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Robert L. Meagher |
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Introduction
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Area harvested (acres) |
Number of mills |
Tons cane/acre |
Tons sugar/acre |
Sugar recovery rate (%) |
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Florida |
433,000 |
7 |
34.5 |
4.16 |
12.05 |
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Hawaii |
43,000 |
6 |
86.7 |
10.65 |
12.28 |
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Louisiana |
358,000 |
19 |
22.7 |
2.52 |
11.09 |
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Texas |
41,000 |
1 |
31.8 |
3.18 |
9.99 |
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Puerto Rico |
26,000 |
6 |
19.2 |
1.54 |
8.00 |
_____________________________________________________________________
Adapted from USDA/ERS publication #SSSV20N2, June 1995; estimated
production, 1995-1996.
Worldwide, sugarcane as an agroecosystem contains many insect
species, both in aerial (above ground) and subterranean (below
ground) habitats. Important pest species that inhabit the above
ground part of sugarcane are in the following orders and families:
Lepidoptera (Pyralidae, Noctuidae, and Castniidae), Homoptera
(Aphididae, Cercopidae, Coccidae, Delphacidae, Diaspididae, and
Pseudococcidae), and Orthoptera (Acridoidea). Soil sugarcane insect
pests are represented by Coleoptera (Curculionidae, Elateridae, and
Scarabaeidae), Isoptera (Mastotermitidae, Rhinotermitidae, and
Termitidae), Hymenoptera (Formicidae), Diptera (Stratiomyidae),
Heteroptera (Cicadidae, Cydnidae, Margarodidae, and Pseudococcidae),
and Orthoptera (Gryllidae and Gryllotalpidae). Readers are encouraged
to refer to Williams et al. (1969) and Meagher et al. (1993) for a
more thorough discussion of sugarcane pests.
Fig. 3. Stem borers, Diatraea
saccharalis (larger moths) and Eoreuma loftini.
The remainder of my discussion will be focused on the life history and pest management of stemborers in sugarcane. Stemborers (Pyralidae and Noctuidae) are pests in all sugarcane growing regions of the world. Management of these pests involves many different strategies, and interested readers should further investigate research not described in this lecture. Most of my discussion will be based on two pyralids found in the US [Fig. 3, adult Diatraea saccharalis (larger moths) and Eoreuma loftini].
Fig. 4. Mature larva of the Mexican rice borer.
The life history of sugarcane stemborers can be generalized as
follows (Smith et al. 1993). Adult moths oviposit on plant leaves,
stems, or cryptically in dried leaves. Eggs may be laid singly or in
masses, and early instar larvae feed cryptically on leaves, whorls,
or other succulent plant tissue. Older larvae (generally third instar
and older) feed almost exclusively within tunnels in stems, making
management by contact insecticides difficult. Tunnels within stems
may be aligned vertically or horizontally, and may extend across more
than one internode (Fig. 4, mature E. loftini). Some
stemborers maintain clean tunnels, removing frass and debris, while
others keep their tunnels filled with frass. The physical condition
of stemborer tunnels has implications for natural enemy selection in
biological control programs, as some parasitoids enter the tunnels to
attack larvae. Pupation occurs within chambers constructed by mature
larvae, often leaving an "emergence window". This structure is a thin
layer of plant tissue that can be pushed open to allow the adult moth
to emerge from the stem.
Historical perspective. Few studies have undertaken
the task of sampling for stemborer eggs and larvae. Studies conducted
in the Caribbean and in Florida have shown that stemboring pyralid
larvae have random or aggregated spatial patterns, depending on
sample size used and field size.. Most sampling for stemborers in
sugarcane involves looking for injury such as leaf feeding and
tunneling within the stem.
Recent research. Sampling studies for Mexican rice
borer larvae and pupae were conducted in Texas sugarcane (Meagher et
al. 1996a). Population density never exceeded 1.0 larvae per stem.
Ratoon fields averaged more larvae per stem than plant cane fields.
There was more stem-to-stem and field-to-field variation in larval
dispersion than among subdivisions within fields.
Most sampling of Mexican rice borer larvae for management
decisions has documented percentage bored internodes (ratio of number
of internodes with tunnels to total internodes present) as an
indirect measure of larval density. However, currently there is no
known relationship between larvae per stem and percentage bored
internodes. This is important since the currently used action
threshold for a chemical control program is 10% leaf sheath
infestation by young larvae and is not correlated with an actual
insect density.
