B. Merle Shepard

Leafminers in vegetables, ornamental plants and weeds in Indonesia: Surveys of host crops, species composition and parasitoids

Extensive surveys of vegetable, ornamental and weedy plant species were conducted in highland and lowland vegetable production areas in Indonesia with the aim of recording leafminer species present and their associated natural enemies. The most common dipterous species reared from samples was the pea leafminer, Liriomyza huidobrensis (Blanchard) (Diptera: Agromyzidae). This introduced pest was particularly serious in highland vegetables in Java, Sumatra and South Sulawesi, causing yield losses as high as 60-70%. Another alien species, the vegetable leafminer, Liriomyza sativae Blanchard, contributed to problems in lowland areas on the north coast of West Java, where cucumbers were heavily damaged. An Asian leafminer species, Chromatomyia horticola Goureau, was more common in snow peas (Pisum sp.). Intensive sampling of leafminer-infested leaves from surveyed host plants yielded 11 species of hymenopteran parasitoids: 10 eulophids (Asecodes sp., Chrysocharis sp., Cirrospilus ambiguus (Hansson and LaSalle), Closterocerus sp., Hemiptarsenus varicornis (Girault), Neochrysocharis formosa (Westwood), Neochrysocharis sp., Pnigalio sp., Quadrastichus sp., Zagrammosoma sp.) and 1 eucoilid (Gronotoma sp.). The most abundant parasitoid species was H. varicornis. Levels of parasitism varied among crops and growing seasons, but were usually low, especially on potato (< 3%). Surveys revealed that most farmers (63%) attempted to control leafminers by applying insecticides twice weekly although these applications were neither effective nor economical according to responses of about 72% of the farmers. An integrated pest management approach is suggested that emphasizes IPM training for vegetable farmers and includes reductionor elimination of broad spectrum chemicals that would adversely affect parasitoids that may already be present as well as those that may be introduced. The initiation of a classical biological control programme is recommended to enhance the limited parasitoid complex present in Indonesia and increase levels of biological control.

Seasonal incidence of Liriomyza huidobrensis (Diptera: Agromyzidae) and its parasitoids on vegetables in Indonesia

Abstract The leafminer Liriomyza huidobrensis (Diptera: Agromyzidae) was first reported in Java, Indonesia in 1994. Since then it has invaded the major vegetable-producing regions of Java and Sumatra. Surveys indicate that this pest attacks over 20 species of vegetable, ornamental and weed hosts. The parasitoid Hemiptarsenus varicornis (Hymenoptera: Eulophidae) was collected from L. huidobrensis -infested plant material in all the sites, and on 19 of the 20 cultivated species surveyed. Potatoes were the most severely attacked crop and nearly 100% yield reduction was observed in some fields. The seasonal activity of the leafminer and its parasitoids was monitored on potato, scallions, and broccoli by collecting weekly leaf samples and holding them in containers in the laboratory until the flies or parasitoids emerged. Leafminer populations were most severe in potato, especially towards the end of the wet season (March 1996). Scallions and broccoli produced higher numbers of H. varicornis than leafminers.

Activity of the Nucleopolyhedrovirus of the Fall Armyworm (Lepidoptera: Noctuidae) on Foliage of Transgenic Sweet Corn Expressing a CryIa(b) Toxin

Abstract The activity of the nucleopolyhedrovirus of the fall armyworm, Spodoptera frugiperda (J. E. Smith) (SfMNPV), on transgenic sweet corn, Zea mays (L.), expressing a CryIA(b) toxin from Bacillus thuringiensis (Berliner), was studied in the laboratory. As the line of Bt corn that we studied has only limited efficacy against the fall armyworm, SfMNPV was evaluated as a supplemental treatment. When fall armyworm larvae reared on transgenic or nontransgenic foliage were fed equal dosages of occlusion bodies (OB), measured either as OB per larva or as OB/mg larval weight, mortality was higher among larvae feeding on transgenic corn. However, when larvae were allowed to feed ad libitum on treated foliage, mortality was higher in larvae on the nontransgenic corn. Rates of food consumption were higher on nontransgenic corn, apparently resulting in ingestion of more OBs and countering increased susceptibility of larvae on transgenic corn.

Plant extracts as ultraviolet radiation protectants for the beet armyworm (Lepidoptera: Noctuidae) Nucleopolyhedrovirus: screening of extracts.

Abstract Sixty-seven plant-derived extracts were tested as ultraviolet (UV) protectants for the nucleopolyhedrovirus (SeMNPV) of the beet armyworm, Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae). In the initial laboratory screening experiment, 25 of the 67 extracts provided protection following UVA/UVB irradiation for 30 min. Fifteen of these 25 extracts provided good UV protection when they were subjected to a more severe UV treatment of UVB/UVB irradiation for 30 min. Four of these 15 extracts (kudzu, peppermint, skullcap, and thyme) provided excellent UV protection for SeMNPVwhen they were irradiated with an even more stringent UV regime of UVB/UVB for 300 min. These findings indicate that these plant extracts may be useful UV protectants for the SeNPV and they should be investigated further to obtain more efficacious formulations for the control of agriculturally important insect pests.

