Rutgers Cooperative Extension
Seasonal updates on diseases, insects, weeds impacting tree fruit and small fruit (blueberry, cranberry, and wine grape). Fruit Pest Alerts are also available via this category feed.
Subscriptions are available via EMAIL and RSS.
Peach:
Plum Curculio (PC): PC adults are active and will damage fruit if not controlled. PC is a key pest to control during the first few weeks after petal fall. Imidan, Avaunt, Actara and Belay are very effective. However, try to delay the use of Actara and Belay for when brown marmorated stink bugs (BMSB) are more of an issue.
This week, the webinar will be concentrated on the topic of farm labor. Since updates are coming to the industry and we have learned of some programs for migrant workers please join us for discussion. Please feel free to bring up other topics.
Ask the Ag Agent – 7:00PM Weekly – Every Wednesday – Farmer Video Conference/Call-In Forum
“Ask the Ag Agent” weekly 1-hour sessions for farmers will be hosted again on Wednesday May 13th and continue each Wednesday until May 27th. The online conferencing/call in events will begin at 7:00PM with an open forum to discuss ag-related questions about production, marketing, regulations and any other topics farmers wish to discuss. All are welcome. Events are hosted by William Bamka, Stephen Komar, Meredith Melendez and Michelle Infante-Casella – Agricultural Agents.
To access via WebEx on a computer go to https://go.rutgers.edu/rc9n3kxt
Or, Join by phone
+1-650-429-3300 USA Toll
Access code: 799 743 872
For additional Rutgers Cooperative Extension educational programs check out https://events.rutgers.edu/njaes/
Please join the NJ Statewide Wine Grape Twilight Meeting on the Wed, May 20, 2020 4:20 pm using the below link. Also, please see below for the program details.
Meeting Host: Hemant Gohil
https://rutgers.webex.com/rutgers/j.php?MTID=mbdbb2eafedfe9d44f3694adeedf61269
Meeting number: 222 571 928:
Password: MJht93B8Pzx
Join by phone +1-650-429-3300
Access code: 222 571 928 [Read more…]
The following insect pests bear special mention for early-season scouting in cranberry bogs:
Blackheaded fireworm – Blackheaded fireworm eggs overwinter on the bed and usually hatch by around mid-May. It is important to catch the first generation, if possible, because the second generation occurs during bloom and is typically much more destructive. Blackheaded fireworm larvae can be detected by sweep net sampling and it is a good idea to look along the edges of beds where vines first begin to grow. Remember: blackheaded fireworm is much easier to control if detected during the early part of the season.
Spotted fireworm – This insect overwinters as a 2nd instar larva. They complete two generations a year. Larvae feed between uprights they have webbed together. First-generation larvae injure the foliage causing it to turn brown as if burned. In New Jersey, first generation adult moths emerge the first week of June, followed by a second-generation of adult emergence in early August. Eggs are laid in masses on weedy hosts. Larvae from second-generation adults emerge in mid-August, and may feed on fruit. Populations of spotted fireworm are regulated by their natural enemies, in particular Trichogramma wasps that parasitize the eggs.
Sparganothis fruitworm – This insect is a serious pest in most cranber
Blackheaded fireworm Larva (Photo by D. Schiffhauer)
ry-growing states. Sparganothis fruitworm completes two generations a year and overwinters as an early-instar larva. Larvae from the 1st generation feed on foliage. In New Jersey, first generation adult moths emerge from mid-June through the first weeks in July; pheromone traps are commonly used to monitor adult flight and population size. Second-generation eggs are laid on cranberry leaves, and larvae will feed on fruit.
Cranberry blossomworm – Adults lay their eggs in October in cranberry beds. The eggs overwinter and hatch over a period of several weeks. Early instars can be found during the first week of May. Larvae go through 6 instars to complete development.
Because the first instars feed during the day (and also at night), scouting can be done during the
Spotted Fireworm Larva
daytime using sweep nets to estimate larval abundance. Larvae turn nocturnal during the later instars. At this time, night sweeping (9 pm – 1 am) is recommended for sampling. Larvae complete their development by June-July. Older instars are very voracious and capable of destroying 100 blossoms within a 3-week period. There is a pre-pupal that lasts until the end of August and a pupal stage that lasts until October. Adults emerge from end of August to end of October.