Historical perspective. The history of chemical use
in US sugarcane production goes back to the early 1920's, when sodium
fluosilicate, cryolite, and ryania were used against sugarcane borer
in Louisiana. Control was usually achieved with weekly applications
of these materials. Chlorinated hydrocarbons were first recommended
for use in the late 1950's with the introduction of endrin. However,
endrin only lasted a few years because of resistance development. The
organophosphates and carbamates entered the market in the early
1960's when azinphosmethyl replaced endrin. Other organophosphate and
carbamate insecticides such as monocrotophos and carbofuran were
recommended through the 1960's and 1970's. Reduction in borer
populations due to insecticide applications not always translated to
an increase in sugar yield or quality, prompting a call for a better
understanding of the relationship between sugarcane borer biology and
the use of insecticides.
In Texas, modern sugarcane production began in 1972 and
organophosphate insecticides, usually aerially applied, were used
against sugarcane borer. These insecticides were moderately
successful, producing a 60-80% reduction in bored internodes.
Insecticidal suppression was the first tactic used against the
Mexican rice borer, an immigrant to the lower Rio Grande Valley of
Texas that was documented in 1980.
Recent research. Sugarcane plots that had weekly
monocrotophos applications during different seasonal timings yielded
increased sugarcane yield and quality and had reduced bored internode
injury compared to untreated plots (Meagher et al. 1994). However,
weekly applications exceed residue limitations and are illegal.
Studies with several insecticides, including monocrotophos and
azinphosmethyl and the synthetic pyrethroid cyfluthrin, showed
statistically significant reductions in percent bored internodes but
rarely an increase in sugarcane yield or commercially recoverable
sugar (Meagher et al. 1994). Currently, a low percentage of sugarcane
acres in south Texas are sprayed with insecticides for stemborer
control.
Figs. 5 & 6. Parasitoids associated with sugarcane stemborer pests.
Historical perspective. Parasitoids. Workers have
used parasitoids, predators, and nematodes as natural enemies against
sugarcane pests for many years. The first parasitoid introduction in
the US was the Cuban fly, Lixophaga diatraeae (Townsend) into
Louisiana. This tachinid fly introduced from Cuba was released
against sugarcane borer from during different intervals from1915 to
the early 1970's. The Cuban fly was also released in Florida from the
1920's to the 1960's. Other parasitoids released included
Alabagrus stigma (Brulle) [= Agathis stigmatera
(Cresson)], introduced from Peru into Florida in the early 1930's
and into Louisiana in the late 1940's and early 1950's, and had been
known to be parasitizing Diatraea spp. in the Caribbean
islands and South America since the 1920's (known as Microdus
or Bassus stigmaterus. Other parasitoid species released in
Louisiana after the original introductions included tachinids,
braconids, and scelionids. Some of the above species have become
established in Louisiana and Florida, but none have provided
consistent stemborer population suppression.
The first non-neotropical parasitoid released in the continental
US was Cotesia (= Apanteles) flavipes (Cameron). This
gregarious, larval endoparasitoid native to southeast Asia was
released in Florida in 1963. Recoveries were made shortly after
release, but C. flavipes was not recovered the following year.
C. flavipes was released and established in Texas against
sugarcane borer in 1977 (Fuchs et al. 1979) and has been successful
at reducing sugarcane borer populations ever since (Meagher et al.,
unpublished data).
The biological control program in Texas for Mexican rice borer has
been extensive and has relied heavily on collection, rearing, and
release of exotic natural enemies. From the period 1981-1988, 50
parasitoid species representing 12 families were imported into the
quarantine facility at Texas A&M University. Over 4.6 million
individuals in 15 species were released in the lower Rio Grande
Valley. Eight species were recovered in at least one year, and two
species were recovered in four or more years.
Recent research. Laboratory studies have
investigated several features of the sugarcane borer -- C.
flavipes relationship (Wiedenmann et al. 1992). Parasitoids had
low attack rates, and a percentage of hosts attacked either
encapsulated parasitoids or died without parasitoid progeny being
produced. These results are most likely due to the new association
between Old World parasitoid and New World host. Cotesia
chilonis (Matsumura), a congeneric species from Japan, was
compared in laboratory studies with three C. flavipes cultures
to determine rates of parasitization and host encapsulation
(Wiedenmann & Smith 1995). C. chilonis parasitized more
hosts and was encapsulated in fewer instances that C.
flavipes.
Because of a severe freeze in 1989 (a low of 15F in December), a
rearing and release program for C. flavipes was initiated in
1990 that continued through 1995. C. flavipes continues to be
collected from sugarcane borer larvae (Meagher et al. unpublished
data).
Previous to the severe 1989 freeze, five exotic species were
released against Mexican rice borer. Three species, Allorhogas
pyralophagus Marsh, Macrocentrus prolificus Wharton, and
Lydella jalisco Woodley, were recovered. The Jalisco fly
(L. jalisco ) (Fig. 5), was collected in Ameca, Jalisco,
Mexico, and rearing procedures were developed at Texas A&M
(Rodriguez-del-Bosque & Smith 1996). Although initially recovered
in 1989, it hasn't been recovered in recent collections (Meagher et
al., unpublished data).
