Topics in Subtropics Blog
When a biocontrol agent turns on you, it can be painful. Recently a grower called in asking about an insect that had bit him when he picked it up. It caused a fearsome pain and some swelling. This insect is an assassin bug, one of the numerous predators out there that help keep pest insects in control.
Assassin bugs (family Reduviidae) belong to the order Hemiptera and the suborder Heteroptera, the so called “true bugs.” Altogether, nearly 7,000 species of assassin bugs have been described worldwide, of which about 50 are native to California. All Hemiptera have tubular mouthparts with stylets that help them pierce tissues of plants and other creatures. The stylets may also help them suck blood. Indeed, 140 species of assassin bugs are specialized to feed on blood. Spreaders of Chagas disease, these are the kissing bugs, so named because they frequently bite people on the face around the mouth.
Within insects, they are one of the third biggest groups of predators that mostly feed on other insects. This determines where they are found: many species sit on flowers or leafs, where they stalk or ambush their prey. Others like to hide in special microhabitats, for example, underneath the bark of trees, and feed on insects – such as certain beetle and fly larvae – that live under the bark.
In general, the greatest numbers of assassin bugs are found in wet tropical places around the world, but some also live in subtropical, arid and even temperate places. About 50 species are native to California and the majority of them also occur in Southern California. In California, you can find different species of these bugs from the low deserts to fairly high elevations in the Sierras. Altogether, we have fewer than 190 species recorded from the United States and Canada, but as you get into Central and South America, diversity increases and the species numbers go up.
A common species in California is the leafhopper assassin bug that is frequently found even in backyards around Riverside. It is widely distributed from Canada to Central America. Although it is native to this region, it has been introduced and become established in Chile, Greece and Spain. Leafhopper assassin bugs hang out on various plants and are beneficial – as are many other assassin bugs – because they eat pests that can be a nuisance to crops and ornamental plants.
The smallest are about 3 millimeters long. The largest can be about 1.5 inches in length. As other true bugs, assassin bugs have “divided” wings, meaning that the forewings have a thick leathery texture close to the head and a more membranous structure further back. Assassin bugs can be recognized by the shape of the beak that is typically curved and pretty thick and has three segments. The bug uses this beak to grab and hold on to its prey. There is no need to panic when you see an assassin bug, but since they can inflict rather painful bites it is best not to touch them. Kissing bugs are somewhat unusual amongst assassin bugs in having a fairly slender and straight beak. Although their bite is painless in contrast to the bite of other assassin bugs, they are much more dangerous: their saliva can cause allergic reactions, and they can also spread Chagas disease.
The protozoan that causes Chagas disease, Trypanosoma cruzi, is not transmitted when the kissing bug bites you and sucks your blood. Instead, it is transmitted soon after the kissing bug has stopped feeding blood. When a kissing bug bites you, you don't feel anything at first because the bug injects an anesthetic and the bite will only get itchy shortly thereafter. Now, after its blood meal, the kissing bug defecates. The feces contain the Chagas-disease-causing protozoans. When you scratch, you get the feces into the wound and your blood stream. We have three species of endemic kissing bugs in California. Many of the specimens of our commonest species are to be found in Southern California; about 20-35 percent according to one of our studies, are infected with the protozoan and could serve as carriers. Typically, our native kissing bugs blood-feed on woodrats, but will also try to feed on other vertebrates, given the opportunity. In addition, dogs that sleep outdoors could also get infected with Chagas disease by eating the kissing bugs.
Persons who are bitten should wash and apply antiseptic to the site of the bite. Oral analgesics, such as aspirin or ibuprofen, may be useful to reduce the pain. Treatment by a physician is not usually needed, though Caladryl® or topical corticosteroids may help reduce swelling or itching at the site of the bite. As with any insect sting or bite, the victim should seek medical attention immediately if there is any sign of anaphylactic reaction, such as generalized swelling, itching, hives or difficulty breathing.
UC IPM Staff Writer
Celebrate 2018 Honey Bee Day
Celebrate National Honey Bee Day by brushing up on your knowledge of bee protection—check out the newly revised Best Management Practices to Protect Bees from Pesticides and Bee Precaution Pesticide Ratings from UC IPM. These resources will help you strike the right balance between applying pesticides to protect crops and reducing the risk of harming our most important pollinators.
The best management practices now contain important information regarding the use of adjuvants and tank mixes, preventing the movement of pesticide-contaminated dust, and adjusting chemigation practices to reduce bee exposure to pesticide-contaminated water. The Bee Precaution Pesticide Ratings have also been updated to include ratings for 38 new pesticides, including insecticides (baits, mixtures, and biological active ingredients), molluscicides (for snail and slug control), and fungicides.
Most tree and row crops are finished blooming by now, but it is a good idea to learn about bee protection year-round. Visit these resources today to choose pesticides that are least toxic to bees and learn how you can help prevent bees from being harmed by pesticide applications.
Bal - Turkish Honey packet
Bowl of Turkish honey
At a recent grower meeting at South Coast Research and Extension Center in Irvine, Carol Lovatt gave a talk on the use of gibberellic acid to increase avocado fruit set and yield. The registration for the use only occurred this spring, barely in time for growers to use it, so not many applied it. Then we had this heat wave in July and a lot of fruit, whether it had been treated or not, fell off. A show of hands was asked of the growers present, who had applied it this spring. Of the 100 people or so in attendance, only five raised their hands. Of course, this is not a scientific survey, but most would try it again this coming spring, even though they might not have seen results this year.