Lepidopteran Pests Monitoring and
Sparganothis fruitworm Larva (Photo by D. Schiffhauer
Control – Use sweep netting for monitoring early lepidopteran pests (pre-bloom). A sweep set consists of 25 sweeps and 1 sweep set is recommended per acre (this may vary depending the size of bogs). The action threshold for false armyworm, blossomworm, other cutworms, and gypsy moth (we use a combined threshold from adding all these caterpillars per sweep) is an average of 4.5 caterpillars in sets of 25 sweeps. For brown and green spanworms is an average of 18 per sweep set. The action threshold for blackheaded fireworm and Sparganothis fruitworm is an average of 1 to 2 per sweep set. We recommend the use of the reduced-risk materials Intrepid, Delegate, Altacor or Exirel if populations exceed action thresholds. Exirel is a newly-registered insecticide in cranberries. These are reduced-risk, softer insecticides that are very effective against lepidopteran pests. More information on these (and other) lepidopteran pests will be provided as the season progresses.
Leafhoppers –There is concern among New Jersey cranberry growers of a potential increase in leafhopper populations because of recent changes in pest management strategies (e.g., adoption of new reduced-risk products and decreased applications of broad-spectrum insecticides). Blunt-nosed leafhopper is of particular concern because
Cranberry blossomworm Larva
they can transmit cranberry false blossom disease. This leafhopper has one generation a year. Adults are found in highest numbers during July, although nymphs or adults may be found from the end of May until October. Eggs are laid in August-September. The eggs overwinter and hatch in May or June. The nymphs go through 5 instars to complete development.
Leafhopper Monitoring and Control: Leafhopper nymphs can be sampled using sweep nets (as described above for lepidopteran pests). Nymphs before bloom are small; thus, you may need to freeze the samples (to kill them), and then count the number of nymphs under a microscope or using a magnifying lens. There is no threshold based on sweep net counts, so decisions should be made based by comparing current numbers with prior infestation history and/or incidence of false blossom disease on those beds.
In cases of high numbers of blunt-nosed leafhopper nymphs, we recommend application of a broad-spectrum insecticide, such as Diazinon (no aerial applications allowed) or Lorsban (only pre-bloom applications allowed for Ocean Spray growers). Broad-
Blunt-nosed leafhopper Nymph (Photo by D. Schiffhauer)
spectrum insecticides will disrupt biological control particularly the natural enemies (predators and parasitoids) of Sparganothis fruitworm, so their use should be restricted only to areas of high leafhopper populations.
Frost Advisory in Effect Monday May 11 through Thursday May 14, 2020.
A frost advisory is in effect for parts of Northern New Jersey for the nights of Monday May 11, Tuesday May 12, and Wednesday May 13 with temperatures at or below freezing predicted. Please take appropriate measures to protect tree fruit, grapes, strawberries and other small fruit.
Below are resources for determining the critical temperatures for tree and small fruit. Note that the critical temperature for damage at a particular bud stage may vary by 4 or 5⁰F depending on temperatures during the previous few days before the cold event.
Tree Fruit
Please note the PPA post from May 6, 2020 “Frost Protection in Orchards – What Should You Monitor?“
Note the critical temperature for some of the most common pome and stone fruit crops In New Jersey is available at:
https://www.canr.msu.edu/news/critical_spring_temperatures_for_tree_fruit_bud_stages.
Additional information on frost protection methods is available at:
Small Fruit
Frost and Freeze Damage on Berry Crops
Kathy Demchak Senior Extension Associate Penn State University
Here is a review of critical temperatures for damage to berry crops, symptoms of the damage, and some key points regarding protecting plants.
Critical Temperatures for Blossoms
Damage to blossoms is the biggest concern; critical temperatures are those at which you can expect damage to occur. Air temperature close to the ground is often much colder (as much as 5°F) than the low temperature reached at the typical eye-level height where we usually post our thermometers, and if your field is in a low spot, may be even colder. We also need to factor in the fact that the blossoms radiate heat into the sky (called radiational cooling), much like your vehicle roof that may have frost on it on the mornings when the low temperature didn’t reach freezing. Of course, low temperatures in any out-of-town rural location are often quite a lot lower than those forecasts; some growers subscribe to services that forecast more accurately for their specific location.
