Archive for August, 2015

Foreign Invasion threat to farming

Creeping MenaceForeign terrorists have been invading our farms and environment for a long time. These terrorists are called Invasive species. An invasive species is a plant or animal that is not native to a specific location (an introduced species); and has a tendency to spread, which is believed to cause damage to the environment, human economy and/or human health. Species that are moved or migrate to an area where they have not been to before can disrupt the ecology of an area because the native species have not evolved to interact with the newcomer. There may be no natural predators to keep the new species in check or the new species may find a food source that has no defense against the newcomer. There are invasive pests that have invaded our forests, waterways, homes and fields.

The following are just a few I’ve chosen to highlight from the USDA APHIS Hungry Pest website:

gypsy moth“The Asian gypsy moth (AGM) is a destructive, non-native pest that feeds on over 600 types of plants. Large infestations of AGM can completely defoliate trees, leaving them weak and more susceptible to disease or attack by other insects. If defoliation is repeated for two or more years, it can lead to the death of large sections of forests, orchards, and landscaping.” Not only damaging our forests but our landscaping in our cities.

Imported Fire Ants are nasty pests. If you have run into these and have been attacked, you’ll know why. They also damage crops and attack livestock.

giant-snailGiant African Snail is one of the most damaging snails in the world because it consumes at least 500 types of plants and can cause structural damage to plaster and stucco structures. This snail can also carry a parasitic nematode that can lead to meningitis in humans.

Some of these pest have been here a long time and have become “established”. The Asian Tiger Mosquito arrived a long time ago, hitching a ride in some imported tires from China. This mosquito carries West Nile Virus (Link for more on West Nile Virus for WebMD). West Nile virus infects humans and horses. Invasive mosquitoes are also carrying yellow fever, Dengue fever and chikungunya fever.

HydrillaInvasive plants can cause problems as well. Hydrilla is an aquatic plant that invaded Florida and has spread across the country. It is an aggressive plant that out competes native aquatic species and destroys native aquatic ecosystems.

What are some of the more important invasive species that agriculture has to deal with? There are quite a few. First I’ll cover a few that directly impact the crops and then I’ll explain some other ways invasive pest cause problems for agriculture.

Let’s start with one that is something I’m dealing with directly, the Asian citrus psyllid. This pest feeds on the new leaf growth of citrus trees cause the leaves to twist and die back. They are not a particularly difficult insect to control. The biggest problem with this pest is that it can, if infected, transmit a bacteria that causes¬†Huanglongbing (HLB or citrus greening) disease.

Citrus GreeningHuanglongbing causes shoots to yellow, asymmetrically (blotchy mottle), and results in asymmetrically shaped fruit with aborted seeds and bitter juice. The disease can kill a citrus tree within 5 to 8 years, and there is no known cure for the disease.This has already devastated the citrus industry in Florida. It has spread to California, first detected in the Los Angeles area. Even with strict regulations in place about moving citrus trees (the pest does not get on the fruit) it still managed to move from Florida to LA and now up into California’s central valley, the largest citrus growing area in the state.Until just a few months ago none of the psylids found were infected with HLB. Quarantines are in place around areas where the psylids have been caught and this means a lot of extra work if you have to move your fruit to a packing house outside of the area. This includes, but not limited to, spraying pesticides before each pick. A farmer may go through and pick many times before all the fruit is harvested.

BMSBAnother invasive pest headed my way but not yet here is the Brown Marmorated Stink Bug (BMSB). It “has been detected in California. Wherever BMSB takes up residence, it causes severe crop and garden losses and becomes a nuisance to people. The ability of BMSB to hitchhike in vehicles and planes has allowed it to spread rapidly to new areas. Since it was introduced to the United States from Asia in the 1990s, BMSB has become established in the mid-Atlantic states as well as in Portland, Ore., and Los Angeles”. (from UCIPM website). This pest has recently been found in large numbers in the Sacramento area and has been found Stockton. A number of other native stink bugs are pests in agriculture¬† They are not easy to control and usually require harsher pesticides to get rid of them. The BMSB has been found to be very hard to control and will definitely be a big impact to our IPM programs as they infest a large number of crops.

These are just two but there are many. Many that have come into California and many that are being tracked for possible entry. You can see a pretty comprehensive list for California here

But other countries are watching us as well and they have their own lists and things they do not want us introducing into their environments. This creates issues for farmers because the packers and shippers must ensure what they are exporting comply with the importing countries regulations concerning these pests. Following is a summary of a few of our pests that we have to take extra measures to control and monitor, and why, in some cases, this causes a problem in our IPM programs.

The Oriental Fruit Moth is a common pest that mainly infests stone fruit (Peaches, Nectarines, Plums, etc). Mexico does not have this pest (or so they claim) so they do not want any fruit coming across the border that may have any of this pest in it. Growers and Packers who want to ship fruit to Mexico must pay into a program for extra monitoring for this pest. This includes paying for inspectors for Mexico to be on site during the growing and harvest season, increased trap density and the costs to have people check these traps more frequently than on a non export field, Since you are not allowed to have ANY of this pest in your fruit you need to make sure you spray every hatch (one a month) even if your trap catches do not indicate a serious infestation. Any trap catches and you are required to spray and you can’t use any of the newer more environmentally friendly products because Mexico doesn’t think they work as well. You really can’t have a good IPM program with someone else dictating what you have to do.

fuller rose beetleFuller Rose beetle is a pest that will lay it’s eggs on citrus fruit, under the stem and can be hard to find. South Korea doesn’t want it. Even if you don’t have it in your fields you are required by the packers to spray at least once before harvest. The citrus industry exports a lot of product and there are other spray programs that are dictated more for appeasing the export markets than for what is going on in the field.

A few years back we had an outbreak of European Grapevine Moth that had hitched a ride on some smuggled grapevines from France over to Napa. They hung out in the Napa area, slowly building populations before someone noticed these were not our common type of worm generally found. Napa doesn’t normally have a big problem with worm pests and this one was causing a lot of problems especially for organic growers. Then it moved. Someone brought infested wood down to Fresno and then the export of table grapes came to a halt. For me, it was just another worm pest that was easily dealt with in my current program but in order to satisfy export markets areas with the pest were quarantined and when and what to spray was dictated by the USDA. No one in those areas could ship out of the US and the industry lost a lot of money.

Spotted Wing Drosophila is a fruit fly that, unlike many of our native fruit flies, will attack undamaged fruit and has many generations in a short period of time. They infest cherries and berries mainly. Also a pest we have to spray for even if we don’t see it because one fly can cause the whole field to be kicked out of an export program.

How do these pest move around? Well, mostly by human activity but also changing climate patterns are opening up new habitats in locations where these pests can move to as well. I mentioned that the European Grapevine moth came in by way of some grapevine cuttings that were transported from France to Napa. They did not go through legal import procedures, otherwise the pests would have been detected. Plants and fruit travel to and from places all the time but if they go through airports or border stations, they can generally be intercepted. But it they do not, hitchhiking pests are never far. This local story is about smuggled fruit being sold by roadside vendors and some had invasive pests on them.

We can all help in the fight against these pests. The USDA’s Hungry Pest website has good information on “What Can You Do“.

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