Gaurav Goyal

New Report of Chaetopsis massyla (Diptera: Ulidiidae) as a Primary Pest of Corn in Florida

ABSTRACT The picture-winged fly Euxesta stigmatias Loew (Diptera: Ulidiidae) has been a serious pest of sweet corn in Florida since the 1930s and had been considered the only fly infesting Florida corn. In a sweet corn variety trial to evaluate E. stigmatias resistance in 2007, adult Chaetopsis massyla (Walker) (Diptera: Ulidiidae) was reared from the ears. Choice and no-choice trials were conducted in 2007 and 2008 to determine the pest nature of C. massyla on corn. In no choice tests, C. massyla pairs were caged on uninfested corn ears in green house and field trials. In choice tests, field collected corn ears were held for fly emergence. No choice tests showed that C. massyla could infest and complete development in ears that had no previous damage. Chaetopsis massyla emerged from corn ears with and without prior infestation by other insect species in choice tests. Subsequently, C. massyla were reared from corn ears collected from locations throughout the major sweet corn growing region of southern Florida. Therefore, we present what we believe to be the first report of C. massyla as a primary pest of corn ears in Florida and in the United States of America.

Mulch as a Potential Management Strategy for Lesser Cornstalk Borer, Elasmopalpus lignosellus (Insecta: Lepidoptera: Pyralidae), in Bush Bean (Phaseolus vulgaris)

ABSTRACT Lesser cornstalk borer (LCB), Elasmopalpus lignosellus (Zeller), is a serious pest of bean (Phaseolus vulgaris L.) and many other crops. The effect of mulching as a management method for LCB was examined in 2 field experiments conducted in small plots (1 m2) at 2 different locations (experiments A and B) in Alachua Co., FL. Both experiments were conducted in the summer and repeated in the fall, 2007. The treatments were arranged in a randomized complete block design with 5 replications at both locations. In experiment A, treatments were bare ground, plots with mulch, and plots with weeds (original weed cover); while in experiment B, treatments were bare ground and mulched plots. The mulch was obtained from a crop of sunn hemp (Crotalaria juncea L.) planted at another location. Data were collected on bean plant mortality, plant growth parameters (fresh weight, height, and length including roots of surviving plants), and population levels of potential predators. LCB attack was less (P ≤ 0.10) in mulched plots compared with bare ground, considering a number of factors such as location and background of field, season, and amount of precipitation. Greater numbers of surviving plants were found in mulched plots compared with bare ground and weedy plots. In general, fresh weight, height, and total length of bean plants were greater in mulched plots compared with other plots. Treatments did not affect numbers of potential predators of LCB. Evidence suggests that LCB attack is reduced by mulches or weeds around host plants.

Alternative plants for development of picture-wingedfly pests of maize

Eleven species of picture‐winged flies (Diptera: Ulidiidae: Lipsanini) have been reported attacking maize [Zea mays L. (Poaceae)] ears in the Americas. Four of these species are sweet corn pests in America north of Mexico: Chaetopsis massyla (Walker), Euxesta annonae (Fabricius), E. eluta Loew, and E. stigmatias Loew. Adults of these four species appear at the beginning of each season following maize‐free periods, suggesting other plants act as food sources for maintenance and development of these flies. Studies were conducted in Florida, USA, to evaluate the suitability of several crop and non‐crop plants commonly occurring near maize plantings as developmental hosts for these flies. Laboratory trials were conducted using laboratory colonies of C. massyla, E. eluta, and E. stigmatias to determine their developmental rates and pupal survivorship on roots, stems, leaves, or fruits of 14 crop and weed species. All three fly species completed development on all tested crops (Brassica oleracea L., Capsicum chinense Jacquin, Capsicum annum L., Carica papaya L., Persea americana Mill., Raphanus sativus L., Saccharum officinarum L., and Solanum lycopersicum L.) and weed species [Amaranthus spinosus L., Portulaca oleracea L., Sorghum halepense (L.), and Typha spp.], except for Daucus carota L. roots and Solanum tuberosum L. tubers. Findings of the current study suggest that the presence of multiple host crops in areas surrounding maize fields may help explain the occurrence of these maize‐infesting ulidiids immediately after prolonged absences of maize.

