Invasive Fruit Fly Quarantine

What to know as a SJV citrus grower?

Sandipa Gautam

Area Citrus IPM Advisor

UC Statewide IPM Program Operations

Several species of invasive fruit flies that belong to the family Tephritidae are considered serious pests of hundreds of agricultural crops including citrus. These flies lay eggs on or near the fruit surface, and when the maggots hatch, they bore into the fruit, making it unfit for human consumption and causing major losses to fruits and vegetable production. California is experiencing an unusually high number of invasive fruit fly detections in the 2023/24 season and several areas in California are now under a fruit fly quarantine. For many invasive fruit fly species, quarantine is triggered when two or more adult flies are caught in a trap or by a single detection of larvae or pupae indicating a breeding population. Core area is 0.5-mile radius around the detection site and a quarantine area is 4.5-mile radius around each detection.

 Counties Currently Impacted by Invasive Fruit Fly Quarantines: 

• Oriental fruit fly: Contra Costa, Riverside, Sacramento, San Bernardino, and Santa Clara Counties (Figure 1)
• Mediterranean fruit fly: Los Angeles County (Figure 2)
• Tau fruit fly: Los Angeles County (Figure 3)
• Queensland fruit fly: Los Angeles and Ventura Counties (Figure 4)

Why is fruit fly quarantine concerning to citrus growers?

Citrus is a known host to all invasive fruit fly species. Fruit fly life cycle begins as eggs laid by adult female on surface or under the fruit rind maggots hatch and bore into the fruit and develop inside the fruit (Figure 5). They drop to the ground and pupate. Many fruit fly species are known to overwinter as prepupae or pupae, but some species like Medfly can overwinter in all life stages inside fruit or as pupae on the ground. Adults emerge in early spring and the life cycle continues. Because eggs and immatures can be present inside the fruit, movement of infested fruit may accidentally transport them to a new area where fruit fly has not been detected.

Invasive fruit flies – what to look for?

Four species of fruit flies are currently regulated in California. The adults may look similar to houseflies but are distinctly different in color and the markings on the body. They are about 5-8 mm in size, much bigger than spotted wing drosophila, another invasive species that has been established in California.

•  Oriental fruit fly: ~8 mm size, bright yellow colored body with a dark T shaped mark on the abdomen (Figure 1).
• Mediterranean fruit fly (Medfly): ~5-6 mm in size, yellow-light brown body, clear wings with brown bands (Figure 2)
• Tau fruit fly: ~7 mm in size, yellow body with black markings (Figure 3)
• Queensland fruit fly: ~5-8 mm in size, wasp-like body, reddish brown in color with distinct yellow markings, clear wings with band along the top margin.

Figure 1. Oriental fruit fly adult with identifying characters (left) and areas in California under quarantine as of January 2024: Contra Costa, Riverside, Sacramento, San Bernardino, and Santa Clara Counties (right).

Figure 2. Mediterranean fruit fly adult with identifying characters (left) and areas in California under quarantine as of January 2024 – Los Angeles County (right).

Figure 3. Tau fruit fly adult with identifying characters (left) and areas in California under quarantine as of January 2024: Los Angeles County (right).

Figure 4. Queensland fruit fly adult with identifying characters (left) and areas in California under quarantine as of January 2024: Ventura County (right).

You can find more information about invasive fruit fly species including interactive quarantine maps, regulatory information and pest profile information below: https://www.cdfa.ca.gov/plant/PDEP/treatment/index.html

Figure 5. Fruit fly larvae are white, legless maggots. They bore into the fruit and feed on pulp. Infested fruit may drop and decay.

 What is happening to prevent fruit fly spread?

The California Department of Food and Agriculture (CDFA), in cooperation with the United States Department of Agriculture (USDA) and County Agricultural Commissioners, has initiated local regulatory measures to eradicate and prevent the statewide spread of Queensland fruit fly, Tau fruit fly, Mediterranean fruit fly and Oriental fruit fly. California Citrus Quality Council (CCQC) in coordination with researchers is developing a systems approach that allows for post-harvest treatment of citrus fruit for movement from the core to pack.  

 What can you do?