Critical temperatures for strawberry blossoms
For strawberries, critical temperatures for flower buds are 10° when just emerging from the crown, 22° when blossoms are emerged but still tightly closed, 26° when closed but petals are visible (“popcorn” stage), and 30° when open. Young green fruit is actually better able to tolerate cold temperatures than open blossoms, having a critical temperature of 28°. Some recommend actually inserting a thermocouple into the flower buds to most accurately measure their temperatures. Just propping up a thermometer at the end of the row so it’s exposed to air on all sides and radiates heat like a blossom would have mirrored the temperatures at which we get damage quite well. Frost-damaged blossoms will have a black center.
Critical temperatures for blueberry
Blueberry blossoms can tolerate colder temperatures than strawberry blossoms. Different sources give somewhat different values for certain stages, so ranges are given here. Critical temperatures are 15-20° at bud swell; 18-23° when flower clusters are still tight; 22-25° when flowers buds in the cluster have separated; 25-26° when flowers are still closed but full-size; and 27° for open blossoms. The stage where the petals have just fallen off is actually the most tender, with a critical temperature of 28°. Petals will turn brown if damaged, and fruit tissue inside the blossom will have a water-soaked appearance.
Critical temperatures for raspberry blossoms
We never used to mention frost damage on raspberries as a possibility, since raspberries typically bloom so late that we are usually past danger of frost by the time they bloom. However, in two out of the past ten years, we had frost damage to open raspberry blossoms; this occurred when temperatures were barely below freezing, which makes me think that the critical temperature is in the 30-32° range. Frost damaged blossoms on raspberries turn black in their center, but this is a little less obvious than on strawberries because the anthers extend beyond the damaged portion.
Frost Protection Methods
For berry crops, frost protection methods consist of either applying water with overhead irrigation or using row covers, or a combination of the two. Other methods such as wind machines and under-canopy irrigation don’t typically provide enough protection for berries or can’t be used due to plant architecture.
Frost protection using overhead irrigation
The theory behind why overhead irrigation works for frost protection is that heat is released as the water freezes (144 BTUs per pound of water), so the blossom temperature stays at 32°. The water application rate must be sufficient to keep a layer of liquid water on the ice that is forming, and coverage must be fairly even. If water completely freezes before additional water is applied by the next sprinkler rotation, heat is no longer being released by the freezing process.
This means that blossom temperatures can drop to ambient air temperature instead of being kept at 32°. When coverage is uneven or it is windy (more than about 3 mph), the application pattern is uneven, and you have more heat loss from evaporation than usual, so you are likely to have more damage than if you had done nothing at all. Irrigation should be kept running in the morning until ice starts to melt from the plants.
Frost protection using overhead irrigation
The theory behind why overhead irrigation works for frost protection is that heat is released as the water freezes (144 BTUs per pound of water), so the blossom temperature stays at 32°. The water application rate must be sufficient to keep a layer of liquid water on the ice that is forming, and coverage must be fairly even. If water completely freezes before additional water is applied by the next sprinkler rotation, heat is no longer being released by the freezing process.
This means that blossom temperatures can drop to ambient air temperature instead of being kept at 32°. When coverage is uneven or it is windy (more than about 3 mph), the application pattern is uneven, and you have more heat loss from evaporation than usual, so you are likely to have more damage than if you had done nothing at all. Irrigation should be kept running in the morning until ice starts to melt from the plants.
Keep in mind that you will need to allow time for the irrigation system to fully wet the plants, and there will be evaporation from the water than will lower the plant temperature at first; for this reason, we generally recommend starting the irrigation when the air temperature is 4° above the critical temperature. Of course, if the low temperature is forecasted to occur very late in the overnight hours and is close to the critical temperature, you will need to judge whether it is worth starting irrigation up or not.
Frost protection using row covers
Row covers can be effective, but they work best on still nights and when you only need 3 or 4° of frost protection. A row cover that is fairly stiff so it doesn’t cling to the plants and ground and maintains some air space works best; clingy ones may not provide much protection. There is one particular 1.25 oz/sq. yd. fabric that works well. It is more expensive than others but has a long field life, so it can be used for multiple seasons and is less expensive in the long run.
Row covers should be pulled over the field during the afternoon to allow some heat buildup under the cover. If it is windy, protection will be less, and if winds are over 5 mph or so, you may not get any protection at all. If you have an old row cover, it can be applied as a second layer underneath the newer cover – this helps on very cold nights and also helps to some degree on windy nights.
