Controlling Tropical Spiderwort

Growers and gardeners in the South-east of the United States are facing a fast-spreading weed called Tropical Spiderwort, Commelina benghalensis. It is also known as Benghal Dayflower. This native of Africa and south Asia was first observed in Florida in 1928. It advanced into Georgia, but was not considered a troublesome weed until 1999.

The main reason Tropical Spiderwort has become a serious weed has to do with recent changes in commercial cropping systems. The biggest of these is the widespread use of Round-up-ready crops. This technology helps growers to better manage weeds, but Commelina has a natural tolerance to glyphosate - the active ingredient in the herbicide Round-up, so it is adapted to that change. It also tolerates other common herbicides.

The impact of Tropical Spiderwort has recently moved beyond open field crops. In autumn 2005, container ornamentals contaminated with the weed were discovered in retail outlets in North Carolina. The plants had been shipped from a South Carolina nursery. Tropical Spiderwort is on the Federal Noxious Weed List, meaning that movement across state boundaries is prohibited. Halting further spread of this weed is crucial in minimizing control costs throughout the region.

So how do you spot tropical spiderwort? "The easiest way to identify it is by the presence of underground flowers," says Agricultural Research Service scientists "Of the 250,000 species of flowering plants, only 36 have underground flowers. Tropical Spiderwort is the only known day-flowering species in the United States with underground blossoms."


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Investigating Compost Teas.

Compost teas are the up and coming thing amongst organic gardeners. These teas are made from compost "brewed" for at least twenty-four hours with all-natural ingredients that boost the growth of beneficial microbes living in the compost. It is believed that compost teas may prove helpful in protecting ornamental plants like rhododendrons, azaleas, viburnums and oak saplings from what's known as Ramorum Blight, also called Ramorum Die-back or Sudden Oak Death. The pathogen, Phytophthora ramorum, which causes these diseases, has been found in at least 20 states in the United States in commercial plant nurseries and more than one-half million otherwise-ready-to-sell plants have had to be destroyed.

Some organic growers and home gardeners already apply compost teas by either spraying them on foliage or drenching plant roots, and although reputed to enhance plant growth and fend off disease, compost teas have not yet been widely investigated by scientists. So the United States Horticultural Crops Research Laboratory and co-investigators are studying compost teas as one of several materials that might provide an effective, affordable, bio-friendly alternative to chemical pesticides for controlling P. ramorum.

In a preliminary experiment at the Horticultural Crops Research Laboratory, researchers treated rhododendron leaves indoors with a helpful bacterium, Paenibacillus polymyxa, taken from compost. The researchers then inoculated the leaves with the ramorum organism. The scientists found that P. polymyxa did not protect the foliage, but they plan to test it again, as well as other potentially protective microbes, using slightly different procedures.


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New US Import Restrictions for Ornamental Fish
Check new importation restrictions
Live fish of most species may be imported into the United States without import requirements from USDA. However, eight species of fish that are susceptible to the disease Spring Viremia of Carp (SVC) have recently come under USDA oversight. These species are: Common Carp, including Koi, Cyprinus carpio; Goldfish, Carassius auratus; Grass Carp, Ctenopharyngodon idellus; Silver Carp, Hypophthalmichthys molitrix; Bighead Carp, Aristichthys nobilis; Crucian Carp, Carassius carassius; Tench, Tinca tinca, and Sheatfish, Silurus glanis.

New regulations have been developed for the importation of live fish and their gametes (eggs and milt) from these species. The regulations pertain to commercial shipments and to fish brought in to the US as personal baggage. Live fish of these species may continue to be imported, provided they are accompanied by a USDA import permit and a veterinary health certificate issued by a full-time veterinary officer or Competent Authority of the National Government of the exporting country.

Importers must now use new identifying Harmonized Tariff Structure import codes assigned by the International Trade Commission for these species on shipping manifests and invoices. The new rules were set to become effective 29th September 2006, but the USDA have extended the period for compliance to 30th October. For further information click here.


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New Insecticidal Compound

A newly introduced class of insecticidal compounds developed by the United States Agricultural Research Service (ARS) and co-operators offers safe and effective alternatives to conventional chemical insecticides. The active ingredients are based on sugar esters that are natural chemicals secreted by wild tobacco plants and Vincetoxicum vines to protect themselves against insect predators. When certain insects rub up against and chew on the plants' leaf hairs, the insects become contaminated with the compound and die.

ARS entomologist Gary J. Puterka, working with US industry co-operators, developed synthetic analogs, or look-alikes, of the natural sugar esters. He and colleagues then screened various synthetic sugar esters to find the most potent among them. Gary Puterka identified several of the new chemical forms that kill test insects instantly, and has been named a co-inventor on two patents that define the chemical structures of the compounds, as well as an environmentally sound processes for their manufacture.

