As more host crops begin to ripen, SWD captures are now being reported in more locations across Massachusetts. Numbers are still quite low but will increase with warm humid temperatures. Farms with susceptible fruit should be ready to implement their management plan
with 4 main tactics, 1) frequent and thorough harvest every 2-3 days, 2) sanitation (no cull fruit left in the field), 3) rapid cooling of harvested fruit, and 4) a spray program with recommended rotations of conventional or organic materials on a 7-day cycle (see here
for table of recommended materials).
Maintaining an open plant canopy
for good air circulation and light penetration is also very helpful in deterring swd from your crop. In raspberries this can be done by thinning new primocanes as they fill in the canopy or by spreading them with a V-Trellis to open up the center of the row.
Finally, performing a salt flotation test
on harvested fruit on a regular basis helps you determine if fruit infestation has occurred before you hear about it from your customers. See here
for a good protocol for this test.
As of July 12, 2016 the US Drought Monitor is reporting over 60% of Massachusetts is in a state of Moderate to Severe Drought. See: http://droughtmonitor.unl.edu/Home/StateDroughtMonitor.aspx?MA
. This worst is in a swath from Northern Hamden County diagonally Northeast to Essex County.
These dry conditions during the fruit ripening period mean that growers must be prepared to irrigate their plantings. How much to irrigate depends somewhat on the soil type where the crop is growing (a silt loam will hold twice as much water as a sandy loam), the crop type (blueberries with shallow roots are more drought sensitive than grapes with deep roots), and also on the method of irrigation (drip irrigation looses less water to evaporation than does overhead irrigation). While there are many ways to calculate exact rates for all different combinations of crop, soil, and delivery system (see July 2016 Berry Notes), the short version is to aim for 2" of water per week to support a ripening berry crop. Be sure that you are using a clean water supply. And, if you are using a municipal water supply, be aware of water use restrictions that may apply. See here for current Massachusetts water use restriction
Black Vine Weevil and other Root Weevils
ID/Life Cycle: There are several root-feeding weevils that are damaging to strawberries; black vine weevil, strawberry root weevil, and the rough strawberry root weevil are the best known. Additionally, green leaf weevils, have also been found feeding on strawberries in Massachusetts and Connecticut.
Black vine weevil adults are black weevils with short, broad snouts. Adults cannot fly because their wing covers are fused together and so they disperse chiefly by walking. The weevils feed at night and hide under leaf litter or in the soil during the day. The grubs are small, whitish and crescent shaped. They have no legs. There is one generation every year.
The black vine weevil overwinters in the soil as a partly grown larva, or "pre-pupa". Larvae resume feeding on roots in the early spring, causing the heaviest damage. Larvae pupate in late May and June for about 10 days. Adults begin emerging in June (600 GDD) and continue through July. Adults feed at night and hide around the base of the plant during the day. After two to three weeks of feeding, egg laying begins, usually in late July (approximately 1400 GDD). Larvae hatch in August (Approximately 1700 GDD) and begin feeding on roots. They continue to feed and grow until winter.
Damage: Larvae feed on roots and crowns, which can weaken the plants or lead to root rots. Adult weevils feed on leaves from May through August, causing notching of the leaf margins, which rarely leads to significant weakening of the plants. Under heavy infestation by root weevils, the plants decline, appear stunted and bear poorly. Infestations are generally in patches in the field.
Monitoring: Degree-day models can predict emergence and development. This can help guide scouting and management activities. Symptoms of adult feeding can be seen on leaf margins beginning in June. The nocturnal adults can be spotted at night with a flashlight. Traps can also be made by placing fold of burlap around the base of the plant, or by creating a pitfall trap by burying a paper cup at soil level. Traps should be checked at least twice a week. It is important to determine when the first adults are emerging so that control measures can be taken before they begin to lay eggs (2-3 weeks after emergence). Emergence is usually toward the end of harvest making chemical control difficult.
(Photos: Univ. of Maine, Washing State University)
- Rotate strawberry fields to non-susceptible crops for at least 3 years before replanting to strawberries to reduce the buildup of root weevils.
- Plow down heavily infested fields should be plowed down as soon as possible after harvest to avoid migration of weevils to nearby fields.
- Avoid locating new strawberry plantings near old ones, especially if infested with root weevils.
- Create a deep trench between an old field and a new planting to capture black vine weevil adults as they migrate to the new field.
- Apply insect pathogenic nematodes in early May or late August if grubs are found in the soil.
- Be sure to keep the field irrigated during periods of active growth to avoid stress on the plants.