 If you are a grower inside the quarantine area, follow regulations about harvesting, processing, or storing fruit. Contact your County Ag Commissioner about the latest regulations, or review FAQs here: https://www.cdfa.ca.gov/plant/fruitfly/docs/Invasive_Fruit_Fly_FAQ_Industry_1-18-24.pdf . If your property is under fruit fly quarantine, follow either pre or postharvest treatment protocols from USDA to move fresh fruit

• Grower outside the quarantine area, stay informed, invest in trapping and pre-quarantine treatments to avoid potential harvest delays should a quarantine be established in the future. For information on prevention and exclusion visit: https://www.cdfa.ca.gov/plant/PE/InteriorExclusion/current_preharvest_treatment.html
• Quarantines boundaries can change rapidly, so it is critical to stay in communication with your local agricultural commissioner.
• Report any suspected invasive fruit fly sightings to CDFA, USDA or your local County Agricultural Commissioner.
• Encourage neighbors, friends, and family to avoid moving any homegrown produce from their properties and to cooperate with agriculture officials working in their area.
• Help spread the “Don't Pack a Pest” message to travelers or those receiving produce in the mail or through other shipping channels.
• Share social media posts created or shared by CDFA, USDA or County Agricultural Commissioners.

Are you interested in learning about the management of sap-sucking pests and ants in citrus orchards? Lindcove is organizing a full-day workshop to bring you recent research advances on sap-sucking insects and ant management. The workshop will focus on ants.

Ants, especially the invasive Argentine ant and the native grey field ant, are serious pests because they protect sap-sucking pests infesting citrus, grapes, and other perennial tree and vine crops, from their natural enemies. In return for protection, hemipteran pests like Asian citrus psyllid mealybugs, soft scales, aphids, and whiteflies reward ants with honeydew, a sticky sugar-rich waste product that ants imbibe and return to nests to feed nest mates. This is an example of food-for-protection mutualism that is highly disruptive to biological control and IPM programs. This workshop will cover the latest developments in ant monitoring and management and will provide overviews of the benefits of ant control and how reductions in ant densities result in very high levels of biological control of important hemipteran pests.

When: 19 September 2023

Where: Conference room, Lindcove Research and Extension Center, 22963 Carson Ave, Exeter, CA 93221

Meeting Registration Link: https://surveys.ucanr.edu/survey.cfm?surveynumber=41086

Workshop Agenda:

Did you know rind scarring damage caused by the same pest could look different in mandarins and sweet oranges?

A NEW extension article "UCANR publication 8708", brings you a pictorial guide to help differentiate between the damages caused by the same pest on mandarin species and sweet oranges.

Early-season insect pests, such as katydids, earwigs, and citrus thrips feeding on newly developing fruit can cause rind scarring damage. Resulting scar damages can lead to the downgrading of fruit in packinghouses causing huge economic losses for growers. Highly valued for the fresh citrus fruit (unblemished), managing these surface-feeding pests and minimizing their damage is vital to California citrus growers. Several resources, such as “Photographic Guide to Citrus Fruit Scarring” UCANR publication 8090, published in 2003 exist to help identify various types of damages. But previous work was mainly based on work with sweet oranges.

With the increasing acreage of mandarins in California, the need for identifying early season rind scarring damage caused by several pests was recognized. Dr. Bodil Cass led a group of researchers from UC Davis in evaluating grower data and conducting experiments at the Lindcove Research and Extension Center. The results of this research are now published as a photographic guide that provides information on how three early-season pests cause damage to mandarin species compared to sweet orange.

What are the main findings?

• Damages caused by early-season pests are different in tango mandarin and clementine mandarin.
• Katydids do not cause feeding damage on tango or Afourer mandarins.
• Katydid damage on clementine looks like worm damage on sweet orange. It can cause maturing fruit to split and then drop.
  
  Figure. 1. Pictorial summary showing the different types of damages caused by katydid feeding on young and mature fruit. 

Low average daily temperatures in 2023 is delaying California red scale season.

Sandipa Gautam

UCCE IPM Advisor

California red scale is a common pest of California citrus attacking leaves, twigs, fruit by sucking plant sap. If the scale numbers are high serious damage can occur to the trees and highly infested fruit may be downgraded in the packinghouse.

