![Strawberries and Caneberries - <span style='font-size:0.5em;'>lygus bug</span>](https://ucanr.edu/blogs/strawberries_caneberries/blogimages/header.jpg)
- Author: Shimat Joseph
- Author: Mark Bolda
Lygus bug (Lygus hesperus) (Fig. 1) is a major pest of strawberry in the Central Coast. Lygus bug populations develop on weed hosts surrounding the strawberry fields such as wild radish, common groundsel, lupines, and mustards (Zalom et al. 2012). Time to time, adults migrate into the strawberry fields and lay eggs. Eggs hatch, and molt through five nymphal stages before molting into adults. Lygus bug feeding on the developing embryos affects the normal development of tissues surrounding the embryo (Handley and Pollard 1993) and affected fruits are misshapen often referred as “catfaced fruit” (Fig. 2) which are deemed unmarketable. Although both nymphs and adults can cause catface injury, nymphs are considered more destructive than adults. The young fruits up to ~10 days after petal fall are considered vulnerable to economic injury from lygus bug feeding (Zalom et al. 2012).
Chemical control continues to be an effective tool for lygus bug control and growers are always seeking effective and softer insecticides for its control. A replicated trial comparing the efficacy of insecticide treatments against lygus bug was conducted in first-year strawberry ‘San Andreas' in Watsonville, CA in 2016. The details on insecticide products and rates used in the trial are shown in Table 1. The insecticides were applied twice at 10 day interval using commercial tractor mounted sprayer. The water volume used for both the applications was 150 gal per acre and was applied at 140 psi. Dyne-Amic (surfactant) was added at 0.25% v/v to all the treatments. Insect samples were collected using regular sized Rubbermaid container by hitting 20 flowering strawberry plants with lid. In addition, 60 fruits were sampled from each plot to determine catface injury.
Pre-count sample did not show any difference in number of adult and nymphal lygus bugs among treatments (Figs. 3 and 4). Overall, all the insecticide treatments reduced the number of lygus bug adults and nymphs compared with untreated plants. The combination treatments using pyrethroid insecticides such as Danitol and Brigade suppressed lygus bugs and general predators such as bigeyed bug, minute pirate bug, and damsel bug as well as spiders (Figs. 5-8). Data show that reduced-risk insecticides, Rimon and Beleaf suppressed lygus bug nymphs as well. Sequoia, not yet registered on strawberry, provided a decent lygus bug control. Sivanto initially provided a good suppression of adults and nymphs but could not adequately sustain the control for more than a week. Two rates of Avaunt (unregistered insecticide on strawberry) was included in this experiment and were comparable to other effective insecticides in this experiment.
Insecticide use certainly reduced catface injury on strawberry fruit. Number of fruits with catface injury was lower in all the insecticide treated plants than untreated except the lower rate of Avaunt (Fig. 9). Catface injury on fruits treated with Sequoia was lower than untreated but not different from other insecticides (except lower rate of Avaunt).
References
Handley, D. T., and J. E. Pollard. 1993. Microscopic examination of tarnished plant bug (Heteroptera: Miridae) feeding damage to strawberry. J. Econ. Entomol. 86: 505-510.