* Restricted Use Material
- Apply recommended insecticides from current New England Small Fruit Management Guide after harvest to suppress adults before they lay eggs. These include but are not limited to:
- Actara @ 4 oz/A
- *Bifenture 10DF @ 8-32 oz/A
- BotaniGard 22WP @ 5lb/A
- *Brigade WSB @ 8-32 oz/A
- Platinum @ 5-12 oz/A
- **Azera @ 1-3.5 pt/A
- **Mycotrol O @ 0.25 - 1 qt/A
** OMRI Listed Material for Organic Production
(Controlling root weevil adults requires the highest allowed rate of labeled insecticides, and is best applied at night when adults are active.)
Japanese Beetle and related species
: Japanese beetle
adults are large metallic green or greenish bronze with reddish wing covers and several white spots near the abdomen tip and along the sides. Larvae are large C-shaped grubs that live in the soil. Asiatic garden beetles
are small and a velvety cinnamon brown color, showing a faint green iridescence in the sunlight. Rose Chafers
and smaller olive colored with long antennae. The larvae (or grubs) of these insects look quite similar to one another and are called white grubs. They are c-shaped, have 3 pairs of legs, grow up to 1” long. They are easily distinguished from the larvae of root weevils, which have no legs.
Grubs overwinter deep in the soil. As spring temperatures increase, the grubs move up in the soil to feed on grass and other small roots. They pupate in late May to June and adults start emerging in late June to mid-July. Adults feed through late summer or early fall. Females lay eggs during July and August, and grubs hatch in 10 to 12 days. Grubs first feed on decaying matter but soon feed on roots as they move deeper to an overwintering site. There is one generation per year.
High populations of larvae can be expected the autumn and spring following a dry summer, especially where blueberry fields are surrounded by turf or have sod row middles. These conditions favor movement of adults into blueberries to feed on foliage/fruit and lay eggs in soil beneath the bushes.
: Michigan State University Japanese Beetle Fact Sheet
: The adults of some species feed on the foliage, flowers and fruits of many plants. Japanese beetle and rose chafer adults can be significant pests of blueberry during harvest when they contaminate the berries. For many years white grubs were a rare problem in blueberry fields, but recently they have become serious pests in some fields, with populations as high as 30 grubs per bush. The grubs consume feeder roots and may also girdle or clip off larger roots. Infested plants may not show any outward signs of injury until a period of drought stress, when the reduced root system cannot provide enough water to the plant. Damaged bushes show low vigor and reduced production. Adults, especially the Japanese beetle and rose chafer, sometimes become serious pests by consuming leaves and scarring the berries.
(Photos: University of Minnesota, Cornell University, Michigan State University)
Monitoring traps can be used to determine early emergence of adult Japanese Beetle. Once early captures are made, remove the traps from the vicinity of the blueberries as they are likely to draw more beetles to the crop area. Traps are not an effective control.
Larvae can be sampled in the soil in June or August (see diagram above) when larvae are close to the surface.
To sample for larvae, cut a defined area of sod (1 square foot, for example) and shake through the soil and roots for grubs. Keep a record of the position and number of grubs per square foot from a number of sites to compare samples over time and between fields. This can help inform growers about whether and when a soil applied treatment can be made with chemical or biological controls listed below.
- Avoid planting on newly turned sod land. Rather, plow the field, let it lie fallow or in a rotational cover crop such as Sudan, buckwheat, or a salable crop such as pumpkins or squash for at least one season prior to planting with blueberries.
- Avoid locating blueberries next to large grassy fields, which would be a source of these beetles.
- Do not use traps as they are more likely to increase the overall population of beetles in the vicinity of the traps.
* Restricted Use Material
- Apply recommended insecticides if scouting reveals a high population. These include but are not limited to:
- Actara @ 3-4oz/A
- Admire Pro @ 2.1-2.8 oz/A
- *Asana XL @ 4.8-9.6 oz/A
- Assail 30 SG @ 4.5-5.3 oz/A
- *Danitol 2.4EC @ 10.6 oz/A
- Imidan 70W @ 1.3 lb/A
- Sevin XLR Plus @ 1-2 qt/A
- **AzaDirect @ 1-3 pt/A
- **Azera @ 1-3.5 pt/A
- **Surround WP @ 12.5-50 lb/A
** OMRI Listed Material for Organic Production
- If repeat applications are needed, rotate insecticides from different IRAC groups to reduce the chance of resistance development in the pest.
Archived IPM Berry Blasts are available at the UMass Extension Fruitadvisor website.
Where brand names for chemicals are used, it is for the reader's information. No endorsement is implied, nor is discrimination intended against products with similar ingredients. Please consult pesticide lables for rates, application instructions and safety precautions. The label is the law. Users of these products assume all associated risks.
We thank Nourse Farms for their underwriting of this newsletter which allows us to keep subscription rates low.
This work was supported in part by funding provided by USDA-NIFA Extension Implementation Program, Award No. 2014-70006-22579