Recently there have been some questions regarding whether anthracnose can survive on row covers. One study showed that spores can survive on fabric (in the study’s case, denim) for 5 weeks. However, typically row covers aren’t still being used when anthracnose lesions are present in PA, but if they are, this may be a concern.
Overhead irrigation – row cover combination
We have had very good results with pulling on row covers and then irrigating over top of them for frost protection. Depending on the night, this has resulted in needing no overhead irrigation at all or delaying the time that we needed to start the irrigation since the temperature under the row cover is higher than the outside temperature, and water use is greatly decreased. You’ll want to pull the row covers back off as soon as you can the next day though to allow the plants to dry, otherwise, it will likely get steamy under the row cover, increasing the possibility of disease issues.
Frost Damage to Vegetative Tissues
Vegetation on small fruit crops is quite hardy in the spring. New vigorously growing raspberry canes can get “nipped” however, sometimes seriously. I can think of two instances when this happened with ours. Once was about 20 years ago when we hit 16° in mid-April when the new canes were about a foot tall, and the second time was about in 2012 when raspberries in our high tunnels had grown to about a foot and then got nailed. Fortunately, these canes are replaced by new canes, so the damage wasn’t devastating for the long haul. The damage, if not noticed could be mistaken for some sort of disease, but the difference is that the plants grow vigorously otherwise, and the damage is all at the same location on the plants throughout the planting.
For more detailed information go to Appendix A of Mid Atlantic Berry Guide Guide
By, Michelle Infante-Casella, Agricultural Agent/Professor, RCE of Gloucester Co. and William Bamka, Agricultural Agent/Associate Professor, RCE of Burlington Co.
Although media reports have triggered panic over the Asian giant hornet (Vespa mandarinia), there are no reports this pest is present anywhere else in North America besides the Pacific Northwest. Rutgers Cooperative Extension, Agriculture and Natural Resource personnel have received inquiries to identify hornets found by the public. In New Jersey, Rutgers Cooperative Extension county offices have not identified any submitted specimens to be the Asian Giant Hornet. The Asian giant hornet has only had confirmed sightings in Washington State and British Columbia, Canada.
“The species has not yet been detected this spring in Washington State or the British Columbia or anywhere else on the West Coast”, said Professor Dina M. Fonseca, director of the Center for Vector Biology in the Department Entomology in the School of Environmental and Biological Sciences at Rutgers–New Brunswick. “We do not know how the species arrived in the United States but it is important to not overreact.”
Washington State University’s information on the Asian giant hornet confirmed the first U.S. sighting of this hornet in the wild. The first two specimens were found in Nanaimo and White Rock, British Columbia, Canada in fall of 2019.
The hornets were reported to be attacking colonies of honeybees in Washington State. The Asian Giant Hornet is known to aggressively attack honeybees and can destroy entire honeybee colonies. Washington State University recently published an extensive fact sheet with identification and guidance for the public. According to the WSU Pest Alert, Asian Giant Hornets are not generally aggressive towards people, but may sting when threatened.
“The Asian giant hornet is unlikely to be present in New Jersey,” Fonseca said. “while citizens in the Pacific Northwest can help detect any emerging hornets this spring, which is critical for its control, the indiscriminate killing of bees, wasps or other hornet lookalikes, would be detrimental because of beneficial roles these insects provide as plant pollinators and predators of agricultural pests.”
An insect that looks similar and can be confused for the Asian giant hornet is the Cicada killer wasp (Sphecius speciosus). They large solitary 
wasps found throughout the U.S. and burrow holes in the soil. Even with their large size, dangerous appearance and “dive-bombing” habit, adult Cicada killer wasps rarely come in contact with people and it is rare they will sting. The males of this species will make “dive-bombing” flight patterns, but do not have a stinger and an attack would not result in a sting. The female’s tubular egg-laying structure on the rear end can function as a very weak stinger. Her mild sting is similar to a slight pin scratch and is not considered by most people to be painful. Rutgers Cooperative Extension has more information on the Cicada Killer Wasp and other bees and wasps.
As more information comes out regarding the Asian giant hornet, it is best to pay attention to where this insect has been confirmed and how far it has spread. It is most likely that the Asian giant hornet would first spread and be reported in surrounding areas bordering Washington State and British Columbia, Canada before any reports would occur on the East Coast. Knowing this information may help to calm fears when seeing other hornets and wasps. As always, take precautions and avoid contact with stinging insects. For identification and recommendations contact your local county Rutgers Cooperative Extension office.