Biology and seasonal phenology of California red scale

California red scale has an interesting life cycle. CRS start out as mobile crawlers from overwintering females from a previous season (Figure 1), which only remain mobile until they find a suitable location to begin feeding. Once they start feeding, they do not move and go through development being attached to the feeding spot. Males are the only other moving stage (Figure 2). They go through active feeding stage (instars) and a dormant period (molting). Females molt twice and males molt four times and emerge as fliers. Males then find and mate with third instar female. Afterwards, gravid female starts producing crawlers, hence completing the life cycle. In the San Joaquin Valley, there are four complete generations of CRS. In years with warm winters/hot summers, fifth generation crawlers/immatures have been found.

Figure 1

Figure 1. CRS female (overturned) showing crawlers. Crawlers move around looking for feeding spot, settle and spend life on the same spot.

Figure 2

Figure 2-2

Figure 2. CRS male adult (top) and CRS males on trap card (bottom)

Monitoring male flights using Pheromone trap cards (Figure 2) and using degree days to predict the next life event - crawlers, male flight is a most used method for monitoring CRS seasonal activity in the San Joaquin valley. After every 550-degree day unit accumulation above the lower developmental threshold of CRS, 53°F, something important happens. My team at Lindcove Research and Extension Center has been monitoring degree days in Kern, Tulare, Fresno, and Madera counties. However, we have not had a biofix (first male flight) this year. Please visit https://lrec.ucanr.edu/Citrus_IPM/Degree_Days/ for degree day updates.

The average mean temperature in 2023 has been lower, what does this mean for CRS season?

Temperature data from CIMIS Station, Kern Co., shows that the cumulative heat units above the CRS lower developmental threshold trails lower than earlier years in 2023. To date, no male fliers have been caught in Kern Co. which is usually a week or more ahead of Fresno, Tulare, or Madera Counties. This indicates that CRS is developing, but at a slower rate than it had been in earlier years (Figure 3). Expect CRS male flights, crawler emergence to be 2-3 weeks late than normal years, at least for the first generation. If the summer temperature pattern stays similar to earlier years, we will have a delay in second and third generation too!

The effect of low temperature delaying the development, thereby affecting emergence and flights, will likely affect spray timing for CRS control in 2023 season.

Figure. 3. Cumulative degree days above the lower developmental threshold, 53°F, for CRS. Note, 2023 (green line) trails below other years.

California red scale trial- 2022

During 2022, our group studied the impact of multiple insecticide treatments on California red scale. The trials took place at the Lindcove Research and Extension Center. The trials were conducted as single tree applications and replicated 10 times. One application was made on July 28, following the crawler emergence. We rated the twigs on 23 September and twigs and fruit on 12 October for the presence of live California red scale. We also rated fruit for infestation by CRS, 0=no red scale, 1=1-10 scale, 2= >10 scales/fruit. The insecticides applied were Movento 10 fl. oz, Sivanto 14 oz, Centaur 46 oz, Senstar  20 oz, and Esteem 16 oz. All insecticides were applied with 1% Omni 6E 415 oil. Foliar applications of insecticides were made using a 100-gal high-pressure D30 diaphragm pump sprayer with mechanical agitation with a hand wand sprayer containing D6-nozzle at 250 psi. Treatments were applied in 750 gallons of water, except for Movento which was applied in 250 GPA, and Centaur which was applied at 1,000 GPA.   

The insecticide that provided the best control in terms of reducing the percentage of fruit infested with >10 scales was Movento (Figure 4). Treatments, namely, Centaur, Senstar, Sivanto, and Movento significantly reduced the total CRS/fruit compared to control. In September, treatments did not significantly reduce CRS/twig compared to the control. In October, Centaur, Sivanto, and Movento, significantly reduced the mean number of mean live CRS on twigs (Figure 5). Treatments should be applied to provide thorough coverage according to the size of the trees, except for Movento which is recommended at 250 GPA at See the UCIPM guidelines for California red scale for more application details.  

Figure 4. Mean live CRS per fruit on October 12 counts following insecticide treatment. All treatments were applied with 1% oil.

Figure 5. Mean live CRS/twig before and after treatments. Treatments were applied on July 28. Pretreatment count was done on July 25, and post-treatments counts were done on September 23, and October 12, respectively.