Major efforts to control the population of Aedes aegypti mosquitoes involve the use of synthetic insecticides, which can be harmful to the environment. Most plant compounds are eco-friendly and some of them have biocontrol potential, whereas a fraction of these compounds is released into the environment through the leaf-leaching process. We evaluated the effects of secondary compounds from Ateleia glazioviana and Eucalyptus grandis senescent leaf leachates on Ae. aegypti larval mortality, adult emergence time, and wing size using a microcosm approach. The microcosms consisted of 10 larvae kept in water (control) and under four treatments with leachates from a combination of plant species and leaching time (7 or 14 days). Chemical analyses of the leachates showed the presence of carboxaldehyde and Heptatriocotanol, which have antimicrobial properties, potentially reducing the food available for larvae. β-Sitosterol, Stigmasterol, α-Amyrin, and Lupeol are compounds with inhibitory, neurotoxic, and larvicidal effects. Both plant species’ leachates increased larval mortality and decreased emergence time due to the presence of compounds toxic to the larvae. Larger organisms emerged in treatments with 7-days leachates, likely due to the high concentration of dissolved organic matter in the leachates. The higher mortality in 7-days leachates may also increase the organic matter from co-specific decomposition, improving adult size. Therefore, if the mosquito population is not locally extinct, compounds present in leaf leachates may act as a resource enhancing larvae growth, potentially increasing survivors’ fitness. In conclusion, biocontrol attempts using urban green spaces may have unexpected outcomes, such as resulting in larger pest organisms.

Whitefly (Bemisia tabaci Gennadius), leafhopper (Amrasca biguttula biguttula Ishida) and large yellow-banded blister beetle (Mylabris phalerata) cause considerable damage to okra, especially under organic farming. Thus, the present study was carried out to test the bioefficacy and environmental safety of six naturally derived components [indigenous water plant extracts, i.e. chilli (Capsicum annum), garlic (Allium sativum L.) and neem (Azadirachta indica A. Juss.) along with cow urine in three different combinations, one commercial botanical (azadirachtin 0.15%), and two formulated entomopathogenic fungi (Verticillium lecanii and Beauveria bassiana)] on aforesaid pests for two consecutive years at field scale. In addition to this, the eco-toxicological effect of naturally derived components was also studied on natural enemies’ populations, viz. spiders and coccinellids. Quaternary mixture application of chilli, garlic, neem leaf and cow urine (CGNC) at 10% w/v was found effective in reducing leafhoppers (94.6%), whiteflies (95.2%) and blister beetle (94.6%) over control. Okra treated with CGNC produced a higher marketable fruit yield (18.44 mg/ha) than those of other treatments. It was also observed that the application of CGNC had no phytotoxic symptoms on okra plants. Application of CGNC was found safer to the natural enemy's population (spiders and coccinellids). Thus, the study suggests that CGNC can be considered as a potential source for managing the population of whitefly, leafhopper and blister beetle without affecting the ecology of natural enemies and it could be a viable eco-friendly option in organic okra production for ensuring food safety and healthy environment.

Cucumber powdery mildew is a destructive foliar disease caused by Podosphaera xanthii (formerly known as Sphaerotheca fuliginea) that substantially damages the yield and quality of crops. The control of this disease primarily involves the use of chemical pesticides that cause serious environmental problems. Currently, numerous studies have indicated that some plant extracts or products potentially have the ability to act as natural pesticides to control plant diseases. It has been reported that turmeric (Curcuma longa L.) and its extract can be used in agriculture due to their insecticidal and fungicidal properties. However, the most effective fungicidal component of this plant is still unknown. In the current study, the crude extract of C. longa L. was found to have a fungicidal effect against P. xanthii. Afterwards, eight fractions (Fr.1–Fr.8) were gradually separated from the crude extract by column chromatography. Fraction 1 had the highest fungicidal effect against this pathogen among the eight fractions. The active compound, (+)-(S)-ar-turmerone, was separated from Fr 1 by semi-preparative high-performance liquid chromatography and identified based on its 1H nuclear magnetic resonance (NMR) and 13C NMR spectrum data. The EC50 value of (+)-(S)-ar-turmerone was found to be 28.7 µg/ml. The compound also proved to have a curative effect. This is the first study to report that the compound (+)-(S)-ar-turmerone has an effect on controlling this disease. These results provide a basis for developing a new phytochemical fungicide from C. longa L. extract.

