong/oblongoval punctures; hindwings absent.

Rice Weevil (Sitophilus oryzae)
Adults, 2-3.5mm long (average 2.5mm); colour: dark brown, nearly black, with four clearly defined reddish spots on the elytra; less shiny than the Grain weevil; 8-segmented antennae; prothorax with round or irregular punctures; hindwings present.

Maize Weevil (Sitophilus zeamais)
Very similar in appearance to the Rice weevil with the characteristics described above, except that the insects are longer, adults reaching a length of 3-3.5mm (average 3mm).

AREAS WHERE FOUND:
Grain weevils are encountered in all temperate and warm-temperate climates and are widely distributed in grain stores throughout Europe. Infestations arise as a result of their regular importation in grain and cereal products and from the fabric of vehicles or buildings used for the transportation and storage of these and other vulnerable commodities. Sacks, too, are an important source of infestation, the insects finding harbourage in the seams and weave. Being well suited to temperate conditions the species will breed readily in South Africa and there may be three or more generations per year in unheated conditions. Both adults and larvae are coldhardy. Rice and Maize weevils are widely distributed in tropical and sub-tropical areas and will be carried to temperate areas on imported commodities. The Maize
weevil will breed on maize in the field, but the Rice weevil only breeds in stored grain. Both insects are less coldhardy than the Grain weevil and will not normally overwinter in unheated premises or grain stored at normal temperatures.

IMPORTANCE AS A PEST:
Grain weevils are important pests of farm-stored grain. They are frequently regarded as primary pests of grain since they are able to infest otherwise undamaged grain. Grain weevils will also attack other hard cereal products, e.g. macaroni and spaghetti. Fine cereal products are unsuitable for breeding purposes unless they become caked. The following damage may be caused:

  1. Reduction in the weight and quality of grain as a result of the larvae feeding on the endosperm. The germ is not always attacked so germination may take place, producing a weak seedling which is vulnerable to attack by moulds, bacteria and other insects. Both larvae and adults will feed upon grains.
  2. Tainting with white, dusty excreta which contaminate the product as well as rendering it unpalatable.
  3. Heating of the grain, accelerating development of the insects and making the commodity liable to caking, moulding and even germination. Temperatures may be attained which actually kill the insects.

Weevil-damaged grain can be readily recognised by the presence of large holes which are the exit holes of the emerging adults. Some idea of the huge numbers of weevils that can be generated is provided by the results of one study in which, 5 weeks after wheat was infested with larval forms, adults were seen to be leaving the grain at a rate of 100 per kg per day.

LIFE-CYCLE:
The Grain weevil can only breed in grain with a moisture content of more than 9.5% and at temperatures within the range 13-35°C. The female lays about 200 eggs at a rate of 2-3 per day depending upon temperature and humidity, placing each one in a small hole bored in the grain and sealing it in with a mucilaginous plug of saliva. At 18-20°C the eggs hatch in 8-11 days to give small, white, legless larvae which feed on the endosperm of the grain. Only one larva develops in small grains such as wheat and rice but large grains such as maize will support the development of several. Larvae are never freeliving and develop entirely within the grain. They moult four times, finally pupating within the grain after 6-8 weeks. The adults emerge after a further 5-16 days and will live for about 9 months. If disturbed they will feign death by drawing their legs up to their bodies and remaining still. At 15°C and a grain moisture content of 11.3% the full life-cycle takes 6 months. The life-cycles of the Rice and Maize weevils follow a similar course to that of the Grain weevil.

CONTROL:
Assessment of infestations
A variety of trapping techniques are available for measuring stored product beetle infestations. These include pit fall traps, bait bags, insect probe traps and adhesive traps. Whatever system is employed adequate records must be kept.

    Hygiene/management
    Stores should be soundly constructed to ensure maintenance of correct storage conditions and allow for easy cleaning. They should be insulated, well ventilated and damp-proof. Cracks and crevices, which may provide harbourages for the beetles, should be kept to a minimum. Commodities should be stacked neatly above the floor level using pallets, away from walls and should not touch the ceiling. A gap between stacks will allow for ventilation, regular inspection, cleaning and, if necessary, treatment with insecticides (see recommended products). Appropriate stock rotation is important and if possible there should be a one-way passage of commodities through the premises. The careful choice of packaging can help to deter insect attack. Generally, thick, tough materials with a smooth, shiny finish are preferred. Packs should be strong and well sealed. It is important to ensure that there are no food residues (stored commodities or secondary sources, e.g. birds’ nests) in which beetles can breed and develop to infest new materials. All infested commodities should be destroyed or fumigated. Stores should be kept scrupulously clean and farm stores should be thoroughly cleaned before harvest. All grain taken into store should be dried to a suitable moisture content (MC) and temperature e.g.