The following are guidelines that were provided on how to use it, if you should so choose this coming spring:
Use of ProGibb LV PlusR Plant Growth Regulator on Avocado to Increase Fruit Size and Yield
Professor of Plant Physiology, Emerita, and Professor in the Graduate Division, Department of Botany and Plant Sciences, University of California, Riverside email@example.com
ProGibb LV PlusR. On March 27, 2018, gibberellic acid (GA3) was approved for use on avocado to increase fruit size and yield. The only material registered for this purpose is ProGibb LV PlusR, a low volatile organic compound (LVOC) formulation, manufactured by Valent BioSciences, Corporation (Libertyville, IL). Only this product may be used; the older formulation sold under the name ProGibbR and other generic GA3 products cannot be used. Note: (i)the restricted entry interval is only 4 hours; (ii) the preharvest interval is 0 days; and (iii) ProGibb LV PlusÒ can be used in certified organic orchards.
Application Time. ProGibb LV PlusR is applied as a foliar spray at the cauliflower stage of avocado inflorescence development. The applications should be made when 50% of the trees in the block have 50% of their bloom at the cauliflower stage. This means that 25% of the bloom will be at an earlier stage of inflorescence development and 25% will be approaching bloom (open flowers). If you are unable to make the application at this time, being slightly late in applying the treatment affords better efficacy than being too early. Note: applications made at full bloom are typically not effective.
ProGibb LV PlusR Dose and Dilution Rate. The sprays should be applied like a pesticide spray to give full canopy coverage, especially of the developing inflorescences, but not sprayed to run-off. For ground application, use 12.5 fluid ounces of ProGibb LV PlusR (25 grams active ingredient [g ai]) in 100 gallons of water/acre. For aerial (helicopter) application, use 12.5 fluid ounces (25 g ai) in 75 gallons of water /acre. The maximum allowable dose is 25 g GA3 (active ingredient)/acre. Note: the results of our research documented that lower and higher doses are less effective.
Spray Solution pH. The final pH of the spray solution in our research was between pH 5.5 to 6.0. ProGibb LV PlusR is stable at pH 4.0 to 8.5. The pH of the water used should be adjusted accordingly. Note: prolonged exposure of GA3 to a pH > 8.5 should be avoided to prevent breakdown of the material.
Additional Information on Spray Volume. In our research, for ground applications, we used the same amount of GA3 (25 g ai/acre) but a spray volume of 200 to 250 gallons of water/acre, depending on tree size, to achieve good coverage without causing the material to run-off the tree and with minimum spray volume left in the tank after application. Use of spray volumes greater than label rate of 100 gallons of water/acre for ground application is the decision of the Agricultural Commissioner for each county. Consult with your County Agricultural Commissioner, if you wish to apply ProGibb LV PlusR (25 g ai) in more than 100 gallons of water/acre as a ground spray. For the aerial (helicopter) application, the greatest efficacy was achieved with ProGibb LV PlusR (12.5 fluid ounces, 25 g ai) in 75 gallons of water/ acre.
Wetting Agent. In our research, we used the organosilicone surfactant Silwett L-77R or Widespread MaxR (Loveland Industries, Greely, CO) at a final concentration of 0.05%. Similar pure organosilicone type surfactants are acceptable.
Photo: Cauliflower stage inflorescence. Source: Salazar-García et al., 1998.
Wildlife isn't always restricted to wild spaces.
Avocado orchards and other agricultural landscapes also buzz with species that forage and reproduce in these spaces. Birds and herbivores are able to find food and shelter in these cultivated areas, but what about carnivores? In a study published in PLOS ONE, researchers at the University of Washington have discovered that mammalian carnivores also occupy avocado orchards in southern California.
The authors used motion-activated cameras to observe animals in orchards and in adjacent wild lands in Santa Barbara and Ventura. Avocado orchards were of particular interest due to their location near native vegetation.
Through their investigation, the researchers detected more carnivores in the avocado orchards than in neighboring wild land sites. At least 7 out of the 11 native carnivores in the area were spotted roaming the orchards, including bear, coyotes, gray foxes and bobcats.
Having delicious avocados handy may explain why some omnivores such as bears and raccoons are present in the area, however, little is known about why animals like bobcats and mountain lions might leave their wild habitat for cultivated land. One possibility is that the orchards provide water and fruits for herbivores, and an increased herbivore population could translate to more prey for the carnivores. The orchards may also serve as shelter, offering forest cover similar to oak woodlands in the area.
These native species cannot always persist in protected reserves, so it is important to learn how cultivated lands can serve their lifestyle and behaviors. The carnivores may not be searching for the perfect guacamole ingredient; however there is no doubt that the avocado orchards are serving as a habitat for a wide range of species.
Citation: Nogeire TM, Davis FW, Duggan JM, Crooks KR, Boydston EE (2013) Carnivore Use of Avocado Orchards across an Agricultural-Wildland Gradient. PLoS ONE 8(7): e68025. doi:10.1371/journal.pone.0068025