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Miscellaneous Insect Pests of Florida Sugarcane 1
D. G. Hall, R. H. Cherry, R. S. Lentini, G. S. Nuessly, and R. A. Gilbert2The sugarcane insect pests discussed in this report are of occasional economic importance in Florida. Because they have not historically been as important as some pests such as the sugarcane borer (Diatraea saccharalis), they have received less research interest and less is known about them. However, growers should be aware of these pests because they have the potential of becoming a problem if conditions favor their reproduction and growth.
Sugarcane Lacebug
The sugarcane lacebug, Leptodictya tabida, was first discovered in Florida in 1990. Damage to sugarcane by this bug was initially noticed in Palm Beach county. This was also the first time the insect was found on sugarcane in the mainland U.S.The adult lacebug is about 1/8" (3.5 mm) long, flat and light-brown or straw colored ( Figure 1 ). The forewings are semi-transparent and finely laced or netlike. Five long, erect spines are present on the head. Nymphs are flat and whitish in color with many long branched, erect spines. Eggs are laid singly into leaf tissue usually on the underside of the leaves. The tip of the egg is left outside the leaf tissue but is covered with a protective cap secreted by the adult female. A generation of lacebugs, from egg to adult, may take 20 to 30 days, with 5 nymphal molts.
In an early survey, some sugarcane plants were infested by more than 100 adult and nymphal lacebugs per leaf. More than 75 eggs were observed on some leaves. Lacebug feeding resulted in light green or yellow speckles on leaves. Some varieties developed a red russetting from the middle to the tip of the leaf as the result of moderate infestations.
Figure 1. Sugarcane lacebug. Based on the condition of plants in most sugarcane fields in Florida that were infested by lacebugs during July-September, 1990, damage appeared to be minor. However, some fields had damage to the upper and spindle leaves. The lacebug may have had an economic impact on these plants.
Varietal differences in lacebug resistance have been noted in Hawaii and Florida.
Egg parasitoids of Leptodictya tabida have been found in Costa Rica and Venezuela, but natural parasite populations have not been observed in Florida.
There are no chemicals labeled for use on lacebugs in Florida at this time. Applications of carbofuran for the control of other sugarcane pests will simultaneously provide some control of lacebugs.
Yellow Sugarcane Aphid
The yellow sugarcane aphid, Sipha flava, is sometimes a noteworthy insect pest of sugarcane ( Figure 2 ). Red spots soon appear at feeding sites on susceptible cultivars. Prolonged feeding results in yellow discoloration and premature leaf death.
Heavy infestations can occur almost any time during the growing season but most frequently occur during the warmer months of the dry season. Aphid feeding leads to reduced growth and tillering and subsequent yield loss of sugarcane.
Figure 2. Yellow sugarcane aphid. There are several mechanisms of sugarcane resistance to damage by the yellow sugarcane aphid. These mechanisms are variety dependent, and include tolerance and antibiotic effects on aphid development. Winged yellow sugarcane aphids usually restrict their primary colonization to susceptible cultivars. Florida susceptible cultivars include CP61-620, CP72-1210, CP72-2086, CP80-1827 and CP89-2143.
Red imported fire ants, predatory earwigs and many species of ladybird beetles exert some control over these aphids. Heavy rains are also important in dislodging and washing aphids from the plants.
Furadan 4F applied at 1.5 pt/acre provides very effective control of the yellow sugarcane aphid.
Lesser Cornstalk Borer
The larva of the lesser cornstalk borer, Elasmopalpus lignosellus, is a slender brown worm with creamy white to bluish-green bands 3/4 to 1" long when full grown ( Figure 3 ).
The larvae bore into young plants at or below the soil surface and usually cause a "dead-heart" similar to the sugarcane borer or wireworms. When they feed at or below the growing point, damage above the growing point appears as rows of holes in emerging leaves. The larvae construct a tubular burrow in the soil extending outward from the cane plant. The burrow consists of soil particles which the borer webs together with silk. The larva pupates in this burrow and transforms into a small moth. The presence of these silk tubes and/or a small circular entrance hole distinguishes deadhearts caused by lesser cornstalk borers from those caused by wireworms.
Figure 3. Lesser cornstalk borer. The life cycle of the lesser cornstalk borer ranges from 38 to 65 days. There is considerable overlapping of generations with no sharp seasonal breaks in populations, although infestations during late summer may be uncommon.
Most damage from this pest occurs to young plants during warm, dry periods. Ratoon cane usually recovers better from lesser cornstalk borer attack than young plant cane.
Although there are parasites of the lesser cornstalk borer, the protection given by the silk tube may make these inefficient as biological control agents.
Carbofuran (Furadan 4F) has recently become available for use on lesser cornstalk borer in sugarcane. A commercial pheromone is available which can be used in traps to identify when and where populations of the lesser cornstalk borer are building up.
