Melon flies could end up costing California farmers over $4.5 billion if they ever get a toe-hold in the state.
Melon flies (Bactrocera cucurbitae) are a type of fruit fly. Native to India and Asia, melon flies were first seen in Hawaii in the late 1800’s. They have now become a devastating pest on the Islands. Quarantine stations have worked long and hard to prevent this pest from entering the Continental U.S. The melon fly was first seen in California in 1956, and several other times since, but whenever melon flies are identified stateside, eradication programs immediately go into affect. These programs use pheromones to attract male melon flies. These males are then sterilized and released. This messes up melon fly breeding. So far, this method has been effective. So, why would a gardener care, if the pest isn’t even here? Because maybe it is.
Melon fly host plants
It would probably be easier to list the plants that are not seen as food by melon flies, but it is important to know where to look, and to know what to watch for, so here’s the fruit fly menu of favorites from your garden:
Melon fly description
The size of a house fly, melon flies are mostly orange or yellow and brown with a pale black T-shape on the abdomen and distinct wing patterns. Wings are clear with a large brown spot at the tip and a brown stripe along the back edge and along the base. Melon fly antennae also have an especially long third segment. Melon fly larvae (maggots) are creamy white, without legs, somewhat flattened at the back end. Maggots are less than 1/2 an inch long. Pupae are somewhat smaller than the maggots, held in a protective case that can be dull white or red, or brownish yellow. Eggs are very tiny, white, and somewhat elliptical.
Melon fly lifecycle
A single female melon fly can lay 1,000 eggs. Eggs are laid on young fruit and tender new stems, which will provide food for newly hatched maggots. Eggs that have been laid under the skin of fruits, or in host plant stems, flowers, and exposed roots, will hatch and the feeding damage begins. There are three larval stages, or instars. After feeding continuously, mature maggots drop to the ground, where they burrow into the top inch of soil and enter a pupal stage. There can be 8 to 10 generations a year.
Melon fly damage
During the heat of the day, adult melon flies rest on the shady undersides of leaves. When temperatures are more comfortable, they feed on nectar, decaying fruit, sap, and bird poop. [Keep in mind, as these pests fly from one food source to another, they can be carrying pathogens from the bird poop to your fruit crop.] Tunneling and feeding create points of entry that allow bacterial, fungal, and viral diseases to enter. Generally, the fruit ends up rotten and inedible.
Melon fly control
Unfortunately, there are not any effective controls available to the home gardener. You can certainly rake up the soil under and around potential host plants, to spot, remove, and report any pupal cases you find, and be sure to quarantine new plants. Currently available insecticides have not been found to work against melon flies.
If you think you see a melon fly, please make every effort to capture or kill it. Then call the CA Pest Hotline at 1-800-491-1899, or your local Department of Agriculture, to report it. Only by working together can we protect commercial agriculture and our own gardens from the melon fruit fly. And don’t smuggle fresh fruit or produce across state lines. There’s a lot more at stake than you might think.
The Mediterranean fruit fly has reappeared in California!
Periodically, in the world of gardening and agriculture, a cry goes out across the fields, farms, and front porches of California, and the world, announcing that a medfly has been found. This time, a medfly has been found in Half Moon Bay
You might think that a tiny fruit fly is No Big Deal, but this short, squat, orangish flying insect has the dubious title of World’s Worst Agricultural Pest.
The California Dept. of Food & Agriculture estimates that a permanent infestation of the Mediterranean fruit fly, or Medfly, would cost California businesses nearly $2 billion a year!
Native to sub-Saharan Africa, medflies (Ceratitis capitata) have slowly been making their way around the globe, usually riding on fruit and other infested crops. Medflies are about 1/4” long. They have a black thorax, marked with silver, and a tan abdomen with dark stripes. The wings are clear, with two light brown bands and gray flecks at the base. Their eggs look like those of other fruit flies: they look like tiny white bananas. Larvae are white, legless, and pointed at the back end. Pupae are encased in a hard, shiny brown puparium.