Zalom, F. G., M. P. Bolda, S. K. Dara, and S. Joseph. 2012. Strawberry: Lygus bug. UC Pest Management Guidelines, UC ANR Publication 3468.http://www.ipm.ucdavis.edu/PMG/r734300111.html
![Figure 1: Lygus bug adult. Figure 1: Lygus bug adult.](https://ucanr.edu/blogs/strawberries_caneberries/blogfiles/38661.jpg)
![Figure 2: Catfacing of strawberry fruit. Figure 2: Catfacing of strawberry fruit.](https://ucanr.edu/blogs/strawberries_caneberries/blogfiles/38662.jpg)
![Table 1 Table 1](https://ucanr.edu/blogs/strawberries_caneberries/blogfiles/38660.jpg)
![Figure 3. Mean number of lygus bug adults collected by week from treated plants. Figure 3. Mean number of lygus bug adults collected by week from treated plants.](https://ucanr.edu/blogs/strawberries_caneberries/blogfiles/38654.jpg)
![Figure 4. Mean number of lygus bug nymphs collected by week from treated plants. Figure 4. Mean number of lygus bug nymphs collected by week from treated plants.](https://ucanr.edu/blogs/strawberries_caneberries/blogfiles/38655.jpg)
![Figure 5. Overall mean number of lygus bug adults collected from treated plants. Figure 5. Overall mean number of lygus bug adults collected from treated plants.](https://ucanr.edu/blogs/strawberries_caneberries/blogfiles/38656.jpg)
![Figure 6. Overall mean number of lygus bug nymphs collected from the plants. Figure 6. Overall mean number of lygus bug nymphs collected from the plants.](https://ucanr.edu/blogs/strawberries_caneberries/blogfiles/38657.jpg)
![Figure 7. Overall mean number of predatory bugs collected from treated plants. Figure 7. Overall mean number of predatory bugs collected from treated plants.](https://ucanr.edu/blogs/strawberries_caneberries/blogfiles/38658.jpg)
![Figure 8. Overall mean of spiders collected from treated plants. Figure 8. Overall mean of spiders collected from treated plants.](https://ucanr.edu/blogs/strawberries_caneberries/blogfiles/38659.jpg)
![Figure 9. Percentage fruit with catface (lygus bug feeding) injury. Figure 9. Percentage fruit with catface (lygus bug feeding) injury.](https://ucanr.edu/blogs/strawberries_caneberries/blogfiles/38663.jpg)
- Posted By: Mark Bolda
- Written by: Mark Bolda
As many Central Coast caneberry growers know, this summer season has seen an astonishing number of lygus bugs in blackberries. Counts of 10 to 20 lygus bugs per shake easily rival the heaviest infestations in strawberry.
However, contrary to the “catfacing” or misshapen fruit left by lygus activity in strawberry, there does not seem to be a documented type of damage from lygus in blackberry. All the same, customers have been getting tetchy about having bugs in their baskets of fruit, so it is indeed important for us as an industry to take this on.
Unfortunately, management of lygus in blackberry has proven to be just as difficult in blackberry as strawberry, perhaps even more so since there are fewer insecticides registered for use in blackberries.
Thrips incidentally occur in blackberry flowers as well and did in great numbers in this trial. Again it is not certain whether or not they cause a lot of damage. Nevertheless, thrips were also evaluated in this trial since they are a known pest in other crops and situations.
The organically registered insecticides MPede and Aza-Direct have shown promise in controlling stink bugs (same insect order as lygus bugs), so the study described below is a screen these two materials compared against a grower applied standard of Diazinon along with an untreated control.
Trial was composed of 4 24 ft x 26 ft replicated treatments in a blackberry field with significant lygus and thrips activity. MPede and Aza-Direct were applied with a motorized backpack sprayer by Brian Deeter from Gowan Company. Diazinon was applied at the label rate by the grower in an adjacent block, so while not part of the experimental design, it did provide reasonably strong information in comparison to the three other treatments.
My research assistant and I did the evaluations which consisted of shaking 3 feet of flowering blackberry hedgerow into a five gallon bucket for the lygus and agitating three mature flowers individually onto a white sheet of paper and counting the expulsed thrips there. Dates of evaluation were August 11 (pre-application), August 15 and August 19 (one week post application).
As the reader can see from the chart below, beyond Diazinon there is little effect on field populations of lygus or thrips from either MPede or Aza-Direct. Furthermore, the lack of thorough control of lygus and thrips by Diazinon, long regarded as one of the most powerful pesticides available to blackberry growers, is unsettling.
