Implications of using two natural enemies of Tuta absoluta (Lepidoptera: Gelechiidae) toward tomato yield enhancement.

Tomato leaf miner (TLM), Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is one of the most destructive tomato pests worldwide. We tested quantity and quality of tomato fruits after simultaneous use of two biological control agents, the predatory mirid bug Nesidiocoris tenuis (Reuter) and the egg parasitoid Trichogramma brassicae Bezdenko against TLM. We varied the timing of predator releases (before or after pest establishment) and the number of parasitoids released (ten or 30 females per week per m2). The highest number of fruits per cage, percentage of undamaged fruits, total yield weight, and undamaged yield weight were all obtained with predator-in-first treatments, with or without parasitoid releases. Furthermore, measures of fruit quality were also highest in predator-in-first treatments, including, highest percentage of water, greatest proportional fresh weight of carbohydrates, most lycopene, most ß-carotene, most flavonoids, and highest total chlorophyll. Thus, our findings support a predator-in-first augmentation approach for management of TLM.

Efficient sex pheromone trapping: catching the sweetpotato weevil, Cylas formicarius.

The sweetpotato weevil, Cylas formicarius (Fabricius) (Coleoptera: Brentidae), is the most serious pest of sweetpotato around the world, damaging sweetpotatoes in the field and in storage, as well as being a quarantine pest. Because the larval period is spent within vines or tubers, and the adults are nocturnal, chemical control frequently is not effective. In addition, there are few natural enemies, and pheromone-based trapping does not appear to reduce the damage level. In the present study, we evaluated a number of parameters that affect pheromone-based trap catch, including trap design, trap size, trap color, and height at which the traps are placed. Pherocon unitraps caught higher numbers than ground, funnel water, or delta traps. Medium-sized traps (13 × 17.5 cm) were more effective than larger or smaller traps. In a color-choice test, C. formicarius preferred red over gray, brown, blue, white, yellow, black, or red traps; light red was more attractive than other shades of red. Maximum catches were obtained when the traps were set 50 cm above the crop canopy. Light-red unitraps with pheromone lures caught more adults than identical traps without lures, suggesting that C. formicarius is influenced by both visual and olfactory cues. Pheromone-baited light-red unitraps, 13 × 17.5 cm, installed 50 cm above the crop canopy, were the most effective at catching C. formicarius adults, and they appear to have the greatest potential for use in trap-and-kill strategies and eradication programs.

Development of an efficient pheromone-based trapping method for the banana root borer Cosmopolites sordidus.

The banana root borer Cosmopolites sordidus (Germar) (Coleoptera: Curculionidae) is a major pest of bananas throughout the world. Chemical control is both undesirable and expensive, where biological control alternatives are limited, and pheromone-based trapping results in low captures. In this study, several important factors that affect pheromone-based catches, such as trap type, trap dimensions, and color and position of the traps, were optimized. Ground traps were found to be superior to ramp and pitfall traps, and larger traps (40 x 25 cm and above) were more efficient than smaller ones (30 x 15 cm). In a color-choice test, the banana weevil clearly preferred brown traps over yellow, red, gray, blue, black, white, and green, with mahogany being more attractive than other shades of brown. In addition, pheromone baited ground traps positioned in the shade of the canopy caught significantly more adults than those placed in sunlight. Therefore, mahogany-brown ground traps 40 x 25 cm appear to be the most efficient at catching C. sordidus adults and have the greatest potential for use in mass trapping and programs for eradication of this pest.

Response of Melittia oedipus (Lepidoptera: Sesiidae) to visual cues is increased by the presence of food source.

Visual and olfactory cues were shown to mediate short-distance orientation to different colors in the presence and in the absence of food in Melittia oedipus Oberthür (Lepidoptera: Sesiidae), a biological control agent of Coccinia grandis (L.) Voigt (Violales: Cucurbitaceae). Yellow was the color most preferred by M. oedipus, and adults landed significantly more on yellow paper moistened with honey-water. The next preferred colors were gray and white with the identical food source. Colors such as red, blue, green, brown, and black were least preferred by M. oedipus and attracted the adults on par with each other. The M. oedipus landings on petri dishes which held yellow-, gray-, and white-colored papers were significantly higher than the colorless petri dishes with olfactory stimuli only. There was no significant difference in landings on different-colored papers moistened with honey-water or with water alone in the morning compared with those in the evening. The cumulative response of M. oedipus to different-colored papers moistened with honey-water was significantly higher than the colored papers moistened with water only. Correspondingly, the response of M. oedipus to yellow-colored paper moistened with honey-water was significantly higher than the yellow-colored paper moistened with water only. Therefore, yellow paper moistened with honey-water can increase the feeding rate of M. oedipus and can be a potential technique in developing mass cultures for field release to control the invasive weed.