Recent trends favoring organic and sustainable turfgrass management practices have led to an increased desire for biologically based alternatives to traditional synthetic herbicides. Thaxtomin A, produced by the bacterium Streptomyces scabies, has been reported to have PRE efficacy on broadleaf weeds, but efficacy of thaxtomin A on annual grassy weeds and safety to newly seeded cool-season turfgrasses have not been reported. Field experiments were conducted to evaluate PRE efficacy of thaxtomin A on smooth crabgrass and annual bluegrass. Monthly applications of thaxtomin A from April to July controlled smooth crabgrass through July but did not provide season-long control equivalent to an industry standard PRE herbicide. An initial application of thaxtomin A at 380 g ai ha−1 followed by two applications at 190 or 380 g ha−1 at 4-wk intervals provided season-long annual bluegrass control similar to an industry standard PRE herbicide. At 380 g ha−1, thaxtomin A reduced tall fescue and perennial ryegrass cover when applied 1 wk before seeding, at seeding, or 1 wk after seeding but was safe at other application timings. Up to three applications of thaxtomin A at 380 g ha−1 at 4-wk intervals did not reduce perennial ryegrass cover. Applications to creeping bentgrass resulted in unacceptable turfgrass injury. These results suggest that thaxtomin A can suppress annual grassy weeds in tall fescue or perennial ryegrass turf when applied at least 2 wk before or after seeding. Furthermore, repeated applications of thaxtomin A can provide effective PRE control of annual bluegrass during overseeded perennial ryegrass establishment.

Field studies were conducted with a biocontrol agent, Pseudomonas syringae pv. tagetis, to determine the optimal application parameters for controlling woollyleaf bursage, a pernicious perennial weed on the Texas Southern High Plains. Parameters investigated were bacterial concentration, time, season, and frequency of application. Pseudomonas syringae pv. tagetis concentration ranging from 104 to 108 colony forming units (CFU)/ml produced similar incidence of disease on woollyleaf bursage. Weekly, biweekly, and triweekly applications were found to be equally effective. Optimal time for application of P. syringae pv. tagetis was at midday. A single application in April, May, or June resulted in higher incidence of disease for 5 wk than the noninoculated plots, whereas single applications in July and August were not consistently different from the noninoculated plots. Weed density was negatively correlated with disease incidence for April, July, and August applications, particularly when correlations were based on disease incidence from 1 to 4 wk prior to weed density measurement. Weed densities during 1997 were lower at the end of the year when bacteria applications were made in April, May, or June, as opposed to July or August, or plots were not inoculated. In 1998, weed density was lower when bacteria applications were made in April as opposed to May or June. These investigations indicate that P. syringae pv. tagetis does infect woollyleaf bursage on the Texas southern High Plains.

Both regulatory and consumer forces have increased the demand for biopesticides, particularly in amenity areas such as turfgrass. Unfortunately, few natural products are available for selective weed control in turfgrass. Two bioherbicides reported to control broadleaf weeds without injuring turfgrass are Phoma macrostoma and thaxtomin A. Field and container experiments were conducted to evaluate PRE and POST efficacy of P. macrostoma and thaxtomin A on regionally important broadleaf weeds. In container experiments, PRE applications of P. macrostoma provided 65 to 100% control of dandelion, marsh yellowcress, and flexuous bittercress, equivalent to that of pendimethalin. Control of yellow woodsorrel, henbit, hairy galinsoga, common chickweed, or annual bluegrass was less than with pendimethalin. In contrast, POST applications did not control any species as well as an industry-standard synthetic auxin herbicide. PRE or POST applications of thaxtomin A controlled six of the eight species tested as well as the industry-standard PRE or POST herbicides. In field tests, overall PRE broadleaf weed control with P. macrostoma and thaxtomin A peaked 4 wk after treatment at 64 and 72%, respectively, and declined afterward, suggesting that these bioherbicides possess short residuals and therefore must be reapplied for season-long control. Overall POST broadleaf weed control using P. macrostoma and thaxtomin A was only 41 and 25%, respectively. PRE followed by early-POST applications of thaxtomin A provided ≥ 86% henbit control. These results suggest that both P. macrostoma and thaxtomin A are capable of controlling certain broadleaf weeds in turfgrass. However, both lack efficacy on some important weed species, particularly chickweed. Thaxtomin A efficacy on henbit was improved by increased dose and by PRE followed by early-POST applications.