Character Rated |
lygus |
thrips |
lygus |
thrips |
lygus |
thrips |
|||||||
Rating Date |
Pre-app |
Pre-app |
8/15/2011 |
8/15/2011 |
8/19/2011 |
8/19/2011 |
|||||||
1 |
MPede + Aza-Direct |
35.75 |
a |
84.50 |
a |
31.50 |
a |
72.00 |
ab |
16.50 |
a |
54.75 |
ab |
2 |
MPede |
28.75 |
a |
56.50 |
a |
37.25 |
a |
120.25 |
a |
19.50 |
a |
67.75 |
a |
3 |
UTC |
36.00 |
a |
73.50 |
a |
34.75 |
a |
104.75 |
a |
15.50 |
a |
52.00 |
ab |
4 |
Diazinon |
22.50 |
a |
38.25 |
a |
11.25 |
b |
34.50 |
b |
11.50 |
a |
24.25 |
b |
Means followed by same letter do not significantly differ (P=.05, Student-Newman-Keuls)
Mean comparisons performed only when AOV Treatment P(F) is significant at mean comparison OSL.
Finally, it will be worth my while to return to this field to evaluate the effect, if any, this pest load is having on fruit development. As already mentioned above, beyond the contamination of harvested fruit, thrips and lygus damage to blackberry has not yet been well defined.
There are a number of pesticides mentioned for management of lygus and thrips in this article. Before using any of these products, check with your local Agricultural Commissioner's Office and consult product labels for current status of product registration, restrictions, and use information.
![Lygus bug adult on unopened blackberry flower Lygus bug adult on unopened blackberry flower](https://ucanr.edu/blogs/strawberries_caneberries/blogfiles/8318.jpg)
- Posted By: Mark Bolda
- Written by: Mark Bolda
Starting Friday and over the weekend, a number of area blackberry growers have reported high numbers of lygus bugs in their fields. I checked on one field this morning, and indeed the level of infestation is astonishing. Somewhere in the area of ten early stage nymphs can fall out from a few shakes at a single spot at any number of points all across the field. This is without precedent in any type of berry and merits some thought and discussion.
The field that was viewed this morning was in full harvest with a lot of fruit in the yet green to pink stage. Primocane was still growing vegetatively with no flowering. I do not think lygus presents any harm to the quality of the fruit or the vegetative plant, other than as an incidental contaminant in the baskets of harvested fruit, much along the lines of what we have recently seen with stinkbugs. Lygus bug feeding damages the flower and developing fruit, so once the druplets have made and the fruit has formed, these bugs will no longer be able to harm it. Since the field examined today has next to no flowers, the nymphs must be feeding on sap from the newly developing vegetative tissue. Whether this causes harm to the plants remains to be seen.
Beyond the contamination of harvested cited above, the possibility that this colossal lygus population shifts over to later bearing varieties which are entering into flowering would give some reason for concern.
Fortunately, blackberry growers have several options available to them to control these pests. One of the best combinations we found from our work in managing lygus in strawberries has been a pyrethroid + neonicotinoid applied when the lygus are very small as they are now. Always bear in mind that this powerful combination of pesticides will weigh heavily on beneficials. Additionally, the neonicotinoids registered in blackberries present some issues with maximum residue limits (MRL's) to fruit exported to Canada.
Organic growers have few options short of border weed removal and vacuuming available to them unfortunately.
There are pesticides mentioned for management of lygus bugs in this article. Before using any of these products, check with your local Agricultural Commissioner's Office and consult product labels for current status of product registration, restrictions, and use information.
![Lygus nymphs. Note the five spots on the back of the larger nymph. The smaller nymphs, for example the two on left, would be very easy for the pest manager to handle.. Lygus nymphs. Note the five spots on the back of the larger nymph. The smaller nymphs, for example the two on left, would be very easy for the pest manager to handle..](https://ucanr.edu/blogs/strawberries_caneberries/blogfiles/7769.jpg)