Sugarcane Delphacid
The sugarcane delphacid, Perkinsiella saccharicida, is a sugarcane pest of Australian origin ( Figure 4 ). It was first discovered in Florida during 1982. Surveys quickly revealed that the delphacid ranged throughout the Florida sugarcane production area. To date, little economic damage has been reported by the pest. However, if a rapid population expansion were to occur, there could be serious economic damage due to its feeding and reproductive activities.
Females deposit eggs into leaf tissue. Two to twelve eggs are laid in a cluster on either side of the leaf, mainly along the midrib, leaf sheaths, and stalk internodes. The egg is 1.0 mm by 0.35 mm, elongate-cylindrical and slightly curved. The narrow end of the egg protrudes just above the surface of the leaf and is covered with a white waxy material secreted by the female.
Figure 4. Sugarcane delphacid. A female can lay up to 300 eggs during her normal 30 day life span. The incubation period varies from 2-3 weeks. The newly hatched nymph is pale, wingless, and starts feeding shortly after hatching. The nymphal period has 5 instars and lasts approximately 32 days.
Damage is caused primarily by actions of the adults and nymphs feeding on the sap of the sugarcane plant. The feeding causes yellowing and/or reddening and desiccation of the leaves. Additional damage results from impaired photosynthesis caused by growth of a sooty mold on honeydew excreted by the insects. Finally, laceration of leaf tissue by the insect's saber-like ovipositor can cause reddening and desiccation of the leaves.
There are several natural enemies of sugarcane delphacids, including predators, parasitoids and pathogens.
Historically, the sugarcane delphacid has been more important as a vector of Fiji disease than as a problem by itself. Fortunately, Fiji disease has never been found in the mainland U.S.
Sugarcane Spider Mites
Spider mites, primarily Oligonychus stickneyi, have been occasional pests of importance in Florida sugarcane since the 1970's ( Figure 5 ). These mites live and feed on the undersides of leaves. They form fine webs in which eggs are laid and young nymphs develop. Leaves infested by mites often develop a red-russetting similar to that associated with lacebugs. Severe damage by spider mites can result in leaf death.
Spider mite infestations generally occur during March - June. The lower leaves of sugarcane are usually colonized first. Damage by spider mites may often be of little consequence. However, prolonged heavy infestations accompanied by extensive damage to the middle and upper leaves of young plants may reduce growth. Predaceous mites, a predaceous thrips, and rainfall help control spider mites.
Figure 5. Spider mites. Although no miticides are currently labeled for use in sugarcane, azinphos-methyl applied for the control of other cane pests may also suppress spider mites. Growers should look carefully for mites if they suspect an infestation - just because a substantial amount of mite damage is present does not mean mites are still present.
West Indian Cane Weevil
The West Indian cane weevil, Metamasius hemipterous, was first found infesting cane in Florida during 1994. Sometimes referred to as the "rotten cane stalk weevil," adult weevils ( Figure 6 ) are usually attracted to sugarcane stalks that already have some sort of injury (e.g., damage by other insects or rats). However, the weevil may be attracted to some varieties such as CP85-1382 that have growth cracks but no other obvious abnormalities.
Eggs of the West Indian cane weevil are laid into sugarcane stalks through cracks or into tissue damaged by rats, insects, wind or mechanical implements. The white, legless larvae from these eggs feed in the stalk and grow to more than an inch in length. A fibrous pupal case is usually constructed within the infested plant, although pupal cases may sometimes be found on the ground around infested stalks. The entire life cycle from egg to adult may be completed in around 8 to 10 weeks, depending on temperature. The tunnels and damage by the weevil can be so extensive that stalks may break. General observations indicate the weevil can cause large yield reductions in varieties as susceptible as CP85-1382. Damaged stalks may be unfit for use as seed.
Figure 6. West Indian cane weevil. A pheromone trapping method is available for the adult weevils that may be useful for identifying when infestations of the pest begin to develop and, consequently, when emergency control measures might be imposed to limit infestations and damage. With respect to biological control, no parasites, predators or pathogens of the rotten cane weevil have yet been observed in Florida. Growing sugarcane varieties resistant to the weevil and limiting rat and insect damage are the key management tactics. No chemical control tactics are currently available. Population levels of adult weevils in an area may be reduced using pheromone traps during the summer and fall, which might help limit infestations in sugarcane.
Footnotes
1. This document is ENY-667, one of a series of the Entomology and Nematology Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Printed October 1991. Revised May 2002. This publication is also a part of the Florida Sugarcane Handbook, an electronic publication of the Agronomy Department. For more information you may contact the editor of the Sugarcane Handbook, R. A. Gilbert (ragilbert@gnv.ifas.ufl.edu). Please visit the EDIS Web site at http://edis.ifas.ufl.edu.2. D. G. Hall, U. S. Sugar Corp., Clewiston, Florida, R. H. Cherry, professor, Entomology and Nematology, R. S. Lentini, former coordinator of computer applications, G. S. Nuessly, associate professor, Entomology and Nematology, and R. A. Gilbert, assistant professor, Agronomy, Everglades Research and Education Center, Belle Glade, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, 32611.
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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.
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