One of the compounds, sorbitol octanoate, has proved less costly to produce than earlier forms patented, and is now undergoing the process of registration with the US. Environment Protection Agency. The analogs kill by breaking down the insect pests' outer waxy coating. The insects then lose water and die from dehydration. The new class of compounds is unique among insecticides because their active ingredients do not leave a detrimental residue on surfaces to which they are applied. What is left over after application becomes inactive upon drying and rapidly degrades. The latest synthetic sugar esters, if licensed, could be a boon to the home and garden market, according to the ARS.


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New Peach Cultivars

Peach 'Gulfking'
Two recently introduced peach cultivars developed by the United States South-eastern Fruit and Nut Research Laboratory, the University of Georgia and University of Florida, will shortly be available to home gardeners. The cultivars, ‘Gulfking’ and ‘Gulfcrest’, were made available to commercial growers in 2003. Both cultivars are known as "non-melting" peaches. That is they resist bruising and remain firm longer while ripening on the tree.

In the United States ‘Gulfking’ typically ripens in early May. When ripe, its skin is mostly red on a deep yellow to orange background. The flesh is firm and sweet and does not turn brown readily when bruised or cut. ‘Gulfcrest’ ripens from early to mid-May, extending the harvest period. The fruit is medium to large and also has a mostly red skin on a deep yellow to orange background. The flesh is firm, with good sweetness, and contains some red flecks in the outer flesh on the sun-exposed side of the fruit. As with ‘Gulfking’, this peach does not brown readily when bruised or cut.


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Mediterranean Fruit Fly Control

Mediterranean Fruit Fly
A product developed by the United States Agricultural Research Service and Suterra LLC is helping to keep the Mediterranean Fruit Fly out of the United States and giving other countries an effective, environmentally friendly control method. The product, BioLure 3-Component Fruit Fly Lure, is being commercialised by Suterra, which holds the exclusive license for the ARS patents. Suterra is marketing it in the United States, Spain, South Africa, Guatemala, Mexico and Peru. Growers and government agencies in these countries are now using BioLure 3-Component Fruit Fly Lure as an effective tool to monitor for the presence of the flies as well as reducing their populations by mass trapping.

Each year in Spain, for example, mass trapping is done on thousands of hectares of citrus groves using BioLure 3-Component Fruit Fly Lure. Spanish plant health agencies have found mass-trapping with the lure is as effective as insecticides at controlling fruit fly damage without leaving pesticide residues on fruit or harming beneficial insects. The product is a combination of three compounds: ammonium acetate, putrescine and trimethylamine. It captures more Mediterranean Fruit Flies and fewer non-target insects, is more consistent between batches and lasts four to eight times as long, as protein baits. It also attracts mostly female flies, which is important in areas where sterile male insect control programmes are being used.


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Tracking and Controlling Mealybugs

The Pink Hibiscus Mealybug (PHM), Maconellicoccus hirsutus, is a devastating pest from south-east Asia, which originated in the United States from the Caribbean. It also has a strong foothold in Central America as well. This insect pest can destroy more than two hundred plant species by injecting them with toxic saliva while sucking their sap. The exotic insect pest recently invaded California and Florida, and has proved to be very difficult to monitor. However, United States Agricultural Research Services scientists have now found a way to lure male mealybugs, making them easier to detect. A team of researchers led by chemist Aijun Zhang at the Chemicals Affecting Insect Behavior Laboratory, in Beltsville, Maryland, has discovered two compounds that together make up the female PHM's sex pheromone. The compounds provide a timely method with which to monitor and ultimately reduce infestations.

The scientists carefully reared thousands of PHMs, using an insect growth regulator that prevents the development of males. Then they painstakingly isolated more than 6,000 virgin females from which they collected pheromone chemicals.After pooling seven collections of airborne sex-chemical extracts from the females, the scientists exposed them to male mealybugs' antennae, which consistently responded to two attractant compounds. The previously unknown natural chemicals were found to be (R)-lavandulyl (S)-2-methylbutanoate and (R)-maconelliyl (S)-2-methylbutanoate.
The researchers then prepared a synthetic version of the pheromone and further demonstrated that the processed mixture was immensely attractive to PHM males. They found the most potency when they mixed one part of the first compound with five parts of the second.

"In many cases, just a few micrograms of the one-to-five blend placed in a single sticky trap captured thousands of males," says Zhang. This blend is effective for monitoring the mealybug's population densities and geographical distribution to help scientists determine where to release natural enemies. "Pheromones decompose relatively quickly, without leaving a harmful residue or damage to the environment," says Zhang. Chemical insecticides, however, break down at a very slow rate, so they tend to linger in soil for decades, which can add to pollution. So biological control methods - where natural predators and parasitoids are used against horticultural pests - are more desirable.

Officials with USDA's Animal and Plant Health Inspection Service, in Riverdale, Maryland, have introduced two exotic wasps to control PHM infestations in the United States and Caribbean. But their efforts had been stalled by an inability to detect the mealybug's presence and prevalence. Now, APHIS officials are using the new pheromone blend as a sex lure to survey the degree of mealybug pest infestations in Florida and California and to track the effectiveness of biological control efforts against the pest.


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