Present status of Maconellicoccus hirsutus (Hemiptera: Pseudococcidae) in the Mariana Islands and its control by two fortuitously introduced natural enemies.

The mealybug Maconellicoccus hirsutus (Green) (Hemiptera: Pseudococcidae), attacks ornamental and fruit crops in the Mariana Islands. Insecticides cannot penetrate the heavy layers of wax that protect the insect's body. We surveyed the mealybug's locally recruited natural enemies and their effects on its population on Guam, Rota, Saipan, and Tinian to assess the need for introduction of exotic natural enemies. We monitored population densities of M. hirsutus, those of its natural enemies, and parasitism rates for 3 yr, 2005-2007. Our surveys revealed the presence of two parasitoids, Anagyrus kamali Moursi (Hymenoptera: Encyrtidae) and Allotropa sp. near mecrida (Walker) (Hymenoptera: Platygastridae), fortuitously introduced to the Mariana Islands with M. hirsutus. The predator Cryptolaemus montrouzieri Mulsant (Coleoptera: Coccinellidae) also was often found feeding on M. hirsutus. Population density of M. hirsutus was below the economic threshold at all locations. Rainfall seemed to affect mean numbers of M. hirsutus and mean numbers of eggs at some locations. On all four islands, the two parasitoids, complemented by the predator, were effectively controlling the M. hirsutus population. No evidence of hyperparasitism was recorded. Currently, economic damage by M. hirsutus is not a concern in the Mariana Islands, and additional parasitoids need not be introduced to control M. hirsutus.

Improved semiochemical-based trapping method for old-house borer, Hylotrupes bajulus (Coleoptera: Cerambycidae).

The old-house borer, Hylotrupes bajulus (Linnaeus) (Coleoptera: Cerambycidae), has been a very serious pest of structural timber in many parts of the world. The available semiochemical-based trapping method typically results in low capture rates. In this study, efforts were made to improve the semiochemical-based trapping method using screen cage assays conducted in the greenhouse. Ground traps baited with two vials of (3R)-ketol + 1-butanol (pheromone baited) caught >21.0% adults than the alternative trap and were seen to be superior to ramp traps baited with identical compounds. Based on adult catches with pheromone-baited traps with different colors, attraction of H. bajulus adults to black was significantly greater than other colors, followed by brown, gray and yellow, red, white, green, and blue. No differences were found in adult catches to pheromone-baited traps with respect to different trap sizes. There were no statistical differences between the different semiochemicals tested. Therefore, black ground traps baited with two vials of (3R)-ketol + 1-butanol plus two vials of ethyl acetate can be effective in the monitoring and potential control of H. bajulus.

Varietal Preferences and Within-Orchard and Tree Distribution of Newly Recorded Gall Midges, Dasineura amaramanjarae and Procontarinia mangiferae (Diptera: Cecidomyiidae), From Commercial Mango Cultivars in Pakistan.

Gall midges (Diptera: Cecidomyiidae) damage mango by feeding on flowers and fruit tissues, inducing galls on leaves, and providing inoculums of anthracnose. Dasineura amaramanjarae Grover and Procontarinia mangiferae (Felt), two gall midges that damage flowers in all mango-growing areas of the world, have recently been recorded in Pakistan, and studies were conducted in 2011 and 2012 on the within-tree and orchard distribution patterns and cultivar preference of both species in Pakistan at one location (Rahim Yar Khan). Both gall midge species were found on all mango cultivars examined (Chaunsa, Fajri, Dusehri, Surkha, Sindhri, and Anwar Ratul), with the most damage occurring to Surkha and Dusehri. Research on midge distribution patterns in different parts of mango orchards (central, southern, northern, eastern, and western sides) showed these species to be found in all areas, with the greatest numbers in the central and southern regions. In addition, both species were most abundant on the lower parts of the mango tree canopy.

Capture of female Hylotrupes bajulus as influenced by trap type and pheromone blend.