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Identifying And Controlling Root Weevil

Root weevils are a plant pest both indoors and outdoors. These destructive little insects will invade the root system of a healthy plant and then proceed to eat the plant from the roots up. Identifying and controlling root weevil in your garden and houseplants can keep your plants from suffering unnecessary damage.

Identifying Root Weevils

Root weevils can be one of several kinds. The most common in the garden is the black vine root weevil or the strawberry root weevil. The black vine weevil attacks shrubs and strawberry weevils attack strawberries. While these are the most common, they are far from the only kind. All plants in your home or garden are susceptible to weevil infestation.

Larval root weevils will look like white grubs or worms and will be found in the soil. Adult weevils are beetle like insects that can be black, brown or grey.

If root weevils are present in your garden or houseplants, there will be damage to both the roots and the leaves. The leaves of the plant will be irregular, as though someone has been taking bites out of the edges. This damage will appear in the night, as root weevils come out to feed at night.

Root Weevil Control

Controlling root weevil is possible. Organic root weevil control methods include purchasing parasitic nematodes or predatory beetles can be bought to hunt down the weevils. You can also hand pick the adults off the plant at night while they are eating. Weevils are also attracted to moisture, so a shallow pan of water can be set out at night and the weevils will climb into it and drown.

Non-organic root weevil control methods are to spray the leaves of the plant with a pesticide and to thoroughly soak the soil with a liquid pesticide. But, remember, when you do this, you may also be killing off beneficial insects and small animals as well.

Finding these insects in the roots and leaves of your plants is unpleasant, but it can be fixed. As always, the best root weevil control is to make sure you never get any in the first place. Be sure to practice good garden hygiene and clean up dead plants and do not over mulch.

www.gardeningknowhow.com

Carrot Diseases and Pests, Symptoms, Control Methods

Introduction to Carrot Diseases and Pests:

Today let us go through the common Carrot Diseases and Pests and thier Symptoms as well control methods

Diseases in Carrots:

Alternaria leaf blight: the infected leaves have green-brown water-soaked lesions which enlarge and turn dark brown or black; infected leaves will turn yellow and die. Wet foliage, rain, fog and warm weather will encourage the development of disease.

Prevention:

  • Wet, warm conditions will keep plants away from diseases.
  • Apply organic fungicides when the first symptoms appear.
  • Treat seeds with organic fungicide or hot water before sowing.
  • Application of gibberellic acid will prevent diseases and promote air circulation.

Black rot:

The disease causes damping-off of seedlings; necrosis in root and crown; foliage blights; this disease will turn lower portion of petioles black; you can observe black ring around petiole and sunken lesions on the taproot. This Disease is spread through infected seed.

Prevention:

  • Black rot is very tough to control and survive in the soil for the long term.
  • Implement long crop rotations.
  • Plow crop residue after every harvest.
  • Use plant resistant varieties.
  • Treat the seeds with hot water before sowing.

Cercospora leaf blight:

The main symptoms of the diseases are small, necrotic flecks on leaves later turn to chlorotic halo and expand into tan brown spots. The lesions cause leaves to wither, curl and die. Infected seed can be a root cause of the diseases and it is spread through wind or water splashes. Young seedlings or foliage is mainly affected with this disease.

Prevention:

  • Used only pathogen-free seed.
  • Implement crop rotation.
  • Plow the crop after every harvest.
  • Use organic fungicide sprays.

Cottony rot:

Small, water-soaked, soft lesions on the crown and roots are the main symptoms of this disease. You can observe white fluffy fungal growth in affected tissues. This fungus can survive up to 10 years.

Prevention:

  • There are seed varieties that are resistant to this disease.
  • Using drip irrigation is a good control.
  • Deep plowing of soil and trimming back foliage to promote air circulation, which can control disease to some extent.

Downy mildew:

The main symptoms of the disease are yellow spots on the upper surface of leaves, white fluffy growth on underside of leaves. You can also observe lesions which turn darker when they mature. This disease mainly affects the young and tender leaves. Foliage wetness will encourage the growth the development of disease.

