Combining Plant Pathogenic Fungi and the Leaf-Mining Fly, Hydrellia pakistanae, Increases Damage to Hydrilla

Four fungal species, F71PJ Acremonium sp., F531 Cylindrocarpon sp., F542, Botrytis sp., and F964 Fusarium culmorum [Wm. G. Sm.] Sacc. were recovered from hydrilla [ Hydrilla verticillata (L. f.) Royle] shoots or from soil and water surrounding hydrilla growing in ponds and lakes in Florida and shown to be capable of killing hydrilla in a bioassay. The isolates were tested singly and in combination with the leaf-mining fly, Hydrellia pakistanae (Diptera: Ephydridae), for their capability to kill or severely damage hydrilla in a bioassay

Biological control of weeds by means of plant pathogens significance for integrated weed management in modern agroecology,

Abstract. Biological control of weeds by using plant pathogens has gained acceptance as a practical, safe, environmentally beneficial, weed management method applicable to agroecosystems. The interest in this weed control approach from public and private groups, and support for research and developmental effort, are on the upswing. This increasing interest is stimulated largely due to major economic, social, and environmental forces that are directing our choices in crop production practices. Some of these changes are market-driven while others are social and ecological in nature. These changes are in turn influencing the choices in weed control methods. In this regard, biocontrol with plant pathogens has been proven a feasible, albeit minor, component of modern integrated weed-management systems. This environmentally beneficial method should be promoted and exploited further to meet the current and future challenges in weed management in agro-ecosystems

Effect of dactylaria higginsii on purple nutsedge (Cyperus rotundus) interference with pepper (Capsicum annuum L)

Greenhouse studies were conducted to evaluate the effect of the fungal pathogen, Dactylaria higginsii, on purple nutsedge interference with 'Capistrano' pepper (Capsicum annuum). Purple nutsedge plants established from tubers were planted at initial densities of 40, 80,160, and 320 plants m-2with pepper in 35-cm diam pots with a commercial potting medium, under nonlimiting fertilization and irrigation conditions. Three to four-leafstage purple nutsedge and four-leafstage pepper plants were inoculated by spraying D. higginsii in 0.5% Metamucil, a carrier; the treatments were carrier only, 104 conidia ml1 carrier, or 106 conidia conidia ml1 carrier. Purple nutsedge at all tuber densities significantly reduced pepper yield in the absence of D. higginsii. Percentage yield loss of pepper was greater in treatment with 104 conidia ml1• However, percentage yield loss of pepper was negligible in treatments with D. higginsii at 106 conidia ml1 when compared to the non-weedy control. The disease progress rate was significantly faster in treatments with 1(1 conidia ml1 (rc = 0.113 - 0.123) compared to 104 conidia mlJ (rc = 0.049 - 0.050). At 106 conidia ml1 , D. higginsii reduced nutsedge interference, provided greater nutsedge control, and increase pepper yield compared to weedy checks

Herbicidal potential of ophiobolins produced by Drechslera gigantea

Drechslera gigantea, a potential mycoherbicide of grass weeds, was isolated in Florida from naturally infected large crabgrass (Digitaria sanguinalis); it produces phytotoxic metabolites in liquid culture. The main metabolite was identified by spectroscopic methods and optical properties as ophiobolin A (1), a well-known phytotoxic sesterterpene produced by several phytopathogenic fungi of important crops and already extensively studied for its interesting biological activities. The other three minor metabolites proved to be related to ophiobolin A and were identified using the same techniques as 6-epi-ophiobolin A and 3-anhydro-6-epi-ophiobolin A (2 and 3) and ophiobolin I (4). Assayed on punctured detached leaves of several grass and dicotyledon weeds, ophiobolin A proved to be on average more phytotoxic as compared to the other related compounds. Some structural features appear to be important for the phytoxicity, such as the hydroxy group at C-3, the stereochemistry at C-6, and the aldehyde group at C-7. Furthermore, grass weeds usually proved to be more sensitive to the phytotoxins than dicotyledons, on which ophiobolin A caused the appearance of large necrosis even at the lowest concentration assayed. This is the first report about the production of ophiobolins from D. gigantea and of the proposed use as potential natural herbicides against grass weeds. © 2006 American Chemical Society

Ophiobolin E and 8-epi-ophiobolin J produced by Drechslera gigantea, a potential mycoherbicide of weedy grasses

Drechslera gigantea, a fungal pathogen isolated from large crabgrass (Digitaria sanguinalis) and proposed as a potential mycoherbicide of grass weeds, produces phytotoxic metabolites in liquid and solid cultures. Ophiobolin A and three minor ophiobolins i.e., 6-epi-ophiobolin A, 3-anhydro-6-epi-ophiobolin A and ophiobolin I were obtained from the liquid culture broths. Interestingly and unexpectedly, ophiobolins also appeared in cultures of this fungus and they were isolated together with the known ophiobolins B and J, and designed as ophiobolin E and 8-epi-ophiobolin J. They were characterized using essentially spectroscopic methods. It is noteworthy that D. gigantea produces such a plethora of bioactive organic substances. Some structure-activity relationship results are also discussed in this report. © 2006 Elsevier Ltd. All rights reserved

Effects of culture age on conidia production, viability and pathogenicity of Dactylaria higginsii.

Effects of culture age on conidia production, viability and pathogenicity of Dactylaria higginsii, a potential bioherbicide for controlling Cyperus rotundus (purple nutsedge) were investigated both in the laboratory and the greenhouse. This fungus was capable of producing conidia after five days of culturing on potato dextrose agar (PDA), with the highest conidia production obtained from the 15 day-old culture compared to other culture ages. Conidia harvested from 15 days of culturing on PDA, produced higher viability and were more pathogenic to purple nutsedge compared to conidia harvested before or after 15 days of culturing. The infection rate of conidia harvested from the 15 day-old cultures was faster (rL0.40 logit/day) compared to the infection rate of conidia harvested from other culture ages

Bostrycin

The title compound, C16H16O8, is a potent nonspecific phyto­toxin. The crystal structure is the average of two tauto­mers, 5,6,7,9,10-penta­hydr­oxy-2-meth­oxy-7-methyl-1,4,5,6,7,8-hexa­hydro­anthracene-1,4-dione and 1,4,5,6,7-pentahydr­oxy-2-meth­­oxy-7-methyl-5,6,7,8,9,10-hexa­hydro­anthracene-9,10-di­one. The cyclo­hexene rings in both tautomers display a half-chair conformation. An extensive O—H⋯O hydrogen-bonding network is present in the crystal structure