Bemisia tabaci (Gennadius) is a global insect pest that transmits many important plant viruses. A field study was conducted on infestation by B. tabaci and incidence of whitefly-transmitted viruses after the application of selected foliar and seed-treated biorational insecticides in seven vegetable and row crops in Egypt. Three foliar insecticides (Actara, Biofly and Neemix) and a treated check (Actellic) were assayed across three weeks on seedlings and mature plants, and two seed-treated insecticides (Actara and Gaucho) and a treated check (Aldicarb) were assayed on seedlings. All of the foliar insecticides led to 60–100% reductions in whitefly infestations in each crop. Biofly and Neemix were the least efficacious insecticides. Incidences of whitefly-transmitted viruses were reduced in each insecticide-treated plot with seedlings of four crops; however, no effect on virus incidence was observed in the experiment with mature plants. Crops of cucumber, eggplant, squash and tomato displayed symptoms characteristic of Cucumber vein yellowing virus, Squash leaf curl virus or Tomato yellow leaf curl virus; however, no symptoms of whitefly-transmitted viruses were observed in green bean, potato or sugar beet. The results show that several biorational insecticides may suppress whitefly populations in seedlings to delay whitefly-transmitted viruses in some vegetable crops in Egypt.

The aim of this study was to identify and develop entomopathogenic fungi as biopesticides for management of Maruca vitrata (Fabricius). Fourteen isolates of Metarhizium anisopliae (Metchnikoff) Sorokin and six of Beauveria bassiana (Bals.-Criv.) Vuill. were screened against first instar larvae of M. vitrata. The two most virulent isolates were selected and further tested for production in four liquid media. Different formulations of one isolate were evaluated against different developmental stages. Metarhizium anisopliae ICIPE 18 and ICIPE 69 caused highest larval mortality of 91 and 81%, with lethal time to 50% mortality (LT50) values of 1.8 and 1.7 days and LC50 of 1.07 × 107 and 3.01 × 106conidia/ml, respectively. ICIPE 69 yielded more biomass and propagules in two liquid media than ICIPE 18. All developmental stages and adult moths were susceptible to fungal infection and horizontal transmission caused a significant reduction in fecundity. Isolate ICIPE 69 was identified as the most potent isolate for managing M. vitrata based on demonstrated efficacy against different developmental stages and amenability to production in liquid media and could be utilized as an alternative to pesticides in cowpea IPM.

A cotton field was used to set up an arena trial for investigating the dose transfer of oil-based ultra-low-volume sprays of Metarhizium anisopliae (Metchnikoff) Sorokin to the cotton bollworm Helicoverpa armigera (Hübner). Two doses of conidia (75 and 50 g/ha, being 3.75 × 1012 and 2.5 × 1012 conidia/ha, respectively) formulated in 2 litres (70:30, kerosene–peanut oil) were applied using a Berthoud ‘Micro Ulva’ to three groups of larvae of cotton bollworms positioned in three rows downwind of a single spray line. Both the distribution of the droplets and the effect of direct contact with spray droplets were quantified. The mean number of droplets decreased from 416 ( ± 60) droplets per cm2 (line 1; 0.4 m) to 45 ( ± 36) droplets per cm2 (line 3; 5 m). To achieve 50% mortality, >10 and >13 days were necessary for 75 and 50 g/ha, respectively. From day 15, the difference in mortality rates was significant between the two treatments. At line 3 (5 m), at 12 days after application, the mortality rate reached 52% for 75 g/ha and 47% for 50 g/ha. The results are discussed in view of optimizing the application of the biopesticides.