Damage caused by medflies
Medflies lay their eggs in the skins of over 250 different fruit, nut, and vegetable crops. When the eggs hatch three days later, the maggots burrow into what we normally eat, making it inedible. Once maggots have eaten their fill, either the rotting fruit falls, or they drop to the ground where they pupate in the soil. In one week, an adult emerges and the whole cycle begins again.
Crops affected by the medfly
It would probably be easier to list the crops not affected by medflies, but this should give you an idea: apples, apricots, avocados, cherries, figs, grapes, grapefruit, lemons, limes, melons, nectarines, oranges, peaches, pears, persimmons, plums, pomegranates, sweet peppers, tangerines, tomatoes, and walnut.
The ripple effect
Like most things in life, this situation is not limited to bug-infested food plants. Commercial and home growers will end up using more pesticides to counteract this insect, which can lead to more ground water contamination and chemical resistant pests. Also, areas with medfly populations are unable to sell their produce, infested or not, to other states and other countries. Finally, native plants that produce fruit or nuts can also be attacked by this pest.
The first appearance of a medfly in California took place in 1975. I remember hearing about it in the news - everyone was talking about it. The government declared a “state of emergency” and 100 square miles were placed under quarantine, and 600 million sterile male medflies were released, to interrupt breeding. Malathion was sprayed all over the place. It cost $1 million and took a year, but the medfly was eradicated. For a time.
When the medfly returned in 1981, Governor Brown delayed aerial spraying of malathion, claiming environmental concerns. That was when we learned that medflies reproduce and feed at astounding rates. In that case, the medflies needed only one month to destroy millions of dollars of crops, and to threaten billions more, over an area of 530 square miles. When it was realized just how devastating this pest could be, the California National Guard was called upon to create highway checkpoints to confiscate infested produce.
Now, when a single medfly is spotted, it is checked for gender and fertility, and then all the stops are pulled: aerial spraying, ground spraying, trapping, irradiation, releasing sterile male medflies, public information, and quarantines. Since 1985, medflies have been found in California in 2007 (Dixon), 2008 (El Cajon), and now in 2017. Currently, there are two active medfly quarantines in California: Fairfield (Solano Co., just north of Contra Costa) and Sun Valley (Los Angeles Co.). The Half Moon Bay infestation brings that number to three.
What can you do?
First, never, ever, EVER smuggle fresh produce, plants, or soil from infested areas into California. Do not mail fresh produce into uninfested areas either. For more information, contact the California Dept. of Food and Agriculture at (650) 363-4700.
IF YOU THINK YOU SEE EVEN ONE MEDFLY, PLEASE REPORT IT!
Do you remember the fire safety lesson from elementary school where they told you that three things had to be in place for fire to occur? [The answer is fuel, heat, and oxygen.] Take any one of those components out of the equation and viola! No fire. Well, plant diseases work much the same way.
The three sides of plant disease
For a disease to take hold in your garden, the environment has to be right, there has to be a host, and, of course, the disease (or pathogen) has to be there. Alter any one of those three and any diseases that do occur will be much less severe and less frequent. Remove one of those three and there won’t be a disease at all. Since prevention is far easier than treatment, the disease triangle is a handy tool for you to use in the garden. Another way to look at these factors is with a Venn diagram. When there is enough overlap between the three conditions, disease can occur.
How healthy plants defend themselves
You may be surprised to learn that many pathogens are already present in your garden. New arrivals are unusual and notable. That’s why quarantines are used. So, if all the disease-carrying pathogens are already present, why doesn’t everything just die a horrible death the moment it appears? Like us, plants have evolved to protect themselves, though not in the same way. Unlike us, plants do not have immune systems. What they do have is chemical warfare that has developed in tandem with pathogens. Plants use these steps to protect themselves, when they are able:
(And all this time, you probably thought that plants were relatively passive, right?)