Distribution of Picture-Winged Flies (Diptera: Ulidiidae) Infesting Corn in Florida

ABSTRACT The picture-winged fly Euxesta stigmatias Loew (Diptera: Ulidiidae) has been a serious pest of sweet corn (Zea mays L.) in Florida since 1930. Several other species in the family are known to infest corn grown in the Caribbean, Central America, and South America. Surveys were conducted throughout Florida to evaluate species richness and distribution of corn-infesting Ulidiidae. Adults were sampled with sweep nets and reared from fly larvae-infested corn ears collected from representative corn fields in 16 and 27 counties in 2007 and 2008, respectively. Four Ulidiidae species were found in corn fields using both sampling techniques. Euxesta eluta Loew and Chaetopsis massyla (Walker) were found throughout the state on field and sweet corn. Euxesta stigmatias was only found in Martin, Miami-Dade, Okeechobee, Palm Beach, and St. Lucie Counties on field and sweet corn. Euxesta annonae (F.) was found in sweet corn in Miami-Dade, Okeechobee, and Palm Beach Counties, but field corn was not sampled in these counties. Euxesta eluta, E. stigmatias, and C. massyla were collected from corn throughout the corn reproductive stage. Raising adults from fly larvae-infested ears provided the best method for assessing rates of ear infestation and species richness. Sweep netting did not provide reliable information on the presence or species composition of ulidiid species infestation. We report for the first time E. annonae and E. eluta as pests of corn in Florida and the USA.

Examination of the Pest Status of Corn-Infesting Ulidiidae (Diptera)

ABSTRACT Larvae of 11 species of picture-winged flies (Diptera: Ulididae) are known to feed on corn plants (Zea mays L. ) in the western hemisphere. Larvae emerge from eggs deposited in leaf axils and corn silk to feed mostly within ears, but the primary versus secondary nature (i.e., pest status) of their infestation is not known for all of these species. Choice and no-choice tests by using a split-plot design were conducted in greenhouse and field trials to determine the pest status on sweet corn of three of these species found in Florida: Chaetopsis massyla (Walker), Euxesta eluta Loew, and E. stigmatias Loew. The main treatments (uninfested ears and ears experimentally infested with either Spodoptera frugiperda [Lepidoptera: Noctuidae] or E. eluta larvae) were applied at first silk. The subtreatments (C. massyla, E. eluta, or E. stigmatias adults caged on ears) were applied 7 d later and maintained for 10 d. All three fly species were reared from uninfested and experimentally infested ears in both choice and no-choice tests in greenhouse and field trials confirming both primary and secondary modes of ear infestation. More flies of all three species emerged from ears that were preinfested with S. frugiperda compared with uninfested ears suggesting either preference for or greater survival within ears previously infested by S. frugiperda. Fewer E. eluta and E. stigmatias emerged from ears preinfested with E. eluta in no-choice field tests, suggesting that previous infestation by this fly may negatively affect oviposition or that older fly larvae affect survival of neonate larvae. All three species studied here should be considered primary pests that can render unprotected sweet corn ears unmarketable.

Comparative Morphology of the Immature Stages of Three Corn-Infesting Ulidiidae (Diptera)