Prevention:

  • Use pathogen-free seed.
  • Maintain spacing and avoid crowding.
  • Implement plant rotate with non-umbelliferous varieties.

Powdery mildew:

You can observe powdery growth on leaves, petioles flowers stalks and bracts. The infected leaves arechlorophylldeficient and severe infections will make the flowers distorted. This disease is spread mainly through the winds. High humidity and moderate temperature will encourage growth of fungus. This infection more in shade areas.

Prevention:

  • Plant disease tolerant varieties.
  • Avoid excess fertilization.
  • Use protective organic fungicides.
  • Application of sulfur in the early season can control disease to some extent.

Bacterial leaf blight:

The symptoms are small, angular, yellow spots on leaves which turns into irregularly shaped, brown, water-soaked lesions with a yellow halo. The centers of lesions will become and brittle. The infected leaves will become curled, the infected flower stalks have lesions with bacterial ooze. Water splashes and poor sanitation are root causes of this disease.

Prevention:

  • Use pathogen-free seed.
  • Avoid using sprinkler irrigation.
  • Use bactericides if necessary.

Soft rot: The main symptoms of the disease are sunken dull orange lesions on taproot. Bacteria will deplete plant tissue. Water saturated soil will increase disease emergence. This bacterium enters into the plant through wounded roots.

Prevention:

  • Use only well-drained soils to plant carrots.
  • Make soil completely dry before every irrigating.
  • Skip the wounding plants during harvest to control the post-harvest development of disease.
  • Good sanitation.

Cavity spot:

The main symptoms of the diseases are sunken, elliptical, gray lesions across the root. The outer layer of the root will turn dark with elongated lesions. The cavities will have small vertical cracks. This fungus sustains for many years in the soil. Wet and soggy soil will increase the chances of the disease.

Prevention:

Avoid the fields that suffered with the carrot spot disease in previous crops. Over-fertilization of plants can also increase the chances of this disease. The Application of organic fungicide can control the disease efficiently.

Damping-off:

The symptoms are soft, rotting of seeds, sometimes the seeds won’t germinate. Damping-off diseases leads to low seed germination, this fungus spreads in the water, penetrates in the soil or on equipment.

Prevention:

Avoid poorly draining soil for planting, cool, wet soil. Planting in the raised beds will promote the soil drainage. Use high quality seeds that germinate quickly. Treat seeds with organic fungicide before planting to control fungal pathogens.

Pests in Carrots:

Aphids: Aphids are small soft bodied insects stay underside of leaves and stems of plants. These insects are usually green or yellow in color. A severe aphid infestation will turn leaves yellow and distorted, necrotic spots on leaves and stunted shoots. Aphids encourage the growth of sooty mold on the leaves.

Prevention:

Prune the infected plants and leaves. Transplants should be aphids free. Use pests’ free varieties. Use reflective mulches made of silver colored plastic which control pests. Use organic insecticidal soaps or oils such as neem or canola oil that are best to control aphids.

Carrot rust fly:

This pest creates tunnels on the taproot. And these tunnels are filled with a rust. The adult flies are small, dark colored flies.

Prevention:

Use of row covers which protect plants from damage, use row covers before adult fly lays eggs on plants. It is recommended to harvest carrots in blocks.

Carrot weevil: This pest forms Irregular dark grooves on the roots. The infected cleaves of plant turn yellow. The adult insect will be in a dark colored beetle and the larvae will be in a white to pinkish white C-shaped grubs.

Prevention: Clean up all the debris of the previous crops. Implement the crop rotation without umbelliferous crops.

Flea beetle:

Beetle forms small holes or pits on the leaves. Young plants and seedlings are mainly susceptible to this disease. If the infestation is severe plant may be killed. Older plants can tolerate these pests.

Prevention:

Use floating row to protect the young plants prior to the attack of pests. Early planting can also protect the plants from common pests. A Thick layer of mulch will prevent beetles. Use some organic pesticides like neem oil or garlic oil, which effectively controlsbeetles.

Root-knot nematodes:

Forked, distorted or stunted taproots are major symptoms of pest attack. This infection reduces the yields.

Prevention:

Solarizing the soil can reduce nematode populations to some extent. There are new carrot varieties that are resistant to nematodes.

Read about: Growing Radish.

www.agrifarming.in

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