Three different types of traps were evaluated for a semiochemical-based trapping method for Hylotrupes bajulus (L.) (Cerambycidae). One, designated the ground trap, was the most efficient under both laboratory and natural conditions and had an active space of about 3.5 m. Significantly more beetles were captured in traps baited with a mixture of synthetic pheromones, (3R)-3-hydroxy-2-hexanone [(3R)-ketol] + 1-butanol, than in those with either single compound or with racemic mixtures. Furthermore, the synthetic lure captured more females than two virgin males in a laboratory bioassay. In addition, doubling the concentration of the synthetic pheromone significantly increased trap catches. The present findings have potential value of the management of this pest.

Olfactory responses of Plutella xylostella natural enemies to host pheromone, larval frass, and green leaf cabbage volatiles.

The parasitoids Trichogramma chilonis (Hymenoptera: Trichogrammatidae) and Cotesia plutellae (Hymenoptera: Braconidae), and the predator Chrysoperla carnea (Neuroptera: Chrysopidae), are potential biological control agents for the diamondback moth, Plutella xylostella (Lepidoptera: Yponomeutidae). We present studies on the interactions between these bioagents and various host-associated volatiles using a Y olfactometer. T chilonis was attracted to a synthetic pheromone blend (Z11-16:Ald, Z11-16:Ac, and Z11-16:OH in a 1:1:0.01 ratio), to Z11-16:Ac alone, and to a 1:1 blend of Z11-16:Ac and Z11-16:Ald. C. plutellae responded to the blend and to Z11-16:Ac and Z11-16:Ald. Male and female C. carnea responded to the blend and to a 1:1 blend of the major components of the pheromone, although no response was elicited by single compounds. Among the four host larval frass volatiles tested (dipropyl disulfide, dimethyl disulfide, allyl isothiocyanate, and dimethyl trisulfide), only allyl isothiocyanate elicited significant responses in the parasitoids and predator, but C. plutellae and both sexes of C. carnea did respond to all four volatiles. Among the green leaf volatiles of cabbage (Brassica oleracea subsp. capitata), only Z3-6:Ac elicited significant responses from T. chilonis, C. plutellae, and C. carnea, but C. plutellae also responded to E2-6:Ald and Z3-6:OH. When these volatiles were blended with the pheromone, the responses were similar to those elicited by the pheromone alone, except for C. carnea males, which had an increased response. The effect of temperature on the response of the biological agents to a mixture of the pheromone blend and Z3-6:Ac was also studied. T. chilonis was attracted at temperatures of 25-35 degrees C, while C. plutellae and C. carnea responded optimally at 30-35 degrees C and 20-25 degrees C, respectively. These results indicate that the sex pheromone and larval frass volatiles from the diamondback moth, as well as volatile compounds from cabbage, may be used by these natural enemies to locate their diamondback moth host.

Emission of Plutella xylostella-induced compounds from cabbages grown at elevated CO2 and orientation behavior of the natural enemies.

Several plant species defend themselves indirectly from herbivores by producing herbivore-induced volatile compounds that attract the natural enemies of herbivores. Here we tested the effects of elevated atmospheric CO(2) (720 micromol mol(-1)) concentration on this indirect defense, physiological properties, and constitutive and induced emissions of white cabbage (Brassica oleracea ssp. capitata, cvs Lennox and Rinda). We monitored the orientation behavior of the generalist predator Podisus maculiventris (Heteroptera: Pentatomidae) and the specialist parasitoid Cotesia plutellae (Hymenoptera: Braconidae) to plants damaged by Plutella xylostella (Lepidoptera: Plutellidae) in the Y-tube olfactometer. Elevated CO(2) levels did not affect stomatal densities but reduced specific leaf area and increased leaf thickness in cv Lennox. In addition to enhanced constitutive monoterpene emission, P. xylostella-damaged cabbages emitted homoterpene (E)-4,8-dimethyl-1,3,7-nonatriene, sesquiterpene (E,E)-alpha-farnesene, and (Z)-3-hexenyl acetate. Growth at elevated CO(2) had no significant effect on the emissions expressed per leaf area, while minor reduction in the emission of homoterpene (E)-4,8-dimethyl-1,3,7-nonatriene and (E,E)-alpha-farnesene was observed at elevated CO(2) in one of two experiments. The generalist predator P. maculiventris discriminated only between the odors of intact and P. xylostella-damaged cv Rinda plants grown at ambient CO(2) concentration, preferring the odor of the damaged plants. The specialist parasitoid C. plutellae preferred the odor of damaged plants of both cultivars grown at ambient CO(2) but did not detect damaged cv Lennox plants grown at elevated CO(2). The results suggest that elevated atmospheric CO(2) concentration could weaken the plant response induced by insect herbivore feeding and thereby lead to a disturbance of signaling to the third trophic level.