Be Prepared for Invasive Pests

Spring is the time to anticipate pest problems that may emerge with the warmer weather of summer. It is a good time to remember what to look out for and to take some preventative steps to keep ahead of the pests. After the very wet winter in California, we might be about to experience an abundance of some of these pests, as well as invasive plants.
Because in California we grow so many crops over such a long season, there are always pests of concern.  Some pests are already under quarantine in certain regions, while other species are not quarantined but are worth preparing for. This blog post will cover a few of the potentially most threatening pests this spring so you can start making a plan to prevent or look out for damage caused by them.
Quarantined Pests 
  • Asian Citrus Psyllid (ACP) and Huanglongbing (HLB): ACP and the associated disease HLB have been frequent topics in the agricultural community because they pose such a severe threat to California citrus. While the ACP is spreading into northern California rapidly and is in some commercial groves, the HLB disease is still only in isolated areas of urban southern California. Vigilance is important and most commercial regions now have biological control programs available as well as region-wide control strategies.
  • Fruit Flies (FF): Various species include Mediterranean FF, Cherry FF, and Oriental FF. The Malaysian fruit fly is the most recent (2016), and has an active quarantine in the Los Angeles area.
  • European Grapevine Moth: There is still a quarantine program in place although no insects have been detected in traps since 2014. This is a major pest of a major crop, so extensive trapping is still ongoing in affected counties.
  • Light Brown Apple Moth (LBAM): While the active quarantine and mandatory spraying have quieted down, this pest is still active in many regions and controls are necessary. Mexico and Canada may still have some trade restrictions on certain crops regarding this pest.
  • Olive Fruit Fly: This pest has spread throughout most of the olive-producing regions of the state and there are no effective controls. Consequently, the olive fruit fly has limited the production of olives for table use in most areas, but olives for oil can still be grown successfully.
Non-Quarantined Pests 
  • Bagrada Bug: In 2015, this invasive stinkbug caused millions of dollars in crop losses of organic mustard-family crops. Since then, infestations haven’t been as destructive. An international team of biologists is working to develop biological control via a natural enemy of bagrada bug. Active in hot weather late in the season, early planning for cropping strategies—such as transplanting rather than direct seeding of mustard family crops—might help avert it.
  • Spotted Wing Drosophila (SWD): A fruit fly related to vinegar fly, this pest can have many generations a year and is particularly important for berries and cherries. It attacks ripening as well as overripe fruit, and in other areas of the country is very difficult to control.
  • Brown Marmorated Stink Bug (BMSB): A serious pest that can travel long distances and cause severe damage to a variety of hosts and infest buildings. It is established in the southern half of California and making its way north.
Organic Considerations
The basics of all organic pest control come into play here. These basics are:
  • sanitation,
  • traps and monitoring,
  • biological controls, and
  • organically-approved sprays. 
Here are a few tips on using these techniques to manage the invasive pests listed above.
  • Sanitation: It is extremely important to pick up and destroy fallen and overripe fruit so there is nowhere for the pest to lay eggs or pupate. This is the number one control for FF (including Olive FF and SWD), and it is also important for the control of many diseases. Giving pickers a separate receptacle for fruit that should not be marketed—but should be removed from the field—is a worthwhile strategy to help keep fields clean so that pests cannot spread.
  • Traps and Monitoring: Some of these pests can be mass trapped, while some of them should have a monitored trapping program to determine when the threshold is reached for a spray control method. Each species listed in this post has a specialized trap that works best, although some, such as LBAM, can have a combined trap that attracts other harmful tortricid moths. The University of California IPM Program Exotic & Invasive Pests page has much more detail about traps in the Management section for each pest.
  • Biological Controls: Research is ongoing on suitable biological controls for many of the invasives affecting agricultural crops. A few wasps have been identified that control ACP, and some of them will be commercially available to growers for the first time this year. For other pests like Olive FF, the parasites from its origination point in Africa do not give acceptable control for use in commercial plantings in the United States. The Center for Invasive Species Research at University of California Riverside issues frequent updates on research into new biological control organisms.
  • Organic Sprays: There are some pests that are very difficult to control organically, but with constant experimentation and attention to the details, most pests can be managed successfully enough to produce a crop. Some of the pests can particularly benefit from barrier film sprays such as kaolin clay to keep pests from penetrating fruit, while others need a precisely timed application of Bacillus thuringiensis (Bt), spinosad, or neem to achieve control. For area-wide pest control efforts, there are usually recommendations of what products to use and when.
Staying ahead of the threat is key to producing a successful crop. We urge you to consult the resources linked to this blog to find out more about invasive species, quarantines, integrated management strategies, and the latest research.