Since the freeze, four species are being recovered from Mexican
rice borer larvae: the native species Chelonus sonorensis
Cameron and Digonogastra solitaria Wharton & Quicke (Fig.
6), and the exotic species A. stigma and A.
pyralophagus (Meagher et al., unpublished data). A. stigma
was collected from Diatraea spp. and imported from Bolivia;
A. pyralophagus was collected from E. loftini in
western Mexico. Results of recent surveys have suggested that
parasitism from these four species has increased (from a low of 5.6%
in 1992 to over 15% in 1994), and collection of A. stigma has
also increased (now over 10% of parasites collected) (Meagher et al.,
unpublished data).
Predators. Comparatively fewer studies have been
completed determining the importance of predators in suppressing
stemborer populations. In Louisiana, research results in the 1960's
documented the interaction between soil insecticides, predator
abundance, and sugarcane borer damage. Predator groups found to be
feeding on different life stages included Formicidae, Carabidae,
Forficulidae, Elateridae, Chrysopidae, and Araneae. Ecological
research in the early 1980's focused on the influence of weedy
habitats and foraging activity of red imported fire ant,
Solenopsis invicta Buren. More extensive research documented
the actual reduction in bored internodes that can be contributed by
predators. In a multi-tactic management experiment where insecticidal
control, varietal resistance, and predation were compared, predation
due to S. invicta was shown to contribute 15.7% towards control
(Bessin et al. 1990). Overwintering populations of sugarcane borer
were also shown to be negatively affected by predators.
Historical perspective. Plant resistance has been an
important management strategy in most sugarcane-growing regions
around the world against stemboring pyralids (Mathes &
Charpentier 1969). In Louisiana, plant resistance has been a
component of the sugarcane IPM program against sugarcane borer for
many years and has been a successful management strategy when used
alone or in combination with other strategies (Bessin et al.
1990).
In Texas, the relative susceptibility of sugarcane progenitors and
clones to stem injury by Mexican rice borer has been measured in
field studies under natural infestation conditions. Results suggested
large variability in bored internodes among progenitors such as
Miscanthus floridulus (Labill) Warb., Erianthus
bengalense (Retz.) Bharadw., E. trinii (Hack.),
Saccharum spontaneum L., and S. officinarum L.
Screening of commercial (cultivars) and noncommercial sugarcane
clones showed variability in E. loftini injury (Pfannenstiel &
Meagher 1991). Field evaluation of sugarcane germplasm for internodes
bored by E. loftini has continued since 1989 (R.L.M.
unpublished data).
Many researchers have tried to determine the factors and
mechanisms of sugarcane resistance. Ovipositional resistance has been
deemed not to be responsible for lower stemborer populations in
sugarcane, but recently characters such as leaf pubescence was shown
to confer resistance against sugarcane borer.
Larval resistance can be separated into "leaf" and "stem"
components. Neonate and young larvae must be able to become
established within the leaves, midribs, and leaf sheaths and obtain
sufficient nutrients before entering stems. The lack of foliar
establishment and mortality of neonate larvae has been described as a
major factor of resistance, with leaf sheath appression, the ability
of a plant to self-trash (shed lower leaves and leaf sheaths), and
leaf midrib hardness documented as specific resistant characters.
However, larval foliar establishment among cultivars as a resistance
factor becomes important only if these differences persist until
stems are invaded; if over longer periods of development, the final
level of infestation is independent of initial numbers, then
differences among cultivars in establishment are not important.
Stem resistance of sugarcane involves the ability of larvae to
enter and become established, tunnel within the stem, and gain enough
nutrition to complete development and emerge as a mature, fecund,
adult. Several factors have been implicated in stem resistance,
although strong correlations between a factor and resistance haven't
been documented. Individual characters mentioned in conferring
resistance include rind hardness, stem diameter, and physical
attributes of the interior part of the stem.
Tolerance has been suggested as a resistance mechanism in the
sugarcane - sugarcane borer crop system, a conclusion based on
genotypes possessing high levels of injury such as bored internodes,
but low levels of damage such as dead tops, adventitious shoots,
secondary tillering, and cane weight loss (White 1993). Overall,
breeding of sugarcane for resistance to stemborers is difficult
because of hereditary characteristics of the plant and limited
knowledge of specific resistant characters.
Recent research. Studies with Mexican rice borer confirm that several mechanisms of stemborer resistance, including antibiosis and nonpreference, are present across sugarcane genotypes (Meagher et al. 1996b). Larval antibiosis results of diet incorporation bioassays suggest the presence of antinutritional components or allelochemicals in some genotypes. Larvae and pupae that developed on the commercial cultivar 'NCo310' were heavier and took fewer days to develop than larvae placed on other cultivars.
