Leafminer, sometimes Leaf Miner. It's that time of year. Those little moths come out in the late afternoon and flit about. They lay their eggs and when they hatch the larvae start burrowing through the leaf. The recent heat and also the generally warm summer have set them off. And it is obvious now. The heat has exacerbated the collapse and drying of the leaves and on older trees it looks like trees have been decorated with a sprinkling of light brownish ornaments. It is disturbing. But it's not the end of the world, like …………ACP can be.
Leafminer adults are tiny moths less than 0.12 in long (2 mm) with wings span twice as wide.
Pretty shocking from a distance
Citrus leafminer larvae feed by creating shallow tunnels, referred to as mines, in young leaves. It is most commonly found on citrus (oranges, mandarins, lemons, limes, grapefruit and other varieties) and closely related trees (kumquat and calamondin). The larvae mine the lower or upper surface of the leaves causing them to curl and look distorted. Mature citrus trees (more than 4 years old) generally tolerate leaf damage without any effect on tree growth or fruit yield. Citrus leafminer is likely to cause damage in nurseries and new plantings because the growth of young trees is retarded by leafminer infestations. However, even when infestations of citrus leafminer are heavy on young trees, trees are unlikely to die. But they can sure struggle pushing new leaves that then get attacked anew.
Several years ago, we did a trial where we sprayed mature trees with leafminers every month for 18 months with a rotation of different chemicals and even the most heavily treated trees had some damage on them. The most heavily infested trees looked horrible, but in that period of time there were no lemon yield differences. Young trees treated with a systemic were able to free themselves of infestation. This has been commented on by others, that soil applied systemics on heavier soils can have problems controlling leafminers.
Photos: Tunnels and the rapidly dried leaf after a heat spell
The latest edition of Topics in Subtropics newsletter is out, Elizabeth Fichtner as editor. Read on.
TOPICS IN THIS ISSUE:
Why has California red scale been so difficult to control?
Navel Orange Nitrogen Fertilization
Recent Advances in Understanding the History of Olive Domestication
- Upcoming UC Olive Center Events
- Author: Christina Herrick
This article is from Florida Grower News. Thanks for Jim Lloyd-butler for pointing it out.
A sister species of the Varroa destructor mite is developing the ability to parasitize European honeybees, threatening pollinators already hard pressed by pesticides, nutritional deficiencies, and disease, a Purdue University study says.
Researchers found that some populations of Varroa jacobsoni mites are shifting from feeding and reproducing on Asian honeybees, their preferred host, to European honeybees, the primary species used for crop pollination and honey production worldwide. To bee researchers, it's a grimly familiar story: V. destructor made the same host leap at least 60 years ago, spreading rapidly to become the most important global health threat to European honeybees.
While host-switching V. jacobsoni mites have not been found outside of Papua New Guinea, Purdue researchers Gladys Andino and Greg Hunt say vigilance is needed to protect European honeybees worldwide from further risk.
“This could represent a real threat,” said Andino, a bioinformatics specialist with Information Technology at Purdue. “If this mite gets out of control and spreads, we might have another situation like V. destructor.”
Varroa mites are obligate parasites, meaning their lifecycle is inextricably entwined with that of their bee hosts. The mites can do serious damage to their hosts' health due to their relatively large size – “think of a tick as big as your fist,” Hunt said. Mites latch on to bees and feed on their hemolymph, insects' rough equivalent to blood, leaving behind open wounds that are susceptible to infection. They can also transmit diseases such as deformed wing virus and have been linked to colony collapse disorder.
To gain insight into the biology behind V. jacobsoni‘s host switch, Andino and Hunt, professor of behavioral genetics and honeybee specialist, studied the differences in gene expression between V. jacobsoni mites that fed and reproduced on Asian honeybees and those that parasitized European honeybees. Knowing which host cues mites respond to and the genes involved could lead to potential control strategies, the researchers said.
“If we can understand the mechanism, we might be able to disrupt, block, or manipulate that,” Andino said. “But first we have to understand what is happening and which genes are involved in allowing the mites to shift to a new host.”
Andino and Hunt said the mites' leap to European honeybees likely occurred within the last decade. Previously, V. jacobsoni mites were occasionally found on European honeybees but seemed unable to produce healthy offspring, limiting their destructive capacity.
Catching the host transition in its early stages will allow researchers to continue to investigate the complex genetic details behind the shift and monitor infected European honeybees, Hunt said.
“This happened once with one species of mite, and it looks like it's happening again. Maybe if we catch this as it's beginning, we'll be able to figure out why it's happening or, down the road, stop it.”
The paper was recently published in BMC Genomics.
Funding for the study and an ongoing genome-sequencing project was provided USDA's-Agricultural Research Service and the USDA National Institute of Food and Agriculture.
This article is from Florida Grower News
Jane Delahoyde, a PCA here in Ventura, recently found an unusual scale in lemon here. It is barnacle scale with a typically long Latin name - Ceroplastes cirripediformis. It is unlikely to be any worse than other scales, but it's something to keep our eyes on. This is one of the soft scales, often called wax scales because of the wax they produce. It turns out that this has been described as being in Southern California for years, but some years they are just more present. For more on "Wax" scales see the Texas A&M site
or our UC IPM website