ABSTRACT Several species of Ulidiidae (Diptera) are primary pests of maize (Zea mays L.). The ability to distinguish their immature stages would be useful for biological studies where their distributions overlap. Morphology of the immature stages was examined for three Ulidiidae that attack maíze in the southeastern United States: Chaetopsis massyla (Walker), Euxesta eluta Loew, and Euxesta stigmatias Loew. Egg, larval, and pupal characters were measured and described with the aid of light and scanning electron microscopy. Because of considerable overlap in character states, only a few traits in each stage could be used to separate these three species. C. massyla eggs had pores restricted to the posterior end, but the pores were evenly distributed in the two Euxesta species. Eggs of the two Euxesta species could not be differentiated. Larval mouth hooks of C. massyla had a distinct tooth on their ventral surface, whereas this tooth was lacking in E. eluta and E. stigmatias. Fewer oral ridges were observed on C. massyla larvae than on E. eluta or E. stigmatias. Posterior spiracular slits were apparent in E. stigmatias versus obscure in E. eluta larvae. The length and spinule arrangements on creeping welts could be used to separate E. eluta and E. stigmatias larvae. Posterior spiracular plates of C. massyla puparia were trapezoidal versus ovoid in the two Euxesta species. Puparium color varied significantly among the three species.

Insect Diapause: A Review

Diapause is defined as a period of suspended development in insects and other invertebrates during unfavorable environmental conditions. Diapause is commonly confused with term “quiescence” as both are dormant development stages. Here this paper aimed to review the research work done on different aspects of diapause. Attempt was made to explain definitions of diapause, incidence, stages and termination of diapause, genetic control, factors affecting diapauses, including temperature, photoperiod, moisture and food, etc..

Developmental Studies of Maize-Infesting Picture-Winged Flies (Diptera: Ulidiidae)

Abstract Eleven species of picture-winged flies (Diptera: Ulidiidae) attack maize (Zea mays L.) in the Americas. Field and laboratory studies were used to determine developmental times on sweet corn ears for the three most common species attacking the crop in the United States, Chaetopsis massyla (Walker), Euxesta eluta Loew, and Euxesta stigmatias Loew. Egg plus larval stage developmental times were evaluated in early Spring and late Fall 2009, and late Spring 2010, by placing newly deposited eggs in protected ears in the field. Newly formed puparia were removed daily from cages and held in the laboratory to determine pupal developmental times. Developmental times were compared with flies reared on artificial diet in the laboratory. Ear- and diet-reared adults were held until their death to determine adult longevity. Developmental times, including for pupae from ear-reared larvae, were significantly affected by species and season. All three species required nearly twice as long to complete development in the late Fall compared to late Spring studies. Flies required 3–13 d longer to complete development on artificial diet than on ears. Euxesta eluta adults lived two to three times longer than the other species, and females of all species lived 10–15% longer than males. Species and seasonal developmental times are discussed in relation to ear developmental times and control strategies. It is estimated that 16–19 generations per year of all three fly species can develop in the field in the sweet corn production area of southern Florida.

Diel Activity of Fauna in Different Habitats Sampled at the Autumnal Equinox

ABSTRACT Experiments were conducted to examine the diurnal responses and abundance of arthropods at the autumn equinox in 2010. Experiments were conducted in 3 different fields, each with a different plant species: sunn hemp (Crotalaria juncea L.), bahiagrass (Paspalum notatum Flugge), and sandbur grass (Cenchrus spp.) using a randomized complete block design. Data were collected on numbers of arthropods caught in pitfall traps and on sticky cards. The long-legged flies (Diptera: Dolichopodidae) and thrips (Thysanoptera) collected were consistently diurnal, while ants (Hymenoptera: Formicidae), springtails (Collembola: Entomobryidae), micro-Diptera and tumbling flower beetles (Coleoptera: Mordellidae) were diurnal in one experiment. Elateridae and Aphididae tended to be nocturnal taxa, but plant height had some effect as well because aphid numbers were significantly higher in tall (182.3 cm) sunn hemp than in short (88.1 cm) sunn hemp at night time only. Cicadellidae were active during both day and night time and showed different levels of activity in pitfall traps and on sticky cards. Pitfall traps were found to be very effective for sampling insect taxa including Formicidae, Elateridae, and Collembola, while micro-Diptera, thrips, aphids, and Mordellidae were commonly caught on sticky cards. Cicadellidae and Dolichopodidae were commonly recovered in pitfall traps and on sticky cards.