Supplemental Control of Lepidopterous Pests on Bt Transgenic Sweet Corn with Biologically-Based Spray Treatments

Abstract Biologically-based spray treatments, including nucleopolyhedroviruses, neem, and spinosad, were evaluated as supplemental controls for the fall armyworm, Spodoptera frugiperda (J. E. Smith), and corn earworm, Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae), on transgenic sweet corn, Zea mays (L.) (Poales: Poaceae), expressing a Cry1Ab toxin from Bacillus thuringiensis Berliner (Bacillales: Bacillaceae) (Bt). Overall, transgenic corn supported lower densities of both pests than did nontransgenic corn. Control of the fall armyworm was improved in both whorl-stage and tassel-stage corn by the use of either a nucleopolyhedrovirus or neem, but the greatest improvement was seen with spinosad. Only spinosad consistently reduced damage to ears, which was caused by both pest species. In general, efficacy of the spray materials did not differ greatly between transgenic and nontransgenic corn.

Green tea extracts as ultraviolet protectants for the beet armyworm, Spodoptera exigua, nucleopolyhedrovirus

Abstract The addition of a caffeinated green tea, Camellia sinensis L., filtrate (1%) to the nucleopolyhedrovirus (SeMNPV) of the beet armyworm, Spodoptera exigua (Hübner), provided almost complete protection following UVB irradiation (30 min) in laboratory tests. There were few differences in UV protection when extracts were prepared at 27 or at 90°C. Moreover, few differences in UV protection were demonstrated following infusion times of 5, 15, 30, and 60 min at 90°C. At a 1% concentration, decaffeinated and caffeinated green teas were equally effective as UV protectants. At lower concentrations (0.1, 0.01, and 0.001%) caffeinated green tea provided greater UV protection (UVB/UVB 30, 60 min). Virus/tea extracts (caffeinated), under field conditions at 1 and 5%, were ineffective as UV screens. At a 10% concentration, some UV protection was provided and UV protection further increased in a concentration-dependent manner.

Effects of Neem (Azadirachta indica A. Juss) on Trissolcus basalis (Wollaston) (Hymenoptera: Scelionidae), a Parasitoid of Nezara viridula (L.) (Hemiptera: Pentatomidae)

The effects of neem (Azadirachtin indica A. Juss) on Trissolcus basalis (Wollaston), an egg parasitoid of Nezara viridula (L.), were assessed in the laboratory and in cowpea (Vigna unguiculata [L.] Walpers). Treatment of N. viridula eggs with 0.5% (225 ppm azadirachtin) aqueous solution of neem had no effect on parasitization by T. basalis, using both choice and no-choice tests. Parasitoid development and emergence from host eggs treated before or after parasitization also were not affected by neem compared with controls. Additionally, neem did not affect longevity of adult parasitoids from treated eggs or the reproductive activity of females compared with controls. In a field choice test using treated and control eggs, parasitism levels were similar. Also, parasitism of eggs was similar in treated and control cowpea plots. These results suggest that neem may be safe to parasitoids of N. viridula and could be an important component of an integrated pest management program in cowpea.

Insect Populations on Bacillus thuringiensis Transgenic Sweet Corn

Insect populations and damage in three plantings (early, mid-, and late-season) of Bacillus thuringiensis (Bt) transgenic sweet corn were compared to a non-transgenic isoline at Charleston, SC, dur...

Effect of Spices upon the Activity of the Gypsy Moth (Lepidoptera: Lymantriidae) Nucleopolyhedrovirus

The ability of host plants to influence the incidence and severity of diseases in insects has been known for more than 20 yrs and may play a critical role in the efficacy of insect pathogens, inclu...

Enhanced activity of the nucleopolyhedrovirus of the fall armyworm (Lepidoptera: Noctuidae) on Bt-transgenic and nontransgenic sweet corn with a fluorescent brightener and a feeding stimulant

Abstract The effects of a nutrient-based feeding stimulant, Coax, and a stilbene-based optical brightener, Blankophor P167, on the activity of the nucleopolyhedrovirus of the fall armyworm, Spodoptera frugiperda (J. E. Smith) (SfMNPV) on transgenic sweet corn, Zea mays L., expressing a CryIA(b) toxin from Bacillus thuringiensis (Berliner), were studied in the laboratory. Both Coax and Blankophor P167 increased virus-induced mortality. The effects of both materials did not differ between transgenic and nontransgenic corn. The greatest increase in virus-induced mortality occurred when Coax and Blankophor P167 were combined. Neither material affected the percentage of larvae killed by the CryIA(b) toxin.