Differences in adult oviposition among genotypes in laboratory,
greenhouse, and field studies were slight: therefore ovipositional
prefernce is probably not important in confering resistance with this
pest.
Laboratory experiments indicated that differences in larval
establishment could be an important resistance character. Mexican
rice borer larvae showed preferences for establishment in certain
genotypes, and it appears larval preference may be locationally
directed among different leaf sheaths within a stem (Meagher et al.
1996b).
Sugarcane stemborers appear to more severely damage stressed
plants than unstressed plants. Whether this relationship is due to
higher larval densities on stressed plants or the degradation of
natural plant tolerance, is not known. Agronomic practices such as
good plant growth management through appropriate fertilization and
irrigation schedules are an obvious advantage towards improved
stemborer management.
Another cultural control technique that has sparked interest is
the use of pheromones for mating disruption. In Texas, the pheromone
for Mexican rice borer was identified and studies were initially
conducted to use it as a monitoring tool. Continued research has made
available the potential use of pheromone in reducing borer
populations by mating disruption (Shaver & Brown 1993). This
technique is designed to permeate the area with pheromone so that
males are unable to locate and mate with females. Mating disruption
has had some success in the cotton and tree fruit agroecosystems.
Bessin, R. T., E. B. Moser & T. E. Reagan. 1990. Integration of control tactics for management of the sugarcane borer (Lepidoptera: Pyralidae) in Louisiana sugarcane. J. Econ. Entomol. 83: 1563-1569.
Fuchs, T. W., F. R. Huffman & J. W. Smith, Jr. 1979. Introduction and establishment of Apanteles flavipes (Hym.: Braconidae) on Diatraea saccharalis (Lep.: Pyralidae) in Texas. Entomophaga 24: 109-114.
Mathes, R. & L. J. Charpentier. 1969. Varietal resistance in sugar cane to stalk moth borers, pp. 175-188. In J. R. Williams, J. R. Metcalfe, R. W. Mungomery & R. Mathes [eds.], Pests of Sugar Cane. Elsevier, New York.
Meagher, R. L., Jr., J. W. Smith, Jr. & K.J.R. Johnson. 1994. Insecticidal management of Eoreuma loftini (Lepidoptera: Pyralidae) on Texas sugarcane: a critical review. J. Econ. Entomol. 87: 1332-1344.
Meagher, R. L., Jr., L. T. Wilson & R. S. Pfannenstiel. 1996a. Sampling Eoreuma loftini (Lepidoptera: Pyralidae) on Texas sugarcane. Environ. Entomol. 25: (in press).
Meagher, R. L., Jr., J. E. Irvine, R. G. Breene, R. S. Pfannenstiel & M. Gallo-Meagher. 1996b. Resistance mechanisms of sugarcane to Mexican rice borer (Lepidoptera: Pyralidae). J. Econ. Entomol. 89: (in press).
Rodriguez-del-Bosque, L. A. & J. W. Smith, Jr. 1996. Rearing and biology of Lydella jalisco (Diptera: Tachinidae), a parasite of Eoreuma loftini (Lepidoptera: Pyralidae) from Mexico. Ann. Entomol. Soc. Am. 89: 88-95.
Shaver, T. N. & H. E. Brown. 1993. Evaluation of pheromone to disrupt mating of Eoreuma loftini (Lepidoptera: Pyralidae) in sugarcane. J. Econ. Entomol. 86: 377-381.
Smith, J. W., Jr., R. N. Wiedenmann & W. A. Overholt. 1993. Parasites of lepidopteran stemborers of tropical gramineous plants. ICIPE Science, Nairobi, Kenya.
White, W. H. 1993. Cluster analysis for assessing sugarcane borer resistance in sugarcane line trials. Field Crops Res. 33: 159-168.
Wiedenmann, R. N. & J. W. Smith, Jr. 1995. Parasitization of Diatraea saccharalis (Lepidoptera: Pyralidae) by Cotesia chilonis and C. flavipes (Hymenoptera: Braconidae). Environ. Entomol. 24: 950-961.
Wiedenmann, R. N., J. W. Smith, Jr. & P. O. Darnell. 1992. Laboratory rearing and biology of the parasite Cotesia flavipes (Hymenoptera: Braconidae) using Diatraea saccharalis (Lepidoptera: Pyralidae) as a host. Environ. Entomol. 21: 1160-1167.
Williams, J. R., J. R. Metcalfe, R. W. Mungomery & R. Mathes
[eds.]. 1969. Pests of Sugar Cane. Elsevier.
Amsterdam.
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Fig. 1. Sugar cane.
Fig. 2. Sugarcane burned prior to harvest.