Symptoms & disease identification
Symptoms of plant disease include wilting, stunting, deformed leaves or other growths, cankers, and chlorosis, just to name a few. If you notice disease symptoms, use that information to figure out what is making your plants sick. Feel free to share questions and photos in the Comments sections, plus there are several online resources and you can always contact your local Master Gardeners for advice. Once you know what your plants are up against, you can use the disease triangle to break the cycle.
Pathogens are disease-carrying bacteria, viruses, or other microorganisms. Many times, if they are not already present, these pathogens catch a ride into a landscape on flying insects, tools, shoes, and newly acquired plants. Chewing insects may simply leave behind a point of entry for disease, or they may be infected themselves, transferring viruses or bacteria to the host plant as they feed. You can interrupt the pathogen side of the triangle with these tips:
You can control common environmental factors with these good cultural practices:
The host is the plant that gets sick. Some diseases affect only a single host, while others can infect many different types of plants. This is where knowing more about your plants can really help. [Did you know that lilacs grown near apple trees are more likely to get bacterial blight? Or that cedar apple rust can only occur when apples are grown within a couple of miles of Eastern red cedar trees?] These tips can help prevent disease by helping the host plant:
Many botanists have added time as a factor, converting the disease triangle into a pyramid. They do this because time can be a critical factor in disease development. Diseases take time to infect a plant and to reproduce. Water sitting on a leaf for a few minutes may do nothing, while several hours of surface water on the same leaf may be deadly. Regularly monitoring plants for signs of disease can put time in your favor.
Keeping plants healthy overall helps them fight pests and diseases the way they have evolved to do so. Plants experiencing heat or water-stress, nutrient deficiencies, inappropriate or nonexistent pruning, or physical damage are less able to defend themselves.
Each microclimate has it own set of problems. Learning about your plants and what they are facing, puts you in control of the disease triangle.
New disease warning!
Imagine a world without oregano. Or celery. Or sage. Or chrysanthemums. It could happen.
There is a new plant disease and its name is Phytophthora tentaculata. [Wait! Come back!]
Just because this disease is tricky to pronounce (Fie-TOF-ther-uh), doesn’t mean you can ignore it. Its name is from the Greek phytón (plant) and phthorá (destruction), so the name phytophthora means “the plant-destroyer”. (The tentaculata part of the name refers to the tentacle shape of these particular pathogens.)
First noted in Germany in 1993, Phytophthora tentaculata hitched a ride on contaminated nursery stock and made its way to Central California and Monterey County, our Bay Area neighbors, in 2012. It is spreading rapidly and is deadly to many of your garden and landscape plants.
According to the Retail Nursery and Garden Center IPM News, Phytophthora tentaculata poses long term potential environmental and economic threat to many California native and non-native plants, as this pathogen can stay in the soil for many years and there is currently no known treatment.
What is Phytophthora tentaculata?
Phytophthora tentaculata is a member of the water mold family. In the world of scientific classification, water molds fall between fungi and algae. These pathogens attack stems and roots and frequently kill their host plants. There are several types of phytophthora, including those that cause potato blight, crown rot, and sudden oak death. You cannot see these organisms with the naked eye, but it is important that you keep a look out for the symptoms and know which plants are currently considered susceptible.
Many California native plants are highly susceptible to Phytophthora tentaculata. The most recent list includes:
Non-native plants that are at risk include:
Symptoms of Phytophthora tentaculata
Preventing Phytophthora tentaculata infestation
Contaminated nursery stock is the most likely way this pest will reach your garden and water management is the best way to prevent infestation. Phytophthora tentaculata are soil borne, which means they spread by sticking to plants, tools, containers, and shoes. Phytophthora tentaculata spores can also travel through the movement of water. This means that spraying an infested plant can transfer the water molds to nearby plants. Since symptoms do not appear right away, it is in your garden’s best interest to stay away from unhealthy-looking plants until you know for sure what is going on. These tips can help you protect your garden:
If Phytophthora tentaculata appears in your garden or landscape, contact your local Cooperative Extension Office right away. They may have helpful advice that will protect your plants and they need to know how far this disease is spreading.
You can grow a surprising amount of food in your own yard. Ask me how!
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